一文深入解析JDBC超时机制

"Thread-Segment-Update-4" daemon prio=10 tid=0x00007f2c6000c000 nid=0x2455 runnable [0x00007f2c55deb000]
  java.lang.Thread.State: RUNNABLE
   at java.net.SocketInputStream.socketRead0(Native Method)
   at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
   at java.net.SocketInputStream.read(SocketInputStream.java:170)
   at java.net.SocketInputStream.read(SocketInputStream.java:141)
   at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:100)
   at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:143)
   at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:173)
   - locked com.mysql.jdbc.util.ReadAheadInputStream@33d807d4
   at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2911)
   at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3332)
   at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3322)
   at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3762)
   at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2435)
   at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2582)
   at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2531)
   - locked com.mysql.jdbc.JDBC4Connection@178ec6c
   at com.mysql.jdbc.ConnectionImpl.setAutoCommit(ConnectionImpl.java:4852)
   - locked com.mysql.jdbc.JDBC4Connection@178ec6c

CancelTask timeoutTask = null;//实现statementTimeout的timer。每一个SQL执行都会创建一个

try {
    //有超时设置会初始化这个timer
    if (locallyScopedConnection.getEnableQueryTimeouts() && this.timeoutInMillis != 0 && locallyScopedConnection.versionMeetsMinimum(5, 0, 0)) {
        timeoutTask = new CancelTask(this);
        locallyScopedConnection.getCancelTimer().schedule(timeoutTask, this.timeoutInMillis);
    }

    if (!isBatch) {
        statementBegins();
    }
    //执行SQL（sync）
    rs = locallyScopedConnection.execSQL(this, null, maxRowsToRetrieve, sendPacket, this.resultSetType, this.resultSetConcurrency,
            createStreamingResultSet, this.currentCatalog, metadataFromCache, isBatch);

    if (timeoutTask != null) {
        timeoutTask.cancel();

        locallyScopedConnection.getCancelTimer().purge();

        if (timeoutTask.caughtWhileCancelling != null) {
            throw timeoutTask.caughtWhileCancelling;
        }

        timeoutTask = null;
    }

    synchronized (this.cancelTimeoutMutex) {
        if (this.wasCancelled) {
            SQLException cause = null;
            //如果是被timer kill，则抛出异常
            if (this.wasCancelledByTimeout) {
                cause = new MySQLTimeoutException();
            } else {
                cause = new MySQLStatementCancelledException();
            }
            resetCancelledState();
            //抛出
            throw cause;
        }
    }

<bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
       <!-- 基本属性 url、user、password -->
       <property name="url" value="jdbc:mysql://127.0.0.2:3306/my?socketTimeout=1000"/>
       <property name="username" value="root" />
       <property name="password" value="123456" />
       <property name="queryTimeout" value="5"/>
        //省略

</bean>
//sql 10s之后返回数据
select sleep(10) ,name from user where id=1

The last packet successfully received from the server was 1,057 milliseconds ago.  The last packet sent successfully to the server was 1,012 milliseconds ago.
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45

com.mysql.jdbc.exceptions.MySQLTimeoutException: Statement cancelled due to timeout or client request
    at com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1390)
    at com.alibaba.druid.pool.DruidPooledStatement.executeQuery(DruidPooledStatement.java:140)

The last packet successfully received from the server was 15,003 milliseconds ago.  The last packet sent successfully to the server was 15,004 milliseconds ago.
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)