mabatis-关联关系

关联关系

• 一对一
• 一对多(一对多)(重点)
• 多对多

查询

添加(需要事务)

说明

保存跟我们单表保存是一样的,如果非要一次保存两个表的数据,需要在业务处理,需要开始事务

级联添加

mapper.xml

• 注意要返回主表的主键值

主表

  <insert id="insert" keyProperty="product.pid" useGeneratedKeys="true">
        INSERT INTO product (name, price)
        VALUES (#{product.name}, #{product.price})
    </insert>

从表

<insert id="insert">
    INSERT INTO product_detail(ex, pid)
    VALUES (#{pd.ex}, #{pd.pid});
</insert>

Mapper接口

public interface ProductDetailMapper {
    int insert(@Param("pd") ProductDetail productDetail);
}

public interface ProductMapper {
    int insert(@Param("product") Product product);
}

Service

@Service
public class IndexServiceImpl implements IndexService {
    @Resource
    ProductMapper productMapper;
    @Resource
    ProductDetailMapper productDetailMapper;

    @Override
    public int saveProduct(Product product) {
        int insert = productMapper.insert(product);
        ProductDetail productDetail = product.getProductDetail();
        productDetail.setPid(product.getPid());
        int insert1 = productDetailMapper.insert(productDetail);
        return 0;
    }
}

测试代码

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration({"classpath:spring-context.xml", "classpath:spring-mybatis.xml"})
public class IndexServiceImplTest {
    @Resource
    IndexService indexService;

    @Test
    public void saveProduct() {
        Product product = new Product();
        product.setName("手机");
        product.setPrice(new BigDecimal("9999.00"));

        ProductDetail productDetail = new ProductDetail();
        productDetail.setEx("测试数据");
        product.setProductDetail(productDetail);

        indexService.saveProduct(product);

    }
}

一对多

分类跟商品 , 一级菜单跟二级菜单

级联保存

对象模型

@Data
public class Category {
    private Integer cateId;
    private String cateName;
    private List<Product> products;
}

@Data
public class Product {
    private Integer pid;

    private String name;

    private BigDecimal price;

    private ProductDetail productDetail;
}

关系模型(外键字段)

CREATE TABLE category
(
    cate_id   int AUTO_INCREMENT PRIMARY KEY,
    cate_name varchar(128) NOT NULL UNIQUE
)

CREATE TABLE product
(
    pid     int AUTO_INCREMENT
        PRIMARY KEY,
    name    varchar(128) NOT NULL,
    price   decimal      NOT NULL,
    cate_id int          null,
    CONSTRAINT name UNIQUE (name),
    CONSTRAINT fk_product_cateid FOREIGN KEY (cate_id) REFERENCES category (cate_id)
);

Mapper接口

public interface CateMapper {
    int insert(@Param("cate") Category category);
}

public interface ProductMapper {
    int insert(@Param("product") Product product);
}

Mapper.xml

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.smart.ssm.mapper.CateMapper">
    <resultMap id="BaseResultMaper" type="Category">
        <id column="cate_id" property="cateId"/>
        <result column="cate_name" property="cateName"/>
    </resultMap>
    <insert id="insert" keyProperty="cate.cateId" useGeneratedKeys="true">
        INSERT INTO category(cate_name)
        VALUES (#{cate.cateName})
    </insert>
</mapper>

<?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">
<mapper namespace="com.smart.ssm.mapper.ProductMapper">
    <resultMap id="BaseResultMap" type="com.smart.ssm.entity.Product">
        <id column="pid" jdbcType="INTEGER" property="pid"/>
        <result column="name" jdbcType="VARCHAR" property="name"/>
        <result column="price" jdbcType="DECIMAL" property="price"/>
        <result property="cateId" column="cate_id"/>
    </resultMap>
    <insert id="insert">
        INSERT INTO product(name, price, cate_id)
        VALUES (#{product.name}, #{product.price}, #{product.cateId})
    </insert>
</mapper>

Service层

@Service
public class IndexServiceImpl implements IndexService {
    @Resource
    CateMapper cateMapper;
    @Resource
    ProductMapper productMapper;
    /**
     * @param category
     * @return
     */
    @Override
    public int saveCate(Category category) {
        int insert = cateMapper.insert(category);
        List<Product> products = category.getProducts();
        for (Product product : products) {
           // 设置关联的外键字段的值  脏数据
            product.setCateId(category.getCateId());
            productMapper.insert(product);
        }
        return insert;
    }
}

测试代码

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration({"classpath:spring-context.xml", "classpath:spring-mybatis.xml"})
public class IndexServiceImplTest {
    @Resource
    IndexService indexService;
    
    @Test
    public void saveCate() {
        Category category = new Category();
        category.setCateName("电脑");
        List<Product> productList = new ArrayList<>();
        category.setProducts(productList);
        for (int i = 0; i < 10; i++) {
            Product product = new Product();
            product.setCateId(category.getCateId());
            product.setPrice(new BigDecimal("999.00"));
            product.setName("test电脑" + i);
            productList.add(product);
        }
        indexService.saveCate(category);
    }
}

级联查询

多表查询

核心点 : 子元素collection

一次性查询所有的数据保存子表的数据

mapper接口

public interface CateMapper {
    List<Category> selectAll();
}

mapper.xml

主表

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.smart.ssm.mapper.CateMapper">
    <resultMap id="BaseResultMap" type="Category">
        <id column="cate_id" property="cateId"/>
        <result column="cate_name" property="cateName"/>
    </resultMap>

    <resultMap id="collectionResultMap" type="Category" extends="BaseResultMap">
        <!--        一对一  以及多对多-->
        <collection property="products" resultMap="com.smart.ssm.mapper.ProductMapper.BaseResultMap"/>
    </resultMap>
    <select id="selectAll" resultMap="collectionResultMap">
        SELECT *
        FROM category c
                 LEFT JOIN product p ON c.cate_id = p.cate_id
    </select>
</mapper>

<?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">
<mapper namespace="com.smart.ssm.mapper.ProductMapper">
    <resultMap id="BaseResultMap" type="com.smart.ssm.entity.Product">
        <id column="pid" jdbcType="INTEGER" property="pid"/>
        <result column="name" jdbcType="VARCHAR" property="name"/>
        <result column="price" jdbcType="DECIMAL" property="price"/>
        <result property="cateId" column="cate_id"/>
    </resultMap>
</mapper>

Service层

@Service
public class IndexServiceImpl implements IndexService {
    @Resource
    CateMapper cateMapper;
    
    public List<Category> getCategoryData() {
        List<Category> categories = cateMapper.selectAll();
        return categories;
    }
}

测试代码

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration({"classpath:spring-context.xml", "classpath:spring-mybatis.xml"})
public class IndexServiceImplTest {
    @Resource
    IndexService indexService;

    @Test
    public void getCategoryData() {
        List<Category> categoryData = indexService.getCategoryData();
        System.out.println(categoryData);
    }
}

注意事项:

性能问题: 一定要注意关联的子数据不能太多

级联修改

在开发中,一般只需要修改主表的状态字段

多对多

开发中能不用就不要使用多对多,因为性能很差

注意: 凡是建立多对多的关系需要第三张表

角色表--- 权限表

语法格式

select   * 
from  表1  left join 第三张表  on  条件   left join 表2  on 条件

关系模型

role(角色表)

CREATE TABLE role
(
    role_id   int AUTO_INCREMENT PRIMARY KEY,
    role_name varchar(64) NOT NULL UNIQUE COMMENT 'admin   user  guest'
)

权限表

CREATE TABLE privilege
(
    privilege_id int AUTO_INCREMENT PRIMARY KEY,
    name         varchar(64) COMMENT '增  删  改 差'
)

第三种表

• 关联权限表的主键
• 关联角色表的主键

CREATE TABLE t_role_privilege
(
    id           int AUTO_INCREMENT PRIMARY KEY,
    privilege_id int NOT NULL REFERENCES privilege (privilege_id),
    role_id      int NOT NULL REFERENCES role (role_id)
)

对象模型

@Data
public class Privilege {
    private Integer privilegeId;
    private String privilegeName;
    private List<Role> roleList;
}

@Data
public class Role {
    private Integer roleId;
    private String roleName;
    private List<Privilege> privilegeList;
}

Mapper.xml

权限

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.smart.ssm.mapper.PrivilegeMapper">
    <resultMap id="BaseResultMap" type="Privilege">
        <id property="privilegeId" column="privilege_id"/>
        <result property="privilegeName" column="name"/>
    </resultMap>
    <resultMap id="collectionResultMap" type="Privilege" extends="BaseResultMap">
        <collection property="roleList" resultMap="com.smart.ssm.mapper.RoleMapper.BaseResultMap"/>
    </resultMap>

    <select id="selectById" resultMap="collectionResultMap">
        SELECT *
        FROM privilege p
                 LEFT JOIN t_role_privilege trp ON p.privilege_id = trp.privilege_id
                 LEFT JOIN role r ON r.role_id = trp.role_id
        WHERE p.privilege_id = #{pid}
    </select>
</mapper>

角色

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.smart.ssm.mapper.RoleMapper">
    <resultMap id="BaseResultMap" type="Role">
        <id property="roleId" column="role_id"/>
        <result property="roleName" column="role_name"/>
    </resultMap>

    <select id="selectById" resultType="com.smart.ssm.entity.Role">
    </select>
</mapper>

Mapper接口

权限

public interface PrivilegeMapper {
    Privilege selectById(@Param("pid") int pid);
}

角色

Service层

@Service
public class AccountServiceImpl implements AccountService {
    @Resource
    PrivilegeMapper privilegeMapper;

    @Override
    public Privilege findById(int pid) {
        Privilege privilege = privilegeMapper.selectById(pid);
        return privilege;
    }
}

测试代码

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration({"classpath:spring-context.xml", "classpath:spring-mybatis.xml"})
public class AccountServiceTest {
    @Resource
    AccountService accountService;

    @Test
    public void findById() {
        Privilege privilege = accountService.findById(2);
        System.out.println(privilege.getPrivilegeName());
        System.out.println(privilege.getRoleList());
    }
}