关于mybatis里面的Executor–转载

原文地址：http://blog.csdn.net/w_intercool/article/details/7893344

使用mybatis查寻数据，跟踪其执行流程

最开始执行的语句

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这里需要找到sqlsession是从哪里来的

getSqlSession是SqlSessionDaoSupport类里面的方法，该类通过spring的自动注入可以把sqlSessionTemplate注入进来，当然这里的sqlSessionTemplate是需要spring配置的

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@Autowired(required = false)是通过类型匹配来注入的，如果没有找到相应对，就不用注入

所以selectList方法为SqlSessionTemlate里面的，再看SqlSessionTemplage，里面的都是通过sqlSessionProxy来执行selectList方法的，也就是通过代理方式来的

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1. PersistenceExceptionTranslatorexceptionTranslator){
3. notNull(sqlSessionFactory,
13. }

这里用到了java的动态代理，详细可以见java api，有详细的说明

SqlSessionInterceptor实现了InvocationHandler，在invoke方法里面的开始有这样代码，那里是真正的sqlsession

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1. SqlSessionTemplate.
3. SqlSessionTemplate.

跟踪geteSqlSession可以找到他的创建来源，见

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继续跟踪可以找到DefaultSqlSessionFactory里面的该方法

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1. Transactiontx=
5. tx=transactionFactory.newTransaction(environment.getDataSource(),level,autoCommit);
9. closeTransaction(tx);
11. }
13. }

通过

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你就知道executor是怎么回来的了

mybatis默认使用了cache，在创建exector时，外面就包了一层CacheExecutor，详细见

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1. executorType=executorType==
3. Executorexecutor;
5. executor=
7. executor=
9. executor=
13. }

CachingExecutor可以使mybatis先从缓存中提取数据，数据缓存中没有数据时才从数据库里面提取数据。