Android使用本地缓存解析远程服务器JSON数据

//1.基础类

public abstract class BaseProtocol<T>{    /**     * 加载appinfo信息     * @param index     * @return     */    public T load(int index)  {        try {            String json = loadLocal(index);            if (json == null) {                json = loadServer(index);                if (json != null)                    save2Local(index, json);            }            if (json != null) {                return paserJson(json);            }        } catch (HttpException e) {            e.printStackTrace();        }        return null;    }    /**     * 根据时间戳来读取本地缓存     * @param index     * @return     */    private String loadLocal(int index) {        BufferedReader br = null;        try {            File dir = FileUtil.getCacheDir();            // getParams() 为了区分包名            File file = new File(dir, getKey() +"_" + index + getParams());            FileReader fr = new FileReader(file);            br = new BufferedReader(fr);            String timeStr = br.readLine();            if (System.currentTimeMillis() > Long.parseLong(timeStr)) {                return null;            } else {                String str = "";                StringWriter sw = new StringWriter();                while ((str = br.readLine()) != null) {                    sw.write(str);                }                return sw.toString();            }        } catch (Exception e) {            e.printStackTrace();        } finally {            try {                if (br != null)                    br.close();            } catch (IOException e) {                e.printStackTrace();            }        }        return null;    }    /**     * 加载服务器数据     * @param index     * @return     * @throws HttpException     */    private String loadServer(int index) throws HttpException {        HttpResult httpResult = HttpHelper.get(HttpHelper.URL + getKey() +"?index=" + index + getParams());        return httpResult !=null ? httpResult.toString() : null;    }    /**     * 给地址添加请求参数     * @return     */    public String getParams() {        return "";    }    private void save2Local(int index, String json) {        BufferedWriter bw = null;        try {            File dir = FileUtil.getCacheDir();            File file = new File(dir, getKey() + "_" + index + getParams());            FileWriter fw = new FileWriter(file);            bw = new BufferedWriter(fw);            long time = (int) (System.currentTimeMillis() + 1000 * 10);            bw.write(time + "");            bw.newLine();            bw.write(json);            bw.flush();        } catch (IOException e) {            e.printStackTrace();        } finally {            try {                bw.close();            } catch (IOException e) {                e.printStackTrace();            }        }    }    /**     * 返回请求的文件夹名称     * @return     */    public abstract String getKey();    /**     * 解析json数据     * @param json     * @return     */    public abstract T paserJson(String json);}

//2.实现类

public class TopProtocol extends BaseProtocol<List<String>> {    @Override    public String getKey() {        return "hot";    }    @Override    public List<String> paserJson(String json) {        List<String> list = new ArrayList<String>();        try {            JSONArray jsonArray = new JSONArray(json);            for (int i = 0; i < jsonArray.length(); i++) {                //JSONObject jsonObject = jsonArray.getJSONObject(i);                //String hot = jsonObject.getString(")                String hot = jsonArray.getString(i);                list.add(hot);            }        } catch (JSONException e) {            e.printStackTrace();        }        return list;    }}

//3.HttpHelper .java 与HttpResult.java

public class HttpHelper {    public static final String URL = "http://127.0.0.1:8090/";    /** get请求，获取返回字符串内容 */    public static HttpResult get(String url) {        HttpGet httpGet = new HttpGet(url);        return execute(url, httpGet);    }    /** post请求，获取返回字符串内容 */    public static HttpResult post(String url, byte[] bytes) {        HttpPost httpPost = new HttpPost(url);        ByteArrayEntity byteArrayEntity = new ByteArrayEntity(bytes);        httpPost.setEntity(byteArrayEntity);        return execute(url, httpPost);    }    /** 下载 */    public static HttpResult download(String url) {        HttpGet httpGet = new HttpGet(url);        return execute(url, httpGet);    }    /** 执行网络访问 */    private static HttpResult execute(String url, HttpRequestBase requestBase) {        boolean isHttps = url.startsWith("https://");//判断是否需要采用https        AbstractHttpClient httpClient = HttpClientFactory.create(isHttps);        HttpContext httpContext = new SyncBasicHttpContext(new BasicHttpContext());        HttpRequestRetryHandler retryHandler = httpClient.getHttpRequestRetryHandler();//获取重试机制        int retryCount = 0;        boolean retry = true;        while (retry) {            try {                HttpResponse response = httpClient.execute(requestBase, httpContext);//访问网络                if (response != null) {                    return new HttpResult(response, httpClient, requestBase);                }            } catch (Exception e) {                IOException ioException = new IOException(e.getMessage());                retry = retryHandler.retryRequest(ioException, ++retryCount, httpContext);//把错误异常交给重试机制，以判断是否需要采取从事                LogUtils.e(e);            }        }        return null;    }    /** http的返回结果的封装，可以直接从中获取返回的字符串或者流 */    public static class HttpResult {        private HttpResponse mResponse;        private InputStream mIn;        private String mStr;        private HttpClient mHttpClient;        private HttpRequestBase mRequestBase;        public HttpResult(HttpResponse response, HttpClient httpClient, HttpRequestBase requestBase) {            mResponse = response;            mHttpClient = httpClient;            mRequestBase = requestBase;        }        public int getCode() {            StatusLine status = mResponse.getStatusLine();            return status.getStatusCode();        }        /** 从结果中获取字符串，一旦获取，会自动关流，并且把字符串保存，方便下次获取 */        public String getString() {            if (!TextUtils.isEmpty(mStr)) {                return mStr;            }            InputStream inputStream = getInputStream();            ByteArrayOutputStream out = null;            if (inputStream != null) {                try {                    out = new ByteArrayOutputStream();                    byte[] buffer = new byte[1024 * 4];                    int len = -1;                    while ((len = inputStream.read(buffer)) != -1) {                        out.write(buffer, 0, len);                    }                    byte[] data = out.toByteArray();                    mStr = new String(data, "utf-8");                } catch (Exception e) {                    LogUtils.e(e);                } finally {                    IOUtils.closeQuietly(out);                    close();                }            }            return mStr;        }        /** 获取流，需要使用完毕后调用close方法关闭网络连接 */        public InputStream getInputStream() {            if (mIn == null && getCode() < 300) {                HttpEntity entity = mResponse.getEntity();                try {                    mIn = entity.getContent();                } catch (Exception e) {                    LogUtils.e(e);                }            }            return mIn;        }        /** 关闭网络连接 */        public void close() {            if (mRequestBase != null) {                mRequestBase.abort();            }            IOUtils.closeQuietly(mIn);            if (mHttpClient != null) {                mHttpClient.getConnectionManager().closeExpiredConnections();            }        }    }}