PersonDAO.java
package dao;
import java.sql.*;
import domain.Person;
import util.JDBCUtils;
/**
* 数据层一个程序
* DAO层返回对象，在业务层通过操作这些对象来实现增删改查
* */
public class PersonDAO {
public Person login(Person user) { //登录
Person existUser = null;
Connection conn = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {//JDBC查询
conn = JDBCUtils.getConnection();
String sql = "select * from person where name=? and password=?"; //数据库编译时
stmt = conn.prepareStatement(sql); //将sql发送给数据库进行编译
//设置sql参数
stmt.setString(1,user.getName()); //传入数据值，不会作为关键字 --防止注入
stmt.setString(2,user.getPassword());
rs = stmt.executeQuery(); //执行sql
//如果登陆成功，只有一条记录
if (rs.next()) {
existUser=new Person(); //表示已登录用户
existUser.setID(rs.getString("ID"));
existUser.setName(rs.getString("name"));
existUser.setPassword(rs.getString("password"));
existUser.setBirthDate(rs.getDate("birthday"));
}
} catch (Exception e) {
e.printStackTrace();
}
System.out.println(user.getName());
System.out.println(user.getPassword());
try {
System.out.println(rs.getString("name"));
} catch (Exception e) {
// TODO: handle exception
System.out.println("2");
}
return existUser;
}
}
这个是个测试文件Test
package dao;
import util.JDBCUtils;
import java.sql.*;
import domain.Person;
public class test {
public static void main(String[] args) {
// TODO Auto-generated method stub
Person existUser = null;
Connection conn = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {//JDBC查询
conn = JDBCUtils.getConnection();
String sql = "select * from person where name=? and password=?"; //数据库编译时
stmt = conn.prepareStatement(sql); //将sql发送给数据库进行编译
//设置sql参数
stmt.setString(1, "Tom"); //传入数据值，不会作为关键字 --防止注入
stmt.setString(2, "12345");
rs = stmt.executeQuery(); //执行sql
//如果登陆成功，只有一条记录
if (rs.next()) {
existUser=new Person(); //表示已登录用户
existUser.setID(rs.getString("ID"));
existUser.setName(rs.getString("name"));
existUser.setPassword(rs.getString("password"));
existUser.setBirthDate(rs.getDate("birthday"));
}
} catch (Exception e) {
e.printStackTrace();
}
try {
System.out.println(rs.getString("name"));
} catch (Exception e) {
// TODO: handle exception
}
System.out.println(existUser.getID());
System.out.println(existUser.getName());
System.out.println(existUser.getPassword());
System.out.println(existUser.getBirthDate());
}
}
这是我做的一个测试 如果直接输入Tom和12345 数据库就会读到 包括结果集rs和新建的person类existuser都有数值
之后我再DAO类里面做测试 user的值能传过来 但是查询过后就没有 rs没有数值 try语句会走向catch
JDBCUtils
package util;
import java.sql.*;
/*
* Person类的JDBC 工具类，抽取公共方法
*/
public class JDBCUtils {
//设置数据库名称和登录用户信息
private static String DRIVERCLASS="com.mysql.cj.jdbc.Driver";
private static String URL="jdbc:mysql://localhost:3306/factory?serverTimezone=UTC";
private static final String USER="root"; //数据库用户
private static final String PASSWORD="12345"; //用户root的连接数据库的密码
private static Connection conn=null; //与数据库的连接；
// 装载驱动
private static void loadDriver() {
try {
//1.加载MYSQL JDBC驱动程序
Class.forName(DRIVERCLASS);
} catch(ClassNotFoundException e) {
e.printStackTrace();
}
}
//建立连接
public static Connection getConnection() throws Exception {
loadDriver();
return (Connection)DriverManager.getConnection(URL, USER, PASSWORD);
}
//释放资源
public static void release(ResultSet rs, Statement stmt, Connection conn) {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
rs = null;
}
release(stmt, conn);
}
public static void release(Statement stmt, Connection conn) {
if (stmt != null) {
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
stmt = null;
}
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
conn = null;
}
}
}
Person.java
package domain;
import java.util.Date;
//传输对象，保存User相关数据
public class Person {
private String ID; //类属性需要与数据库中的字段一一对应
private String name;
private String password;
private Date birthday;
public Person() {
super();
}
public Person(String iD, String name, String password, Date birthDate) {
super();
ID = iD;
this.name = name;
this.password = password;
this.birthday = birthDate;
}
public String getID() {
return ID;
}
public void setID(String iD) {
ID = iD;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Date getBirthDate() {
return birthday;
}
public void setBirthDate(Date birthDate) {
this.birthday = birthDate;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
personservice.java
package service;
import domain.Person;
import dao.PersonDAO;
/**
* 业务层一个程序
* */
public class PersonService {
/**
* 根据用户名 和 密码查询其它信息
* @param user
* @return 如果返回null证明 用户名或者密码错误
*/
public Person login(Person user) {
PersonDAO userDAO = new PersonDAO(); //查询， 将 user对象传递 DAO
return userDAO.login(user);
}
}
我最后解决了 原来是下面lib没有jar包 jsp访问不了mysql
