de.tsl2.nano.persistence.replication.hibernate.EntityReplication Maven / Gradle / Ivy

Go to download
package de.tsl2.nano.persistence.replication.hibernate;

import java.io.File;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Consumer;

import javax.persistence.EntityManager;
import javax.persistence.Persistence;
import javax.xml.bind.JAXB;

import org.hibernate.ReplicationMode;
import org.hibernate.Session;

/**  * Replicates entities through hibernatesession.replicate(). EntityManagers will be load through their persistence unit names. 
 * To use it, 
 *   - create a META-INF/persistence.xml in your classpath
 *   - describe the two persistence-units (source and destination)
 *   - call: new EntityManager(mySourceUnit, myDestUnit).replicate(myBeans)
 *   
 * 
 * @author Tom, Thomas Schneider
 * @version $Revision$ 
 */

public class EntityReplication {
    private EntityManager src;
    private EntityManager dest;
    
    public EntityReplication(String srcPersistenceUnit, String destPersistenceUnit) {
        src = Persistence.createEntityManagerFactory(srcPersistenceUnit).createEntityManager();
        dest = Persistence.createEntityManagerFactory(destPersistenceUnit).createEntityManager();
    }
    
    public EntityReplication(EntityManager src, EntityManager dest) {
        this.src = src;
        this.dest = dest;
    }

    public  void replicateFromIDs(Class entityClass, Object...ids) {
        T[] entities = Arrays.stream(ids).
                map(id -> src.find(entityClass, id, readOnlyHints())).
                toArray(s -> (T[])java.lang.reflect.Array.newInstance(entityClass, s));
        replicate((Consumer)null, (Consumer)EntityReplication::strategySerialize, entities);
    }
    
    public  void replicate(Class entityClass, T...entities) {
        replicate((Consumer)null, (Consumer)EntityReplication::strategySerialize, entities);
    }
    
    public  void replicate(Consumer transformer, Consumer strategy, T...entities) {
        Session hibernateSession = dest.unwrap(Session.class);
        Arrays.stream(entities).forEach(e -> {
            //entity must be detached from src session
            src.detach(e);
            if (transformer != null)
                transformer.accept(e);
            if (strategy != null)
                strategy.accept(e);
            });
        dest.flush();
    }
    
    public static void strategySerialize(Object entity) {
        JAXB.marshal(entity, new File(entity.getClass().getSimpleName() + ".xml"));
    }
    
    public static void strategyHibReplicate(Session hibernateSession, Object entity) {
        hibernateSession.replicate(entity, ReplicationMode.OVERWRITE);
    }
    
    public static  T load(String fileName, Class entityClass) {
        return JAXB.unmarshal(new File(fileName), entityClass);
    }
    private Map readOnlyHints() {
        HashMap hints = new HashMap<>();
        hints.put("org.hibernate.readOnly", true);
        return hints;
    }

    public static void main(String[] args) throws ClassNotFoundException {
        EntityReplication repl = new EntityReplication(args[0], args[1]);
        Class cls = Class.forName(args[2]);
        repl.replicateFromIDs(cls, args[3]);
    }
}