Spring的JdbcTemplate使用，是否还需要手工或者aop指定关闭conn连接（ 使用JdbcTemplate是否需要关闭连接）...

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：

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1. //-------------------------------------------------------------------------
2. // Methods dealing with prepared statements
3. //-------------------------------------------------------------------------
5. publicObject execute(PreparedStatementCreator psc, PreparedStatementCallback action)
6. throwsDataAccessException {
8. Assert.notNull(psc,"PreparedStatementCreator must not be null");
9. Assert.notNull(action,"Callback object must not be null");
10. if(logger.isDebugEnabled()) {
11. String sql = getSql(psc);
12. logger.debug("Executing prepared SQL statement"+ (sql !=null?" ["+ sql +"]":""));
13. }
15. Connection con = DataSourceUtils.getConnection(getDataSource());
16. PreparedStatement ps =null;
17. try{
18. Connection conToUse = con;
19. if(this.nativeJdbcExtractor !=null&&
20. this.nativeJdbcExtractor.isNativeConnectionNecessaryForNativePreparedStatements()) {
21. conToUse =this.nativeJdbcExtractor.getNativeConnection(con);
22. }
23. ps = psc.createPreparedStatement(conToUse);
24. applyStatementSettings(ps);
25. PreparedStatement psToUse = ps;
26. if(this.nativeJdbcExtractor !=null) {
27. psToUse =this.nativeJdbcExtractor.getNativePreparedStatement(ps);
28. }
29. Object result = action.doInPreparedStatement(psToUse);
30. handleWarnings(ps);
31. returnresult;
32. }
33. catch(SQLException ex) {
34. // Release Connection early, to avoid potential connection pool deadlock
35. // in the case when the exception translator hasn't been initialized yet.
36. if(pscinstanceofParameterDisposer) {
37. ((ParameterDisposer) psc).cleanupParameters();
38. }
39. String sql = getSql(psc);
40. psc =null;
41. JdbcUtils.closeStatement(ps);
42. ps =null;
43. DataSourceUtils.releaseConnection(con, getDataSource());
44. con =null;
45. throwgetExceptionTranslator().translate("PreparedStatementCallback", sql, ex);
46. }
47. finally{
48. if(pscinstanceofParameterDisposer) {
49. ((ParameterDisposer) psc).cleanupParameters();
50. }
51. JdbcUtils.closeStatement(ps);
52. DataSourceUtils.releaseConnection(con, getDataSource());
53. }
54. }

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：

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1. /**
2. * Close the given Connection, obtained from the given DataSource,
3. * if it is not managed externally (that is, not bound to the thread).
4. * @param con the Connection to close if necessary
5. * (if this is <code>null</code>, the call will be ignored)
6. * @param dataSource the DataSource that the Connection was obtained from
7. * (may be <code>null</code>)
8. * @see #getConnection
9. */
10. publicstaticvoidreleaseConnection(Connection con, DataSource dataSource) {
11. try{
12. doReleaseConnection(con, dataSource);
13. }
14. catch(SQLException ex) {
15. logger.debug("Could not close JDBC Connection", ex);
16. }
17. catch(Throwable ex) {
18. logger.debug("Unexpected exception on closing JDBC Connection", ex);
19. }
20. }
22. /**
23. * Actually close the given Connection, obtained from the given DataSource.
24. * Same as {@link #releaseConnection}, but throwing the original SQLException.
25. * <p>Directly accessed by {@link TransactionAwareDataSourceProxy}.
26. * @param con the Connection to close if necessary
27. * (if this is <code>null</code>, the call will be ignored)
28. * @param dataSource the DataSource that the Connection was obtained from
29. * (may be <code>null</code>)
30. * @throws SQLException if thrown by JDBC methods
31. * @see #doGetConnection
32. */
33. publicstaticvoiddoReleaseConnection(Connection con, DataSource dataSource)throwsSQLException {
34. if(con ==null) {
35. return;
36. }
38. if(dataSource !=null) {
39. ConnectionHolder conHolder = (ConnectionHolder) TransactionSynchronizationManager.getResource(dataSource);
40. if(conHolder !=null&& connectionEquals(conHolder, con)) {
41. // It's the transactional Connection: Don't close it.
42. conHolder.released();
43. return;
44. }
45. }
47. // Leave the Connection open only if the DataSource is our
48. // special SmartDataSoruce and it wants the Connection left open.
49. if(!(dataSourceinstanceofSmartDataSource) || ((SmartDataSource) dataSource).shouldClose(con)) {
50. logger.debug("Returning JDBC Connection to DataSource");
51. con.close();
52. }
53. }

主要下面这几行代码:

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1. // Leave the Connection open only if the DataSource is our
2. // special SmartDataSoruce and it wants the Connection left open.
3. if(!(dataSourceinstanceofSmartDataSource) || ((SmartDataSource) dataSource).shouldClose(con)) {
4. logger.debug("Returning JDBC Connection to DataSource");
5. con.close();
6. }

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