Druid源码之DruidXADataSource

·1.创建连接，是跟普通连接不一样的，拿的XA的连接

像mysql，是这个com.mysql.jdbc.jdbc2.optional.MysqlXAConnection

public static XAConnection createXAConnection(Driver driver, Connection physicalConn) throws SQLException {
        final int major = driver.getMajorVersion();
        if (major == 5) {
            if (utilClass == null && !utilClassError) {
                try {
                    utilClass = Class.forName("com.mysql.jdbc.Util");

                    Method method = utilClass.getMethod("isJdbc4");
                    utilClass_isJdbc4 = (Boolean) method.invoke(null);

                    class_5_connection = Class.forName("com.mysql.jdbc.Connection");
                    method_5_getPinGlobalTxToPhysicalConnection = class_5_connection.getMethod("getPinGlobalTxToPhysicalConnection");

                    class_5_suspendableXAConnection = Class.forName("com.mysql.jdbc.jdbc2.optional.SuspendableXAConnection");
                    constructor_5_suspendableXAConnection = class_5_suspendableXAConnection.getConstructor(class_5_connection);

                    class_5_JDBC4SuspendableXAConnection = Class.forName("com.mysql.jdbc.jdbc2.optional.JDBC4SuspendableXAConnection");
                    constructor_5_JDBC4SuspendableXAConnection = class_5_JDBC4SuspendableXAConnection.getConstructor(class_5_connection);

                    class_5_MysqlXAConnection = Class.forName("com.mysql.jdbc.jdbc2.optional.MysqlXAConnection");
                    constructor_5_MysqlXAConnection = class_5_MysqlXAConnection.getConstructor(class_5_connection, boolean.class);
                } catch (Exception ex) {
                    ex.printStackTrace();
                    utilClassError = true;
                }
            }

            try {
                boolean pinGlobTx = (Boolean) method_5_getPinGlobalTxToPhysicalConnection.invoke(physicalConn);
                if (pinGlobTx) {
                    if (!utilClass_isJdbc4) {
                        return (XAConnection) constructor_5_suspendableXAConnection.newInstance(physicalConn);
                    }

                    return (XAConnection) constructor_5_JDBC4SuspendableXAConnection.newInstance(physicalConn);
                }

                return (XAConnection) constructor_5_MysqlXAConnection.newInstance(physicalConn, Boolean.FALSE);
            } catch (Exception e) {
                e.printStackTrace();
            }

        } else if (major == 6 || major == 8) {
            if (method_6_getValue == null && !method_6_getValue_error) {
                try {
                    class_6_connection = Class.forName("com.mysql.cj.api.jdbc.JdbcConnection");
                } catch (Throwable t) {
                }
                
                try {
                    // maybe 8.0.11 or higher version, try again with com.mysql.cj.jdbc.JdbcConnection
                    if (class_6_connection == null) {
                        class_6_connection = Class.forName("com.mysql.cj.jdbc.JdbcConnection");
                        method_6_getPropertySet = class_6_connection.getMethod("getPropertySet");
                        Class<?> propertySetClass = Class.forName("com.mysql.cj.conf.PropertySet");

                        NoSuchMethodException noSuchMethodException = null;
                        try {
                            method_6_getBooleanReadableProperty = propertySetClass
                                    .getMethod("getBooleanReadableProperty", String.class);
                            method_6_getValue = Class.forName("com.mysql.cj.conf.ReadableProperty")
                                    .getMethod("getValue");
                        } catch (NoSuchMethodException error) {
                            noSuchMethodException = error;
                        }
                        if (method_6_getBooleanReadableProperty == null) {
                            method_6_getBooleanReadableProperty = propertySetClass
                                    .getMethod("getBooleanProperty", String.class);
                            method_6_getValue = Class.forName("com.mysql.cj.conf.RuntimeProperty")
                                    .getMethod("getValue");
                        }

                    }
                    else { 
                        method_6_getPropertySet = class_6_connection.getMethod("getPropertySet");
                        method_6_getBooleanReadableProperty = Class.forName("com.mysql.cj.api.conf.PropertySet").getMethod("getBooleanReadableProperty", String.class);
                        method_6_getValue = Class.forName("com.mysql.cj.api.conf.ReadableProperty").getMethod("getValue");
                    }
                } catch (Exception ex) {
                    ex.printStackTrace();
                    method_6_getValue_error = true;
                }
            }

            try {
                // pinGlobalTxToPhysicalConnection
                Boolean pinGlobTx = (Boolean) method_6_getValue.invoke(
                        method_6_getBooleanReadableProperty.invoke(
                                method_6_getPropertySet.invoke(physicalConn)
                                , "pinGlobalTxToPhysicalConnection"
                        )
                );

                if (pinGlobTx != null && pinGlobTx) {
                    try {
                        if (method_6_getInstance == null && !method_6_getInstance_error) {
                            class_6_suspendableXAConnection = Class.forName("com.mysql.cj.jdbc.SuspendableXAConnection");
                            method_6_getInstance = class_6_suspendableXAConnection.getDeclaredMethod("getInstance", class_6_connection);
                            method_6_getInstance.setAccessible(true);
                        }
                    } catch (Throwable ex) {
                        ex.printStackTrace();
                        method_6_getInstance_error = true;
                    }
                    return (XAConnection) method_6_getInstance.invoke(null, physicalConn);
                } else {
                    try {
                        if (method_6_getInstanceXA == null && !method_6_getInstanceXA_error) {
                            class_6_JDBC4SuspendableXAConnection = Class.forName("com.mysql.cj.jdbc.MysqlXAConnection");
                            method_6_getInstanceXA = class_6_JDBC4SuspendableXAConnection.getDeclaredMethod("getInstance", class_6_connection, boolean.class);
                            method_6_getInstanceXA.setAccessible(true);
                        }
                    } catch (Throwable ex) {
                        ex.printStackTrace();
                        method_6_getInstanceXA_error = true;
                    }
                    return (XAConnection) method_6_getInstanceXA.invoke(null, physicalConn, Boolean.FALSE);
                }
            } catch (InvocationTargetException e) {
                Throwable cause = e.getCause();
                if (cause instanceof RuntimeException) {
                    throw (RuntimeException) cause;
                }
            } catch (Exception e) {
                e.printStackTrace();
                method_6_getInstance_error = true;
            }
        }

        throw new SQLFeatureNotSupportedException();
    }

2.DruidXADataSource除了实现XA的获取连接，其他都是继承DruidDataSource

public class DruidXADataSource extends DruidDataSource implements XADataSource {

    private final static Log  LOG              = LogFactory.getLog(DruidXADataSource.class);

    private static final long serialVersionUID = 1L;

    private Object            h2Factory        = null;

    @Override
    public XAConnection getXAConnection() throws SQLException {
        DruidPooledConnection conn = this.getConnection();

        Connection physicalConn = conn.unwrap(Connection.class);

        XAConnection rawXAConnection = createPhysicalXAConnection(physicalConn);

        return new DruidPooledXAConnection(conn, rawXAConnection);
    }

    protected void initCheck() throws SQLException {
        super.initCheck();

        DbType dbType = DbType.of(this.dbTypeName);
        if (JdbcUtils.H2.equals(dbType)) {
            h2Factory = H2Utils.createJdbcDataSourceFactory();
        }
    }

    private XAConnection createPhysicalXAConnection(Connection physicalConn) throws SQLException {
        DbType dbType = DbType.of(this.dbTypeName);

        if (dbType == null) {
            throw new SQLException("xa not support dbType : " + this.dbTypeName);
        }

        switch (dbType) {
            case oracle:
                try {
                    return OracleUtils.OracleXAConnection(physicalConn);
                } catch (XAException xae) {
                    LOG.error("create xaConnection error", xae);
                    return null;
                }
            case mysql:
            case mariadb:
                return MySqlUtils.createXAConnection(driver, physicalConn);
            case postgresql:
                return PGUtils.createXAConnection(physicalConn);
            case h2:
                return H2Utils.createXAConnection(h2Factory, physicalConn);
            case jtds:
                return new JtdsXAConnection(physicalConn);
            default:
                throw new SQLException("xa not support dbType : " + this.dbTypeName);

        }
    }

    @Override
    public XAConnection getXAConnection(String user, String password) throws SQLException {
        throw new UnsupportedOperationException("Not supported by DruidDataSource");
    }

}

3.XA事务的提交,是两阶段,XA的事务和本地的事务是互相独立的,XA结束前，本地事务不能提交;反之则一样

像mysql，步骤如下,引用官方,https://dev.mysql.com/doc/refman/5.7/en/xa-states.html

mysql> XA START 'xatest';
Query OK, 0 rows affected (0.00 sec)

mysql> INSERT INTO mytable (i) VALUES(10);
Query OK, 1 row affected (0.04 sec)

mysql> XA END 'xatest';
Query OK, 0 rows affected (0.00 sec)

mysql> XA PREPARE 'xatest';
Query OK, 0 rows affected (0.00 sec)

mysql> XA COMMIT 'xatest';
Query OK, 0 rows affected (0.00 sec)

3.PooledConnection是一个接口,java注释是提供连接器管理的钩子;DruidPooledConnection实现了这个接口，这个接口也有关闭方法，Druid也实现了这个方法，但是DruidDataSource回收连接，实际上不会调用这个方法的，目前也搜不到这个close方法最终哪里会调用

    public void close() throws SQLException {
        if (this.disable) {
            return;
        }

        DruidConnectionHolder holder = this.holder;
        if (holder == null) {
            if (dupCloseLogEnable) {
                LOG.error("dup close");
            }
            return;
        }

        DruidAbstractDataSource dataSource = holder.getDataSource();
        boolean isSameThread = this.getOwnerThread() == Thread.currentThread();

        if (!isSameThread) {
            dataSource.setAsyncCloseConnectionEnable(true);
        }

        if (dataSource.isAsyncCloseConnectionEnable()) {
            syncClose();
            return;
        }

        if (!CLOSING_UPDATER.compareAndSet(this, 0, 1)) {
            return;
        }

        try {
            for (ConnectionEventListener listener : holder.getConnectionEventListeners()) {
                listener.connectionClosed(new ConnectionEvent(this));
            }

            List<Filter> filters = dataSource.getProxyFilters();
            if (filters.size() > 0) {
                FilterChainImpl filterChain = new FilterChainImpl(dataSource);
                filterChain.dataSource_recycle(this);
            } else {
                recycle();
            }
        } finally {
            CLOSING_UPDATER.set(this, 0);
        }

        this.disable = true;
    }