关于java：Spring Boot＆amp;

Spring Boot & Postgres: relation “sub_comment” does not exist

我有两个实体：Comment和SubComment。一个Comment可以有多个SubComment。我正试图与hibernate建立一对多/多对一的双向关系。

我不知道怎么了。这两个表似乎都是在psql中正确创建的。

注释.java

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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;
}
}

子组件.java

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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;
}
}

号

我得到这个错误：

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

号

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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

应用程序属性

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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

。

相关讨论

你错过了@JoinColumn。由于基于字段的访问，您将得到另一个错误。改用基于属性的访问：

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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;
}
}

在此也进行更改：

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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;
}
}

号

将以下内容粘贴到您的application.properties文件中：

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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

在pom.xml文件中粘贴以下内容：

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

。

如需进一步参考，请参阅此stackoverflow post。