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

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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.youkuaiyun.com/u012228718/article/details/42028951
https://www.cnblogs.com/fengli9998/p/8028250.html