HttpClient学习系列 -- 学习总结

jar包：

 HttpClient 4.x版本

 

简要介绍

HttpComponents 包括 HttpCore包和HttpClient包

HttpClient：Http的执行http请求

DefaultHttpClient：httpClient默认实现

HttpGet、HttpPost：Get、Post方法执行类

HttpResponse：执行返回的Response，含http的header和执行结果实体Entity

HttpEntity：Http返回结果实体，不含Header内容

HttpParam：连接参数，配合连接池使用

PoolingClientConnectionManager：连接池

 

基础Get方法

		// 默认的client类。
		HttpClient client = new DefaultHttpClient();
		// 设置为get取连接的方式.
		HttpGet get = new HttpGet(url);
		// 得到返回的response.
		HttpResponse response = client.execute(get);
		// 得到返回的client里面的实体对象信息.
		HttpEntity entity = response.getEntity();
		if (entity != null) {
			System.out.println( entity.getContentEncoding());
			System.out.println( entity.getContentType());
			// 得到返回的主体内容.
			InputStream instream = entity.getContent();
			BufferedReader reader = new BufferedReader(new InputStreamReader(instream, encoding));
			System.out.println(reader.readLine());
			// EntityUtils 处理HttpEntity的工具类
			// System.out.println(EntityUtils.toString(entity));
		}

		// 关闭连接.
		client.getConnectionManager().shutdown();

 

 

基础Post方法

 

		DefaultHttpClient httpclient = new DefaultHttpClient();
		HttpPost httpost = new HttpPost(url);
		// 添加参数
		List<NameValuePair> formparams = new ArrayList<NameValuePair>();
		formparams.add(new BasicNameValuePair("p", "1"));
		formparams.add(new BasicNameValuePair("t", "2"));
		formparams.add(new BasicNameValuePair("e", "3"));

		UrlEncodedFormEntity urlEntity =  new UrlEncodedFormEntity(formparams, "UTF-8");
		httpost.setEntity(urlEntity);

		HttpResponse response = httpclient.execute(httpost);
		HttpEntity entity = response.getEntity();

		System.out.println("Login form get: " + response.getStatusLine() + entity.getContent());
	//	dump(entity, encoding);
		System.out.println("Post logon cookies:");
		List<Cookie> cookies = httpclient.getCookieStore().getCookies();
		for (int i = 0; i < cookies.size(); i++) {
			System.out.println("- " + cookies.get(i).toString());
		}
		// 关闭请求
		httpclient.getConnectionManager().shutdown();

 

 

保留Session，保留用户+密码状态

Demo1，只支持单线程

 

		DefaultHttpClient httpclient = new DefaultHttpClient(
			new ThreadSafeClientConnManager());

		HttpPost httpost = new HttpPost(url);
		// 添加参数
		List<NameValuePair> formparams = new ArrayList<NameValuePair>();
		formparams.add(new BasicNameValuePair("p", "1"));
		formparams.add(new BasicNameValuePair("t", "2"));
		formparams.add(new BasicNameValuePair("e", "3"));
		// 设置请求的编码格式
		httpost.setEntity(new UrlEncodedFormEntity(formparams, Consts.UTF_8));
		// 登录一遍
		httpclient.execute(httpost);
		// 然后再第二次请求普通的url即可。
		httpost = new HttpPost(url2);
		BasicResponseHandler responseHandler = new BasicResponseHandler();
		System.out.println(httpclient.execute(httpost, responseHandler));
		httpclient.getConnectionManager().shutdown();
 
		return "";

 

 

 

Demo2：第二次请求带上第一次请求的Cookie 

    用于在用户+密码等候后，后续根据第一次请求的URL获取的Cookie，把这些Cookie添加到第二次请求的Cookie中

 

 

DefaultHttpClient httpclient = new DefaultHttpClient();
		HttpPost httpost = new HttpPost(url);
		// 添加参数
		List<NameValuePair> formparams = new ArrayList<NameValuePair>();
		formparams.add(new BasicNameValuePair("uname", name));
		formparams.add(new BasicNameValuePair("pass", "e0c10f451217b93f76c2654b2b729b85"));
		formparams.add(new BasicNameValuePair("auto_login","0"));
		formparams.add(new BasicNameValuePair("a","1"));
		formparams.add(new BasicNameValuePair("backurl","1"));
 
		UrlEncodedFormEntity urlEntity =  new UrlEncodedFormEntity(formparams, "UTF-8");
		httpost.setEntity(urlEntity);
		HttpContext localContext = new BasicHttpContext();

		HttpResponse response = httpclient.execute(httpost,localContext);
		HttpEntity entity = response.getEntity();
		// 打印获取值
		System.out.println(Arrays.toString(response.getAllHeaders()));
		System.out.println(EntityUtils.toString(entity));
 
		// 第二次请求，使用上一次请求的Cookie
		DefaultHttpClient httpclient2 = new DefaultHttpClient();
		HttpPost httpost2 = new HttpPost("http://my.ifeng.com/?_c=index&_a=my");
		// 获取上一次请求的Cookie
		CookieStore cookieStore2 = httpclient2.getCookieStore();
		// 下一次的Cookie的值，将使用上一次请求
		CookieStore cookieStore = httpclient.getCookieStore();
		List<Cookie> list = cookieStore.getCookies();
		for(Cookie o : list){
			System.out.println(o.getName() + " = " + o.getValue() + " 12");;
			cookieStore2.addCookie(o);
		}
 
		HttpResponse response2 = httpclient2.execute(httpost2);
		HttpEntity entity2 = response2.getEntity();
		System.out.println(Arrays.toString(response2.getAllHeaders()));
		System.out.println(EntityUtils.toString(entity2));

 

 

 

获取访问上下文：

 

 

		HttpClient httpclient = new DefaultHttpClient();
		// 设置为get取连接的方式.
		HttpGet get = new HttpGet(url);
		HttpContext localContext = new BasicHttpContext();
		// 得到返回的response.第二个参数，是上下文，很好的一个参数！
		httpclient.execute(get, localContext);

		// 从上下文中得到HttpConnection对象
		HttpConnection con = (HttpConnection) localContext
				.getAttribute(ExecutionContext.HTTP_CONNECTION);
		System.out.println("socket超时时间：" + con.getSocketTimeout());

		// 从上下文中得到HttpHost对象
		HttpHost target = (HttpHost) localContext
				.getAttribute(ExecutionContext.HTTP_TARGET_HOST);
		System.out.println("最终请求的目标:" + target.getHostName() + ":"
				+ target.getPort());

		// 从上下文中得到代理相关信息.
		HttpHost proxy = (HttpHost) localContext
				.getAttribute(ExecutionContext.HTTP_PROXY_HOST);
		if (proxy != null)
			System.out.println("代理主机的目标:" + proxy.getHostName() + ":"
					+ proxy.getPort());

		System.out.println("是否发送完毕:"
				+ localContext.getAttribute(ExecutionContext.HTTP_REQ_SENT));

		// 从上下文中得到HttpRequest对象
		HttpRequest request = (HttpRequest) localContext
				.getAttribute(ExecutionContext.HTTP_REQUEST);
		System.out.println("请求的版本:" + request.getProtocolVersion());
		Header[] headers = request.getAllHeaders();
		System.out.println("请求的头信息: ");
		for (Header h : headers) {
			System.out.println(h.getName() + "--" + h.getValue());
		}
		System.out.println("请求的链接:" + request.getRequestLine().getUri());

		// 从上下文中得到HttpResponse对象
		HttpResponse response = (HttpResponse) localContext
				.getAttribute(ExecutionContext.HTTP_RESPONSE);
		HttpEntity entity = response.getEntity();
		if (entity != null) {
			System.out.println("返回结果内容编码是：" + entity.getContentEncoding());
			System.out.println("返回结果内容类型是：" + entity.getContentType());
		}

 

 

 

 

连接池和代理：

   每次使用最后一句new DefaultHttpClient(cm, httpParams);获取新的HttpClient

   里面还有一条如何设置代理

 

		// HttpParams 
		HttpParams httpParams  = new BasicHttpParams();  
		// HttpConnectionParams 设置连接参数
		 // 设置连接超时时间  
        HttpConnectionParams.setConnectionTimeout(httpParams, 30000);  
        // 设置读取超时时间  
        HttpConnectionParams.setSoTimeout(httpParams, 60000); 

		SchemeRegistry schemeRegistry = new SchemeRegistry();
		schemeRegistry.register(
		         new Scheme("http", 80, PlainSocketFactory.getSocketFactory()));
//		schemeRegistry.register(
//		         new Scheme("https", 443, SSLSocketFactory.getSocketFactory()));
		PoolingClientConnectionManager cm = new PoolingClientConnectionManager(schemeRegistry);
		// 设置最大连接数  
		cm.setMaxTotal(200);
		// 设置每个路由默认最大连接数  
		cm.setDefaultMaxPerRoute(20);
//		// 设置代理和代理最大路由
//		HttpHost localhost = new HttpHost("locahost", 80);
//		cm.setMaxPerRoute(new HttpRoute(localhost), 50);
        // 设置代理，
        HttpHost proxy = new HttpHost("10.36.24.3", 60001);
        httpParams.setParameter(ConnRoutePNames.DEFAULT_PROXY,  proxy);
		
		HttpClient httpClient = new DefaultHttpClient(cm, httpParams);

 

自动重连

   如果某次请求请求失败，可以自动重连

 

DefaultHttpClient httpClient = new DefaultHttpClient();
			// 可以自动重连
			HttpRequestRetryHandler requestRetryHandler2 = new HttpRequestRetryHandler() {  
		        // 自定义的恢复策略  
		        public synchronized boolean retryRequest(IOException exception, int executionCount, HttpContext context) {  
		            // 设置恢复策略，在发生异常时候将自动重试3次  
		            if (executionCount > 3) {    
		                // 超过最大次数则不需要重试    
		                return false;    
		            }    
		            if (exception instanceof NoHttpResponseException) {    
		                // 服务停掉则重新尝试连接    
		                return true;    
		            }    
		            if (exception instanceof SSLHandshakeException) {    
		                // SSL异常不需要重试    
		                return false;    
		            }   
		            HttpRequest request = (HttpRequest) context.getAttribute(ExecutionContext.HTTP_REQUEST);  
		            boolean idempotent = (request instanceof HttpEntityEnclosingRequest);  
		            if (!idempotent) {  
		                // 请求内容相同则重试  
		                return true;  
		            }  
		            return false;  
		        }  
		    }; 
			httpClient.setHttpRequestRetryHandler(requestRetryHandler2); 

 

 

 

 

 

使用自定义ResponseHandler处理返回的请求

 

 

			HttpClient httpClient = new DefaultHttpClient();
			HttpGet get = new HttpGet(url);
				// 定义一个类处理URL返回的结果
				ResponseHandler<byte[]> handler = new ResponseHandler<byte[]>() {
					public byte[] handleResponse(HttpResponse response)
							throws ClientProtocolException, IOException {
						HttpEntity entity = response.getEntity();
						if (entity != null) {
							return EntityUtils.toByteArray(entity);
						} else {
							return null;
						}
					}
				};
				// 不同于 httpClient.execute(request)，返回值是HttpResponse；返回值右ResponseHandler决定
				byte[] charts = httpClient.execute(get, handler);
				FileOutputStream out = new FileOutputStream(fileName);
				out.write(charts);
				out.close();
 
				httpClient.getConnectionManager().shutdown();

 

 

参考文献

 

 

• HttpClient官网   api 下载  
• HttpClient官方pdf  
• httpclient4.2.2的几个常用方法，登录之后访问页面问题，下载文件  

 

 

评论

1 楼 wrrwhn 2014-12-12  

很多基本场景都描述到了，很到位的入门学习，非常感谢。