HttpClient学习系列

超、凢脫俗 2022-08-26 15:18 148阅读 0赞

**[http://www.myexception.cn/open-source/1075326.html][http_www.myexception.cn_open-source_1075326.html]**

**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**

**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();

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