Persistence.Custom.Generator.OpenJPA

CustomGenerator.java

package com.domain.project;

import java.io.Serializable;
import java.util.Hashtable;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;

import org.apache.openjpa.kernel.Seq;
import org.apache.openjpa.kernel.StoreContext;
import org.apache.openjpa.meta.ClassMetaData;

public class CustomGenerator implements Seq {
	
	private static final Map<Object, AtomicInteger> SEQUENCERS = new Hashtable<Object, AtomicInteger>();
	
	private static Serializable next(final Object object) {
		
		AtomicInteger sequencer = SEQUENCERS.get(object);
		if(null== sequencer) {
			sequencer = new AtomicInteger( (int)System.currentTimeMillis() );
			SEQUENCERS.put(object, sequencer);
		}
		
		return new Integer(sequencer.getAndIncrement());
	}
	
	private static Serializable current(final Object object) {
		
		AtomicInteger sequencer = SEQUENCERS.get(object);
		if(null!= sequencer) {
			return new Integer(sequencer.get());
		}
		
		return null;
	}
	

	@Override
	public void allocate(int arg0, StoreContext arg1, ClassMetaData arg2) {
	}

	@Override
	public void close() {
	}

	@Override
	public Object current(StoreContext context, ClassMetaData meta) {
		return CustomGenerator.current(meta.getDescribedType());
	}

	@Override
	public Object next(StoreContext context, ClassMetaData meta) {
		return CustomGenerator.next(meta.getDescribedType());
	}

	@Override
	public void setType(int type) {
	}

}

usage.md

import

import javax.persistence.Column;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.SequenceGenerator;

usage

@Id
@SequenceGenerator(name = "SQ_GEN", sequenceName = "com.domain.project.CustomGenerator()")
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SQ_GEN")
@Column(name = "entity_id", length = 10, nullable = false)
private Integer id;