ID 열 키 생성을 사용할 수 없습니다.

ID 열 키 생성을 사용할 수 없습니다. (TABLE_PER_CLASS)

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com.something.SuperClass :

@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public abstract class SuperClass implements Serializable {
    private static final long serialVersionUID = -695503064509648117L;

    long confirmationCode;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO) // Causes exception!!!
    public long getConfirmationCode() {
        return confirmationCode;
    }

    public void setConfirmationCode(long confirmationCode) {
        this.confirmationCode = confirmationCode;
    }
}

com.something.SubClass :

@Entity
public abstract class Subclass extends SuperClass {
    private static final long serialVersionUID = 8623159397061057722L;

    String name;

    @Column(nullable = false)
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

이 예외를 제공합니다.

Caused by: org.hibernate.MappingException: Cannot use identity column key
generation with <union-subclass> mapping for: com.something.SuperClass

ID를 생성하는 가장 쉽고 편리한 방법은 무엇입니까? 상속 전략을 변경하고 싶지 않습니다.

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여기서 문제는 "클래스 별 테이블"상속과 GenerationType.Auto. MsSQL의 ID 열을 고려하십시오. 열 기반입니다. "클래스 별 테이블"전략에서는 클래스 당 하나의 테이블을 사용하고 각 테이블에는 ID가 있습니다.

시험:

@GeneratedValue(strategy = GenerationType.TABLE)

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I wonder if this is a database dialect specific problem, since watching a youtube tutorial with PostgreSQL as the underlying database I saw that the creator of the video run succefully an app with the default @GeneratedValue. In my case (the underlying database is MySQL) I had to modify the @GeneratedValue strategy to GenerationType.TABLE exactly as zoidbeck proposes.

Here is the video : https://www.youtube.com/watch?v=qIdM4KQOtH8

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In our case, we use a PostreSQL database for dev and production and an in-memory hsqldb database for tests. We are using a sequence in both cases to generate an id. Apparently GenerationType.AUTO defaults to SEQUENCE for postgres, but failed in our local tests (must default to something else for hsqldb).

So the solution that worked for us, explicitly use GenerationType.SEQUENCE.

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Agree with zoidbeck's answer. You need to change strategy to:

@GeneratedValue(strategy = GenerationType.TABLE)

But that's not all, you need to create a new table, what will hold your abstract's table primary key sequence. Modify your mapping to

@Id
@GeneratedValue(strategy = GenerationType.TABLE, generator = "ConfirmationCodeGenerator")
@TableGenerator(table = "SEQUENCES", name = "ConfirmationCodeGenerator")
public long getConfirmationCode() {
   return confirmationCode;
}

And a new table in database should look like following:

When you ran your application, Hibernate will insert a row where sequence_name will be the entity name (SuperClass in this example) and sequence_next_hi_value value will be automatically incremented and used for new records of all implementing subclasses's tables.

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you can use @MappedSuperclass for inheritance

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There is a SQL standard Compliance in between MySQL and PostgreSQL. PostgreSQL Postgres understands a good subset of SQL92/99 plus some object-oriented features to these subsets. Postgres is capable of handling complex routines and rules as declarative SQL queries, subqueries, views, multi-user support, transactions, query optimization, inheritance, and arrays. Does not support selecting data across different databases.

MySQL MySQL uses SQL92 as its foundation. Runs on countless platforms. Mysql can construct queries that can join tables from different databases. Supports both left and right outer joins using both ANSI and ODBC syntax. As of MySQL 4.1 from that release on, MySQL will handle subqueries. Views supported as of release 5.

For a detailed description please visit. http://www-css.fnal.gov/dsg/external/freeware/pgsql-vs-mysql.html

참고URL : https://stackoverflow.com/questions/916169/cannot-use-identity-column-key-generation-with-union-subclass-table-per-clas