【mybatis-session包】

• 目录
• • 概 述
• 小结
• 参考资料和推荐阅读

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mybatis提供session 包，是整个mybatis应用的对外接口包。

public interface SqlSession extends Closeable {

  
   T selectOne(String statement);

  
   T selectOne(String statement, Object parameter);

  
   List selectList(String statement);

  
   List selectList(String statement, Object parameter);

  
   List selectList(String statement, Object parameter, RowBounds rowBounds);

  
   Map selectMap(String statement, String mapKey);

  
   Map selectMap(String statement, Object parameter, Str

而SqlSession对象是由SqlSessionFactory生产出来的。

  SqlSession openSession();

  SqlSession openSession(boolean autoCommit);

  SqlSession openSession(Connection connection);

  SqlSession openSession(TransactionIsolationLevel level);

  SqlSession openSession(ExecutorType execType);

  SqlSession openSession(ExecutorType execType, boolean autoCommit);

  SqlSession openSession(ExecutorType execType, TransactionIsolationLevel level);

  SqlSession openSession(ExecutorType execType, Connection connection);

SqlSessionFactory又是由SqlSessionFactoryBuilder创建的。

 public SqlSessionFactory build(Reader reader) {
    return build(reader, null, null);
  }

  public SqlSessionFactory build(Reader reader, String environment) {
    return build(reader, environment, null);
  }

  public SqlSessionFactory build(Reader reader, Properties properties) {
    return build(reader, null, properties);
  }

  public SqlSessionFactory build(Reader reader, String environment, Properties properties) {
    try {
      XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties);
      return build(parser.parse());
    } catch (Exception e) {
      throw ExceptionFactory.wrapException("Error building SqlSession.", e);
    } finally {
      ErrorContext.instance().reset();
      try {
        reader.close();
      } catch (IOException e) {
        // Intentionally ignore. Prefer previous error.
      }
    }
  }

  public SqlSessionFactory build(InputStream inputStream) {
    return build(inputStream, null, null);
  }

  public SqlSessionFactory build(InputStream inputStream, String environment) {
    return build(inputStream, environment, null);
  }

  public SqlSessionFactory build(InputStream inputStream, Properties properties) {
    return build(inputStream, null, properties);
  }

  public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) {
    try {
      XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
      return build(parser.parse());
    } catch (Exception e) {
      throw ExceptionFactory.wrapException("Error building SqlSession.", e);
    } finally {
      ErrorContext.instance().reset();
      try {
        inputStream.close();
      } catch (IOException e) {
        // Intentionally ignore. Prefer previous error.
      }
    }
  }

通过配置生成对应的sqlsession.
这里还有一个DefaultSqlSession,和DefaultSqlSessionFactory：

有openSession 获取对应的实例：

  private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
    Transaction tx = null;
    try {
      final Environment environment = configuration.getEnvironment();
      final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
      tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
      final Executor executor = configuration.newExecutor(tx, execType);
      return new DefaultSqlSession(configuration, executor, autoCommit);
    } catch (Exception e) {
      closeTransaction(tx); // may have fetched a connection so lets call close()
      throw ExceptionFactory.wrapException("Error opening session.  Cause: " + e, e);
    } finally {
      ErrorContext.instance().reset();
    }
  }

SqlSessionManager
这里主要实现了SqlSessionManager的管理，

 private final SqlSessionFactory sqlSessionFactory;
  private final SqlSession sqlSessionProxy;

  private final ThreadLocal localSqlSession = new ThreadLocal<>();

  private SqlSessionManager(SqlSessionFactory sqlSessionFactory) {
    this.sqlSessionFactory = sqlSessionFactory;
    this.sqlSessionProxy = (SqlSession) Proxy.newProxyInstance(
        SqlSessionFactory.class.getClassLoader(),
        new Class[]{SqlSession.class},
        new SqlSessionInterceptor());
  }

  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));
  }

这里的实物级别一共4类：

 NONE(Connection.TRANSACTION_NONE),
  READ_COMMITTED(Connection.TRANSACTION_READ_COMMITTED),
  READ_UNCOMMITTED(Connection.TRANSACTION_READ_UNCOMMITTED),
  REPEATABLE_READ(Connection.TRANSACTION_REPEATABLE_READ),
  SERIALIZABLE(Connection.TRANSACTION_SERIALIZABLE);

我们做个测试：

@Test
  void shouldCommitInsertedAuthor() {
    try {
      manager.startManagedSession();
      AuthorMapper mapper = manager.getMapper(AuthorMapper.class);
      Author expected = new Author(500, "cbegin", "******", "cbegin@somewhere.com", "Something...", null);
      mapper.insertAuthor(expected);
      manager.commit();
      Author actual = mapper.selectAuthor(500);
      assertNotNull(actual);
    } finally {
      manager.close();
    }
  }

测试通过：

mybatis-session包简单分析：

1.链接: link