讀mybatis源碼之十四：mybatis事務處理

1、自身事務處理

public void doxxxxx(){
 TransactionFactory transactionFactory = new JdbcTransactionFactory();
 userMapper userDao=getSession().getMapper(UserMapper.class);
 Transaction newTransaction=transactionFactory.newTransaction(getSession().getConnection());
 try {
  userDao.insert(xxx);
  userDao.update(xxx);
 } catch (Exception e) {
  newTransaction.rollback();
  e.printStackTrace();
 } finally {
    newTransaction.close();
 }
}

可以看出主要是事務連接。

2、與spring集成後，事務處理

BlogMapper mapper = (BlogMapper)app.getBean("blogMapper");
    Blog sblog = new Blog();
    sblog.setId(2);
    sblog.setName("測試加密555");
    sblog.setAddr("測試加密--------------123444");
    mapper.insertBlogByObj(sblog);

這種數據能夠提交上去，爲什麼呢？ 看看與spring集成後它的處理方式

首先看如何得到mapper的，通過MapperFactoryBean的getObject（）    方法得到

  public T getObject() throws Exception {
    return getSqlSession().getMapper(this.mapperInterface);
  }

那getSqlSession()又是如何得到的呢？跟蹤是通過SqlSessionTemplate得到，SqlSessionTemplate裏面是什麼呢？

發現是一個sqlSessionProxy代理：

 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());
  }

具體看SqlSessionInterceptor，就可以看出爲什麼spring集成後，不顯示提交，也能自動提交了：

  private class SqlSessionInterceptor implements InvocationHandler {
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
      final 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) {
          Throwable translated = SqlSessionTemplate.this.exceptionTranslator.translateExceptionIfPossible((PersistenceException) unwrapped);
          if (translated != null) {
            unwrapped = translated;
          }
        }
        throw unwrapped;
      } finally {
        closeSqlSession(sqlSession, SqlSessionTemplate.this.sqlSessionFactory);
      }
    }
  }

  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);

        }

這部分重點，如果配置了事務，就由配置事務處理，沒有配置就直接提交，所以這裏相當於他幫你提交了。

closeSqlSession裏面也是一樣，如果有事務，是session釋放，如果沒有就是session關閉，跟蹤下去就是事務關閉，mybatis  spring結合后里面SpringManagedTransaction的close，用的DataSourceUtils的releaseConnection

  public void close() throws SQLException {

    releaseConnection(this.connection, this.dataSource);

  }