Spring Boot & Postgres：关系“sub_comment”不存在

Question

I have two entities: Comment , and SubComment . A Comment can have multiple SubComment s. I'm trying to establish a one to many/many to one bidirectional relationship with Hibernate.

I do not know what is wrong. Both of the tables seem to have been created correctly in PSQL.

Comment.java

import javax.persistence.*;
import java.util.Set;

@Entity
public class Comment {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    @Column
    private String text;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "comment")
    private Set<SubComment> subComment;

    public long getId() {
        return id;
    }

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

    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }
}

SubComment.java

import javax.persistence.*;

@Entity
public class SubComment {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    private String text;

    @ManyToOne
    private Comment comment;

    public long getId() {
        return id;
    }

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

    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }

    public Comment getComment() {
        return comment;
    }

    public void setComment(Comment comment) {
        this.comment = comment;
    }
}

I'm getting this error:

Error executing DDL via JDBC StatementCaused by: org.postgresql.util.PSQLException: ERROR: relation "sub_comment" does not exist

Hibernate: create table "user" (id  bigserial not null, email varchar(255), name varchar(255), username varchar(255), primary key (id))
Hibernate: create table comment (comment_id  bigserial not null, text varchar(255), primary key (comment_id))
Hibernate: create table sub_comment (sub_comment_id  bigserial not null, text varchar(255), comment_comment_id int8, primary key (sub_comment_id))
Hibernate: alter table sub_comment add constraint FK87789n34vmns9eeyw6jgc5ghp foreign key (comment_comment_id) references comment

application.properties

spring.jpa.hibernate.ddl-auto=create-drop
spring.datasource.url=jdbc:postgresql://localhost:5432/dbname
spring.datasource.data-username=username
spring.datasource.driver-class-name=org.postgresql.Driver

spring.jpa.show-sql=true
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.PostgreSQLDialect
spring.jpa.database-platform=org.hibernate.dialect.PostgreSQL9Dialect
spring.jpa.properties.hibernate.temp.use_jdbc_metadata_defaults = false

Answer 1

You missed @JoinColumn . You will get another error due to field based access. Use Property based access instead:

import javax.persistence.*;

@Entity
@Table(name = "subcomment")
public class SubComment implements Serializable {

    private static final long serialVersionUID = -3009157732242241606L;

    private long id;
    private String text;
    private Comment comment;

    @Id
    @Column(name = "sub_id")
    @GeneratedValue(strategy = GenerationType.AUTO)
    public long getId() {
        return id;
    }

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

    @Basic
    @Column(name = "sub_text")
    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }

    @ManyToOne
    @JoinColumn(name = "sub_fk_c_id", referencedColumnName = "c_id") // here the exact field name of your comment id in your DB
    public Comment getComment() {
        return comment;
    }

    public void setComment(Comment comment) {
        this.comment = comment;
    }
}

Also make changes here too:

import javax.persistence.*;

@Entity
@Table(name = "comment")
public class Comment implements Serializable {

    private static final long serialVersionUID = -3009157732242241606L;    

    private long id;
    private String text;
    private Set<SubComment> subComment = new HashSet<>();

    @OneToMany(mappedBy = "comment", targetEntity = SubComment.class)
    public Set<SubComment> getSubComment() {
        return subComment;
    }

    public void setSubComment(Set<SubComment> subComment) {
        this.subComment = subComment;
    }

    @Id
    @Column(name = "c_id")
    @GeneratedValue(strategy = GenerationType.AUTO)
    public long getId() {
        return id;
    }

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

    @Basic
    @Column(name = "c_text")
    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }
}

Paste the following in your application.properties file:

spring.jpa.properties.hibernate.id.new_generator_mappings = false
spring.jpa.properties.hibernate.format_sql = true
logging.level.org.hibernate.SQL=DEBUG
logging.level.org.hibernate.type.descriptor.sql.BasicBinder=TRACE
spring.jpa.hibernate.ddl-auto=create

In your pom.xml file paste these:

    <dependency>
        <groupId>org.postgresql</groupId>
        <artifactId>postgresql</artifactId>
        <scope>runtime</scope>
    </dependency>

For further reference see this stackoverflow post .

Answer 2

I know that this answer is late but maybe it will help someone, their problem is that they have not configured the schema, which is why they are throwing that error.

Here is how to configure the schema in postgresql:

spring.jpa.properties.hibernate.default_schema = "his schema"

Answer 3

Many sub comments have belonged to one comment and model should look like that (comment_id you can generate eg UUID.randomUUID().toString() )

@Entity
@Table(name = "comment")
public class Comment{

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

@Column(name = "comment_id")
String commentId;

}

@Entity
@Table(name = "sub_comment")
public class SubComment{

...
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "comment_id", referencedColumnName = "comment_id")
Comment comment;
...
}

If You use eg liquidbase to control your data source :

  - changeSet:
      id: 1
      author: author.name
      changes:
      - addForeignKeyConstraint:
          baseColumnNames: comment_id
          baseTableName: sub_comment
          constraintName: fk_comment_subcomment
          referencedColumnNames: comment_id
          referencedTableName: comment

Answer 4

Had a similar problem and my issue was that I was missing referencedColumnName under my SubCategory class.

Had this

  @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.MERGE)
    @JoinColumn(name = "category_id, nullable = false)
    private Category category;

Instead of

@ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.MERGE)
    @JoinColumn(name = "category_id", referencedColumnName = "id", nullable = false)
    private Category category;

so my subcategory table was not being created.