詳解MyBatis工作原理

 /**
     * 1、根據xml配置文件（全局配置文件mybatis-config.xml）創建一個SqlsessionFactory對象，mybatis-config.xml有數據源一些環境信息
     * 2、sql映射文件EmployeeMapper.xml配置瞭每一個sql，以及sql的封裝規則等。
     * 3、將sql映射文件註冊在全局配置文件中
     * 4、寫代碼：
     * 4.1.根據全局配置文件得到sqlsessionFactory
     * 4.2.使用SqlSession工程進行crud,sqlseesion就代表和數據庫進行會話，用完close
     * 4.3.使用sql標識告知mybatis來執行哪個sql,sql都是保存在sql映射文件中
     *
     * @throws IOException
     */
    @Test
    public void test() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        //2、獲取SqlSession實例，能直接執行已經映射瞭的sql語句，selectOne：sql唯一標識，執行sql要用到的參數
        SqlSession openSession = sqlSessionFactory.openSession();
        try {
            Employee employee = openSession.selectOne("com.ming.dao.EmployeeMapper.getEmpByID", 1);
            System.out.println(employee);
        } finally {
            openSession.close();
        }
    }

public Configuration parse() {
    if (parsed) {
      throw new BuilderException("Each XMLConfigBuilder can only be used once.");
    }
    parsed = true;
    parseConfiguration(parser.evalNode("/configuration"));
    return configuration;
  }

  @Test
    public void testInterface() throws IOException {
        SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
        SqlSession sqlSession = sqlSessionFactory.openSession();
        try {
            EmployeeMapper employeeMapper = sqlSession.getMapper(EmployeeMapper.class);
            Employee employee = employeeMapper.getEmpByID(1);
            System.out.println(employee);
            Employee employee2 = employeeMapper.getEmpByID(5);
            System.out.println(employee2);
            System.out.println(employee==employee2);

        }finally {
            sqlSession.close();
        }
    }

 StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameter, rowBounds, resultHandler, boundSql);
  public StatementHandler newStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, 	RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
    StatementHandler statementHandler = new RoutingStatementHandler(executor, mappedStatement, parameterObject, rowBounds, resultHandler, boundSql);
    statementHandler = (StatementHandler) interceptorChain.pluginAll(statementHandler);
    return statementHandler;
  }