Java MySQL更新查询

Question

我收到错误"无法发布数据".

这是SSCCE

//package mysqltest;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.applet.Applet;
import java.awt.TextArea.*;
import java.sql.*;
import java.util.*;
import javax.swing.plaf.*;
import javax.swing.plaf.basic.*;
import java.net.*;
import java.applet.*;

    public class test extends JApplet {

      public JTextArea c;

      public void init() {

          c = new JTextArea();

          add(c);
          c.append("Looking for database...");

        Connection conn = null;
        Properties props = new Properties();
        String url = "jdbc:mysql://localhost:3306/";
        String dbName = "mystik";
        String driver = "com.mysql.jdbc.Driver";
        String userName = "root";
        String password = "";
        String loggedusername = getParameter("name");
        try {
          Class.forName(driver).newInstance();
          props.put("user", "root");
          conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mystik", props);
          c.append("\nConnected to the database");


                        c.append("\nGetting stats for: " + loggedusername);
                        PreparedStatement statement = conn.prepareStatement( "select * from `user` where `username` = '"+loggedusername+"'");
                        ResultSet result = statement.executeQuery();
                        // just a dumb mysql statement!
                        while(result.next())
                        {
                        c.append("\nUsername: "+result.getString(2)+ "\nLevel: "+result.getString(6)+"\nEXP: "+result.getString(8)+"\n");
                        }

                        PreparedStatement updateEXP = conn.prepareStatement( "update`user` set `exp` = '666'  where `username` = '"+loggedusername+"'");
                        ResultSet updateEXP_done = updateEXP.executeQuery();

                        while(result.next())
                        {
                        c.append("\nUsername: "+result.getString(2)+ "\nLevel: "+result.getString(6)+"\nEXP: "+result.getString(8)+"\n");
                        }


          conn.close();
          c.append("\nDisconnected from database");
        } catch (Exception e) {
          e.printStackTrace();
        }

      }

    }

它的工作原理......而且只是updatejava查询没有.

这是JTextArea看到的内容:

Looking for database...
Connected to the database
Getting stats for: weka
Username: weka
Level: 1
EXP: 1

这是我的错误:

added manifest
adding: test.class(in = 2440) (out= 1308)(deflated 46%)
adding: mysql-connector-java-5.1.13-bin.jar(in = 767492) (out= 735869)(deflated
4%)

Warning:
The signer certificate will expire within six months.
java.sql.SQLException: Can not issue data manipulation statements with executeQu
ery().
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1075)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:989)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:984)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:929)
        at com.mysql.jdbc.StatementImpl.checkForDml(StatementImpl.java:436)
        at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:
2176)
        at test.init(test.java:53)
        at sun.applet.AppletPanel.run(AppletPanel.java:424)
        at java.lang.Thread.run(Thread.java:619)

最后,这是我如何编译使用.bat文件.

@ECHO OFF
C:
CD \wamp\www\mystikrpg\mysqltest
javac -cp mysql-connector-java-5.1.13-bin test.java
jar cvf mysqlTry.jar test.class mysql-connector-java-5.1.13-bin.jar
jarsigner -keystore dankey -storepass soccer -keypass soccer mysqlTry.jar gamerpg
appletviewer -J-Djava.security.policy=game.policy mysqltry.html

我该如何解决这个错误？谢谢.

Answer 1

AS PreparedStatement文档：

执行此 PreparedStatement 对象中的 SQL 语句，该语句必须是 SQL INSERT、UPDATE 或 DELETE 语句；或不返回任何内容的 SQL 语句，例如 DDL 语句。

要执行更新、删除或插入数据库中任何数据的查询，您不能使用executeQuery...您必须使用：.executeUpdate(query)

所以这段代码（错误）：

   PreparedStatement updateEXP = conn.prepareStatement("update `user` set `exp` = '666'  where `username` = '"+loggedusername+"'");
   ResultSet updateEXP_done = updateEXP.executeQuery();

必须看起来像（好）：

正确使用

   PreparedStatement updateEXP = conn.prepareStatement("update `user` set `exp` = ? ");
   updateEXP.setString(1, loggedusername);
   ResultSet updateEXP_done = updateEXP.executeUpdate();

Answer 2

还要考虑使用用户名的参数:

PreparedStatement updateEXP = conn.prepareStatement("update用户setexp = '666' where用户名= ? ");

updateEXP.setString(1, loggedusername);

ResultSet updateEXP_done = updateEXP.executeUpdate();