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：