httpclient基本用法

1. maven基础依赖
   
   org.apache.httpcomponents
   httpclient
   x.x.x
   

2. HttpClient 的基本用法
   // 初始化httpclient
   CloseableHttpClient httpclient = HttpClients.createDefault();
   // 简单生成get请求
   HttpGet httpget = new HttpGet(“http://localhost/”);
   // 存放返回内容的类
   CloseableHttpResponse response = httpclient.execute(httpget);

   try{
   <…>
   } finally{
   response.close();
   }

3. 生成 HTTP 请求
   方法一：
   HttpGet httpGet = new HttpGet(“http://www.google.com/search?hl=en&q=httpclient&btnG=Google+Search&aq=f&oq=”);

   方法二：
   URI uri = new URIBuilder()
   .setScheme(“http”)
   .setHost(“www.google.com”)
   .setPath("/search")
   .setParameter(“q”, “httpclient”)
   .setParameter(“btnG”, “Google Search”)
   .setParameter(“aq”, “f”)
   .setParameter(“oq”, “”)
   .build();
   HttpGet httpGet = new HttpGet(uri);

4. 构建 HTTP 响应
   HttpResponse response = new BasicHttpResponse(HttpVersion.HTTP_1_1, HttpStatus.SC_OK, “OK”);

   System.out.println(response.getProtocolVersiong());
   System.out.println(response.getStatusLine().getStatusCode());
   System.out.println(response.getStatusLine().getReasonPhrase());
   System.out.println(response.getStatusLine().toString());

5. 添加信息头
   HttpResponse response = new BasicHttpResponse(HttpVersiong.HTTP_1_1, HttpStatus.SC_OK, “OK”);
   response.addHeader(“Set-Cookie”, “cl=a; path=/; domain=localhost”);
   response.addHeader(“Set-Cookie”, “cl=b; path=”/"; c3=c; domain=“localhost”");
   Header h1 = response.getFirstHeader(“Set-Cookie”);
   System.out.println(h1);
   Header h2 = response.getLastHeader(“Set-Cookie”);
   System.out.println(h2);
   Header[] hs = response.getHeaders(“Set-Cookie”);
   System.out.println(hs.length);

6. 生成 HTTP 实体
   5.0 默认 HttpEntity entity1 = response1.getEntity();
   4.5版本
   string类型的实体
   StringEntity myEntity = new StringEntity(“important message”,
   ContentType.create(“text/plain”, “UTF-8”));

   System.out.println(myEntity.getContentType());
   System.out.println(myEntity.getContentLength());
   System.out.println(EntityUtils.toString(myEntity));
   System.out.println(EntityUtils.toByteArray(myEntity).length);

   file类型的实体
   File file = new File(“somefile.txt”);
   FileEntity entity = new FileEntity(file, ContentType.create(“text/plain”, “UTF-8”));

   HttpPost httppost = new HttpPost(“http://localhost/action.do”);
   httppost.setEntity(entity);

   表单类型的实体
   List formparams = new ArrayList();
   formparams.add(new BasicNameValuePair(“param1”, “value1”));
   formparams.add(new BasicNameValuePair(“param2”, “value2”));
   UrlEncodedFormEntity entity = new UrlEncodeFormEntity(formparams, Consts.UTF-8);
   HttpPost httppost = new HttpPost(“http://localhost/handler.do”);
   httppost.setEntity(entity);

7. 确保 HTTP 实体被消耗
   EntityUtils.consume(entity1)

8. HTTP代理
   方式一：
   HttpHost proxy = new HttpHost(“someproxy”, 8080);
   DefaultProxyRoutePlanner routePlanner = new DefaultProxyRoutePlanner(proxy);
   CloseableHttpClient httpclient = HttpClients.custom()
   .setRoutePlanner(routePlanner)
   .build();
   方式二：
   SystemDefaultRoutePlanner routePlanner = new SystemDefaultRoutePlanner(ProxySelector.getDefault());
   CloseableHttpClient httpclient = HttpClients.custom()
   .setRoutePlanner(routePlanner)
   .build();
   方式三：
   HttpRoutePlanner routePlanner = new HttpRoutePlanner(){
   public HttpRoute determineRoute(
   HttpHost target,
   HttpRequest request,
   HttpContext context ) throws HttpException {
   return new HttRoute(target, null, new HttpHost(“someproxy”, 8080), “https”.equalsIgnoreCase(target.getSchemeName()));
   }
   };

   CloseableHttpClient httpclient = HttpClients.custom()
   .setRoutePlanner(routePlanner)
   .build();
   }
   }