Springboot JPA级联操作的实现(一对一、一对多、多对多)

目录

• （1）一对一，@OneToOne
• （2）一对多，@OneToMany 和 @ManyToOne
• （3）多对多，@ManyToMany

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.cla编程客栈ss, 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(vandroidalue = {"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
    @GeneMXNKGwVtratedValue(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 Stri编程客栈ng 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 = php@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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