"Repeated column in mapping for entity" on ID field

Question

I'm making Spring application with Hibernate and I'm just trying to get relations between my entities working. I set up annotations for all foreign keys and now I get "Repeated column in mapping for entity" error. I was trying to find a solution here on SO, but I didn't really understand some of the answers and I don't think they are applicable to my code. I had this problem earlier with another project, where all ID fields were named just id and when I explicitly defined column name by @Column(name = "") and typed that name in @JoinColumn parameters it worked. Now I had the same error, but defining explicit names for ID fields didn't help.

Here's my entity class:

@Entity
public class Task implements Serializable, Discussable {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "task_id")
    private long id;

    private String name;

    @ManyToMany
    @JoinTable(
            name = "user_task",
            joinColumns = @JoinColumn(name = "task_id"),
            inverseJoinColumns = @JoinColumn(name = "user_id")
    )
    private Set<User> assigneeUsers;

    @Enumerated(EnumType.ORDINAL)
    private Status status; //alt + enter

    private Priority priority;

    private Date deadline;

    private String description;

    @ManyToOne
    @JoinColumn(name = "task_id")
    private Task parentTask;

    @OneToMany(mappedBy = "parentTask")
    private Set<Task> subtasks;

    @Enumerated(EnumType.ORDINAL)
    private Type type;

    @OneToOne(cascade = CascadeType.REMOVE)
    @JoinColumn(name = "channel_id")
    private Channel channel;

    @ManyToOne
    @JoinColumn(name = "project_id")
    private Project project;

// getters, setters and default constructor

The result I get when trying to compile is:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaAutoConfiguration.class]: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1628) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1078) ~[spring-context-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:857) ~[spring-context-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543) ~[spring-context-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.5.8.RELEASE.jar:1.5.8.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693) [spring-boot-1.5.8.RELEASE.jar:1.5.8.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360) [spring-boot-1.5.8.RELEASE.jar:1.5.8.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) [spring-boot-1.5.8.RELEASE.jar:1.5.8.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118) [spring-boot-1.5.8.RELEASE.jar:1.5.8.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107) [spring-boot-1.5.8.RELEASE.jar:1.5.8.RELEASE]
    at com.github.mesayah.assistance.AssistanceApplication.main(AssistanceApplication.java:20) [classes/:na]
Caused by: javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.persistenceException(EntityManagerFactoryBuilderImpl.java:954) ~[hibernate-entitymanager-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:882) ~[hibernate-entitymanager-5.0.12.Final.jar:5.0.12.Final]
    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:60) ~[spring-orm-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:353) ~[spring-orm-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:370) ~[spring-orm-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:359) ~[spring-orm-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1687) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1624) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    ... 16 common frames omitted
Caused by: org.hibernate.MappingException: Repeated column in mapping for entity: com.github.mesayah.assistance.model.Task column: task_id (should be mapped with insert="false" update="false")
    at org.hibernate.mapping.PersistentClass.checkColumnDuplication(PersistentClass.java:830) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.mapping.PersistentClass.checkPropertyColumnDuplication(PersistentClass.java:848) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.mapping.PersistentClass.checkColumnDuplication(PersistentClass.java:870) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.mapping.PersistentClass.validate(PersistentClass.java:605) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.mapping.RootClass.validate(RootClass.java:265) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.boot.internal.MetadataImpl.validate(MetadataImpl.java:329) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:443) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:879) ~[hibernate-entitymanager-5.0.12.Final.jar:5.0.12.Final]
    ... 22 common frames omitted

So I think the problem is with private Task parentTask; or private Set<User> asigneeUsers; because only these members use mapping for "task_id". But I can't figure out what in particular is wrong with this code.

Answer 1

The error that you are seeing:

Repeated column in mapping for entity: 
com.github.mesayah.assistance.model.Task column: task_id 
(should be mapped with insert="false" update="false")

This tells you that the column task_id inside the entity Task has been associated with more than one property.

You can associate the same column to multiple properties in a mapping; however, only one of the mappings can control the persistence behavior while the others are read-only.

As a trivial example:

public class MyEntity {
  @Column(name = "NAME")
  private String name;
  @Column(name = "NAME", insertable = false, updatable = false)
  private String name2;
}

The property name in this example will always be inserted and updated. This property controls the persistence of the column NAME. The property name2 will never be inserted nor updated and simply acts as a read-only field for column NAME.

If I had not included insertable = false, updatable = false on the column mapping, then Hibernate would have given the same error message you're seeing.

Now that you understand the technical reasons of the error message, your problem is as Maciej Kowalski mentions. You should likely have mapped your parent reference differently:

@ManyToOne
@Column(name = "parent_task_id")
private Task parentTask;

Conceptually, what you're looking for is your child Task which has a column task_id to also have a second column that references the foreign-key to the parent Task. This foreign key must be stored in a new column, aptly named parent_task_id.