萌新java连接MySQL数据库出现java.lang.NullPointerException错误是为什么,求大佬看一下代码解答

package Stu;
import java.util.*;
public class StuManage {
public void menu(){
connectSQL s=new connectSQL();
int xuhao;
String b1 = null,c1=null,b111=null;
int a = 0,a1=0,b11=0,c11=0;
Scanner scanner=new Scanner(System.in);
System.out.println("欢迎来到学生信息管理系统");
System.out.println("1.新增学生");
System.out.println("2.修改学生");
System.out.println("3.删除学生");
System.out.println("4.查询学生");
System.out.println("5.显示所有学生信息");
System.out.println("6.退出该系统");
System.out.println("请选择(1-5):");
xuhao=scanner.nextInt();
switch (xuhao) {
case 1:
s.open();
stuadd();
s.down();
break;
case 2:
update();
break;
case 3:
studel();
s.open();
s.shanchu(a);
s.down();
break;
case 4:
stuList();
s.open();
s.chaxun(b11);
s.down();
break;
case 5:
xianshi();
s.open();
s.xianshi();
s.down();
break;
case 6:
System.exit(0);
break;
default:
System.out.println("输入有误:程序自动退出,请重启程序");
break;
}
}
public void stuadd(){
connectSQL x=new connectSQL();
Scanner s=new Scanner(System.in);
String select,jieshou,name=null;
int no=0,phone=0;
System.out.println("====新增学生====");
System.out.println("学号:");
no=s.nextInt();
jieshou=s.nextLine();
System.out.println("姓名:");
name=s.nextLine();
System.out.println("手机号:");
phone=s.nextInt();
System.out.println("您输入的信息为:学号:"+no+" "+"姓名:"+name+" "+"手机号:"+phone);
System.out.println("是否保存?y/n");
jieshou=s.nextLine();
select=s.nextLine();
if(select.equals("y")){
x.tianjia(no,name,phone);
System.out.println("保存成功!");
}
else if(select.equals("n")){
System.out.println("请重新输入");
}
}
package Stu;
import java.sql.*;
public class connectSQL {
Connection con=null;
PreparedStatement st=null;
ResultSet rs=null;

public void open(){
try {
    Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();
}
String uri="jdbc:mysql://localhost:3306/qinyewei?user=root&password=123456&userSSL=ture";
try{
    con=DriverManager.getConnection(uri);
}
catch(SQLException e){
    System.out.println(e);
}
}
public void down(){
    try {
        con.close();
    } catch (SQLException e) {
        // TODO 自动生成的 catch 块
        e.printStackTrace();
    }

}
void xianshi(){
    try{
    st=con.prepareStatement("select * from stu");
    rs=st.executeQuery();                       
    while(rs.next()) {                          
        String a=rs.getString(1);
        String b=rs.getString(2);
        String c=rs.getString(3);
        System.out.printf("%s\t",a);
        System.out.printf("%5s\t",b);
        System.out.println(c);
    }
    }

    catch (SQLException e) {
        // TODO 自动生成的 catch 块
        e.printStackTrace();
    }
}
void tianjia(int a1,String b1,int c1) {
    try {
        System.out.println(a1);
        System.out.println(b1);
        System.out.println(c1);
        st=con.prepareStatement("insert stu values(?,?,?)");
        st.setInt(1,a1);
        st.setString(2,b1);
        st.setInt(3,c1);
        int i=st.executeUpdate(); 
        System.out.println("添加了"+i+"条记录");
        this.xianshi(); 
    } catch (Exception e) {
        // TODO 自动生成的 catch 块
        e.printStackTrace();
    }
}
运行后输入1、学号、姓名、手机号以后出现错误是为什么呢?

欢迎来到学生信息管理系统
1.新增学生
2.修改学生
3.删除学生
4.查询学生
5.显示所有学生信息
6.退出该系统
请选择(1-5):
1
====新增学生====
学号:
123123
姓名:
weqwe
手机号:
123123
您输入的信息为:学号:123123 姓名:weqwe 手机号:123123
是否保存?y/n
y
123123
weqwe
123123
java.lang.NullPointerException保存成功!

at Stu.connectSQL.tianjia(connectSQL.java:56)
at Stu.StuManage.stuadd(StuManage.java:72)
at Stu.StuManage.menu(StuManage.java:22)
at Stu.Main.main(Main.java:7)

第56行代码是
st=con.prepareStatement("insert stu values(?,?,?)");

2个回答

System.out.println(a1);
System.out.println(b1);
System.out.println(c1);
st=con.prepareStatement("insert stu values(?,?,?)");
st.setInt(1,a1);
st.setString(2,b1);
st.setInt(3,c1);
int i=st.executeUpdate(); 
System.out.println("添加了"+i+"条记录");

根据你的描述,看这段代码,你只把前三行输出出来了,然后就是输出的你外部调用那部分的“保存成功”,所以我觉得你的问题是

st=con.prepareStatement("insert stu values(?,?,?)");
st.setInt(1,a1);
st.setString(2,b1);
st.setInt(3,c1);

这部分,你可以debug一下,看看st是否为空、null,因为你的java.lang.NullPointerException异常是空指针异常,就是当用null.时就会出现的问题,希望注意下“null点”的问题,你先试试,希望对你有帮助

st=con.prepareStatement("insert stu values(?,?,?)"); 

debug看下con是否为空null,如果为null看下数据库连接getConnection那里是否有问题,不为null换一个版本更高点的连接jar包

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Therefore, database queries may be performed during view rendering. 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com.xintujiuzhang.aimanagement.controller.BackgroundManagementLoginController.joinHWI(java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.847 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/log/computer_login],methods=[GET]}" onto public java.lang.String com.xintujiuzhang.aimanagement.controller.ComputerLoginController.jumpDEM(java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.847 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/authority/department_management],methods=[GET]}" onto public java.lang.String com.xintujiuzhang.aimanagement.controller.DepartmentManagementController.jumpDEM(java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.848 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/authority/dictionary_management],methods=[GET]}" onto public java.lang.String com.xintujiuzhang.aimanagement.controller.DictionaryManagementController.jumpDM(java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.848 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/equipment/hardware_devices],methods=[GET]}" onto public java.lang.String com.xintujiuzhang.aimanagement.controller.EquipmentManagementController.jumpDM(java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.848 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/queryGetServerStatusInterface],methods=[GET]}" onto public java.util.Map<java.lang.String, java.lang.Object> com.xintujiuzhang.aimanagement.controller.GetServerStatusInterfaceController.queryGetServerStatus(java.lang.String,java.lang.String) 2019-08-05 10:29:20.848 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/queryHandwritingInterface],methods=[GET]}" onto public java.util.Map<java.lang.String, java.lang.Object> com.xintujiuzhang.aimanagement.controller.HandwritingInterfaceController.queryHandwriting(java.lang.String,java.lang.String,java.lang.Integer,java.util.Date) 2019-08-05 10:29:20.849 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/identity/identity_management],methods=[GET]}" onto public java.lang.String com.xintujiuzhang.aimanagement.controller.IdentityManagementController.jumpDM(java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.849 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/queryInstallationRequest],methods=[GET]}" onto public java.util.Map<java.lang.String, java.lang.Object> com.xintujiuzhang.aimanagement.controller.InstallationRequestInterfaceController.queryInstallationRequest(java.lang.String,java.lang.String,java.lang.String) 2019-08-05 10:29:20.849 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/queryLicenseInterface],methods=[GET]}" onto public java.util.Map<java.lang.String, java.lang.Object> com.xintujiuzhang.aimanagement.controller.LicenseInterfaceController.queryLicense(java.lang.String,java.lang.String,java.lang.String,java.lang.String,java.lang.String,java.util.Date) 2019-08-05 10:29:20.851 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/]}" onto public java.lang.String com.xintujiuzhang.aimanagement.controller.MainController.main(java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.851 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/login],methods=[GET]}" onto public org.springframework.web.servlet.ModelAndView com.xintujiuzhang.aimanagement.controller.MainController.login() 2019-08-05 10:29:20.851 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/login],methods=[POST]}" onto public java.lang.String com.xintujiuzhang.aimanagement.controller.MainController.login(java.lang.String,java.lang.String,java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.851 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/main],methods=[GET]}" onto public java.lang.String com.xintujiuzhang.aimanagement.controller.MainController.jumpmain(java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.852 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/authority/menu_management],methods=[GET]}" onto public java.lang.String com.xintujiuzhang.aimanagement.controller.MenuManagementController.jumpMM(java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.852 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/log/module_browsing],methods=[GET]}" onto public java.lang.String com.xintujiuzhang.aimanagement.controller.ModuleBrowsingController.jumpTM(java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.852 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/log/module_operation],methods=[GET]}" onto public java.lang.String com.xintujiuzhang.aimanagement.controller.ModuleOperationController.jumpMM(java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.852 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/deletehandwriting],methods=[POST]}" onto public void com.xintujiuzhang.aimanagement.controller.NotesController.deletehandwriting(java.lang.String) 2019-08-05 10:29:20.852 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/updatehandwriting],methods=[POST]}" onto public void com.xintujiuzhang.aimanagement.controller.NotesController.updatehandwriting(com.xintujiuzhang.aimanagement.pojo.Handwriting) 2019-08-05 10:29:20.852 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/addhandwriting],methods=[POST]}" onto public void com.xintujiuzhang.aimanagement.controller.NotesController.addhandwriting(com.xintujiuzhang.aimanagement.pojo.Handwriting) 2019-08-05 10:29:20.853 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/querynotes],methods=[GET]}" onto public com.xintujiuzhang.aimanagement.pojo.Handwriting com.xintujiuzhang.aimanagement.controller.NotesController.querynotes(java.lang.String) 2019-08-05 10:29:20.853 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/authority/parameter_settings],methods=[GET]}" onto public java.lang.String com.xintujiuzhang.aimanagement.controller.parameterSettingsController.jumpPS(java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.853 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/authority/role_authorization],methods=[GET]}" onto public java.lang.String com.xintujiuzhang.aimanagement.controller.RoleAuthorizationController.jumpRA(java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.853 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/log/service_call],methods=[GET]}" onto public java.lang.String com.xintujiuzhang.aimanagement.controller.ServiceCallController.jumpRA(java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.853 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/authority/task_management],methods=[GET]}" onto public java.lang.String com.xintujiuzhang.aimanagement.controller.TaskManagementController.jumpTM(java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.854 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/authority/user_management]}" onto public java.lang.String com.xintujiuzhang.aimanagement.controller.UserController.jnmpUM(java.util.Map<java.lang.String, java.lang.Object>) 2019-08-05 10:29:20.854 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/queryUserInterface],methods=[GET]}" onto public java.util.Map<java.lang.String, java.lang.Object> com.xintujiuzhang.aimanagement.controller.UserInterfaceController.queryLicense(java.lang.String,java.lang.String,java.lang.Integer,java.util.Date) 2019-08-05 10:29:20.854 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/queryVersionCheckingInterface],methods=[GET]}" onto public java.util.Map<java.lang.String, java.lang.Object> com.xintujiuzhang.aimanagement.controller.VersionCheckingInterfaceController.queryVersionChecking(java.lang.String,java.lang.String,java.lang.String,java.lang.String,java.lang.String,java.lang.Integer,java.util.Date) 2019-08-05 10:29:20.854 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/queryVersionupdateInterface],methods=[GET]}" onto public java.util.Map<java.lang.String, java.lang.Object> com.xintujiuzhang.aimanagement.controller.VersionUpdateInterfaceController.queryVersionupdate(java.lang.String,java.lang.String,java.lang.String,java.util.Date) 2019-08-05 10:29:20.857 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error]}" onto public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController.error(javax.servlet.http.HttpServletRequest) 2019-08-05 10:29:20.857 INFO 7416 --- [ restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],produces=[text/html]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse) 2019-08-05 10:29:20.881 INFO 7416 --- [ restartedMain] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler] 2019-08-05 10:29:20.881 INFO 7416 --- [ restartedMain] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler] 2019-08-05 10:29:20.906 INFO 7416 --- [ restartedMain] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler] 2019-08-05 10:29:21.115 INFO 7416 --- [ restartedMain] o.s.b.d.a.OptionalLiveReloadServer : LiveReload server is running on port 35729 2019-08-05 10:29:21.164 INFO 7416 --- [ restartedMain] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup 2019-08-05 10:29:21.165 INFO 7416 --- [ restartedMain] o.s.j.e.a.AnnotationMBeanExporter : Bean with name 'dataSource' has been autodetected for JMX exposure 2019-08-05 10:29:21.170 INFO 7416 --- [ restartedMain] o.s.j.e.a.AnnotationMBeanExporter : Located MBean 'dataSource': registering with JMX server as MBean [com.zaxxer.hikari:name=dataSource,type=HikariDataSource] 2019-08-05 10:29:21.196 INFO 7416 --- [ restartedMain] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path '' 2019-08-05 10:29:21.198 INFO 7416 --- [ restartedMain] com.xintujiuzhang.aimanagement.App : Started App in 8.458 seconds (JVM running for 8.828) Exception in thread "Thread-12" java.lang.RuntimeException: java.lang.NullPointerException at com.mysql.jdbc.JDBC4Connection$1$1.run(JDBC4Connection.java:106) Caused by: java.lang.NullPointerException at com.mysql.jdbc.ConnectionImpl.abortInternal(ConnectionImpl.java:1240) at com.mysql.jdbc.JDBC4Connection$1$1.run(JDBC4Connection.java:104) **在执行一些方法后“Thread-12”会不断增加** **ps:“Thread-668"**

JAVA连接数据库时出错 MySQL数据库 出现这样的错误 该怎么解决

JAVA连接数据库时出错 MySQL数据库 出现这样的错误 该怎么解决![图片](https://img-ask.csdn.net/upload/201612/24/1482562787_633201.jpg)

jdbc连接数据库的com.mysql.jdbc.CommunicationsException问题

我使用jdbc连接数据库,连接不上,上网搜了很多,有人说是数据库请求超时问题,也有说是数据库url,账号或者密码配置错误,我检查了都没有问题。还有一点奇怪的是,我用jdbc-odbc桥连接又可以连上数据库,用可视化工具也可以连上,但是用jdbc方式连接不上。。。我现在想着应该是哪里的配置有问题,请教各位大神,看看有谁知道或者遇到过,谢谢大家了 这是我的程序 ``` public static void main(String[] args) { Connection ct = null; Statement sm = null; ResultSet rs = null; try { //1、加载驱动(作用是把需要的驱动程序加入内存) Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); //2、得到连接(指定连接到哪个数据源) //如果配置数据源选择的是Windows nt验证方式,则不需要用户名和密码 ct = DriverManager.getConnection("jdbc:odbc:MyTest", "root", "root"); //3、创建Statement或者PreparedStatement[区别] //Statement用处是,用于发送sql语句 sm = ct.createStatement(); //4、执行(crud、备份数据库、删除数据库......) //查询,显示所有部门信息 //ResultSet结果集,可以理解成一个表行的结果集 rs = sm.executeQuery("select * from dept"); //因为rs指向结果集的第一行的前一行, //循环取出 while (rs.next()) { int deptno = rs.getInt(1); String dname = rs.getString(2); String loc = rs.getString(3); System.out.println(deptno+" "+dname+" "+loc); } } catch(Exception e) { e.printStackTrace(); } finally { //关闭资源 //关闭顺序是谁后创建谁先关闭 try { //为了程序健壮 if (rs != null) { rs.close(); } if (sm != null) { sm.close(); } if (ct != null) { ct.close(); } } catch (SQLException e) { e.printStackTrace(); } } } ``` 这些是报的异常 ``` com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.net.SocketException MESSAGE: Permission denied: recv failed STACKTRACE: java.net.SocketException: Permission denied: recv failed at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.read(SocketInputStream.java:152) at java.net.SocketInputStream.read(SocketInputStream.java:122) at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:105) at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:148) at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:176) at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1899) at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:481) at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:964) at com.mysql.jdbc.Connection.createNewIO(Connection.java:2544) at com.mysql.jdbc.Connection.<init>(Connection.java:1474) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:264) at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:146) at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:195) at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:184) at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:200) at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1086) at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1073) at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:44) at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1810) at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:648) ** END NESTED EXCEPTION ** Last packet sent to the server was 0 ms ago. at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:552) at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:964) at com.mysql.jdbc.Connection.createNewIO(Connection.java:2544) at com.mysql.jdbc.Connection.<init>(Connection.java:1474) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:264) at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:146) at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:195) at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:184) at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:200) at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1086) at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1073) at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:44) at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1810) at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:648) ```

java.lang.NullPointerException?空指向异常是与数据库有关吗?

java.lang.NullPointerException com.wgh.tools.ConnDB.executeQuery(ConnDB.java:56) com.wgh.dao.DiaryDao.queryDiary(DiaryDao.java:28) com.wgh.servlet.DiaryServlet.listAllDiary(DiaryServlet.java:249) com.wgh.servlet.DiaryServlet.doPost(DiaryServlet.java:52) com.wgh.servlet.DiaryServlet.doGet(DiaryServlet.java:66) javax.servlet.http.HttpServlet.service(HttpServlet.java:624) javax.servlet.http.HttpServlet.service(HttpServlet.java:731) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) com.wgh.filter.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:24) 空指向异常,这个是与数据库有关吗?怎么解决,请高手帮忙解答,感激不尽。

ecplise连接数据库mysql8.0出错

ecplise2019-03连接数据库mysql8.0出错,我的ecplise连接SQL是好的 import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; public class a1 { public static void main(String []args) { Connection conn = null; PreparedStatement ps = null; ResultSet rs = null; // The newInstance() call is a work around for some // broken Java implementations try { Class.forName("com.mysql.jdbc.Driver"); System.out.println("加载成功"); conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/shop?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=UTC","root","qing980104"); System.out.println("连接成功"); } } catch (SQLException ex) { // handle any errors System.out.println("连接失败"); } } } 结果显示 Exception in thread "main" java.lang.ClassNotFoundException: com.microsoft.sqlserver.jdbc.SQLServerDriver at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:583) at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178) at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521) at java.base/java.lang.Class.forName0(Native Method) at java.base/java.lang.Class.forName(Class.java:315) at experiment1.a1.main(a1.java:7) 我把代码换成运行成功的SQL连接代码,然后改了下 import java.sql.*; public class a1 { public static void main(String[] args) throws SQLException, ClassNotFoundException { // TODO Auto-generated method stub Class.forName("com.mysql.cj.jdbc.Driver"); Connection conn= DriverManager.getConnection(jdbc:mysql://127.0.0.1:3306/shop?serverTimezone=GMT%2B8","root","qing980104"); Statement stm=conn.createStatement(); ResultSet re=stm.executeQuery("select * from book"); while(re.next()) { System.out.println("书名:"+re.getString(1)+"书号:"+re.getString(2)+"价格:"+re.getString(3)); } re.close(); stm.close(); conn.close(); } } 结果显示 Exception in thread "main" java.sql.SQLException: Access denied for user ''@'localhost' (using password: NO) at mysql.connector.java@8.0.15/com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129) at mysql.connector.java@8.0.15/com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) at mysql.connector.java@8.0.15/com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) at mysql.connector.java@8.0.15/com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:835) at mysql.connector.java@8.0.15/com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:455) at mysql.connector.java@8.0.15/com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:240) at mysql.connector.java@8.0.15/com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:199) at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:677) at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:251) at mysql.connector.java@8.0.15/com.mysql.cj.jdbc.admin.TimezoneDump.main(TimezoneDump.java:70) 我以前写的java课设中连接数据库也是显示上面(using password: NO)这个结果 网上有说是MySQL8.0用了强密码的缘故,我重下装了改成旧方式,但还是不行,我又重装了n次,结果现在只能是旧方式,无法改成强密码方式。而且程序还是不行。求大佬解答

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Eclipse中代码要无法连接mysql数据库,求大神指教

结果显示是这样: Exception in thread "main" java.lang.ClassNotFoundException: com.mysql.jdbc.Driver at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Unknown Source) at power.db.DButil.main(DButil.java:13) ![图片说明](https://img-ask.csdn.net/upload/201512/29/1451359223_810658.jpg)

使用dbcp连接数据库报错java.lang.NumberFormatException: For input string: "20 "?

内容: 换了一个工程就可以跑得动 报错: ``` java.lang.NumberFormatException: For input string: "20 " at java.base/java.lang.NumberFormatException.forInputString(Unknown Source) at java.base/java.lang.Integer.parseInt(Unknown Source) at java.base/java.lang.Integer.parseInt(Unknown Source) at org.apache.commons.dbcp.BasicDataSourceFactory.createDataSource(BasicDataSourceFactory.java:228) at com.ekihin.part01.day20.DBCPDemo.<clinit>(DBCPDemo.java:21) at com.ekihin.part01.day20.DBCPDemoTest.main(DBCPDemoTest.java:15) Exception in thread "main" java.lang.NullPointerException at com.ekihin.part01.day20.DBCPDemo.getConnection(DBCPDemo.java:29) at com.ekihin.part01.day20.DBCPDemoTest.main(DBCPDemoTest.java:15) ``` 类: ``` import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; public class DBCPDemoTest { public static void main(String[] args) throws Exception { Connection conn = null; PreparedStatement ps = null; ResultSet rs = null; String sql = "Update emp set ename = ? where ename = ? "; conn = DBCPDemo.getConnection(); ps = conn.prepareStatement(sql); ps.setObject(1, "彭奕滨"); ps.setObject(2, "ekihin"); int rows = 0; rows = ps.executeUpdate(); System.out.println(rows); DBCPDemo.closeAll(conn, ps, rs); } } ``` ``` import java.io.IOException; import java.sql.Connection; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.Properties; import javax.sql.DataSource; import org.apache.commons.dbcp.BasicDataSourceFactory; public class DBCPDemo { private static DataSource ds = null; static { Properties pt = new Properties(); try { pt.load(DBCPDemo.class.getClassLoader().getResourceAsStream("dbcpconfig.properties")); ds = BasicDataSourceFactory.createDataSource(pt); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } public static Connection getConnection() throws SQLException{ //返回一个连接对象,不要用DriverManager获取,而是连接池中获取 return ds.getConnection(); } //关闭所有资源的统一代码 public static void closeAll(Connection conn,Statement st,ResultSet rs){ //负责关闭 if(conn != null){ try { conn.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } if(st != null){ try { st.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } if(rs != null){ try { rs.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } } ```

新人求解java连接mysql,向数据库添加数据,出错

package test; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.Statement; import java.util.Scanner; public class test{ public static void main(String[] args)throws Exception { // 加载数据库驱动,注册到驱动管理器 Class.forName("com.mysql.jdbc.Driver"); // 数据库连接字符串 String url = "jdbc:mysql://localhost:3306/test"; // 数据库用户名 String username = "root"; // 数据库密码 String password = "2443243838"; // 创建Connection连接 Connection conn = DriverManager.getConnection(url,username,password); // 判断 数据库连接是否为空 Statement st=conn.createStatement(); Scanner scanner = new Scanner(System.in); System.out.println("1,数据注册\t"); System.out.println("2,登录\t"); System.out.println("请输入你要做的操作:\t"); int n= scanner.nextInt(); if(n==1){ // 输出连接信息 System.out.println("请输入用户名字:"); String username1 = scanner.next(); System.out.println("请输入密码:"); String password1 = scanner.next(); String sql="select * from user where username='"+username1+"'"; ResultSet ra= st.executeQuery(sql); if(ra.next()){ System.out.println("用户已存在"); }else{ sql="insert into user values=('"+username1+"','"+password1+"')"; int i=st.executeUpdate(sql); if(i!=0){ System.out.println("添加成功"); }else{ System.out.println("添加失败"); } } // 关闭数据库连接 }else if(n==2){ }else{ // 输出连接信息 System.out.println("数据库连接失败!"); } } } 1,数据注册 2,登录 请输入你要做的操作: 1 请输入用户名字: 刘备 请输入密码: 123456 Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '=('刘备','123456')' at line 1 at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) at java.lang.reflect.Constructor.newInstance(Unknown Source) at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) at com.mysql.jdbc.Util.getInstance(Util.java:386) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1053) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4096) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4028) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2490) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2651) at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2728) at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1811) at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1725) at test.test.main(test.java:43)

关于java项目访问数据库的问题

我用spring的定时任务,第一次操作数据库的时候没问题。但是10分钟后再次操作执行方法操作数据库就会报以下错误: org.springframework.transaction.CannotCreateTransactionException: Could not open JDBC Connection for transaction; nested exception is com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure The last packet successfully received from the server was 616,228 milliseconds ago. The last packet sent successfully to the server was 24,213 milliseconds ago. at org.springframework.jdbc.datasource.DataSourceTransactionManager.doBegin(DataSourceTransactionManager.java:240) at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:371) at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:335) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:105) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202) at $Proxy34.insertObject(Unknown Source) at com.supinfo.test.AutoGenerateData.generateData(AutoGenerateData.java:46) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.springframework.util.MethodInvoker.invoke(MethodInvoker.java:273) at org.springframework.scheduling.quartz.MethodInvokingJobDetailFactoryBean$MethodInvokingJob.executeInternal(MethodInvokingJobDetailFactoryBean.java:264) at org.springframework.scheduling.quartz.QuartzJobBean.execute(QuartzJobBean.java:86) at org.quartz.core.JobRunShell.run(JobRunShell.java:202) at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:525) Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure The last packet successfully received from the server was 616,228 milliseconds ago. The last packet sent successfully to the server was 24,213 milliseconds ago. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) at java.lang.reflect.Constructor.newInstance(Unknown Source) at com.mysql.jdbc.Util.handleNewInstance(Util.java:409) at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1118) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3055) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2941) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3489) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1959) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2113) at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2562) at com.mysql.jdbc.ConnectionImpl.setAutoCommit(ConnectionImpl.java:4956) at com.mchange.v2.c3p0.impl.NewProxyConnection.setAutoCommit(NewProxyConnection.java:881) at org.springframework.jdbc.datasource.DataSourceTransactionManager.doBegin(DataSourceTransactionManager.java:223) ... 16 more Caused by: java.net.SocketException: Software caused connection abort: recv failed at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.read(Unknown Source) at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:114) at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:161) at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:189) at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2499) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2952) ... 24 more

ecplise连接mysql本地数据库登录失败!求大神知道怎么回事!

Mon Nov 06 03:47:19 CST 2017 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification. java.sql.SQLException: Access denied for user 'root'@'localhost' (using password: YES) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:964) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3973) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3909) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:873) at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1710) at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1226) at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2191) at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2222) at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2017) at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:779) at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:513) at com.mysql.jdbc.Util.handleNewInstance(Util.java:425) at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:389) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:330) at java.sql.DriverManager.getConnection(DriverManager.java:582) at java.sql.DriverManager.getConnection(DriverManager.java:185) at my01.Login_main01.loginButton_actionPerformed(Login_main01.java:78) at my01.Login_main01.actionPerformed(Login_main01.java:105) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995) at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387) at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242) at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236) at java.awt.Component.processMouseEvent(Component.java:6297) at javax.swing.JComponent.processMouseEvent(JComponent.java:3275) at java.awt.Component.processEvent(Component.java:6062) at java.awt.Container.processEvent(Container.java:2039) at java.awt.Component.dispatchEventImpl(Component.java:4660) at java.awt.Container.dispatchEventImpl(Container.java:2097) at java.awt.Component.dispatchEvent(Component.java:4488) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4575) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4236) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4166) at java.awt.Container.dispatchEventImpl(Container.java:2083) at java.awt.Window.dispatchEventImpl(Window.java:2489) at java.awt.Component.dispatchEvent(Component.java:4488) at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:674) at java.awt.EventQueue.access$400(EventQueue.java:81) at java.awt.EventQueue$2.run(EventQueue.java:633) at java.awt.EventQueue$2.run(EventQueue.java:631) at java.security.AccessController.doPrivileged(Native Method) at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87) at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98) at java.awt.EventQueue$3.run(EventQueue.java:647) at java.awt.EventQueue$3.run(EventQueue.java:645) at java.security.AccessController.doPrivileged(Native Method) at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87) at java.awt.EventQueue.dispatchEvent(EventQueue.java:644) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161) at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)![图片](https://img-ask.csdn.net/upload/201711/06/1509965515_190525.jpg)

java连接MYSQL数据库第一次可以,第二次报错

做项目在做一个用户首次登陆输入手机号码,发送随机密码的功能模块,首次点击完全没问题,系统会发送短信(中国移动的短信机的原理是连接它的数据库,插入一条数据即可)问题就出在连接数据库的问题上,再次发送,则后台报错ResultSet is from UPDATE. No Data.。 报错信息如下 ``` 严重: Exception occurred during processing request: ResultSet is from UPDATE. No Data. java.sql.SQLException: ResultSet is from UPDATE. No Data. at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1073) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:982) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:927) at com.mysql.jdbc.ResultSetImpl.next(ResultSetImpl.java:7152) at com.mysql.jdbc.ConnectionImpl.loadServerVariables(ConnectionImpl.java:3867) at com.mysql.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:3404) at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2385) at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2154) at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:792) at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:513) at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:381) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305) at java.sql.DriverManager.getConnection(DriverManager.java:582) at java.sql.DriverManager.getConnection(DriverManager.java:185) at DAO.dbconnection2.<init>(dbconnection2.java:16) at action.testsendaction.execute(testsendaction.java:38) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) ``` dbconnection2.java 是创建连接,代码如下: ``` package DAO; import java.sql.Connection; import java.sql.DriverManager; public class dbconnection2 { private static final String DRIVER = "com.mysql.jdbc.Driver"; private static final String URL = "jdbc:mysql://*******:3306/mas?useUnicode=true&characterEncoding=gb2312"; private static final String USER = "ywz"; private static final String PASSWORD = "yw690"; private Connection con; public dbconnection2() throws Exception{ Class.forName(DRIVER); this.con = DriverManager.getConnection(URL, USER, PASSWORD); } public Connection getConnection() { return this.con; } public void closecon() throws Exception { if(this.con != null) { try { this.con.close(); } catch(Exception e) { throw e; } } } } ``` action代码: ``` public class testsendaction extends ActionSupport{ private String list; public String getList() { return list; } public void setList(String list) { this.list = list; } public String getContent() { return content; } public void setContent(String content) { this.content = content; } private String content; public String execute() throws Exception{ dbconnection2 dbc2 = new dbconnection2(); Statement s1 = dbc2.getConnection().createStatement(); Random ran = new Random(); String pwd = ""; for(int i=0;i<6;i++) { pwd += ran.nextInt(10)+""; } System.out.println("ranpwd="+pwd); String mess = "本信息来自工资查询系统,用于用户的首次登陆,登陆密码为:"+pwd+" ,登陆成功后,请自行修改密码。"; String send = "insert into api_mt_6(mobiles,content) values('"+list+"','"+mess+"')"; s1.executeUpdate(send); System.out.println("send:"+send); s1.close(); dbc2.closecon(); return SUCCESS; } } ``` 报错是在数据库连接的new语句上。 连接最后也有关闭。但是就是不能进行二次访问数据库。只能重启下tomcat,然后又可以登录一次,第二次也无法连接了。 找了好久都没发现原因,希望大家帮帮忙 ,谢谢了!

求大神抽时间看看,java连接本地mysql数据库出现connection reset错误

小弟弄这个小问题弄了好久,通过各种渠道找方法最后实在是没有办法了,望大神抽时间帮忙看看,谢谢 代码如下 import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.sql.Statement; public class MysqlConnection { public static void main(String[] args) { try { Class.forName("com.mysql.jdbc.Driver"); String url="jdbc:mysql://localhost:3306/test"; Connection con=DriverManager.getConnection(url, "root",""); Statement stmt=con.createStatement(); String sql="select * from msg"; boolean m=stmt.execute(sql); if(m){ System.out.println("succ"); }else System.out.println("false"); } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } } } 出现如下错误: com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.net.SocketException MESSAGE: Connection reset STACKTRACE: java.net.SocketException: Connection reset at java.net.SocketInputStream.read(Unknown Source) at java.net.SocketInputStream.read(Unknown Source) at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:105) at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:148) at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:176) at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1899) at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:481) at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:964) at com.mysql.jdbc.Connection.createNewIO(Connection.java:2544) at com.mysql.jdbc.Connection.<init>(Connection.java:1474) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:264) at java.sql.DriverManager.getConnection(Unknown Source) at java.sql.DriverManager.getConnection(Unknown Source) at com.iotek.mysql.MysqlConnection.main(MysqlConnection.java:16) ** END NESTED EXCEPTION ** Last packet sent to the server was 27 ms ago. at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:552) at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:964) at com.mysql.jdbc.Connection.createNewIO(Connection.java:2544) at com.mysql.jdbc.Connection.<init>(Connection.java:1474) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:264) at java.sql.DriverManager.getConnection(Unknown Source) at java.sql.DriverManager.getConnection(Unknown Source) at com.iotek.mysql.MysqlConnection.main(MysqlConnection.java:16)

IntelliJ IDEA 连接数据库报错

![图片说明](https://img-ask.csdn.net/upload/201804/27/1524817634_789388.png) Connection to MySQL - docdb@localhost failed java.sql.SQLException: The connection property 'zeroDateTimeBehavior' acceptable values are: 'CONVERT_TO_NULL', 'EXCEPTION' or 'ROUND'. The value 'convertToNull' is not acceptable. at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:127) at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:95) at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:87) at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:61) at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:71) at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:85) at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:440) at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:230) at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:226) at com.intellij.database.remote.jdbc.impl.RemoteDriverImpl.connect(RemoteDriverImpl.java:27) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:497) at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:323) at sun.rmi.transport.Transport$1.run(Transport.java:200) at sun.rmi.transport.Transport$1.run(Transport.java:197) at java.security.AccessController.doPrivileged(Native Method) at sun.rmi.transport.Transport.serviceCall(Transport.java:196) at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:568) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:826) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$254(TCPTransport.java:683) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$1/16470434.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:682) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:276) at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:253) at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:162) at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(RemoteObjectInvocationHandler.java:194) at java.rmi.server.RemoteObjectInvocationHandler.invoke(RemoteObjectInvocationHandler.java:148) at com.sun.proxy.$Proxy172.connect(Unknown Source) at sun.reflect.GeneratedMethodAccessor686.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:497) at com.intellij.execution.rmi.RemoteUtil.invokeRemote(RemoteUtil.java:124) at com.intellij.execution.rmi.RemoteUtil.access$100(RemoteUtil.java:36) at com.intellij.execution.rmi.RemoteUtil$RemoteInvocationHandler.invoke(RemoteUtil.java:229) at com.sun.proxy.$Proxy173.connect(Unknown Source) at com.intellij.database.dataSource.LocalDataSource.getConnection(LocalDataSource.java:240) at com.intellij.database.dataSource.LocalDataSource.getConnection(LocalDataSource.java:208) at com.intellij.database.dataSource.DataSource.getConnection(DataSource.java:361) at com.intellij.database.dataSource.DataSource.performJdbcOperation(DataSource.java:405) at com.intellij.database.dataSource.AbstractDataSource.refreshMetaData(AbstractDataSource.java:32) at com.intellij.database.dataSource.DataSourceUiUtil$3.run(DataSourceUiUtil.java:180) at com.intellij.openapi.progress.impl.CoreProgressManager$TaskRunnable.run(CoreProgressManager.java:563) at com.intellij.openapi.progress.impl.CoreProgressManager$8.run(CoreProgressManager.java:367) at com.intellij.openapi.progress.impl.CoreProgressManager$2.run(CoreProgressManager.java:152) at com.intellij.openapi.progress.impl.CoreProgressManager.a(CoreProgressManager.java:452) at com.intellij.openapi.progress.impl.CoreProgressManager.executeProcessUnderProgress(CoreProgressManager.java:402) at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:54) at com.intellij.openapi.progress.impl.CoreProgressManager.runProcess(CoreProgressManager.java:137) at com.intellij.openapi.application.impl.ApplicationImpl$10$1.run(ApplicationImpl.java:617) at com.intellij.openapi.application.impl.ApplicationImpl$8.run(ApplicationImpl.java:400) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) at org.jetbrains.ide.PooledThreadExecutor$1$1.run(PooledThreadExecutor.java:56) Caused by: java.lang.RuntimeException: com.mysql.cj.exceptions.WrongArgumentException: The connection property 'zeroDateTimeBehavior' acceptable values are: 'CONVERT_TO_NULL', 'EXCEPTION' or 'ROUND'. The value 'convertToNull' is not acceptable. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:422) at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:59) at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:103) at com.mysql.cj.conf.DefaultPropertySet.initializeProperties(DefaultPropertySet.java:194) at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:382) at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:230) at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:226) at com.intellij.database.remote.jdbc.impl.RemoteDriverImpl.connect(RemoteDriverImpl.java:27) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:497) at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:323) at sun.rmi.transport.Transport$1.run(Transport.java:200) at sun.rmi.transport.Transport$1.run(Transport.java:197) at java.security.AccessController.doPrivileged(Native Method) at sun.rmi.transport.Transport.serviceCall(Transport.java:196) at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:568) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:826) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$254(TCPTransport.java:683) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$1/16470434.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:682) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) Caused by: java.lang.RuntimeException: com.mysql.cj.exceptions.CJException: The connection property 'zeroDateTimeBehavior' acceptable values are: 'CONVERT_TO_NULL', 'EXCEPTION' or 'ROUND'. 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org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:135) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:673) at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2503) at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2492) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Unknown Source) 网页上显示错误: type Exception report message Error instantiating servlet class Web.SearchK description The server encountered an internal error that prevented it from fulfilling this request. exception javax.servlet.ServletException: Error instantiating servlet class Web.SearchK org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518) org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091) org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:673) org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2503) org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2492) java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) java.lang.Thread.run(Unknown Source) root cause java.lang.NoClassDefFoundError: Search/searchkey Web.test.tt(test.java:15) Web.SearchK.<init>(SearchK.java:24) sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) java.lang.reflect.Constructor.newInstance(Unknown Source) java.lang.Class.newInstance(Unknown Source) org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518) org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091) org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:673) org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2503) org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2492) java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) java.lang.Thread.run(Unknown Source) root cause java.lang.ClassNotFoundException: Search.searchkey org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1333) org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1167) Web.test.tt(test.java:15) Web.SearchK.<init>(SearchK.java:24) sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) java.lang.reflect.Constructor.newInstance(Unknown Source) java.lang.Class.newInstance(Unknown Source) org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518) org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091) org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:673) org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2503) org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2492) java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) java.lang.Thread.run(Unknown Source) note The full stack trace of the root cause is available in the Apache Tomcat/8.0.28 logs.

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