How to define index by several columns in hibernate entity?

Question

Morning.

I need to add indexing in hibernate entity. As I know it is possible to do using @Index annotation to specify index for separate column but I need an index for several fields of entity.

I've googled and found jboss annotation @Table, that allows to do this (by specification). But (I don't know why) this functionality doesn't work. May be jboss version is lower than necessary, or maybe I don't understant how to use this annotation, but... complex index is not created.

Why index may not be created?

jboss version 4.2.3.GA

Entity example:

package somepackage;
import org.hibernate.annotations.Index;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
@org.hibernate.annotations.Table(appliesTo = House.TABLE_NAME,
    indexes = {
            @Index(name = "IDX_XDN_DFN",
                    columnNames = {House.XDN, House.DFN}
            )
    }
)

public class House {
    public final static String TABLE_NAME = "house";
    public final static String XDN = "xdn";
    public final static String DFN = "dfn";

    @Id
    @GeneratedValue
    private long Id;

    @Column(name = XDN)
    private long xdn;

    @Column(name = DFN)
    private long dfn;

    @Column
    private String address;

    public long getId() {
        return Id;
    }

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

    public long getXdn() {
        return xdn;
    }

    public void setXdn(long xdn) {
        this.xdn = xdn;
    }

    public long getDfn() {
        return dfn;
    }

    public void setDfn(long dfn) {
        this.dfn = dfn;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

When jboss/hibernate tries to create table "house" it throws following exception:

Reason: org.hibernate.AnnotationException: @org.hibernate.annotations.Table references an unknown table: house

Answer 1

You'd better go with a composite primary key.

This article explains how to do it with JPA annotations. It uses @Embeddable and @EmbeddedId

Answer 2

Please try the following:

@Entity
@org.hibernate.annotations.Table(appliesTo = House.TABLE_NAME,
    indexes = {
            @Index(name = "IDX_XDN_DFN",
                    columnNames = {House.XDN, House.DFN}
            )
    }
)
@Table(name="house")
public class House {
    ...
}

Note that this should also allow you to create a multi-column index (based on the index name):

@Index(name = "index1")
public String getFoo();

@Index(name = "index1")
public String getBar();

P.S.: What version of Hibernate are you using BTW? What database/dialect?

Answer 3

You have to have hibernate.hbm2ddl.auto set to create in persistence.xml. When set to update hibernate won't create indexes.

hibernate.hbm2ddl.auto = create