import java.io.File;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

import my.httpClient.MD5Helper;

import org.apache.http.client.cache.HttpCacheEntry;

import org.apache.http.client.cache.HttpCacheStorage;

import org.apache.http.client.cache.HttpCacheUpdateCallback;

import org.apache.http.client.cache.HttpCacheUpdateException;

public class DiskCache implements HttpCacheStorage {

    public DiskCache() {

    }

    public HttpCacheEntry getEntry(String url) throws IOException {

        HttpCacheEntry entry = null;

        // 一个文件一个缓存项，使用 请求的url进行hash

        String path = getPath(url);

        // System.out.println("path:" + path);

        // 判断文件是否存在

        File file = new File(path);

        if (file.exists() == false) {

            return null;

        }

        try {

            ObjectInputStream in = new ObjectInputStream(new FileInputStream(

                    path));

            entry = (HttpCacheEntry) in.readObject();

            in.close();

        //    System.out.println("object read here:");

        } catch (ClassNotFoundException e) {

            e.printStackTrace();

        }

        return entry;

    }

    public void putEntry(String url, HttpCacheEntry entry) throws IOException {

        String path = getPath(url);

        ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(

                path));

        out.writeObject(entry);

        // System.out.println("object has been written..");

        out.close();

    }

    public void removeEntry(String url) throws IOException {

        String path = getPath(url);

        // 判断文件是否存在

        File file = new File(path);

        if (file.exists() == true) {

            file.delete();

        }

    }

    public void updateEntry(String url, HttpCacheUpdateCallback callback)

            throws IOException, HttpCacheUpdateException {

        String path = getPath(url);

        HttpCacheEntry existingEntry = null;

        // 判断文件是否存在，若文件存在，则取出文件的内容

        File file = new File(path);

        if (file.exists() == true) {

            ObjectInputStream in = new ObjectInputStream(new FileInputStream(

                    path));

            try {

                existingEntry = (HttpCacheEntry) in.readObject();

            } catch (ClassNotFoundException e) {

                e.printStackTrace();

            }

            in.close();

            System.out.println("object read here:");

        }

        HttpCacheEntry updatedEntry = callback.update(existingEntry); // 获取更新过的缓存实体

        // 不管存在不存在，都用保存新的实体项。

        putEntry(url, updatedEntry);

    }

    /*

     * 根据url地址获取缓存项在文件系统中的存储地址

     */

    private String getPath(String url) {

        String key = MD5Helper.string2MD5(url);

        String path = "c:\\http-cache\\" + key;

        return path;

    }

}