Java Spring Boot JPA Hibernate：即使实体类中存在@Id，也没有为实体错误指定标识符

Spring Boot JPA Hibernate: No identifier specified for entity error even when @Id is present in the entity class

提问by Sambhav

I am getting a "No Identifier error" the entity class "QuestionResponse" has an two @Id fields . There is a OneToMany relationship between Question and QuestionResponse and OnetoMany relationship between Response and QuestionResponse and all these classes are designed based on https://docs.jboss.org/hibernate/orm/5.2/userguide/html_single/Hibernate_User_Guide.html#associations-many-to-many-bidirectional-with-link-entity

我收到“无标识符错误”实体类“QuestionResponse”有两个 @Id 字段。Question 和 QuestionResponse 之间存在一对多关系，Response 和 QuestionResponse 之间存在一对多关系，所有这些类都是基于https://docs.jboss.org/hibernate/orm/5.2/userguide/html_single/Hibernate_User_Guide.html#associations-设计的多对多双向链接实体

I am using Postgres 9.5, Spring Boot 2.0.1 and deploying it on WildFly 11

我正在使用 Postgres 9.5、Spring Boot 2.0.1 并将其部署在 WildFly 11 上

Thanks!

谢谢！

questions.sql

问题.sql

CREATE TABLE questions( 
    id BIGSERIAL PRIMARY KEY,
    question VARCHAR(255)
);

respones.sql

响应文件

CREATE TABLE responses( 
    id BIGSERIAL PRIMARY KEY,
    response VARCHAR(255)
);

question_respone.sql #

question_respone.sql #

CREATE TABLE question_response(
    question_id bigint REFERENCES questions ON DELETE CASCADE,
    response_id bigint REFERENCES responses ON DELETE CASCADE,
    PRIMARY KEY ( question_id, response_id)
);

Question.java

问题.java

@Entity
@Table(name = "questions")
public class Question{


    @Id
    @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="qid_seq")
    @SequenceGenerator(name = "qid_seq", sequenceName="questions_id_seq")
    @Column(name = "id")
    private Long id;


    @Column(name = "questionText")
    private String questionText;

    @OneToMany(mappedBy = "question", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<QuestionResponse> responses;

    public Question() {}

    public Question(String questionText) {
        super();
        this.questionText = questionText;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getQuestionText() {
        return questionText;
    }

    public void setQuestionText(String questionText) {
        this.questionText = questionText;
    }

    public List<QuestionResponse> getResponses() {
        return responses;
    }
}

QuestionResponse.java

问答.java

@Entity
@Table(name = "question_response")
public class QuestionResponse {

    @Id
    @ManyToOne 
    private Question question;

    @Id
    @ManyToOne 
    private Response response;



    public QuestionResponse() {
        super();
    }

    public QuestionResponse(Question question, Response response) {
        super();
        this.question= question;
        this.response = response;
    }

    public Question getQuestion() {
        return question;
    }

    public void setQuestion(Question question) {
        this.question = question;
    }

    public Response getResponse() {
        return response;
    }

    public void setResponse(Response response) {
        this.response = response;
    }

}

Response.java

响应.java

@Entity
@Table(name = "responses")
public class Response {

    @Id
    @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="rid_seq")
    @SequenceGenerator(name = "rid_seq", sequenceName="questions_id_seq")
    @Column(name = "id")
    private Long id;

    @Column(name = "responseText")
    private String responseText;

    @OneToMany(mappedBy = "response", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<QuestionResponse> question;

    public Response() {}

    public Response(String responseText) {
        super();
        this.responseText = responseText;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getResponseText() {
        return responseText;
    }

    public void setResponseText(String responseText) {
        this.responseText = responseText;
    }

    public List<QuestionResponse> getQuestion() {
        return question;
    }

}

WildFly console

WildFly 控制台

13:54:49,581 ERROR [org.springframework.boot.SpringApplication] (ServerService Thread Pool -- 86) Application run failed: org.springframework.beans.factory.BeanCreationException:
 Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]:
 Invocation of init method failed; nested exception is org.hibernate.AnnotationException:
 No identifier specified for entity: com.poc.questionnarie.QuestionResponse

回答by Luay Abdulraheem

In JPA, you cannot use the @Idannotation on more than one field in an entity, unlessyou are defining it as a composite primary key. So you need to add @IdClassto your QuestionResponseentity so that it consists multiple primary key fields.

在 JPA 中，您不能@Id在实体中的多个字段上使用注释，除非您将其定义为复合主键。因此，您需要添加@IdClass到您的QuestionResponse实体中，使其包含多个主键字段。

This might not relate to your issue, but it would also be worth having a look at this articlethat shows the best way to use the @ManyToManyannotation with JPA.

这可能与您的问题无关，但也值得一看这篇文章，该文章展示了在@ManyToManyJPA 中使用注释的最佳方法。