javamysql更新查询
我收到错误“无法发布数据” 这是SSCCEjavamysql更新查询,java,mysql,jdbc,Java,Mysql,Jdbc,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.
//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();
}
}
}
而且它是有效的。。。只是update
java查询没有
以下是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,这里是我如何使用.bat文件编译的
@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
如何修复此错误?
谢谢。作为文档:
执行此数据库中的SQL语句
PreparedStatement对象,它必须
可以是SQL插入、更新或删除
陈述或者一个SQL语句
不返回任何内容,例如DDL
声明
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(查询)
所以这个代码(错了):
必须看起来像(好):
正确用法
根据Javadoc,DML查询(
INSERT
,UPDATE
,DELETE
)需要使用而不是使用来执行。它返回一个包含受影响行数的int
PreparedStatement updateEXP = conn.prepareStatement( "update`user` set `exp` = '666' where `username` = '"+loggedusername+"'");
int affectedRows = updateEXP.executeUpdate();
这就是说,应该在finally
块中关闭conn
(和语句
和结果集
!),否则在调用close()
之前抛出异常时,它仍将打开。您使用的PreparedStatement
也是错误的。您仍然通过简单的字符串连接来内联列值,而不是将它们设置为参数化值。您没有利用它的SQL注入预防功能
另见:
PreparedStatement updateeExp=conn.prepareStatement(“更新
userset
exp='666',其中
username=?”代码>
updateEXP.setString(1,loggedusername)代码>
ResultSet updateEXP_done=updateEXP.executeUpdate()代码>好的,谢谢!我得到了它。现在,当我调用第二个结果whiel循环时。。。它将不可见,并直接转到“断开与数据库的连接”。您只能使用一次准备好的语句吗?ResultSet
的next()
方法向前移动到下一行,在第一行结束后,ResultSet
位于末尾。如果要(再次)在ResultSet
中查看,请调用result.first()
PreparedStatement updateEXP = conn.prepareStatement("update `user` set `exp` = ? ");
updateEXP.setString(1, loggedusername);
ResultSet updateEXP_done = updateEXP.executeUpdate();
PreparedStatement updateEXP = conn.prepareStatement( "update`user` set `exp` = '666' where `username` = '"+loggedusername+"'");
int affectedRows = updateEXP.executeUpdate();