我已经在这方面工作了将近一天半,我似乎无法解决这个错误.我不知道为什么要关闭ResultSet.也许你们中的一些人可以帮助我.
MySQLDatabase：
package net.gielinor.network.sql;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public abstract class MySQLDatabase {
private String host;
private String database;
private String username;
private String password;
private Connection connection = null;
private Statement statement;
public MySQLDatabase(String host,String database,String username,String password) {
this.host = host;
this.database = database;
this.username = username;
this.password = password;
}
public abstract void cycle() throws SQLException;
public abstract void ping();
public void connect() {
try {
Class.forName("com.mysql.jdbc.Driver").newInstance();
connection = DriverManager.getConnection(String.format("jdbc:mysql://%s/%s",host,database),username,password);
statement = connection.createStatement();
} catch (Exception e) {
e.printStackTrace();
}
}
public void ping(String table,String variable) {
try {
statement.executeQuery(String.format("SELECT * FROM `%s` WHERE `%s` = 'null'",table,variable));
} catch (Exception e) {
connect();
}
}
public ResultSet query(String query) throws SQLException {
if (query.toLowerCase().startsWith("select")) {
return statement.executeQuery(query);
} else {
statement.executeUpdate(query);
}
return null;
}
public Connection getConnection() {
return connection;
}
}
MySQLHandler
package net.gielinor.network.sql;
import java.io.FileInputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
import net.gielinor.network.sql.impl.MySQLDonation;
public class MySQLHandler extends Thread {
private static final MySQLHandler mysqlHandler = new MySQLHandler();
public static MySQLHandler getMySQLHandler() {
return mysqlHandler;
}
private static ListMySQLDonation
package net.gielinor.network.sql.impl;
import java.sql.ResultSet;
import java.sql.SQLException;
import net.gielinor.game.model.player.Client;
import net.gielinor.game.model.player.PlayerHandler;
import net.gielinor.game.model.player.PlayerSave;
import net.gielinor.network.sql.MySQLDatabase;
public final class MySQLDonation extends MySQLDatabase {
public MySQLDonation(String host,String password) {
super(host,password);
}
@Override
public void cycle() throws SQLException {
ResultSet results = query("SELECT * FROM `gieli436_purchases`.`donations`");
if (results == null) {
return;
}
while (results.next()) {
String username = results.getString("username").replace("_"," ");
System.out.println("name=" + username);
Client client = (Client) PlayerHandler.getPlayer(username.toLowerCase());
System.out.println(client == null);
if (client != null && !client.disconnected) {
int creditamount = results.getInt("creditamount");
if (creditamount <= 0) {
continue;
}
handleDonation(client,creditamount);
query(String.format("DELETE FROM `gieli436_purchases`.`donations` WHERE `donations`.`username`='%s' LIMIT 1",client.playerName.replaceAll(" ","_")));
}
}
}
@Override
public void ping() {
super.ping("donations","username");
}
private void handleDonation(Client client,int creditamount) throws SQLException {
client.credits = (client.credits + creditamount);
client.sendMessage("Thank you for your purchase. You have received " + creditamount + " store credits.");
PlayerSave.save(client);
}
}
这里发生异常：在MySQLDonation中的while循环中,实际的堆栈跟踪是这样的：
java.sql.SQLException: Operation not allowed after ResultSet closed
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1055)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926)
at com.mysql.jdbc.ResultSetImpl.checkClosed(ResultSetImpl.java:794)
at com.mysql.jdbc.ResultSetImpl.next(ResultSetImpl.java:7077)
at net.gielinor.network.sql.impl.MySQLDonation.cycle(Unknown Source)
at net.gielinor.network.sql.MySQLHandler.run(Unknown Source)
有了这些信息,让我说这确实有用,我得到了我的信息以及游戏中的内容,但它重复了,就像用户永远不会从查询中删除一样,因此它给了他们无限的奖励.如果您需要更多信息,请随时询问.
最佳答案
运行“删除”查询时,将使用“选择”查询中使用的相同“语句”.当您在同一个Statement上重新执行时,前一个ResultSet将关闭.
为避免这种情况,您应该在每次执行查询时创建一个新的Statement.所以删除statement = connection.createStatement();从MySQLDatabase类中的connect()方法,并将该类中的所有语句替换为connection.createStatement().您也可以选择完全删除私有变量语句.
你可以阅读更多关于它here.
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