SpringBoot+Mybatis实现关联查询

　　　　　　　　　　　　　　　　　　SpringBoot+Mybatis实现关联查询

　　今天学习了下Mybatis的动态查询，然后接着上次的Demo改造了下实现表的关联查询。

　　话不多说，开始今天的小Demo

　　首先接着上次的项目 https://www.cnblogs.com/Leslie-/p/9469045.html

　　然后呢我们在数据库中创建新的两张表

　　如下图所示：

　　然后呢，关联查询当然要在User表里面添加新的属性

　　接下来在项目中添加Car的实体类以及address的实体类

package com.example.demo.entity;

/**
 * author:lrh
 * Date:2018/8/15
 * Time:14:08
 */
public class Address {
    private Integer id;

    private String address;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

package com.example.demo.entity;

/**
 * author:lrh
 * Date:2018/8/15
 * Time:14:23
 */
public class Car {

    private Integer id;

    private String color;

    private String car;

    private Integer userid;


    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

    public String getCar() {
        return car;
    }

    public void setCar(String car) {
        this.car = car;
    }

    public Integer getUserid() {
        return userid;
    }

    public void setUserid(Integer userid) {
        this.userid = userid;
    }
}

　　还有就是得添加下User实体类的属性

添加如下：

创建CarMapper和AddressMapper

　　再CarMapper里面添加selectAllCar的方法以及注解

@Repository
@Mapper
public interface CarMapper {
    @Select("SELECT * FROM car WHERE userid = #{userid}")
    public List<Car> selectAllCar();
}

　　AddressMapper里面添加select的方法以及注解

@Repository
@Mapper
public interface AddressMapper {
    @Select("SELECT * FROM address WHERE id = #{id}")
    public Address selectByID(Integer id);
}

　　最后再UserMapper里面调用，在下比较懒就懒得新写了，直接在原先的selectByPrimaryKey方法上面加了。。

   @Select("SELECT * FROM user WHERE id = #{id}")
    @Results({
            @Result(property = "address" ,column = "addressid",
                            one = @One(select = "com.example.demo.dao.AddressMapper.selectByID")),
            @Result(property = "cars" ,column = "id",
                            many = @Many(select = "com.example.demo.dao.CarMapper.selectAllCar"))

            //column代表将该属性作为参数传入,property代表将查询出来的数据交给该属性
    })
    User selectByPrimaryKey(Integer id);

最后启动DemoAppliction

嗯。。大功告成。。告辞告辞

SpringBoot+Mybatis实现关联查询

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