Mybatis事务管理

JerryXia 发表于 2019-01-27 05:25:25 , 阅读 (0)

JdbcTransaction使用JDBC的Connection对象的提交和回滚来管理事务，并通过内部的DataSource对象来获取Connection对象。

public class JdbcTransaction implements Transaction {    private static final Log log = LogFactory.getLog(JdbcTransaction.class);    protected Connection connection;            //当前JDBC连接    protected DataSource dataSource;            //数据源    protected TransactionIsolationLevel level;  //事务级别    protected boolean autoCommmit;    public JdbcTransaction(DataSource ds, TransactionIsolationLevel desiredLevel, boolean desiredAutoCommit) {        dataSource = ds;        level = desiredLevel;        autoCommmit = desiredAutoCommit;    }    public JdbcTransaction(Connection connection) {        this.connection = connection;    }    /**     * 延迟加载Connection对象     */    public Connection getConnection() throws SQLException {        if (connection == null) {            openConnection();        }        return connection;    }    /**     * 提交事务     */    public void commit() throws SQLException {        if (connection != null && !connection.getAutoCommit()) {            if (log.isDebugEnabled()) {                log.debug("Committing JDBC Connection [" + connection + "]");            }            connection.commit();        }    }    /**     * 回滚事务     */    public void rollback() throws SQLException {        if (connection != null && !connection.getAutoCommit()) {            if (log.isDebugEnabled()) {                log.debug("Rolling back JDBC Connection [" + connection + "]");            }            connection.rollback();        }    }    /**     * 关闭事务     */    public void close() throws SQLException {        if (connection != null) {            resetAutoCommit();            if (log.isDebugEnabled()) {                log.debug("Closing JDBC Connection [" + connection + "]");            }            connection.close();        }    }    protected void setDesiredAutoCommit(boolean desiredAutoCommit) {        try {            if (connection.getAutoCommit() != desiredAutoCommit) {                if (log.isDebugEnabled()) {                    log.debug("Setting autocommit to " + desiredAutoCommit + " on JDBC Connection [" + connection + "]");                }                connection.setAutoCommit(desiredAutoCommit);            }        } catch (SQLException e) {            throw new TransactionException("Error configuring AutoCommit.  "            + "Your driver may not support getAutoCommit() or setAutoCommit(). "            + "Requested setting: " + desiredAutoCommit + ".  Cause: " + e, e);        }    }    /**     * 重置事务为自动提交     */    protected void resetAutoCommit() {        try {            if (!connection.getAutoCommit()) {                if (log.isDebugEnabled()) {                    log.debug("Resetting autocommit to true on JDBC Connection [" + connection + "]");                }                connection.setAutoCommit(true);            }        } catch (SQLException e) {            log.debug("Error resetting autocommit to true "            + "before closing the connection.  Cause: " + e);        }    }    /**     * 从数据源获取Connection对象     */    protected void openConnection() throws SQLException {        if (log.isDebugEnabled()) {            log.debug("Opening JDBC Connection");        }        connection = dataSource.getConnection();        if (level != null) {            connection.setTransactionIsolation(level.getLevel());        }        setDesiredAutoCommit(autoCommmit);    }}

而真正创建事务，是通过工厂类JdbcTransactionFactory

public class JdbcTransactionFactory implements TransactionFactory {    public void setProperties(Properties props) {    }    public Transaction newTransaction(Connection conn) {        return new JdbcTransaction(conn);    }    public Transaction newTransaction(DataSource ds, TransactionIsolationLevel level, boolean autoCommit) {        return new JdbcTransaction(ds, level, autoCommit);    }}

ManagedTransaction

ManagedTransaction本身并不做任何事务管理，其忽略了事务提交回滚的动作，而是交由容器去管理事务。

public class ManagedTransaction {    ...    public void commit() throws SQLException {    // Does nothing    }    public void rollback() throws SQLException {    // Does nothing    }    ...}

同样ManagedTransaction的创建，是通过ManagedTransactionFactory工厂类

public class ManagedTransactionFactory implements TransactionFactory {    private boolean closeConnection = true;     //关闭事务时是否关闭连接    public void setProperties(Properties props) {        if (props != null) {            String closeConnectionProperty = props.getProperty("closeConnection");            if (closeConnectionProperty != null) {                closeConnection = Boolean.valueOf(closeConnectionProperty);            }        }    }    public Transaction newTransaction(Connection conn) {        return new ManagedTransaction(conn, closeConnection);    }    public Transaction newTransaction(DataSource ds, TransactionIsolationLevel level, boolean autoCommit) {        return new ManagedTransaction(ds, level, closeConnection);    }

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