Struts example source code file (MemoryStorage.java)

This example Struts source code file (MemoryStorage.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Struts tags/keywords

cannot, class, class, createexception, createexception, hashmap, identity, identity, io, map, object, serializable, serializable, storageexception, updateexception, util

The Struts MemoryStorage.java source code

/*
 * $Id: MemoryStorage.java 476710 2006-11-19 05:05:14Z mrdon $
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.struts2.showcase.application;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;

import org.apache.struts2.showcase.exception.CreateException;
import org.apache.struts2.showcase.exception.DuplicateKeyException;
import org.apache.struts2.showcase.exception.StorageException;
import org.apache.struts2.showcase.exception.UpdateException;
import org.apache.struts2.showcase.model.IdEntity;

/**
 * MemoryStorage.
 * Very simple in-memory persistence emulation.
 *
 */

public class MemoryStorage implements Storage {

    private static final long serialVersionUID = 8611213748834904125L;


    private Map memory = new HashMap();

    private Map getEntityMap ( Class entityClass ) {
        if (entityClass != null) {
            Map tryMap = (Map) memory.get(entityClass);
            if (tryMap == null) {
                synchronized(memory) {
                    tryMap = new HashMap();
                    memory.put(entityClass, tryMap);
                }
            }
            return tryMap;
        } else {
            return null;
        }
    }

    private IdEntity intStore( Class entityClass, IdEntity object ) {
        getEntityMap(entityClass).put(object.getId(), object);
        return object;
    }

    public IdEntity get( Class entityClass, Serializable id ) {
        if (entityClass != null && id != null) {
            return (IdEntity) getEntityMap(entityClass).get(id);
        } else {
            return null;
        }
    }

    public Serializable create ( IdEntity object ) throws CreateException {
        if (object == null) {
            throw new CreateException("Either given class or object was null");
        }
        if (object.getId() == null) {
            throw new CreateException("Cannot store object with null id");
        }
        if (get(object.getClass(), object.getId()) != null) {
            throw new DuplicateKeyException("Object with this id already exists.");
        }
        return intStore(object.getClass(), object).getId();
    }

    public IdEntity update ( IdEntity object ) throws UpdateException {
        if (object == null) {
            throw new UpdateException("Cannot update null object.");
        }
        if ( get(object.getClass(), object.getId())==null ) {
            throw new UpdateException("Object to update not found.");
        }
        return intStore(object.getClass(), object);
    }

    public Serializable merge ( IdEntity object ) throws StorageException {
        if (object == null) {
            throw new StorageException("Cannot merge null object");
        }
        if (object.getId() == null || get(object.getClass(), object.getId())==null) {
            return create(object);
        } else {
            return update(object).getId();
        }
    }

    public int delete( Class entityClass, Serializable id ) throws CreateException {
        try {
            if (get(entityClass, id) != null) {
                getEntityMap(entityClass).remove(id);
                return 1;
            } else {
                return 0;
            }
        } catch (Exception e) {
            throw new CreateException(e);
        }
    }

    public int delete( IdEntity object ) throws CreateException {
        if (object == null) {
            throw new CreateException("Cannot delete null object");
        }
        return delete(object.getClass(), object.getId());
    }

    public Collection findAll( Class entityClass ) {
        if (entityClass != null) {
            return getEntityMap(entityClass).values();
        } else {
            return new ArrayList();
        }
    }

    public void reset() {
        this.memory = new HashMap();
    }

}