Jpa 对多对多实现、懒加载

梦里梦外; 2021-12-16 02:17 297阅读 0赞

### 参考：[https://www.jianshu.com/p/91d3096f38a0][https_www.jianshu.com_p_91d3096f38a0] ###

实体：Device  与 Group 是多对多的关系

Group 维护端：

@Data
    @Entity(name = "t_group")
    public class Group extends BaseEntity{
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private int id;
        @Column(name = "category_id",nullable = true)
        private int categoryId;
        //分组名
        private String name;
    
        @JsonIgnoreProperties(value = {"groupList"})
        @ManyToMany(fetch = FetchType.LAZY)
        @JoinTable(name = "t_group_device",joinColumns = @JoinColumn(name = "group_id"),
                inverseJoinColumns = @JoinColumn(name = "device_id"))
        private List<Device> deviceList;
    }

Device

@Data
    @Entity(name = "t_device")
    public class Device extends BaseEntity{
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private int id;
        //设备二级分类id
        @Column(nullable = true)
        private int categoryId;
        //设备源id
        @Column(nullable = true)
        private int sourceId;
        //设备名称
        private String name;
        //设备类型 1：实体设备  2：虚拟设备 3：系统设备
        @Column(nullable = true)
        private int type;
        //设备描述
        private String description;
        //设备实例化状态
        @Column(nullable = true)
        private int status;
    
        @JsonIgnoreProperties(value = {"deviceList"})
        @ManyToMany(mappedBy = "deviceList",fetch = FetchType.LAZY)
        private List<Group> groupList;
    
    }

发现懒加载无法生效：

1.添加依赖：

<dependency>
                <groupId>com.fasterxml.jackson.datatype</groupId>
                <artifactId>jackson-datatype-hibernate5</artifactId>
                <version>2.9.8</version>
    
     </dependency>

2.yml 配置

spring:
        jpa:
            properties:
                hibernate:
                      enable_lazy_load_no_trans: true

3.添加配置文件

@Configuration
    public class WebMvcConfiguration implements WebMvcConfigurer {
    
        /**
         * 解决jpa懒加载
         */
        @Bean
        public MappingJackson2HttpMessageConverter mappingJackson2HttpMessageConverter() {
            MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
            ObjectMapper mapper = converter.getObjectMapper();
            mapper.registerModule(hibernate5Module());
            return converter;
        }
    
        @Bean
        public Hibernate5Module hibernate5Module() {
            Hibernate5Module module = new Hibernate5Module();
            module.disable(Hibernate5Module.Feature.USE_TRANSIENT_ANNOTATION);
            module.enable(Hibernate5Module.Feature.SERIALIZE_IDENTIFIER_FOR_LAZY_NOT_LOADED_OBJECTS);
            return module;
        }
    
    }

转载于:https://www.cnblogs.com/baizhuang/p/11057918.html

[https_www.jianshu.com_p_91d3096f38a0]: https://www.jianshu.com/p/91d3096f38a0