spring整合mybatis sqlSession释放问题

阳光穿透心脏的1/2处 2021-09-14 08:32 355阅读 0赞

[http://blog.csdn.net/u011686226/article/details/52704158][http_blog.csdn.net_u011686226_article_details_52704158]

MapperFactoryBean

![Center][]

MapperFactoryBean实现了FactoryBean，所以

MapperFactoryBean.getObject -> SqlSessionTemplate.getMapper() -> Configuration.getMapper() -> MapperRegistry.getMapper() ->

mapperProxyFactory.newInstance(sqlSession);

最后用jdk动态代理生成了代理类，代理的接口是MapperProxyFactory的mapperInterface（就是Mapper），InvocationHandler是MapperProxy。

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        if(Object.class.equals(method.getDeclaringClass())) {
            try {
                return method.invoke(this, args);
            } catch (Throwable var5) {
                throw ExceptionUtil.unwrapThrowable(var5);
            }
        } else {
            MapperMethod mapperMethod = this.cachedMapperMethod(method);
            return mapperMethod.execute(this.sqlSession, args);
        }
    }

invoke调用了sqlSession，这个sqlSession实际上是SqlSessionTemplate。这个template的构造函数

public SqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType,
        PersistenceExceptionTranslator exceptionTranslator) {
    
      notNull(sqlSessionFactory, "Property 'sqlSessionFactory' is required");
      notNull(executorType, "Property 'executorType' is required");
    
      this.sqlSessionFactory = sqlSessionFactory;
      this.executorType = executorType;
      this.exceptionTranslator = exceptionTranslator;
      this.sqlSessionProxy = (SqlSession) newProxyInstance(
          SqlSessionFactory.class.getClassLoader(),
          new Class[] { SqlSession.class },
          new SqlSessionInterceptor());
    }

也初始化了一个代理sqlSessionProxy ，每次查询或者删除都是使用这个代理类的方法

public <T> T selectOne(String statement) {
      return this.sqlSessionProxy.<T> selectOne(statement);
    }

这个代理类使用了SqlSessionInterceptor，SqlSessionInterceptor会尝试获取当前线程的sqlsession,如果没有就使用sqlsessionfactory创建。

private class SqlSessionInterceptor implements InvocationHandler {
      @Override
      public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        SqlSession sqlSession = getSqlSession(
            SqlSessionTemplate.this.sqlSessionFactory,
            SqlSessionTemplate.this.executorType,
            SqlSessionTemplate.this.exceptionTranslator);
        try {
          Object result = method.invoke(sqlSession, args);
          if (!isSqlSessionTransactional(sqlSession, SqlSessionTemplate.this.sqlSessionFactory)) {
            // force commit even on non-dirty sessions because some databases require
            // a commit/rollback before calling close()
            sqlSession.commit(true);
          }
          return result;
        } catch (Throwable t) {
          Throwable unwrapped = unwrapThrowable(t);
          if (SqlSessionTemplate.this.exceptionTranslator != null && unwrapped instanceof PersistenceException) {
            // release the connection to avoid a deadlock if the translator is no loaded. See issue #22
            closeSqlSession(sqlSession, SqlSessionTemplate.this.sqlSessionFactory);
            sqlSession = null;
            Throwable translated = SqlSessionTemplate.this.exceptionTranslator.translateExceptionIfPossible((PersistenceException) unwrapped);
            if (translated != null) {
              unwrapped = translated;
            }
          }
          throw unwrapped;
        } finally {
          if (sqlSession != null) {
            closeSqlSession(sqlSession, SqlSessionTemplate.this.sqlSessionFactory);
          }
        }
      }
    }

完成了每次请求sqlSession的获取和释放。

也就是我们写的dao最后一个代理，每次涉及数据库操作时会调用SqlSessionTemplate，SqlSessionTemplate也有一个代理类，在在代理类里面获取sqlsession，然后发生实际的操作。

http://www.cnblogs.com/daxin/p/3544188.html

http://ju.outofmemory.cn/entry/62780

http://fangjian0423.github.io/2014/09/06/MapperScannerConfigurer-analysis/

[http_blog.csdn.net_u011686226_article_details_52704158]: http://blog.csdn.net/u011686226/article/details/52704158
[Center]: /images/20210527/43cad8497f9f4696aa485e72866ba664.png