Mybatis SqlSessionManager

SqlSessionManager 实现了SqlSessionFactory和SqlSession，

 private final SqlSessionFactory sqlSessionFactory;//session工厂类
  private final SqlSession sqlSessionProxy;//session 代理

  private final ThreadLocal localSqlSession = new ThreadLocal();//当前线程session

  private SqlSessionManager(SqlSessionFactory sqlSessionFactory) {
    this.sqlSessionFactory = sqlSessionFactory;
    this.sqlSessionProxy = (SqlSession) Proxy.newProxyInstance(
        SqlSessionFactory.class.getClassLoader(),
        new Class[]{SqlSession.class},
        new SqlSessionInterceptor());
  }//通过jdk代理模式获取session代理

以下是读取配置文件然后生成SqlSessionManager

public static SqlSessionManager newInstance(Reader reader) {
    return new SqlSessionManager(new SqlSessionFactoryBuilder().build(reader, null, null));
  }

  public static SqlSessionManager newInstance(Reader reader, String environment) {
    return new SqlSessionManager(new SqlSessionFactoryBuilder().build(reader, environment, null));
  }

  public static SqlSessionManager newInstance(Reader reader, Properties properties) {
    return new SqlSessionManager(new SqlSessionFactoryBuilder().build(reader, null, properties));
  }

  public static SqlSessionManager newInstance(InputStream inputStream) {
    return new SqlSessionManager(new SqlSessionFactoryBuilder().build(inputStream, null, null));
  }

  public static SqlSessionManager newInstance(InputStream inputStream, String environment) {
    return new SqlSessionManager(new SqlSessionFactoryBuilder().build(inputStream, environment, null));
  }

  public static SqlSessionManager newInstance(InputStream inputStream, Properties properties) {
    return new SqlSessionManager(new SqlSessionFactoryBuilder().build(inputStream, null, properties));
  }

以下通过SqlSessionFactory 来生成SqlSessionManager 。（个人认为这个是集成springboot 等的入口，后续待验证）

public static SqlSessionManager newInstance(SqlSessionFactory sqlSessionFactory) {
    return new SqlSessionManager(sqlSessionFactory);
  }

通过本线程获取connection

 public Connection getConnection() {
    final SqlSession sqlSession = localSqlSession.get();
    if (sqlSession == null) {
      throw new SqlSessionException("Error:  Cannot get connection.  No managed session is started.");
    }
    return sqlSession.getConnection();
  }

代理的处理类

private class SqlSessionInterceptor implements InvocationHandler {
    public SqlSessionInterceptor() {
        // Prevent Synthetic Access
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
      final SqlSession sqlSession = SqlSessionManager.this.localSqlSession.get();
      if (sqlSession != null) {
        try {
          return method.invoke(sqlSession, args);
        } catch (Throwable t) {
          throw ExceptionUtil.unwrapThrowable(t);
        }
      } else {
        final SqlSession autoSqlSession = openSession();
        try {
          final Object result = method.invoke(autoSqlSession, args);
          autoSqlSession.commit();
          return result;
        } catch (Throwable t) {
          autoSqlSession.rollback();
          throw ExceptionUtil.unwrapThrowable(t);
        } finally {
          autoSqlSession.close();
        }
      }
    }
  }