java.sql.SQLException:数据库连接已关闭

问题描述：

我的Java SQLite驱动程序(JDBC)出现问题.当我要加载数据库时，它说已加载，但始终关闭.我将代码分隔在不同的文件中:

I have a problem with the SQLite driver for Java (JDBC). When I want to load a database, it says that it was loaded, but instatly it was closed. I seperated my code in different files:

SQLite.java

package net.jeddsan;

import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.SQLException;

public class SQLite {
    public static Connection createOrOpenDatabase(String database) {

        String url = "jdbc:sqlite:" + database;

        try (Connection conn = DriverManager.getConnection(url)) {
            if (conn != null) {
                System.out.println("A new database has been created.");
                conn.setAutoCommit(false);
                return conn;
            }else{
                return null;
            }

        } catch (SQLException e) {
            System.out.println(e.getMessage());
            return null;
        }
    }
}

MainController.java

@Override
    public void initialize(URL url, ResourceBundle rb) {
        c = SQLite.createOrOpenDatabase("test.db");

        try {
            sta = c.createStatement();
            sta.executeQuery("INSERT INTO token (token) VALUES ('123')");
            sta.close();
        } catch (SQLException ex) {
            Logger.getLogger(MainController.class.getName()).log(Level.SEVERE, null, ex);
        }
        try {
            c.close();
        } catch (SQLException ex) {
            Logger.getLogger(MainController.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

SCHWERWIEGEND: null
java.sql.SQLException: database connection closed
    at org.sqlite.core.CoreConnection.checkOpen(CoreConnection.java:336)
    at org.sqlite.jdbc4.JDBC4Connection.createStatement(JDBC4Connection.java:38)
    at org.sqlite.jdbc3.JDBC3Connection.createStatement(JDBC3Connection.java:193)
    at net.jeddsan.MainController.initialize(MainController.java:103)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2548)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3214)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
    at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
    at net.jeddsan.koradesktop.start(koradesktop.java:22)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
    at java.lang.Thread.run(Thread.java:745)

答

当离开范围时，此try-with-resources构造将在Connection上调用方法close:

This try-with-resources construct will invoke method close on Connection when you leave its scope:

try (Connection conn = DriverManager.getConnection(url)) {
    return conn;
}

因此，您可以有效地返回关闭的连接.

So, you effectively return closed connection.

将其更改为常规的try构造以返回实时连接:

Change it to regular try construct to return live connection:

try {
    Connection conn = DriverManager.getConnection(url);
    return conn;
} catch (SQLException e) {
    return null;
}

java.sql.SQLException:数据库连接已关闭

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