Java 如何修复com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException：连接关闭后不允许进行任何操作。例外？

这是我保存记录的查询

这是我的JDBC类。

这是我第一次尝试在mysql中处理事务。我知道这不是借口。但是我对这个连接的处理只有一个粗略的概念。如果我的代码不完善，请给我一个演示答案

如何修复连接关闭后不允许操作的异常？多谢各位

还添加了堆栈跟踪。我想还有两个地方也发现了同样的错误。他们在运行此查询之前到达。

---

您是否知道您实际上是从GUI中访问后端的？您正在将参数从textfields直接传递到数据库。这是一个主要混蛋的来源。至少验证您的输入，否则将提前终止您的工作合同

至于您的错误：抱歉，但是这段代码需要进行重大重构。单凭行数，这段代码就做得太多了。第一条金科玉律：保持你的方法简短。第二条金科玉律：把它们变短

事实上，你自己不明白发生了什么，这对你来说是一个巨大的红灯，表明你需要重新考虑你的设计

• 使使用JDBC.putData（）编写东西的方法独立
• 对JDBC.getData（）执行相同的操作
• 看到一种模式正在出现

我想这是对JDBC中connection.close（）的过早调用。通过将操作细分为更多的原子操作，您可以更好地对代码进行推理，从而理解手边的错误

很抱歉没有提供解决方案，但从长远来看，坚持一些代码原则会让您受益匪浅。学习它们！越快越好，因为我需要更多的因果报应： 阅读罗伯特·C·马丁的《清洁代码》。

然后你将走上启蒙的道路，从而使用道工厂（暗示）和道设计模式（也暗示），成为编码神。恭喜你

好的，这里有一个关于重构的小指南。未完成且未经测试，我想我搞错了SQL插入序列（不知道在哪里使用了哪个transactionId）。但我希望你能有个主意。 祝你今天愉快，欢迎来到牙买加

package mysqlfix;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Date;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JTextField;

public class JDBC {

    static Connection con = null;
    static boolean b;
    static PreparedStatement state;

    public static void setCon() {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/lottery", "root", "123");
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    public static Connection getCon() throws Exception {
        if (con == null) {
            setCon();
        }
        return con;
    }

    public static boolean putData(String sql) {
        try {
            getCon().setAutoCommit(false);
            state = getCon().prepareStatement(sql);
            state.executeUpdate();
            getCon().commit();
            b = true;
        } catch (Exception e) {
            e.printStackTrace();
            b = false;
        }
        return b;
    }

// connection commit
    public static void commit() {
        try {
            con.commit();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    // rollback data
    public static void rollback() {
        if (con != null) {
            try {
                con.rollback();
            } catch (SQLException ex) {
                Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }

// close statement
    public static void putClose() {
        try {
            state.close();
        } catch (SQLException ex) {
            Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    // close connection

    public static void conClose() {
        try {
            con.setAutoCommit(true);
            con.close();
        } catch (SQLException ex) {
            Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

// clear prepared statement
    public static void putClear() {
        try {
            if (state != null && !state.isClosed()) {
                state.close();
            }
        } catch (SQLException ex) {
            Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

// clear the connection
    public static void conClear() {
        try {
            if (con != null && !con.isClosed()) {
                con.setAutoCommit(true);
                con.close();
            }
        } catch (SQLException ex) {
            Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

    public static ResultSet getData(String sql) throws Exception {
        Statement state = getCon().createStatement();
        ResultSet rs = state.executeQuery(sql);
        return rs;
    }

    public void saveTotal(JTextField txtGtotal, JTextField txtPTotal) {
        SuperDAO superDAO = new SuperDAO();

        if (superDAO.getMaxIdFromOrder() > 0) {
            Date date1;
            date1 = new Date();
            String txtGTotalFromTextField = txtGtotal.getText();
            String txtPTotalFromTextField = txtPTotal.getText();
            boolean b1 = false;
                    //regarding the transaction id...
            //this changes whilst updating the table transaction.

            int transactionId = -1;
            if (txtGTotalFromTextField.matches("[a-zA-Z]")) {
                transactionId = superDAO.insertOrderIntoTransaction(date1, txtGTotalFromTextField);
                //b1 = JDBC.putData("insert into transaction(tr_date, amount, tr_type) values ('" + date1 + "' , '" + txtGTotalFromTextField + "' , 'order')");
            }
            if (transactionId > 0) {
                try {
                } catch (Exception ex) {
                    Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
                }
                if (txtPTotalFromTextField.matches("[a-zA-Z]")) {
                    transactionId = superDAO.insertProfitIntoTransaction(date1, txtGTotalFromTextField);
                }
                JDBC.putData("insert into o_de(or_id, tr_id, oday, gtotal) values ('" + superDAO.getMaxIdFromOrder() + "' , '" + transactionId + "','" + date1 + "','" + txtGtotal.getText() + "' )");
                JDBC.putData("insert into order_profit(or_id, tr_id, ptotal) values ('" + superDAO.getMaxIdFromOrder() + "' , '" + transactionId + "','" + txtPTotal.getText() + "' )");

                                                        //JDBC.commit();
                //JOptionPane.showMessageDialog(null, "Order Saved Sucessfully..");
                JDBC.putClose();
                JDBC.conClose();

            }

        }

    }

}



package mysqlfix;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Date;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author edm
 */
public class SuperDAO {

    Connection conn;

    public SuperDAO() {
        try {
            this.conn = JDBC.getCon();
        } catch (Exception ex) {
            Logger.getLogger(SuperDAO.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

    public int getMaxIdFromOrder() {

        try {
            ResultSet rs = JDBC.getData("select MAX(or_id) as or_id from `order`");
            if (rs.first()) {

                return rs.getInt("or_id");
            }
        } catch (SQLException ex) {
            Logger.getLogger(SuperDAO.class.getName()).log(Level.SEVERE, null, ex);
        } catch (Exception ex) {
            Logger.getLogger(SuperDAO.class.getName()).log(Level.SEVERE, null, ex);
        }
        return -1;
    }

    public int getMaxIdFromTransaction() {
        ResultSet rs;
        try {
            rs = JDBC.getData("select MAX(tr_id) as tr_id from transaction");
            if (rs.first()) {
            return rs.getInt("tr_id");
        }
        } catch (Exception ex) {
            Logger.getLogger(SuperDAO.class.getName()).log(Level.SEVERE, null, ex);
        }
        return -1;
    }


    public int insertOrderIntoTransaction(Date date, String text) {
        JDBC.putData("insert into transaction(tr_date, amount, tr_type) values ('" + date + "' , '" + text + "' , 'order')");
        return getMaxIdFromTransaction();
    }

     public int insertProfitIntoTransaction(Date date, String text) {
        JDBC.putData("insert into transaction(tr_date, amount, tr_type) values ('" + date + "' , '" + text + "' , 'profit')"); 

        return getMaxIdFromTransaction();
    }



}

当然，旅程不会就此结束。我没有完成JDBC saveTotal（）。我刚开始，剩下的就交给你了

---

请注意，我没有针对数据库测试此代码（某些sql ddl文件丢失）。另外，我没有使用回滚机制。此外，saveTotal（）存在于JDBC中，它不属于JDBC。在GUI中使用saveTotal（如果需要的话），并让所有数据库访问通过SuperDAO进行。这不是最好的设计，但也不是太抽象，您可以很容易地看到关注点的分离如何使代码更具可读性和可维护性

“试一试”之母…发生在哪一行？发布完整堆栈跟踪：问题中添加了D..@布兰尼斯拉夫·拉齐奇：谢谢。。我甚至不知道是笑还是哭但是为了澄清，你是说像这样的事情。。preparedStatementInsert=dbConnection.prepareStatement（insertTableSQL）；preparedStatementInsert.setInt（1999）；准备好的报表插入设置字符串（2，“mkyong101”）；准备好的报表插入设置字符串（3，“系统”）；preparedStatementInsert.executeUpdate（）；如果你能告诉我你到底在说什么，我就欠你一顿饭。。谢谢。当然可以笑；-）但是如果这段代码投入生产，半年后你必须修复这些bug，你会哭的。请将我的帖子视为专业开发人员（还没有高级开发人员）的智慧。我在你所在的地方。只是就是什么让我的代码更稳定给出建议。你很快就会到的◕ᴥ◕至于您的第一条注释：是的，请验证输入字符串，然后使用PreparedStatement将其插入到查询中。如果您的输入字段仅包含字母，请验证对数据库的输入以遵循这些规则。正则表达式帮助很大：要检查字符串是否只包含字母，请使用以下命令：“aagbvcfdfg”.matches（“[a-zA-Z]”）。这样，您就不允许使用“；”或“\”等特定字符，从而禁用SQL注入攻击。阅读SQL注入。。。通过谷歌搜索，不用谢。祝您未来的编码企业好运。

     package Modle;

  import java.sql.Connection;
  import java.sql.DriverManager;
  import java.sql.PreparedStatement;
  import java.sql.ResultSet;
  import java.sql.SQLException;
  import java.sql.Statement;
  import java.util.logging.Level;
  import java.util.logging.Logger;

  public class JDBC {

static Connection con = null;
static boolean b;
static PreparedStatement state;

public static void setCon() {
    try {
        Class.forName("com.mysql.jdbc.Driver");
        con = DriverManager.getConnection("jdbc:mysql://localhost:3306/lottery", "root", "123");
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

public static Connection getCon() throws Exception {
    if (con == null) {
        setCon();
    }
    return con;
}

public static boolean putData(String sql) {
    try {
        getCon().setAutoCommit(false);
        state = getCon().prepareStatement(sql);
        state.executeUpdate();
        b = true;
    } catch (Exception e) {
        e.printStackTrace();
        b = false;
    }
    return b;
}

// connection commit
public static void commit() {
    try {
        con.commit();
    } catch (Exception e) {
        e.printStackTrace();
    }

}

  // rollback data
  public static void rollback() {
    if (con != null) {
        try {
            con.rollback();
        } catch (SQLException ex) {
            Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

// close statement
public static void putClose() {
    try {
        state.close();
    } catch (SQLException ex) {
        Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
    }
}
 // close connection

  public static void conClose() {
    try {
        con.setAutoCommit(true);
        con.close();
    } catch (SQLException ex) {
        Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
    }
}

// clear prepared statement
public static void putClear() {
    try {
        if (state != null && !state.isClosed()) {
            state.close();
        }
    } catch (SQLException ex) {
        Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
    }
}

// clear the connection
public static void conClear() {
    try {
        if (con != null && !con.isClosed()) {
            con.setAutoCommit(true);
            con.close();
        }
    } catch (SQLException ex) {
        Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
    }
}

public static ResultSet getData(String sql) throws Exception {
    Statement state = getCon().createStatement();
    ResultSet rs = state.executeQuery(sql);
    return rs;
 }
 }

com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed    after connection closed.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.Util.getInstance(Util.java:386)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1013)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:982)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:927)
at com.mysql.jdbc.ConnectionImpl.throwConnectionClosedException(ConnectionImpl.java:1206)
at com.mysql.jdbc.ConnectionImpl.checkClosed(ConnectionImpl.java:1198)
at com.mysql.jdbc.ConnectionImpl.createStatement(ConnectionImpl.java:2484)
at com.mysql.jdbc.ConnectionImpl.createStatement(ConnectionImpl.java:2466)
at Modle.JDBC.getData(JDBC.java:115)
at Controler.NewOrderCon2.saveTotal(NewOrderCon2.java:196)
at lottery.NewOrder.jButton6ActionPerformed(NewOrder.java:2350)
at lottery.NewOrder.access$1200(NewOrder.java:28)
at lottery.NewOrder$13.actionPerformed(NewOrder.java:537)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:729)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:688)
at java.awt.EventQueue$3.run(EventQueue.java:686)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:702)
at java.awt.EventQueue$4.run(EventQueue.java:700)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:699)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

package mysqlfix;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Date;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JTextField;

public class JDBC {

    static Connection con = null;
    static boolean b;
    static PreparedStatement state;

    public static void setCon() {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/lottery", "root", "123");
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    public static Connection getCon() throws Exception {
        if (con == null) {
            setCon();
        }
        return con;
    }

    public static boolean putData(String sql) {
        try {
            getCon().setAutoCommit(false);
            state = getCon().prepareStatement(sql);
            state.executeUpdate();
            getCon().commit();
            b = true;
        } catch (Exception e) {
            e.printStackTrace();
            b = false;
        }
        return b;
    }

// connection commit
    public static void commit() {
        try {
            con.commit();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    // rollback data
    public static void rollback() {
        if (con != null) {
            try {
                con.rollback();
            } catch (SQLException ex) {
                Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }

// close statement
    public static void putClose() {
        try {
            state.close();
        } catch (SQLException ex) {
            Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    // close connection

    public static void conClose() {
        try {
            con.setAutoCommit(true);
            con.close();
        } catch (SQLException ex) {
            Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

// clear prepared statement
    public static void putClear() {
        try {
            if (state != null && !state.isClosed()) {
                state.close();
            }
        } catch (SQLException ex) {
            Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

// clear the connection
    public static void conClear() {
        try {
            if (con != null && !con.isClosed()) {
                con.setAutoCommit(true);
                con.close();
            }
        } catch (SQLException ex) {
            Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

    public static ResultSet getData(String sql) throws Exception {
        Statement state = getCon().createStatement();
        ResultSet rs = state.executeQuery(sql);
        return rs;
    }

    public void saveTotal(JTextField txtGtotal, JTextField txtPTotal) {
        SuperDAO superDAO = new SuperDAO();

        if (superDAO.getMaxIdFromOrder() > 0) {
            Date date1;
            date1 = new Date();
            String txtGTotalFromTextField = txtGtotal.getText();
            String txtPTotalFromTextField = txtPTotal.getText();
            boolean b1 = false;
                    //regarding the transaction id...
            //this changes whilst updating the table transaction.

            int transactionId = -1;
            if (txtGTotalFromTextField.matches("[a-zA-Z]")) {
                transactionId = superDAO.insertOrderIntoTransaction(date1, txtGTotalFromTextField);
                //b1 = JDBC.putData("insert into transaction(tr_date, amount, tr_type) values ('" + date1 + "' , '" + txtGTotalFromTextField + "' , 'order')");
            }
            if (transactionId > 0) {
                try {
                } catch (Exception ex) {
                    Logger.getLogger(JDBC.class.getName()).log(Level.SEVERE, null, ex);
                }
                if (txtPTotalFromTextField.matches("[a-zA-Z]")) {
                    transactionId = superDAO.insertProfitIntoTransaction(date1, txtGTotalFromTextField);
                }
                JDBC.putData("insert into o_de(or_id, tr_id, oday, gtotal) values ('" + superDAO.getMaxIdFromOrder() + "' , '" + transactionId + "','" + date1 + "','" + txtGtotal.getText() + "' )");
                JDBC.putData("insert into order_profit(or_id, tr_id, ptotal) values ('" + superDAO.getMaxIdFromOrder() + "' , '" + transactionId + "','" + txtPTotal.getText() + "' )");

                                                        //JDBC.commit();
                //JOptionPane.showMessageDialog(null, "Order Saved Sucessfully..");
                JDBC.putClose();
                JDBC.conClose();

            }

        }

    }

}



package mysqlfix;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Date;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author edm
 */
public class SuperDAO {

    Connection conn;

    public SuperDAO() {
        try {
            this.conn = JDBC.getCon();
        } catch (Exception ex) {
            Logger.getLogger(SuperDAO.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

    public int getMaxIdFromOrder() {

        try {
            ResultSet rs = JDBC.getData("select MAX(or_id) as or_id from `order`");
            if (rs.first()) {

                return rs.getInt("or_id");
            }
        } catch (SQLException ex) {
            Logger.getLogger(SuperDAO.class.getName()).log(Level.SEVERE, null, ex);
        } catch (Exception ex) {
            Logger.getLogger(SuperDAO.class.getName()).log(Level.SEVERE, null, ex);
        }
        return -1;
    }

    public int getMaxIdFromTransaction() {
        ResultSet rs;
        try {
            rs = JDBC.getData("select MAX(tr_id) as tr_id from transaction");
            if (rs.first()) {
            return rs.getInt("tr_id");
        }
        } catch (Exception ex) {
            Logger.getLogger(SuperDAO.class.getName()).log(Level.SEVERE, null, ex);
        }
        return -1;
    }


    public int insertOrderIntoTransaction(Date date, String text) {
        JDBC.putData("insert into transaction(tr_date, amount, tr_type) values ('" + date + "' , '" + text + "' , 'order')");
        return getMaxIdFromTransaction();
    }

     public int insertProfitIntoTransaction(Date date, String text) {
        JDBC.putData("insert into transaction(tr_date, amount, tr_type) values ('" + date + "' , '" + text + "' , 'profit')"); 

        return getMaxIdFromTransaction();
    }



}