Springboot JPA级联操作的实现(一对一、一对多、多对多)
作者：zhong_bao
本文深入解析JPA中的一对一、一对多和多对多级联操作,包括实体间的关系建立、查询、保存、刷新和删除等操作,具有一定的参考价值,感兴趣的可以了解一下
自从接触了JPA，就对立面的级联操作很费解，特此做一下学习。JPA提供的Entity级联可以建立一对一、一对多、多对多的关系，覆盖查询、保存、刷新、删除等操作。
（1）一对一，@OneToOne
TUser与TGender成一对一关系
@Entity
@Data
@Table(name = "user",schema = "hr")
@JsonIgnoreProperties(value = {"handler","hibernateLazyInitializer","fieldHandler"})
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
@GenericGenerator(name = "jpa-uuid", strategy = "uuid")
public class TUser {
@Id
@GeneratedValue(generator="jpa-uuid")
@Column(name = "user_id")
private String id;
@Column(name = "user_name")
private String name;
@Column(name = "user_describe")
private String desc;
//@JoinColumn的name指的是当前表user的字段gender_id,referencedColumnName指关联表gender的字段id
@OneToOne(cascade = {CascadeType.MERGE, CascadeType.PERSIST,CascadeType.REMOVE,CascadeType.ALL})
@JoinColumn(name = "gender_id",referencedColumnName = "id")
private TGender genderId;
}
而TGender为：
@Entity
@Data
@Table(name = "gender",schema = "hr")
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
@JsonIgnoreProperties(value = {"handler","hibernateLazyInitializer","fieldHandler"})
public class TGender {
@Id
@GenericGenerator(name = "jpa-uuid", strategy = "uuid")
private String id;
private String sex;
//可维护可不维护，mappedBy就是被维护端，被TUser类中的属性“genderId”维护
@OneToOne(mappedBy = "genderId", cascade = {CascadeType.MERGE, CascadeType.REFRESH}, optional = false)
private TUser tUser;
（2）一对多，@OneToMany 和 @ManyToOne
两个是一起用的，以Company和User为例子，一个公司有多个职工
@Entity
@Data
@Table(name = "user",schema = "hr")
@JsonIgnoreProperties(value = {"handler","hibernateLazyInitializer","fieldHandler"})
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
@GenericGenerator(name = "jpa-uuid", strategy = "uuid")
public class TUser {
@Id
@GeneratedValue(generator="jpa-uuid")
@Column(name = "user_id")
private String id;
@Column(name = "user_name")
private String name;
@Column(name = "user_describe")
private String desc;
@OneToOne(cascade = {CascadeType.MERGE, CascadeType.PERSIST,CascadeType.REMOVE,CascadeType.ALL})
@JoinColumn(name = "gender_id",referencedColumnName = "id")
private TGender genderId;
//@JoinColumn的name指的是当前表user的字段company_id,referencedColumnName指关联表company的字段id
@ManyToOne(cascade = {CascadeType.ALL})
@JoinColumn(name = "company_id",referencedColumnName = "id")
private TCompany companyId;
}
TCompany 为：
@Entity
@Data
@Table(name = "company",schema = "hr")
@JsonIgnoreProperties(value = {"handler","hibernateLazyInitializer","fieldHandler"})
@GenericGenerator(name = "jpa-uuid", strategy = "uuid")
public class TCompany {
@Id
@GeneratedValue(generator="jpa-uuid")
private String id;
private String name;
//查询时建议把userList忽略
//可维护可不维护，mappedBy就是被维护端，被TUser类中的属性“companyId”维护
@OneToMany(mappedBy="companyId",cascade = {CascadeType.ALL})
private List<TUser> userList;
}
（3）多对多，@ManyToMany
已TUser和TRole为例子
@Entity
@Data
@Table(name = "user",schema = "hr")
@JsonIgnoreProperties(value = {"handler","hibernateLazyInitializer","fieldHandler"})
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
@GenericGenerator(name = "jpa-uuid", strategy = "uuid")
public class TUser {
@Id
@GeneratedValue(generator="jpa-uuid")
@Column(name = "user_id")
private String id;
@Column(name = "user_name")
private String name;
@Column(name = "user_describe")
private String desc;
//使用JoinTable属性把中间表关联起来，中间表主键为自增，joinColumns指的当前表user,name 属性指向中间表的user_id,referencedColumnName 指向user中的id,inverseJoinColumns是role表,name 属性指向中间表的role_id,referencedColumnName 指向role中的id
@ManyToMany(cascade = {CascadeType.MERGE, CascadeType.PERSIST,CascadeType.REMOVE})
@JoinTable(name = "user_role", schema = "hr",
joinColumns = @JoinColumn(name = "user_id", referencedColumnName = "user_id"),
inverseJoinColumns = @JoinColumn(name = "role_id", referencedColumnName = "id"))
private List<TRole> roleSet = new ArrayList<>();
}
TRole为：
@Entity
@Data
@Table(name = "role",schema = "hr")
@GenericGenerator(name = "jpa-uuid", strategy = "uuid")
public class TRole {
@Id
@GeneratedValue(generator="jpa-uuid")
private String id;
private String name;
@Column(name = "role_desc")
private String desc;
//mappedBy就是被维护端，被TUser类中的属性“roleSet”维护
@ManyToMany(mappedBy = "roleSet",cascade = {CascadeType.PERSIST,CascadeType.REMOVE})
private List<TUser> userSet = new ArrayList<>();
}
依赖
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.8.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<dependencies>
<!-- Compile -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- config -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-configuration-processor</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>
<dependency>
<groupId>io.springfox</groupId>
<artifactId>springfox-swagger2</artifactId>
<version>2.9.2</version>
</dependency>
<dependency>
<groupId>io.springfox</groupId>
<artifactId>springfox-swagger-ui</artifactId>
<version>2.9.2</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.47</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
<!-- Test -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<scope>runtime</scope>
<optional>true</optional>
</dependency>
</dependencies>
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