ps.executeUpdate（sql）throws com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException：SQL構文でエラーが発生しました

Question

Xamppサーバーでmysqlを使用して単純なデータベース接続を学習しています。データベースはphpmyadminで実装されています。私はNetBeans IDEのjavaサーブレットからデータベースにアクセスしています。

package com.DBcheck; 

import java.io.IOException; 
import java.io.PrintWriter; 
import java.sql.Connection; 
import java.sql.DriverManager; 
import java.sql.PreparedStatement; 
import java.sql.SQLException; 
import java.util.logging.Level; 
import java.util.logging.Logger; 
import javax.servlet.ServletException; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
import java.sql.*; 


public class NewServlet extends HttpServlet { 


protected void processRequest(HttpServletRequest request, HttpServletResponse response) 
     throws ServletException, IOException, ClassNotFoundException, SQLException { 
    response.setContentType("text/html;charset=UTF-8"); 
    try (PrintWriter out = response.getWriter()) { 
     /* TODO output your page here. You may use following sample code. */ 
     Class.forName("com.mysql.jdbc.Driver"); 

     Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/profilebuilder","root",""); 

     String sql="insert into signupdetailstable(FirstName) values(?)"; 
     PreparedStatement ps=con.prepareStatement(sql); 

     ps.setString(1, "nirmal");   
     int log=ps.executeUpdate(sql); 
     out.println(log); 
    } 
} 


@Override 
protected void doGet(HttpServletRequest request, HttpServletResponse response) 
     throws ServletException, IOException { 
    try { 
     processRequest(request, response); 
    } catch (ClassNotFoundException ex) { 
     Logger.getLogger(NewServlet.class.getName()).log(Level.SEVERE, null, ex); 
    } catch (SQLException ex) { 
     Logger.getLogger(NewServlet.class.getName()).log(Level.SEVERE, null, ex); 
    } 
} 


@Override 
protected void doPost(HttpServletRequest request, HttpServletResponse response) 
     throws ServletException, IOException { 
    try { 
     processRequest(request, response); 
    } catch (ClassNotFoundException ex) { 
     Logger.getLogger(NewServlet.class.getName()).log(Level.SEVERE, null, ex); 
    } catch (SQLException ex) { 
     Logger.getLogger(NewServlet.class.getName()).log(Level.SEVERE, null, ex); 
    } 
} 


@Override 
public String getServletInfo() { 
    return "Short description"; 
}// </editor-fold> 

} 

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '?)' at line 1 
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.jdbc.Util.handleNewInstance(Util.java:377) 
at com.mysql.jdbc.Util.getInstance(Util.java:360) 
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:978) 
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3887) 
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3823) 
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2435) 
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2582) 
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2526) 
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1618) 
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1549) 
at com.DBcheck.NewServlet.processRequest(NewServlet.java:50) 
at com.DBcheck.NewServlet.doGet(NewServlet.java:68) 
at javax.servlet.http.HttpServlet.service(HttpServlet.java:687) 
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) 
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682) 
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318) 
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160) 
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734) 
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673) 
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99) 
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174) 
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:415) 
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:282) 
at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459) 
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167) 
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:201) 
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:175) 
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235) 
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119) 
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284) 
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201) 
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133) 
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112) 
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77) 
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:561) 
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112) 
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117) 
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56) 
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137) 
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:565) 
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:545) 
at java.lang.Thread.run(Thread.java:745) 

のようなエラーは、誰もがこの例外が言おうとしているもの助けることができる私を示すこのコードは？

Answer 1

非常に間違いがあります。あなたはStatement#executeUpdate(String)代わりのPreparedStatement#executeUpdate()を使用している：

代わり ​​

、あなたがしたい：

int log=ps.executeUpdate(); 
// Nothing here ---------^ 

PreparedStatementがexecuteUpdate(String)を持っている唯一の理由は、それがStatementのサブクラスであるということです。しかし、あなたは正しくやった声明、構築するときPreparedStatementで、あなたはSQLを供給：

PreparedStatement ps=con.prepareStatement(sql); 

をそして、あなたははexecuteUpdateにそれを供給しない。