Mybatis进阶学习笔记——输出映射

输出映射（例如一个方法的返回至使用什么类型去接收）

1.基本类型

     <!-- 统计记录数 -->
     <select id="queryTotalCount" resultType="long">
         SELECT COUNT(*) FROM t_customer
     </select>

public Long queryTotalCount();

    /**
     * 输出映射
     */
    @Test
    public void test2() {
        SqlSession sqlSession = SessionUtils.getSession();
        // getMapper(): 返回指定接口的动态代理的实现类对象
        CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
        Long count = dao.queryTotalCount();
        System.out.println(count);
        sqlSession.commit();
        sqlSession.close();
    }

2.JavaBean类型（*常用类型）

     <select id="queryCustomer" parameterType="int" resultType="Customer">
         SELECT * FROM t_customer WHERE id=#{value}
     </select>

public Customer queryCustomer(Integer id);

     /**
      * 输出映射
      */
     @Test
     public void test2() {
         SqlSession sqlSession = SessionUtils.getSession();
         // getMapper(): 返回指定接口的动态代理的实现类对象
         CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
         Customer c = dao.queryCustomer(1);
         System.out.println(c);
         sqlSession.commit();
         sqlSession.close();
     }

3.ResultMap类型（用于解决表的字段名称和实体类的属性名称不一致的情况）

resultType使用要求：JavaBean中的属性名要和数据库字段名保持一致。

     <!-- 定义ResultMap -->
     <!--
         含义说明：
         type：我们需要封装成的实体类
         id：定义的名称，供下方代码使用
      -->
     <resultMap type="CustomerRM" id="customerResultMap">
         <!--
             id：映射主键
             column：数据库字段
             property：实体类中的命名
          -->
         <id column="id" property="custId"/>
         <result column="name" property="custName"/>
         <result column="gender" property="custGender"/>
         <result column="telephone" property="custTelephone"/>
     </resultMap>

     <select id="queryCustomerResultMap" parameterType="int" resultMap="customerResultMap">
     <!-- resultMap：方法的返回值类型，也就是上方定义的type="CustomerRM"中的CustomerRM对象 -->
         SELECT * FROM t_customer WHERE id=#{value}
     </select>

     /**
      * 输出映射
      */
     @Test
     public void test2() {
         SqlSession sqlSession = SessionUtils.getSession();
         // getMapper(): 返回指定接口的动态代理的实现类对象
         CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
         CustomerRM c =  dao.queryCustomerResultMap(1);
         System.out.println(c);
         sqlSession.commit();
         sqlSession.close();
     }

CustomerRM.java：

 package cn.sm1234.domain;

 public class CustomerRM {

     private Integer custId;
     private String custName;
     private String custGender;
     private String custTelephone;
     public Integer getCustId() {
         return custId;
     }
     public void setCustId(Integer custIid) {
         this.custId = custIid;
     }
     public String getCustName() {
         return custName;
     }
     public void setCustName(String custName) {
         this.custName = custName;
     }
     public String getCustGender() {
         return custGender;
     }
     public void setCustGender(String custGender) {
         this.custGender = custGender;
     }
     public String getCustTelephone() {
         return custTelephone;
     }
     public void setCustTelephone(String custTelephone) {
         this.custTelephone = custTelephone;
     }
     @Override
     public String toString() {
         return "CustomerRM [custId=" + custId + ", custName=" + custName + ", custGender=" + custGender
                 + ", custTelephone=" + custTelephone + "]";
     }

 }

数据库字段截图：