Httpclient与RestTemplate的比较（比httpClient更优雅的Restful URL访问）

一、HttpClient

（一）HttpClient 客户端

1、HttpClient 是 apache 的开源，需要引入两个包：httpclient-4.2.4.jar 和 httpcore-4.2.2.jar。

/**
 * HttpClien 的客户端访问
 */
private void httpClientVisit() {  

    String clientResponse = "";
    try {  

        HttpClient client = new DefaultHttpClient();
        HttpPost request = new HttpPost(mUrl);  

        //不是表单数据提交，这边使用 StringEntity 即可
        //UrlEncodedFormEntity等都是 HttpEntity 接口的实现类
        StringEntity entity = new StringEntity(mRequestXml, "UTF-8");//编码
        entity.setContentType("text/xml");
        request.setEntity(entity);
        // 发送请求
        HttpResponse response = client.execute(request);  

        org.apache.http.HttpEntity httpEntity = response.getEntity();  

        if (httpEntity != null) {
            // EntityUtils.toString 如果不指定编码，EntityUtils默认会使用ISO_8859_1进行编码
            clientResponse = EntityUtils.toString(httpEntity, "UTF-8");// 记得设置编码或者如下
            // clientResponse = new String(EntityUtils.toString(httpEntity).getBytes("ISO_8859_1"), "UTF-8");
        }  

        if (clientResponse == null || "".equals(clientResponse)) {
            System.err.println("clientResponse is null or empty.");  

        }  

        System.out.println(clientResponse);  

    } catch (Exception e) {
        e.printStackTrace();
    }  

}

（二）HttpClient 详解

1、Post方式访问

/**
  * post方式提交表单（模拟用户登录请求）
  */
 public void postForm() {    

    String url = "http://localhost:8080/Java_WS_Server/rest/surpolicy/sendXml";  

     // 创建默认的httpClient实例.
    HttpClient client = new DefaultHttpClient();
     // 创建httppost
     HttpPost httppost = new HttpPost(url);
     // 创建参数队列
     List<NameValuePair> formparams = new ArrayList<NameValuePair>();
     formparams.add(new BasicNameValuePair("username", "admin"));
     formparams.add(new BasicNameValuePair("password", "123456"));
     UrlEncodedFormEntity uefEntity;
     try {
         uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8"); //编码
         httppost.setEntity(uefEntity);
         System.out.println("executing request " + httppost.getURI());
         HttpResponse response = client.execute(httppost);
Header[] headers = response.getAllHeaders();
for(int i=0; i<headers.length; i++){
    System.out.println(headers[i].getName());
}  

         try {
             HttpEntity entity = response.getEntity();
             if (entity != null) {
                 System.out.println("--------------------------------------");
                 System.out.println("Response content: " + EntityUtils.toString(entity, "UTF-8"));  //编码
                 System.out.println("--------------------------------------");
             }
         } finally {    

         }
     } catch (ClientProtocolException e) {
         e.printStackTrace();
     } catch (UnsupportedEncodingException e1) {
         e1.printStackTrace();
     } catch (IOException e) {
         e.printStackTrace();
     } finally {    

     }
 }

　　2、Get方式访问

/**
 * 发送 get请求
 */
public void get() {
    try {
        HttpClient client = new DefaultHttpClient();
        // 创建httpget.
        HttpGet httpget = new HttpGet("http://www.baidu.com/");
        System.out.println("executing request " + httpget.getURI());
        // 执行get请求.
        HttpResponse response = client.execute(httpget);
        try {
            // 获取响应实体
            HttpEntity entity = response.getEntity();
            System.out.println("--------------------------------------");
            // 打印响应状态
            System.out.println(response.getStatusLine());
            if (entity != null) {
                // 打印响应内容长度
                System.out.println("Response content length: " + entity.getContentLength());
                // 打印响应内容
                System.out.println("Response content: " + EntityUtils.toString(entity));
            }
            System.out.println("------------------------------------");
        } finally {
        }
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    }  catch (IOException e) {
        e.printStackTrace();
    } finally {}
}

3、乱码问题：

1）利用：UrlEncodedFormEntity等 entity 容器，实现发送内容的编码：

UrlEncodedFormEntity uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8"); //编码

StringEntity entity = new StringEntity(mRequestXml, "UTF-8");//编码

2、EntityUtils.toString()方法的转码，实现返回内容的编码：

EntityUtils.toString 如果不指定编码，EntityUtils默认会使用ISO_8859_1进行编码

clientResponse = EntityUtils.toString(httpEntity, "UTF-8");// 记得设置编码或者如下

clientResponse = new String(EntityUtils.toString(httpEntity).getBytes("ISO_8859_1"), "UTF-8");

二、RestTemplate

（一）RestTemplate 客户端

1、RestTemplate 是Spring的封装，需要spring的包 spring-web-3.0.7.RELEASE.jar

2、客户端代码：

/**
 * RestTemplate 客户端访问
 */
private void RestTemplateVisit() {
    String returnXml = ""; // 核心返回结果报文字符串  

    try {  

        //复杂构造函数的使用
        SimpleClientHttpRequestFactory requestFactory = new SimpleClientHttpRequestFactory();
        requestFactory.setConnectTimeout(1000);// 设置超时
        requestFactory.setReadTimeout(1000);  

        //利用复杂构造器可以实现超时设置，内部实际实现为 HttpClient
        RestTemplate restTemplate = new RestTemplate(requestFactory);  

        //设置HTTP请求头信息，实现编码等
        HttpHeaders requestHeaders = new HttpHeaders();
        // requestHeaders.set("Accept", "text/");
        requestHeaders.set("Accept-Charset", "utf-8");
        requestHeaders.set("Content-type", "text/xml; charset=utf-8");// 设置编码  

        //利用容器实现数据封装，发送
        HttpEntity<String> entity = new HttpEntity<String>(mRequestXml, requestHeaders);
        returnXml = restTemplate.postForObject(mUrl, entity, String.class);  

        // 转码原因：RestTemplate默认是使用org.springframework.http.converter.StringHttpMessageConverter来解析
        // StringHttpMessageConverter 默认用的 ISO-8859-1来编码的
        returnXml = new String(returnXml.getBytes("ISO-8859-1"), "utf-8");  

    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    }  

    System.out.println("restTemplate客户端访问返回： \n" + returnXml);
}

　　具体的参考这个博客：

http://blog.csdn.net/u012228718/article/details/42028951