【Java】查询数据时报错，请各大神指点~（附源码）

Question

请求流程：
1、访问SearchList.jsp时请求servlet：SearchById;
2、SearchById 的doPost方法访问showInfoDao.findModeResult(sql);
3、JdbcUtils中对sql进行数据库查询，并将查询结果返回，展示在SearchList.jsp页面；

在第3步，数据库连接成功，查询的时候出现了“com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax;”
报错信息如下：

 doGet 请求
doPost请求
数据库连接成功！
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 'from??personinfo' 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:406)
    at com.mysql.jdbc.Util.getInstance(Util.java:381)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1030)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3515)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3447)

    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1951)
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2101)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2554)
    at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1761)
    at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1912)
    at com.bdwm.dao.ShowInfoDao.findModeResult(ShowInfoDao.java:18)
    at com.bdwm.servlet.SearchById.doPost(SearchById.java:71)
    at com.bdwm.servlet.SearchById.doGet(SearchById.java:49)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:436)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1078)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2517)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2506)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)
[]

Answer 1

 check the manual that corresponds to your MySQL server version for the right syntax to use near 'from??personinfo' at line 1
 这不提示很明显，是sql有问题吗，  from和personinfo中间两个??，看看是不是编码有问题了
 把那个sql拷贝出来，在记事本中粘贴一下，然后再从记事本中拷贝到代码中试试