Spring的JdbcTemplate自动关闭连接_jdbctemplate 关闭连接

作者：代码探险家 | 2024-06-23 06:21:37

踩

jdbctemplate 关闭连接

来源：https://blog.csdn.net/partner4java/article/details/7012196

JdbcTemplate类使用DataSource得到一个数据库连接。然后，他调用StatementCreator实例创建要执行的语句。下一步，他调用StatementCallBack完成。
一旦StatementCallBack返回结果，JdbcTemplate类完成所有必要清理工作关闭连接。如果StatementCreator或StatementCallBack抛出异常，JdbcTemplate类会捕获他们，并转换为Spring数据访问异常。

看一个JdbcTemplate里面的比较核心的一个方法：

 
   view plain 
   copy to clipboard 
   print 
   ? 
  
//-------------------------------------------------------------------------  
// Methods dealing with prepared statements  
//-------------------------------------------------------------------------  
  
public Object execute(PreparedStatementCreator psc, PreparedStatementCallback action)  
        throws DataAccessException {  
  
    Assert.notNull(psc, "PreparedStatementCreator must not be null");  
    Assert.notNull(action, "Callback object must not be null");  
    if (logger.isDebugEnabled()) {  
        String sql = getSql(psc);  
        logger.debug("Executing prepared SQL statement" + (sql != null ? " [" + sql + "]" : ""));  
    }  
  
    Connection con = DataSourceUtils.getConnection(getDataSource());  
    PreparedStatement ps = null;  
    try {  
        Connection conToUse = con;  
        if (this.nativeJdbcExtractor != null &&  
                this.nativeJdbcExtractor.isNativeConnectionNecessaryForNativePreparedStatements()) {  
            conToUse = this.nativeJdbcExtractor.getNativeConnection(con);  
        }  
        ps = psc.createPreparedStatement(conToUse);  
        applyStatementSettings(ps);  
        PreparedStatement psToUse = ps;  
        if (this.nativeJdbcExtractor != null) {  
            psToUse = this.nativeJdbcExtractor.getNativePreparedStatement(ps);  
        }  
        Object result = action.doInPreparedStatement(psToUse);  
        handleWarnings(ps);  
        return result;  
    }  
    catch (SQLException ex) {  
        // Release Connection early, to avoid potential connection pool deadlock  
        // in the case when the exception translator hasn't been initialized yet.  
        if (psc instanceof ParameterDisposer) {  
            ((ParameterDisposer) psc).cleanupParameters();  
        }  
        String sql = getSql(psc);  
        psc = null;  
        JdbcUtils.closeStatement(ps);  
        ps = null;  
        DataSourceUtils.releaseConnection(con, getDataSource());  
        con = null;  
        throw getExceptionTranslator().translate("PreparedStatementCallback", sql, ex);  
    }  
    finally {  
        if (psc instanceof ParameterDisposer) {  
            ((ParameterDisposer) psc).cleanupParameters();  
        }  
        JdbcUtils.closeStatement(ps);  
        DataSourceUtils.releaseConnection(con, getDataSource());  
    }  
}  

显然，我们在finally里面看到了关闭调用，在看看这个关闭调用方法内部：

 
   view plain 
   copy to clipboard 
   print 
   ? 
  
/** 
* Close the given Connection, obtained from the given DataSource, 
* if it is not managed externally (that is, not bound to the thread). 
* @param con the Connection to close if necessary 
* (if this is <code>null</code>, the call will be ignored) 
* @param dataSource the DataSource that the Connection was obtained from 
* (may be <code>null</code>) 
* @see #getConnection 
*/  
public static void releaseConnection(Connection con, DataSource dataSource) {  
    try {  
        doReleaseConnection(con, dataSource);  
    }  
    catch (SQLException ex) {  
        logger.debug("Could not close JDBC Connection", ex);  
    }  
    catch (Throwable ex) {  
        logger.debug("Unexpected exception on closing JDBC Connection", ex);  
    }  
}  
  
/** 
* Actually close the given Connection, obtained from the given DataSource. 
* Same as {@link #releaseConnection}, but throwing the original SQLException. 
* <p>Directly accessed by {@link TransactionAwareDataSourceProxy}. 
* @param con the Connection to close if necessary 
* (if this is <code>null</code>, the call will be ignored) 
* @param dataSource the DataSource that the Connection was obtained from 
* (may be <code>null</code>) 
* @throws SQLException if thrown by JDBC methods 
* @see #doGetConnection 
*/  
public static void doReleaseConnection(Connection con, DataSource dataSource) throws SQLException {  
    if (con == null) {  
        return;  
    }  
  
    if (dataSource != null) {  
        ConnectionHolder conHolder = (ConnectionHolder) TransactionSynchronizationManager.getResource(dataSource);  
        if (conHolder != null && connectionEquals(conHolder, con)) {  
            // It's the transactional Connection: Don't close it.  
            conHolder.released();  
            return;  
        }  
    }  
  
    // Leave the Connection open only if the DataSource is our  
    // special SmartDataSoruce and it wants the Connection left open.  
    if (!(dataSource instanceof SmartDataSource) || ((SmartDataSource) dataSource).shouldClose(con)) {  
        logger.debug("Returning JDBC Connection to DataSource");  
        con.close();  
    }  
}  

主要下面这几行代码:

 
   view plain 
   copy to clipboard 
   print 
   ? 
  
// Leave the Connection open only if the DataSource is our  
// special SmartDataSoruce and it wants the Connection left open.  
if (!(dataSource instanceof SmartDataSource) || ((SmartDataSource) dataSource).shouldClose(con)) {  
    logger.debug("Returning JDBC Connection to DataSource");  
    con.close();  
}  

哦，可以看到大部分情况下是自动关闭，除非你使用的SmartDataSource，且SmartDataSource指定了允许关闭。

有些时候，你引入了JdbcTemplate或者DaoSupport，但是有时还需要自己额外的拿到conn进行操作，如下：
jdbcTemplate.getDataSource().getConnection()
那么，你应该就需要关闭连接了

声明：本文内容由网友自发贡献，不代表【wpsshop博客】立场，版权归原作者所有，本站不承担相应法律责任。如您发现有侵权的内容，请联系我们。转载请注明出处：https://www.wpsshop.cn/w/代码探险家/article/detail/748950