Java JDBC MySQL异常:“0”;结果集关闭后不允许操作";
我已经在这方面工作了将近一天半,但我似乎无法解决这个错误。我不知道为什么要关闭结果集。也许你们中的一些人可以帮我 MySQL数据库:Java JDBC MySQL异常:“0”;结果集关闭后不允许操作";,java,mysql,jdbc,Java,Mysql,Jdbc,我已经在这方面工作了将近一天半,但我似乎无法解决这个错误。我不知道为什么要关闭结果集。也许你们中的一些人可以帮我 MySQL数据库: 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; publ
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 List<MySQLDatabase> updateList;
private static String host;
private static String database;
private static String username;
private static String password;
@Override
public void run() {
while (true) {
for (MySQLDatabase database : updateList) {
try {
if (database.getConnection() == null) {
database.connect();
} else {
database.ping();
}
database.cycle();
} catch (Exception ex) {
ex.printStackTrace();
}
try {
Thread.sleep(10000);
} catch (Exception ex) {
}
}
}
}
private static void loadProperties() {
Properties p = new Properties();
try {
p.load(new FileInputStream("./sql.ini"));
host = p.getProperty("host");
database = p.getProperty("database");
username = p.getProperty("username");
password = p.getProperty("password");
} catch (Exception ex) {
System.out.println("Error loading MySQL properties.");
}
}
public static String getHost() {
return host;
}
static {
loadProperties();
updateList = new ArrayList<MySQLDatabase>();
updateList.add(new MySQLDonation(host, database, username, password));
}
}
有了这些信息,让我说这确实有效,我得到了我的信息和游戏中没有的东西,但它会重复,就像用户永远不会从查询中删除,所以它会给他们无限的奖励。如果您需要更多信息,请随时询问。当您运行
Delete
查询时,您使用的语句与Select
查询中使用的语句相同。在同一语句上重新执行时,上一个结果集将关闭
为了避免这种情况,每次执行查询时都应该创建一个新的语句。所以删除statement=connection.createStatement()从MySQLDatabase
类中的connect()
方法中选择code>,并将该类中的所有statement
替换为connection.createStatement()
。您也可以选择删除私有变量语句
您可以阅读更多信息。当我们对不同类型使用相同的语句对象时,会出现此错误
检查语句对象 你的查询函数是做什么的。它可能正在关闭ResultSet.public ResultSet查询(字符串查询)抛出SQLException{if(query.toLowerCase().startsWith(“select”){return statement.executeQuery(query);}else{statement.executeUpdate(query);}return null;}存在“query”,如果字符串等于select,则执行查询;否则,我们将向指定的query.mysqlgeneration.ping发送更新,并调用super.ping,它是抽象的!这段代码没有编译…@Aubin这怎么会是我的问题?这与例外完全无关。代码编译得很好。mysqlgeneration扩展了MySQLDatabase,它是ping的父级,因此我可以调用super.ping(…)@user1787084在主机中传递什么?你绝对确定你正在连接到数据库吗?好的,这更有意义。是我的“删除”查询导致了问题还是表的初始查询?是删除查询。如果你把它从循环中去掉,你的代码会工作,但我相信逻辑是错误的。怎么会这样呢?介意再详细解释一下吗?好的,@galuano1,我删除了语句实例和“query”方法,并为每个查询提供了自己的语句。来聊天室吧
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 database, String username, String password) {
super(host, database, username, 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);
}
}
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)