com.impetus.kundera.ejb.EntityManagerFactoryBuilder.java Source code

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Here is the source code for com.impetus.kundera.ejb.EntityManagerFactoryBuilder.java

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/*
 * Copyright 2010 Impetus Infotech.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.impetus.kundera.ejb;

import java.net.URL;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

import javax.persistence.EntityManagerFactory;
import javax.persistence.PersistenceException;
import javax.persistence.spi.PersistenceUnitTransactionType;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Builds EmtityManagerFactory instances from classpath.
 * 
 * @author animesh.kumar
 */
public class EntityManagerFactoryBuilder {

    /** The Constant log. */
    private static final Log log = LogFactory.getLog(EntityManagerFactoryBuilder.class);

    /** The Constant PROVIDER_IMPLEMENTATION_NAME. */
    private static final String PROVIDER_IMPLEMENTATION_NAME = KunderaPersistence.class.getName();

    /**
    * Builds up EntityManagerFactory for a given persistenceUnitName and
    * overriding properties.
    * 
    * @param persistenceUnitName
    *            the persistence unit name
    * @param override
    *            the override
    * @return the entity manager factory
    */
    public EntityManagerFactory buildEntityManagerFactory(String persistenceUnitName,
            Map<Object, Object> override) {
        PersistenceMetadata metadata = getPersistenceMetadata(persistenceUnitName);

        Properties props = new Properties();
        // Override properties
        Properties metadataProperties = metadata.getProps();
        // Make sure, it's empty or Unmodifiable
        override = override == null ? Collections.EMPTY_MAP : Collections.unmodifiableMap(override);

        // Take all from Metadata and override with supplied map 
        for (Map.Entry<Object, Object> entry : metadataProperties.entrySet()) {
            Object key = entry.getKey();
            Object value = entry.getValue();

            if (override.containsKey(key)) {
                value = override.get(key);
            }
            props.put(key, value);
        }

        // Now take all the remaining ones from override
        for (Map.Entry<Object, Object> entry : override.entrySet()) {
            Object key = entry.getKey();
            Object value = entry.getValue();

            if (!props.containsKey(key)) {
                props.put(key, value);
            }
        }

        log.info("Building EntityManagerFactory for name: " + metadata.getName() + ", and Properties:" + props);
        return new EntityManagerFactoryImpl(metadata, props);
    }

    /**
     * Gets the persistence metadata.
     * 
     * @param persistenceUnitName
     *            the persistence unit name
     * @return the persistence metadata
     */
    private PersistenceMetadata getPersistenceMetadata(String persistenceUnitName) {
        log.info("Look up for persistence unit: " + persistenceUnitName);

        List<PersistenceMetadata> metadatas = findPersistenceMetadatas();

        // If there is just ONE persistenceUnit, then use this irrespective of the name
        if (metadatas.size() == 1) {
            return metadatas.get(0);
        }

        // Since there is more persistenceUnits, you must provide a name to look up
        if (isEmpty(persistenceUnitName)) {
            throw new PersistenceException("No name provided and several persistence units found");
        }

        // Look for one that interests us
        for (PersistenceMetadata metadata : metadatas) {
            if (metadata.getName().equals(persistenceUnitName)) {
                return metadata;
            }
        }

        throw new PersistenceException(
                "Could not find persistence unit in the classpath for name: " + persistenceUnitName);
    }

    /**
     * Find persistence metadatas.
     * 
     * @return the list
     */
    private List<PersistenceMetadata> findPersistenceMetadatas() {
        try {
            Enumeration<URL> xmls = Thread.currentThread().getContextClassLoader()
                    .getResources("META-INF/persistence.xml");

            if (!xmls.hasMoreElements()) {
                log.info("Could not find any META-INF/persistence.xml " + "file in the classpath");
            }

            Set<String> persistenceUnitNames = new HashSet<String>();
            List<PersistenceMetadata> persistenceUnits = new ArrayList<PersistenceMetadata>();

            while (xmls.hasMoreElements()) {
                URL url = xmls.nextElement();
                log.trace("Analyse of persistence.xml: " + url);
                List<PersistenceMetadata> metadataFiles = PersistenceXmlLoader.findPersistenceUnits(url,
                        PersistenceUnitTransactionType.RESOURCE_LOCAL);

                // Pick only those that have Kundera Provider
                for (PersistenceMetadata metadata : metadataFiles) {
                    // check for provider
                    if (metadata.getProvider() == null
                            || PROVIDER_IMPLEMENTATION_NAME.equalsIgnoreCase(metadata.getProvider())) {
                        persistenceUnits.add(metadata);
                    }

                    // check for unique names
                    if (persistenceUnitNames.contains(metadata.getName())) {
                        throw new PersistenceException(
                                "Duplicate persistence-units for name: " + metadata.getName());
                    }
                    persistenceUnitNames.add(metadata.getName());
                }
            }

            return persistenceUnits;
        } catch (Exception e) {
            if (e instanceof PersistenceException) {
                throw (PersistenceException) e;
            } else {
                throw new PersistenceException(e);
            }
        }
    }

    // helper class
    /**
     * Checks if is empty.
     * 
     * @param str
     *            the str
     * @return true, if is empty
     */
    private static boolean isEmpty(String str) {
        return null == str || str.isEmpty();
    }
}