xmlstorage.java

Gmail API for Java 一个gmail信箱的客户端

package siuying.gm.app.gmailer4j;

import java.util.*;
import siuying.gm.structure.*;
import java.io.*;
import java.util.logging.*;
import com.tagtraum.sixbs.*;
import com.tagtraum.sixbs.adapters.util.*;

/**
 * Open a directory, use files under this directorys as data store
 * @todo use some caching technique to improve performance
 * @version 0.1
 */
public class XMLStorage implements GMStorage{
    /**
     * if the storage is opened
     */
    private boolean opened;

    /**
     * url of the storage
     */
    private String url;

    /**
     * file postfix that used by the data store, default ".xml"
     */
    private String postfix;

    /**
     * list of all items in storage
     */
    protected HashSet items;

    protected static Logger logger = Logger.getLogger(XMLStorage.class.getName());

    /**
     * Filefilter that list only xml
     */
    private static FileFilter filter;

    private XMLStorage(){
        items = new HashSet();
        postfix = ".xml";
        opened = false;
    }

    public String getPostfix(){
        return postfix;
    }

    public void setPostfix(String postfix){
        this.postfix = postfix;
        this.filter = new PostfixFileFilter(postfix);
    }

    /**
     * Open a XMLThreadStorage by url
     * @param String pathname directory to store the XML files
     * @throws IOException when open directory failed
     */
    public static XMLStorage getXMLStorage(String path) throws IOException{
        logger.info("Setting up XML Thread Storage ... ");

        File dataDir = new File(path);

        if (!dataDir.exists()){
          // try to create the directory if not exist
          dataDir.mkdirs();
        }

        if (!dataDir.isDirectory()){
            throw new IOException("Parameter path not exist or not a directory: " + path);
        }
        XMLStorage newStore = new XMLStorage();
        newStore.setUrl(path);
        newStore.setPostfix(".xml");
        return newStore;
    }

    /**
     * Open a XMLThreadStorage by url
     * @param String pathname directory to store the XML files
     * @param String postfix the files type treated as xml files, e.g. ".xml"
     * @throws IOException when open directory failed
     */
    public static XMLStorage getXMLStorage(String path, String postfix) throws IOException{
        XMLStorage store = XMLStorage.getXMLStorage(path);
        store.setPostfix(postfix);
        return store;
    }

    public void setUrl(String url) throws NullPointerException{
        if (url == null) throw new NullPointerException("URL cannot be null. ");

        if (url.equals("")) throw new IllegalArgumentException("URL must not be empty!");

        this.url = url;
    }

    public String getUrl(){
        return url;
    }

    public void open() throws IOException {
        logger.info("Opening directory ... " + url);

        File dataDir = new File(url);

        if (!dataDir.exists()){
          // try to create the directory if not exist
          dataDir.mkdirs();
        }

        if (!dataDir.isDirectory()){
            throw new IOException("Parameter path not exist or not a directory: " +
                                  url + " (" + dataDir.getAbsolutePath() + ")");
        }

        logger.fine("Listing file ... ");
        File[] xmlFiles = dataDir.listFiles(filter);

        // add files to store if it match the postfix we specified
        for(int i=0; i<xmlFiles.length; i++){
          items.add(xmlFiles[i].getName());
        }

        logger.info("Number of files added: " + items.size());

        opened = true;
    }

    public void close(){
        opened = false;
    }

    /**
     * check if the thread with id specified existed in the store
     * @param id the id of the thread
     */
    public boolean containsId(String id){
        // check if the file have been downloaded
        return items.contains((id + postfix).intern());
    }

    /**
     * save thread as xml
     * @throws NullPointerException when id or thread is null
     * @throws IllegalArgumentException when id is empty string
     */
    public void put(String id, Object thread) throws IOException, NullPointerException {
        if (id == null || thread == null){
            throw new NullPointerException("id or thread cannot be null!");
        }

        if (id.equals("")) {
            throw new IllegalArgumentException("id must not be empty!");
        }

        FileWriter writer = null;
        SIXBSWriter out = null;
        try{
            writer = new FileWriter(url + File.separator + id + postfix);
            out = new SIXBSWriter(writer);
            out.writeObject(thread);
        }finally{
            try{
                out.close();
                writer.close();
            }catch(Exception e){}
        }

        items.add(id + postfix);
        logger.info("Thread added, id: " + url + File.separator + id + postfix );
    }

    /**
     * get thread from xml store by id
     * @throws NullPointerException when id or thread is null
     * @throws IllegalArgumentException when id is empty string
     */
    public Object get(String id) throws IOException, NullPointerException{
        if (id == null) throw new NullPointerException("id cannot be null. ");
        if (id.equals("")) throw new IllegalArgumentException("id must not be empty!");

        FileReader reader = new FileReader(new File(url + File.separator + id + postfix));
        SIXBSReader in = null;
        Object thread = null;

        try{
            in = new SIXBSReader(reader);
            thread = in.readObject();
        }finally{
            try{
                in.close();
                reader.close();
            }catch(Exception e){}
        }
        logger.info("Object loaded, id: " + id );
        return thread;
    }

    /**
     * remove thread xml file
     * @throws NullPointerException when id is null
     */
    public void remove(String id) throws NullPointerException, SecurityException {
        if (id == null) throw new NullPointerException("id cannot be null. ");

        if (id.equals("")) {
            throw new IllegalArgumentException("id must not be empty!");
        }
        File file = new File(url + File.separator + id + postfix);
        boolean exist = file.exists();

        if(exist){
            file.delete();
        }

        logger.info("Thread deleted, id: " + id );
        items.remove(id + postfix );
    }

    /**
     * do nothing in this implementation
     * as we save every time we access file
     */
    public void flush() throws IOException {

    }

    public Iterator iterator() {
        return items.iterator();
    }
}