如何从Android调用RESTful Web服务？

Question

我使用Jersey Framework和Java在Netbean IDE中编写了一个REST Web服务.

对于用户需要提供用户名和密码的每个请求,我知道此身份验证不是最佳做法(使用curl命令,如:)curl -u username:password -X PUT http://localhsot:8080/user.

现在我想从Android类调用REST Web服务.

我该怎么办？

我有一个使用DefaultHttpClient和的Android类CredentialUsernameAndPassword,但是当我在Eclipse中运行它时,有时会遇到运行时异常或SDK异常.

Answer 1

这是一个示例restclient类

public class RestClient
{
    public enum RequestMethod
    {
        GET,
        POST
    }
    public int responseCode=0;
    public String message;
    public String response;
    public void Execute(RequestMethod method,String url,ArrayList<NameValuePair> headers,ArrayList<NameValuePair> params) throws Exception
    {
        switch (method)
        {
            case GET:
            {
                // add parameters
                String combinedParams = "";
                if (params!=null)
                {
                    combinedParams += "?";
                    for (NameValuePair p : params)
                    {
                        String paramString = p.getName() + "=" + URLEncoder.encode(p.getValue(),"UTF-8");
                        if (combinedParams.length() > 1)
                            combinedParams += "&" + paramString;
                        else
                            combinedParams += paramString;
                    }
                }
                HttpGet request = new HttpGet(url + combinedParams);
                // add headers
                if (headers!=null)
                {
                    headers=addCommonHeaderField(headers);
                    for (NameValuePair h : headers)
                        request.addHeader(h.getName(), h.getValue());
                }
                executeRequest(request, url);
                break;
            }
            case POST:
            {
                HttpPost request = new HttpPost(url);
                // add headers
                if (headers!=null)
                {
                    headers=addCommonHeaderField(headers);
                    for (NameValuePair h : headers)
                        request.addHeader(h.getName(), h.getValue());
                }
                if (params!=null)
                    request.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));
                executeRequest(request, url);
                break;
            }
        }
    }
    private ArrayList<NameValuePair> addCommonHeaderField(ArrayList<NameValuePair> _header)
    {
        _header.add(new BasicNameValuePair("Content-Type","application/x-www-form-urlencoded"));
        return _header;
    }
    private void executeRequest(HttpUriRequest request, String url)
    {
        HttpClient client = new DefaultHttpClient();
        HttpResponse httpResponse;
        try
        {
            httpResponse = client.execute(request);
            responseCode = httpResponse.getStatusLine().getStatusCode();
            message = httpResponse.getStatusLine().getReasonPhrase();
            HttpEntity entity = httpResponse.getEntity();

            if (entity != null)
            {
                InputStream instream = entity.getContent();
                response = convertStreamToString(instream);
                instream.close();
            }
        }
        catch (Exception e)
        { }
    }

    private static String convertStreamToString(InputStream is)
    {
        BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        StringBuilder sb = new StringBuilder();
        String line = null;
        try
        {
            while ((line = reader.readLine()) != null)
            {
                sb.append(line + "\n");
            }
            is.close();
        }
        catch (IOException e)
        { }
        return sb.toString();
    }
}

Answer 2

最近发现第三方库 - Square Retrofit可以很好地完成这项工作.

定义REST端点

public interface GitHubService {
   @GET("/users/{user}/repos")
   List<Repo> listRepos(@Path("user") String user,Callback<List<User>> cb);
}

获得具体服务

RestAdapter restAdapter = new RestAdapter.Builder()
    .setEndpoint("https://api.github.com")
    .build();
GitHubService service = restAdapter.create(GitHubService.class);

调用REST端点

List<Repo> repos = service.listRepos("octocat",new Callback<List<User>>() { 
    @Override
    public void failure(final RetrofitError error) {
        android.util.Log.i("example", "Error, body: " + error.getBody().toString());
    }
    @Override
    public void success(List<User> users, Response response) {
        // Do something with the List of Users object returned
        // you may populate your adapter here
    }
});

该库为您处理json序列化和deserailization.您也可以自定义序列化和反序列化.

Gson gson = new GsonBuilder()
    .setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES)
    .registerTypeAdapter(Date.class, new DateTypeAdapter())
    .create();

RestAdapter restAdapter = new RestAdapter.Builder()
    .setEndpoint("https://api.github.com")
    .setConverter(new GsonConverter(gson))
    .build();

Answer 3

无论你做什么都停下来!:)

将RESTful客户端实现为SERVICE,并将密集型网络内容委托给与活动无关的组件:SERVICE.

观看这个富有洞察力的视频 http://www.youtube.com/watch?v=xHXn3Kg2IQE,其中Virgil Dobjanschi正在解释他对这一挑战的方法......