Spring Boot 整合JPA 数据模型关联使用操作(一对一、一对多、多对多)

    @Test
    public void testUserSave() {
        User defUser1 = UserMock.getDefUser1();
        UserCart defUserCart1 = UserCartMock.getDefUserCart1();
        defUser1.setUserCart(defUserCart1);
        defUserCart1.setUser(defUser1);
        // 此时保存用户，用户购物车应该也被保存
        userRepository.save(defUser1);
        List <UserCart> all = userCartRepository.findAll();
        Assert.assertNotNull(all);
        Assert.assertTrue(all.size() == 1);
    }

    @Test
    public void testUserCartDelete() {
        User defUser1 = UserMock.getDefUser1();
        UserCart defUserCart1 = UserCartMock.getDefUserCart1();
        defUser1.setUserCart(defUserCart1);
        // 此时保存用户，用户购物车应该也被保存
        userRepository.save(defUser1);
        // 此时删除用户购物车并不会删除用户
        userCartRepository.deleteAll();
        List <User> all1 = userRepository.findAll();
        Assert.assertNotNull(all1);
        Assert.assertTrue(all1.size() == 1);
    }

    @Test
    public void testUserDelete() {
        User defUser1 = UserMock.getDefUser1();
        UserCart defUserCart1 = UserCartMock.getDefUserCart1();
        defUser1.setUserCart(defUserCart1);
        // 此时保存用户，用户购物车应该也被保存
        userRepository.save(defUser1);
        // 此时删除用户购物车并不会删除用户
        userRepository.delete(defUser1);
        List <UserCart> all = userCartRepository.findAll();
        Assert.assertTrue(all.size() == 0);
    }

@Data
@Entity
@Table(name = "cascade_order")
public class Order {

    @Id
    @GeneratedValue
    private Long id;
    
    private String orderNo;
    
    private Integer count;
    
    private Double money;

    @OneToMany(mappedBy = "order",
            cascade = CascadeType.ALL,
            fetch = FetchType.EAGER)
    private List<OrderItem> orderItems;
    
    /**
    * 重写toString防止死循环
    * @return 
    */
    @Override 
    public String toString() {
        return "OrderItem{" + "id=" + id + ", productId='" + productId + '\'' + ", money=" + money
               + ", count=" + count + ", productName='" + productName + '\'' + ", order=" + order
               + '}';
    }
    
}

@Data
@Entity
@Table(name = "cascade_order_item")
public class OrderItem {

    @Id
    @GeneratedValue
    private Long id;

    private String productId;

    private Double money;
    
    private Integer count;
    
    private String productName;
    
    @ManyToOne(targetEntity = Order.class,
            cascade = {},
            fetch = FetchType.EAGER)
    @JoinColumn(
            // 设置在OrderItem表中的关联字段(外键)
            name="order_id"
    )
    // 防止json序列化死循环问题解决
    @JsonBackReference
    private Order order;
}

    @Test
    public void testOrder() {
        Order defOrder1 = OrderMock.getDefOrder1();
        List <OrderItem> allDefOrder = OrderItemMock.getAllDefOrder();
        // order 维持orderItem关系
        defOrder1.setOrderItems(allDefOrder);
        // orderItem维持order关系
        allDefOrder.forEach(o -> o.setOrder(defOrder1));
        Order save = orderRepository.save(defOrder1);
        List <OrderItem> all = orderItemRepository.findAll();
        Assert.assertTrue(all.size() == allDefOrder.size());

        orderItemRepository.delete(all.get(0));
        Order order = orderRepository.findById(save.getId()).get();
        Assert.assertNotNull(order);

        orderRepository.deleteById(order.getId());
        List <OrderItem> all1 = orderItemRepository.findAll();
        Assert.assertTrue(all1.size() == 0);

    }

@Data
@Entity
@Table(name = "cascade_user")
public class User {

    @Id
    @GeneratedValue
    private Long id;
    
    private String name;
    
    private Integer age;
    
    private Double point;

    @ManyToMany(targetEntity = UserTag.class,
            cascade = {},
            fetch = FetchType.LAZY)
    // 假如不定义，jpa会生成“表名1”+“_”+“表名2”的中间表
    @JoinTable(
            // 定义中间表的名称
            name = "cascade_user_tag_table",
            // 定义中间表中关联User表的外键名
            joinColumns = {
                    @JoinColumn(name = "user_id",
                            referencedColumnName = "id")
            },
            // 定义中间表中关联UserTag表的外键名
            inverseJoinColumns = {
                    @JoinColumn(name = "tags_id",
                            referencedColumnName = "id")
            }
    )
    private Set<UserTag> tags;

}

@Data
@Entity
@Table(name = "cascade_user_tag")
public class UserTag {

    @Id
    @GeneratedValue
    private Long id;
    
    private String tagName;

    @ManyToMany(mappedBy = "tags",
            cascade = {},
            fetch = FetchType.LAZY)
    private List<User> userList;
}

    @Test
    public void testUserTag() {
        User defUser1 = UserMock.getDefUser1();
        UserTag defTag1 = UserTagMock.getDefTag1();
        UserTag defTag2 = UserTagMock.getDefTag2();
        defUser1 = userRepository.save(defUser1);
        defTag1 = userTagRepository.save(defTag1);
        defTag2 = userTagRepository.save(defTag2);

        defUser1.getTags().add(defTag1);
        defUser1.getTags().add(defTag2);

        defUser1 = userRepository.save(defUser1);
        // 此时会报错，因为中间表关系为User维护
        try {
            userTagRepository.delete(defTag2);
        } catch (Exception e) {
            log.info(e.getCause().getMessage());
            Assert.assertTrue(e instanceof DataIntegrityViolationException);
        }
        // 修改User表中关系
        defUser1.setTags(new HashSet <>());
        defUser1.getTags().add(defTag1);
        defUser1 = userRepository.save(defUser1);
        // 此时可以删除
        userTagRepository.delete(defTag2);
        // 直接删除用户没问题
        userRepository.delete(defUser1);
    }