這一篇部落格我們學習一下Mybatis呼叫儲存過程的使用和執行流程。首先我們先建立一個簡單的儲存過程

DELIMITER $
CREATE PROCEDURE mybatis.ges_user_count(IN age INT, OUT user_count INT)
BEGIN  
SELECT COUNT(*) FROM users WHERE users.age=age INTO user_count;
END 
$

接下來是儲存過程的呼叫，執行如下命令就可以完成儲存過程的呼叫。

接下來我們看看利用Mybatis是如何呼叫儲存過程的。

userMapper.xml新增儲存過程呼叫配置：

<select id="count" statementType="CALLABLE" parameterMap="getUserCountMap">
      CALL mybatis.ges_user_count(?,?)
</select>

public class Learn1Main {

	public static void main(String [] args){
		
		//mybatis的配置檔案
	    String resource = "learn/mybatis-config.xml";
	    //使用類載入器載入mybatis的配置檔案（它也載入關聯的對映檔案）
	    InputStream is = Learn1Main.class.getClassLoader().getResourceAsStream(resource);
	    //構建sqlSession的工廠
	    SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);
	    SqlSession session = sessionFactory.openSession();
	    Map<String, Integer> parameterMap = new HashMap<String, Integer>();
	    parameterMap.put("age", 12);
	    parameterMap.put("user_count", -1);
	    session.selectOne("com.tianjunwei.learn.learn1.entity.User.count", parameterMap);
	    Integer result = parameterMap.get("user_count");
	    System.out.println(result);
	    
	}
}
 

其最終的執行過程在DefaultResultSetHandler中，呼叫普通的sql和儲存過程之間還是有所區別的，Sql語句的執行是使用CallableStatement。

  //
  // HANDLE OUTPUT PARAMETER
  //
  //呼叫儲存過程返回結果，將結果值放在引數中
  @Override
  public void handleOutputParameters(CallableStatement cs) throws SQLException {
    final Object parameterObject = parameterHandler.getParameterObject();
    final MetaObject metaParam = configuration.newMetaObject(parameterObject);
    final List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
	//迴圈處理每個引數
    for (int i = 0; i < parameterMappings.size(); i++) {
      final ParameterMapping parameterMapping = parameterMappings.get(i);
	  //判斷引數的模式
      if (parameterMapping.getMode() == ParameterMode.OUT || parameterMapping.getMode() == ParameterMode.INOUT) {
        if (ResultSet.class.equals(parameterMapping.getJavaType())) {
          handleRefCursorOutputParameter((ResultSet) cs.getObject(i + 1), parameterMapping, metaParam);
        } else {
          final TypeHandler<?> typeHandler = parameterMapping.getTypeHandler();
          metaParam.setValue(parameterMapping.getProperty(), typeHandler.getResult(cs, i + 1));
        }
      }
    }
  }

  private void handleRefCursorOutputParameter(ResultSet rs, ParameterMapping parameterMapping, MetaObject metaParam) throws SQLException {
    try {
      final String resultMapId = parameterMapping.getResultMapId();
      final ResultMap resultMap = configuration.getResultMap(resultMapId);
      final DefaultResultHandler resultHandler = new DefaultResultHandler(objectFactory);
      final ResultSetWrapper rsw = new ResultSetWrapper(rs, configuration);
      handleRowValues(rsw, resultMap, resultHandler, new RowBounds(), null);
      metaParam.setValue(parameterMapping.getProperty(), resultHandler.getResultList());
    } finally {
      // issue #228 (close resultsets)
      closeResultSet(rs);
    }
  }