objectstore.java

利用SyncML开发客户端程序的中间件

/*
 * Copyright (C) 2006-2007 Funambol
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
 */

package com.funambol.storage;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.Enumeration;

import javax.microedition.rms.InvalidRecordIDException;
import javax.microedition.rms.RecordEnumeration;
import javax.microedition.rms.RecordStore;
import javax.microedition.rms.RecordStoreException;
import javax.microedition.rms.RecordStoreNotOpenException;

import com.funambol.util.Log;

/** 
 * This class uses the J2ME RMS to store and retrieve objects
 * using the rms positional access.
 *
 * To persist an object using ObjectStore, it must implement the
 * com.funambol.storage.Serializable interface.
 *
 * @param name is the name of the RecordStore to be managed 
 */
public class ObjectStore {

    // ---------------------------------------------- Attributes
    private RecordStore rs;
    private RecordEnumeration re;
    private ObjectFilter of;
    private ObjectComparator oc;
    
    // ---------------------------------------------- Constructors
    /** 
     * Creates a new instance of ObjectStore.
     */
    public ObjectStore() {
        rs = null;
        re = null;
    }
    
    /**
     * Get all object of the ObjectStore
     * @param s Serializable Object to be returned
     * @return Enumeration of Serializable object found 
     */
    public Enumeration getObjects(Serializable s) {
        return new ObjectEnumeration(this.rs, this.of, this.oc, s);
    }
    /**
     * @return Store name
     */
    public String getName() throws RecordStoreNotOpenException {
        return rs.getName();
    } 

    /** 
     * Open an existing RecordStore, or throws an exception if not present.
     * If the name is the same of the currently open one, no action is
     * taken, otherwise the old one is closed.
     *
     * @param name is the name of the RecordStore to be managed 
     * @return true if the record store has been open or created
     *         false if it was cached
     */
    public boolean open(String name) throws RecordStoreException {
        return openStore(name, false);
    }
    
    /** 
     * Creates a new RecordStore, or open an existing one.
     *
     * @param name is the name of the RecordStore to be managed
     * @return true if the record store has been open or created
     *         false if it was cached
     * 
     */
    public boolean create(String name) throws RecordStoreException {
        return openStore(name, true);
    }
    
    /**
     * private method used by open and create to share code.
     */
    private boolean openStore(String name, boolean create)
    throws RecordStoreException  {
        // Check if is requested to open a new record store
        if(rs != null){
            if(rs.getName().equals(name)){
                return false; // equal: keep the old one
            }
            else {
                close();
            }
        }
        rs = RecordStore.openRecordStore(name, create);
        return true;
    }

    /** 
     * Close the current RecordStore, if open.
     *
     */
    public void close() throws RecordStoreException {
        if(rs != null){
            rs.closeRecordStore();
        }        
        rs = null;
        re = null;
    }
    
    /**
     * Return the number of records in this ObjectStore
     *
     * @return the number of records present or -1 if the ObjectStore is not
     *         open.
     */
    public int size() {
        int ret = 0;
        try {
            if(rs != null) {
                ret = rs.getNumRecords();
            } else {
                return -1;
            }
        } catch (RecordStoreNotOpenException ex) {
            Log.error("Can't get size of ObjectStore: recordstore not open.");
            ret = -1; 
        }
        return ret;
    }

    /**
     *  Get the first valid index in the record store.
     *
     *  @return the first valid index in the record store, or 0 if empty.
     */
    public int getFirstIndex() throws RecordStoreException {
        //TODO: could we use false here to improve performances?
        re = rs.enumerateRecords(null, null, true);
        return getNextIndex();
    }

    /**
     *  Get the next valid index in the record store.
     *
     *  @return the next valid index in the record store, or 0 if no
     *          more record are present.
     */
    public int getNextIndex() throws RecordStoreException {

        if(re.hasNextElement()){
            return re.nextRecordId();
        }
        else {
            return 0;
        }
    }

    /**
     *  Store the serializable object in a new record.
     *
     *  @param obj the serializable object
     *  @return the index in the recordstore
     */
    public int store(Serializable obj) throws RecordStoreException, IOException {
        ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
        DataOutputStream out = new DataOutputStream(byteStream);

        obj.serialize(out);

        byte[] data = byteStream.toByteArray();
        int ret = rs.addRecord(data, 0, data.length);
        obj = null;
        data = null;
        byteStream = null;
        out = null;
        return ret; 
    }

    /**
     *  Store the serializable object in an existent record.
     *
     *  @param obj the serializable object
     *  @return the index in the recordstore
     */
    public int store(int index, Serializable obj)
    throws RecordStoreException, IOException {
        ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
        DataOutputStream out = new DataOutputStream(byteStream);

        obj.serialize(out);

        byte[] data = byteStream.toByteArray();
        rs.setRecord(index, data, 0, data.length);
        obj = null;
        return index;
    }
    
    /**
     *  Retrieve the serialize object from the record store.
     *
     *  @param obj the serializable object
     *  @param index the index in the recordstore
     * 
     *  @return a reference to the object, or null if the object is
     *          empty in the store.
     */
    public Serializable retrieve(int index, Serializable obj)
    throws RecordStoreException, IOException {
        byte data[] = rs.getRecord(index);

        if (data != null) {
            ByteArrayInputStream dataStream = new ByteArrayInputStream(data);
            DataInputStream in = new DataInputStream(dataStream);

            obj.deserialize(in);
        }
        else {
            return null;
        }

        return obj;
    }

    /**
     *  Remove the object from the store.
     *
     *  @param index the index in the recordstore
     */
    public void remove(int index) throws RecordStoreException {
        rs.deleteRecord(index);
    }
    
    /**
     *  Returns the amount of additional room (in bytes) available for this
     *  record store to grow.
     *
     *  @return the amount of storage left for this store.
     */
    public int getAvaliableStorage() {
        try {
            return rs.getSizeAvailable();

        } catch(RecordStoreNotOpenException e) {
            // Should not happen
            e.printStackTrace();
            Log.error("ObjectStore.getAvaliableStorage: "+e.toString());
            return 0;
        }
    }

    /**
     * Add a RecordListener to the recordStore
     */
    public void addStoreListener(ObjectStoreListener listener) {
        rs.addRecordListener(listener);
    }
    
    /**
     * Add a RecordListener to the recordStore
     */
    public void removeStoreListener(ObjectStoreListener listener) {
        rs.removeRecordListener(listener);
    }
    
    /**
     * Set Filter for this ObjectStore
     */
    public void setObjectFilter(ObjectFilter newOf) {
        this.of = newOf;
    }
    
    /**
     * Remove Filter after usage
     */
    public void removeObjectFilter() {
        this.of = null;
    }
    
    /**
     * Set Comparator for this ObjectStore
     */
    public void setObjectComparator(ObjectComparator newOc) {
        this.oc = newOc;
    }
    
    /**
     * Set Comparator for this ObjectStore
     */
    public void removeObjectComparator() {
        this.oc = null;
    }
}