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本文主要研究一下sharding-jdbc的XAConnectionWrapper

XAConnectionWrapper

incubator-shardingsphere-4.0.0-RC1/sharding-transaction/sharding-transaction-2pc/sharding-transaction-xa/sharding-transaction-xa-core/src/main/java/org/apache/shardingsphere/transaction/xa/jta/connection/XAConnectionWrapper.java

public interface XAConnectionWrapper {
    
    /**
     * Wrap a normal connection to XA connection.
     *
     * @param xaDataSource XA data source
     * @param connection connection
     * @return sharding XA connection
     */
    XAConnection wrap(XADataSource xaDataSource, Connection connection);
}

• XAConnectionWrapper定义了wrap接口，返回XAConnection

MySQLXAConnectionWrapper

incubator-shardingsphere-4.0.0-RC1/sharding-transaction/sharding-transaction-2pc/sharding-transaction-xa/sharding-transaction-xa-core/src/main/java/org/apache/shardingsphere/transaction/xa/jta/connection/dialect/MySQLXAConnectionWrapper.java

@RequiredArgsConstructor
public final class MySQLXAConnectionWrapper implements XAConnectionWrapper {
    
    private static final String MYSQL_XA_DATASOURCE_5 = "com.mysql.jdbc.jdbc2.optional.MysqlXADataSource";
    
    private static final String MYSQL_XA_DATASOURCE_8 = "com.mysql.cj.jdbc.MysqlXADataSource";
    
    @SneakyThrows
    @Override
    public XAConnection wrap(final XADataSource xaDataSource, final Connection connection) {
        Connection physicalConnection = unwrapPhysicalConnection(xaDataSource.getClass().getName(), connection);
        Method method = xaDataSource.getClass().getDeclaredMethod("wrapConnection", Connection.class);
        method.setAccessible(true);
        return (XAConnection) method.invoke(xaDataSource, physicalConnection);
    }
    
    @SneakyThrows
    private Connection unwrapPhysicalConnection(final String xaDataSourceClassName, final Connection connection) {
        switch (xaDataSourceClassName) {
            case MYSQL_XA_DATASOURCE_5:
                return (Connection) connection.unwrap(Class.forName("com.mysql.jdbc.Connection"));
            case MYSQL_XA_DATASOURCE_8:
                return (Connection) connection.unwrap(Class.forName("com.mysql.cj.jdbc.JdbcConnection"));
            default:
                throw new UnsupportedOperationException(String.format("Cannot support xa datasource: `%s`", xaDataSourceClassName));
        }
    }
}

• MySQLXAConnectionWrapper实现了XAConnectionWrapper接口，其wrap方法首先通过unwrapPhysicalConnection获取physicalConnection，然后反射执行XADataSource的wrapConnection方法

MySQLXAConnectionWrapperTest

incubator-shardingsphere-4.0.0-RC1/sharding-transaction/sharding-transaction-2pc/sharding-transaction-xa/sharding-transaction-xa-core/src/test/java/org/apache/shardingsphere/transaction/xa/jta/connection/dialect/MySQLXAConnectionWrapperTest.java

@RunWith(MockitoJUnitRunner.class)
public final class MySQLXAConnectionWrapperTest {
    
    private XADataSource xaDataSource;
    
    @Mock
    private Connection connection;
    
    @Before
    @SuppressWarnings("unchecked")
    public void setUp() throws SQLException, ClassNotFoundException {
        Connection connection = (Connection) mock(Class.forName("com.mysql.jdbc.Connection"));
        DataSource dataSource = DataSourceUtils.build(HikariDataSource.class, DatabaseType.MySQL, "ds1");
        xaDataSource = XADataSourceFactory.build(DatabaseType.MySQL, dataSource);
        when(this.connection.unwrap((Class<Object>) any())).thenReturn(connection);
    }
    
    @Test
    public void assertCreateMySQLConnection() throws SQLException {
        XAConnection actual = new MySQLXAConnectionWrapper().wrap(xaDataSource, connection);
        assertThat(actual.getXAResource(), instanceOf(XAResource.class));
        assertThat(actual.getConnection(), instanceOf(Connection.class));
    }
}

• MySQLXAConnectionWrapperTest验证了wrap及unwrap方法

小结

MySQLXAConnectionWrapper实现了XAConnectionWrapper接口，其wrap方法首先通过unwrapPhysicalConnection获取physicalConnection，然后反射执行XADataSource的wrapConnection方法

doc

• XAConnectionWrapper