mybatis关联查询+模糊查询(两表关联一对多+一对一)

通过顾客-订单关系来表示关联查询

1.建表

（1）tbl_customer表

(2)tbl_order表

其中customer_id为外键与tbl_customer表的id相关联

2.创建实体类

(1)Customer.java

package com.gem.entity;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.List;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Customer {

    private Long id;
    private String name;
    private String phone;

/**   关联(一对多)*/
    private List<Order> orders;

}

(2)order.java

package com.gem.entity;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.Date;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Order {

    private Long id;
    private String no;
    private Date createdate;
    private Double price;

    //多对一
    private Customer customer;

}

3.创建映射文件

CustomerMapper.java

package com.gem.mapper;

import com.gem.entity.Customer;
import com.gem.entity.Order;
import org.apache.ibatis.annotations.Param;

import java.util.List;

public interface CustomerMapper {

    /**
     * 关联查询
     * 根据用户姓名(模糊)查询用户信息，如果该用户有订单，则级联查询出他所有的
     */
    List<Customer> selectCustomerAndOrderByName(String name);

    /**
     * 关联查询
     * 根据订单价格范围，查询该订单,并且级联查询出该所属客户
     */
    List<Order> selectOrderAndCustomerByPrice(@Param("min") Double min,@Param("max") Double max);


    /**
     * 关联查询
     * 查询用户信息，如果该用户有订单，则级联查询出他所有的订单信息(订单信息延迟加载)
     */
    List<Customer> selectCustomerAndOrder();


}

4.创建xml文件

CustomerMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--命名空间必须与对应的Mapper接口保持一致-->
<mapper namespace="com.gem.mapper.CustomerMapper">

    <select id="selectCustomerAndOrderByName" parameterType="String" resultMap="customerAndOrderMap">
        select c.id cid,c.name,c.phone,o.id oid,o.no,o.createdate,o.price from tbl_customer c left join tbl_order o
        on o.customer_id=c.id where c.name like "%"#{name}"%"
    </select>

<!--    定义ResultMap,作用是用来封装结果集-->
    <resultMap id="customerAndOrderMap" type="customer">
        <id column="cid" property="id" />
        <result column="name" property="name"/>
        <result column="phone" property="phone"/>
<!--        一个顾客对应多个订单信息-->
        <collection property="orders" ofType="order">
            <id column="oid" property="id"/>
            <result column="no" property="no"/>
            <result column="createdate" property="createdate"/>
            <result column="price" property="price"/>
        </collection>
    </resultMap>


<!--    根据订单价格范围，查询该订单,并且级联查询出该所属客户-->
    <select id="selectOrderAndCustomerByPrice" parameterType="Double" resultMap="orderAndcustomerMap">
        select o.*,c.id cid,c.name,c.phone from tbl_order o join tbl_customer c
        on o.customer_id=c.id where o.price between #{min} and #{max}
    </select>

    <!--    定义ResultMap,作用是用来封装结果集-->
<!--    resultMap可以通过extends来己成，实现复用-->
    <resultMap id="orderAndcustomerMap" type="order">
        <id column="id" property="id"/>
        <result column="no" property="no"/>
        <result column="createdate" property="createdate"/>
        <result column="price" property="price"/>
<!--        一个订单只对应一个顾客-->
        <association property="customer" javaType="customer">
            <id column="cid" property="id" />
            <result column="name" property="name"/>
            <result column="phone" property="phone"/>
        </association>
    </resultMap>
</mapper>

5.生成测试类

CustomerMapperTest.java

package com.gem.mapper;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;

import static org.junit.Assert.*;

public class CustomerMapperTest {

    SqlSession sqlSession;
    CustomerMapper customerMapper;

    @Before
    public void setUp() throws IOException {
        //加载mybatis配置文件
        InputStream in = Resources.getResourceAsStream("mybatis.xml");
        //获取SqlSessionFactory连接工厂
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        //获取连接
        sqlSession = sqlSessionFactory.openSession(true);
        //获取mapper代理对象
        customerMapper = sqlSession.getMapper(CustomerMapper.class);
    }

    @After
    public void tearDown() {
        if (sqlSession != null) {
            sqlSession.close();
        }
    }

    @Test
    public void selectCustomerAndOrderByName() {

        customerMapper.selectCustomerAndOrderByName("a").forEach(System.out::println);
    }

    @Test
    public void selectCustomerByOrderPrice() {

        customerMapper.selectOrderAndCustomerByPrice(1000.00,2000.00).forEach(System.out::println);
    }



}

 下面是项目文件