HttpClient学习系列 -- 学习总结
jar包：
?HttpClient?4.x版本
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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
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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
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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
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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 "";??
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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
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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CookieDefaultHttpClient httpclient2 = new DefaultHttpClient();HttpPost httpost2 = new HttpPost("http://my.ifeng.com/?_c=index&_a=my");// 获取上一次请求的CookieCookieStore 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));??
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获取访问上下文：
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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());}??
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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
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// 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
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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);??
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使用自定义ResponseHandler处理返回的请求
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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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参考文献
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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???
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