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疯狂 — Mon, 24 Dec 2012 07:16:00 GMT

摘要: 关于tomcat和sessionCookieName和SESSION_PARAMETER_NAME以及(qi��ng)disableURLRewriting参数原理和��?nbsp; 阅读全文

疯狂 2012-12-24 15:16 发表评论

疯狂 — Fri, 18 Nov 2011 03:25:00 GMT

如果单独使用hibernate可参考上一��文�?a href="http://www.tkk7.com/freeman1984/archive/2011/08/04/355808.html">http://www.tkk7.com/freeman1984/archive/2011/08/04/355808.html

首先hibernate的Connection release mode有以下几�U�：(x��)
1 after_statement 2 after_transaction 3 on_close 其中after_statement 用在jta�?�Q?span style="color: red">on_close �?.1之前遗留的（也许是�ؓ(f��)spring留的-_-�Q�，也就�?.1之前默认是on_close �Q�但3.1之后默认如果单独使用hibernate是after_transaction�Q?/strong>如果有第三方事务��理�Q�就用第三方提供的默认��|��spring��是默认使用�?ji��n)on_close�?br />在spring��理事务中我们看看系�l�启动后默认使用的配�|�：(x��)
1,ransaction strategy: org.springframework.orm.hibernate3.SpringTransactionFactory使用spring事务�{�略
2�Q�hibernate内部 Automatic session close at end of transaction: disabled 因�ؓ(f��)已经交给spring�?br />3   Connection release mode: auto 默认�Q�也��是没有配置hibernate.connection.release_mode的时候，但是�q�里有地斚w��要注意：(x��)也就是前面提到的使用�W�三方策略时的问题：(x��)看一下代码：(x��)
String releaseModeName = PropertiesHelper.getString( Environment.RELEASE_CONNECTIONS, properties, "auto" );
        log.info( "Connection release mode: " + releaseModeName );
        ConnectionReleaseMode releaseMode;
        if ( "auto".equals(releaseModeName) ) {
            releaseMode = transactionFactory.getDefaultReleaseMode();        }

        else {
            releaseMode = ConnectionReleaseMode.parse( releaseModeName );
            if ( releaseMode == ConnectionReleaseMode.AFTER_STATEMENT && !connections.supportsAggressiveRelease() ) {
                log.warn( "Overriding release mode as connection provider does not support 'after_statement'" );
                releaseMode = ConnectionReleaseMode.AFTER_TRANSACTION;
            }
        }
其中�U�色部分��是调用�?ji��n)spring提供的默认��|��而spring的默认��|��(x��)在jta和cmt中都默认使用的是after_statement

/** *//**
     * Sets connection release mode "on_close" as default.
     *
This was the case for Hibernate 3.0; Hibernate 3.1 changed
     * it to "auto" (i.e. "after_statement" or "after_transaction").
     * However, for Spring's resource management (in particular for
     * HibernateTransactionManager), "on_close" is the better default.
     */
    public ConnectionReleaseMode getDefaultReleaseMode() {
        return ConnectionReleaseMode.ON_CLOSE;
    }

而spring��Z��么要使用on_close �Q�而不是用after_transaction ,我们��x��opensessioninview的原理也许能明白�Q�session在view成还要��用，所以不能再transaction使用完后关闭JDBC connection�Q�必��要在session之后�Q�所以要使用on_close�Q?/span>也就是在on session(flush.auto�Q�或者f(xi��)lush.Eagerly) 关闭�Q�。这�U�情况hibernate内部�q�会(x��)在spring关闭JDBC connection后提�C?费解�Q�因为after transaction之后session没有关闭�Q�但�?nbsp;Connection release mode配置的是on_close,session的关闭和 Connection 的关闭都由spring来管理，hibernate��׃��知道�?�Q�所以hibernate有好的提�C�如�?其实session�Q�已�l�关闭。当焉��着session的关闭jdbc链接释放回连接池)�Q?/span>
transaction completed on session with on_close connection release mode; be sure to close the session to release JDBC resources!�Q?br />
。当然我们也可以使用after_transaction �Q�这�U�情况对使用�~�程式事务非帔R��用�?br />

疯狂 2011-11-18 11:25 发表评论

疯狂 — Tue, 25 Oct 2011 02:59:00 GMT
看spring的queryForObject(如果查询�l�果条数�?或者大�?)都会(x��)�q�回异常�Q�我们希望没查到�q�回null�Q�这��h��们就可以�l�用��h��C�没有找刎ͼ�要不我们的每个queryforObject�Q�queryForInt...�{�等�Ҏ(gu��)��都需要手动拦截这个异常来判断为空�Q�才能做出判断�?br />先看下spring的这�D�|��码：(x��)
public <T> T queryForObject(String sql, Object[] args, RowMapper<T> rowMapper) throws DataAccessException {
  List<T> results = query(sql, args, new RowMapperResultSetExtractor<T>(rowMapper, 1));
  return DataAccessUtils.requiredSingleResult(results);
}
public static <T> T requiredSingleResult(Collection<T> results) throws IncorrectResultSizeDataAccessException {
  int size = (results != null ? results.size() : 0);
  if (size == 0) {//记录为o�q�回异常
   throw new EmptyResultDataAccessException(1);//此异常��承自IncorrectResultSizeDataAccessException
  }
  if (results.size() > 1) {有多条记录返回异�?br />   throw new IncorrectResultSizeDataAccessException(1, size);
  }
  return results.iterator().next();
}

下面是我的一个方法，其他的方法请大家补充�Q?br />写一个接口定义规则：(x��)
public interface JdbcTemplateCallBack<T> {
    public  T querys(JdbcTemplate jdbcTemplate);
}
然后是BaseDao的通用的方法：(x��)

/** *//**
     * 可以用于处理查询queryfor 为空或者多条的时候返回异常的情况�Q�现在返回null,主要是拦截IncorrectResultSizeDataAccessException异常,以及(qi��ng)子类
     * @param jdbcTemplateCallBack
     * @return
     * @throws DaoException
     */
    public <T> T queryNullAble(JdbcTemplateCallBack<T> jdbcTemplateCallBack) throws DaoException {
        try {
            return jdbcTemplateCallBack.querys(getJdbcTemplate());
        } catch (Exception e) {
                if((e instanceof IncorrectResultSizeDataAccessException)
                        &&((IncorrectResultSizeDataAccessException)e).getActualSize()==0)
                    return null;
            //其他的异常正常抛�?/span>
            throw new DaoException(e);
        }
    }

最后是调用实例�Q�根据id查用��P��(j��)�Q?br />
public SUser getUserByColunm(final String columnName, final Object value) throws DaoException {
        return queryNullAble(new JdbcTemplateCallBack<SUser>() {
            public SUser querys(JdbcTemplate jdbcTemplate) {
                return jdbcTemplate.queryForObject("select *  from suser where "+columnName+"=?", new BeanPropertyRowMapper(SUser.class),value);
            }
        });
    }

具体的工�E�可以在http://www.tkk7.com/freeman1984/archive/2011/10/24/361899.html里面下蝲�?br />

疯狂 2011-10-25 10:59 发表评论

xsocket源码解读

疯狂 — Wed, 19 Oct 2011 09:34:00 GMT
     摘要: xsocket源码解读  阅读全文

疯狂 2011-10-19 17:34 发表评论

android Tabhost部�g

疯狂 — Wed, 18 Nov 2009 07:44:00 GMT
     摘要: �l�合源代码和实例来说明TabHost的用法�?实例代码下蝲�?nbsp; 阅读全文

疯狂 2009-11-18 15:44 发表评论