JDBC：无法连接第二次

嗨全部我试图连接一个数据库。下面我给出了代码。我可以连接到数据库，但如果第一次和第二次之间的差异大于mysql数据库的“等待超时”，则无法第二次连接。我正在使用mysql数据库。我得到“通信链路故障”的问题 WAIT_TIMEOUT为10秒（为方便起见）为8小时，我的数据库我给你的代码JDBC：无法连接第二次

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(); 
} 
}

，我测试样

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.."); 
}

并且它发出异常，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)

来源

2010-12-06 user531260

“Srver_Path” - >是一个错字吗？ – darioo 2010-12-06 08:28:44

你是在代理之后吗？ – 2010-12-06 08:36:05

检查连接超时设置。

来源

2010-12-06 08:32:50 lalit

也许你应该关闭ResultSet以及Statement。这个link有一些正确的做法。

来源

2010-12-06 08:36:48 Raghuram

Srver_Path不是找到mysql服务器的错字问题 – user531260 2010-12-06 09:14:22

你的问题是，你正在尝试重用jConn其在超时后自动关闭。所以当你尝试并再次使用它时，会抛出异常。根据什么你正在尝试做的，我建议（为简单起见）..

关闭jConn通过typeing jConn.close（）;
然后当你需要再次使用db重新连接时使用jConn = DriverManager.getConnection（“DB_URL”，“user”，“password”）;

来源

2010-12-06 08:45:52 Paul

JDBC：无法连接第二次

回答

相关问题