JDBC：無法連接第二次

嗨全部我試圖連接一個數據庫。下面我給出了代碼。我可以連接到數據庫，但如果第一次和第二次之間的差異大於mysql數據庫的「等待超時」，則無法第二次連接。我正在使用mysql數據庫。我得到「通信鏈路故障」的問題 WAIT_TIMEOUT爲10秒（爲方便起見）爲8小時，我的數據庫我給你的代碼JDBC：無法連接第二次

public class DatabaseManager { 
private static Connection jConn; 
private static DatabaseManager manager; 

public Boolean getUser(){ 
    Statement jStmt = null; 
    ResultSet rs = null; 
    try { 

    String query = "SELECT * FROM USER "; 
    System.out.println(query); 
    jStmt = jConn.createStatement(); 
    rs = jStmt.executeQuery(query); 
    while (rs.next()) { 

    } 
    }catch (Exception e) { 
    e.printStackTrace(); 
    return false; 
    } 
    return true; 
} 

    public static synchronized DatabaseManager getInstance() { 
    if (manager == null) { 
    try { 
    manager = initialize(); 
    } catch (DatabaseInitializationException e) { 
    // e.printStackTrace(); 
    // throw new RuntimeException("Database Initialization 
    // Exception"); 
    } 
    } 
    return manager; 
} 
     private static DatabaseManager initialize() 
    throws DatabaseInitializationException { 

    try { 
    Class.forName(serverSrv.readPropertyValue("Srver_Path", 
    "DBdriver")); 
    } catch (ClassNotFoundException e) { 
    throw new DatabaseInitializationException(e.getMessage()); 
    } 
    try { 
    jConn = DriverManager.getConnection("DB_URL","user","password"); 
    System.out.println("Excecuted initialize() for Database "); 
    } catch (SQLException e) { 
    throw new DatabaseInitializationException(e.getMessage()); 
    } 
    return new DatabaseManager(); 
} 
}

，我測試樣

public static void main(String[] args) { 
    long st = System.currentTimeMillis(); 
    long end ; 
    DatabaseManager dm = DatabaseManager.getInstance(); 

    if(dm.getUser()) 
    System.out.println("success"); 
    else 
    System.out.println("failed.."); 

    do{ 
    end = System.currentTimeMillis(); 
    }while((end-st)<12*1000); 

    if(dm.getUser()) 
    System.out.println("success"); 
    else 
    System.out.println("failed.."); 
}

並且它發出異常，如

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure 

Last packet sent to the server was 0 ms ago. 
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) 
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) 
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) 
at java.lang.reflect.Constructor.newInstance(Unknown Source) 
at com.mysql.jdbc.Util.handleNewInstance(Util.java:406) 
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074) 
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2873) 
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2763) 
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3299) 
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1837) 
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1961) 
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2537) 
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2466) 
at com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1383) 
at mypackage.db.DatabaseManager.getUser(DatabaseManager.java:127) 
at mypackage.test.Test.main(Test.java:23) 
Caused by: java.net.SocketException: Software caused connection abort: recv failed 
at java.net.SocketInputStream.socketRead0(Native Method) 
at java.net.SocketInputStream.read(Unknown Source) 
at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:113) 
at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:160) 
at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:188) 
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2329) 
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2774)

來源

2010-12-06 user531260

「Srver_Path」 - >是一個錯字嗎？ – darioo 2010-12-06 08:28:44

你是在代理之後嗎？ – 2010-12-06 08:36:05

檢查連接超時設置。

來源

2010-12-06 08:32:50 lalit

也許你應該關閉ResultSet以及Statement。這個link有一些正確的做法。

來源

2010-12-06 08:36:48 Raghuram

Srver_Path不是找到mysql服務器的錯字問題 – user531260 2010-12-06 09:14:22

你的問題是，你正在嘗試重用jConn其在超時後自動關閉。所以當你嘗試並再次使用它時，會拋出異常。根據什麼你正在嘗試做的，我建議（爲簡單起見）..

關閉jConn通過typeing jConn.close（）;
然後當你需要再次使用db重新連接時使用jConn = DriverManager.getConnection（「DB_URL」，「user」，「password」）;

來源

2010-12-06 08:45:52 Paul

JDBC：無法連接第二次

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