當前位置：首頁 > 编程资源 > 编程问答 >内容正文

编程问答

HttpClient学习系列 -- 学习总结

發布時間：2024/6/21 编程问答 29 豆豆

生活随笔收集整理的這篇文章主要介紹了 HttpClient学习系列 -- 学习总结小編覺得挺不錯的,現在分享給大家,幫大家做個參考.

jar包：

?HttpClient?4.x版本

簡要介紹

HttpComponents 包括 HttpCore包和HttpClient包

HttpClient：Http的執行http請求

DefaultHttpClient：httpClient默認實現

HttpGet、HttpPost：Get、Post方法執行類

HttpResponse：執行返回的Response，含http的header和執行結果實體Entity

HttpEntity：Http返回結果實體，不含Header內容

HttpParam：連接參數，配合連接池使用

PoolingClientConnectionManager：連接池

基礎Get方法

Java代碼 ?

//?默認的client類。??

HttpClient?client?=?new?DefaultHttpClient();??

//?設置為get取連接的方式.??

HttpGet?get?=?new?HttpGet(url);??

//?得到返回的response.??

HttpResponse?response?=?client.execute(get);??

//?得到返回的client里面的實體對象信息.??

HttpEntity?entity?=?response.getEntity();??

if?(entity?!=?null)?{??

????System.out.println(?entity.getContentEncoding());??

????System.out.println(?entity.getContentType());??

????//?得到返回的主體內容.??

????InputStream?instream?=?entity.getContent();??

????BufferedReader?reader?=?new?BufferedReader(new?InputStreamReader(instream,?encoding));??

????System.out.println(reader.readLine());??

????//?EntityUtils?處理HttpEntity的工具類??

????//?System.out.println(EntityUtils.toString(entity));??

}??

//?關閉連接.??

client.getConnectionManager().shutdown();??

基礎Post方法

Java代碼 ?

????DefaultHttpClient?httpclient?=?new?DefaultHttpClient();??

????HttpPost?httpost?=?new?HttpPost(url);??

????//?添加參數??

????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());??

????}??

????//?關閉請求??

????httpclient.getConnectionManager().shutdown();??

保留Session，保留用戶+密碼狀態

Demo1，只支持單線程

Java代碼 ?

DefaultHttpClient?httpclient?=?new?DefaultHttpClient(??

????new?ThreadSafeClientConnManager());??

HttpPost?httpost?=?new?HttpPost(url);??

//?添加參數??

List<NameValuePair>?formparams?=?new?ArrayList<NameValuePair>();??

formparams.add(new?BasicNameValuePair("p",?"1"));??

formparams.add(new?BasicNameValuePair("t",?"2"));??

formparams.add(new?BasicNameValuePair("e",?"3"));??

//?設置請求的編碼格式??

httpost.setEntity(new?UrlEncodedFormEntity(formparams,?Consts.UTF_8));??

//?登錄一遍??

httpclient.execute(httpost);??

//?然后再第二次請求普通的url即可。??

httpost?=?new?HttpPost(url2);??

BasicResponseHandler?responseHandler?=?new?BasicResponseHandler();??

System.out.println(httpclient.execute(httpost,?responseHandler));??

httpclient.getConnectionManager().shutdown();??

return?"";??

Demo2：第二次請求帶上第一次請求的Cookie?

? ? 用于在用戶+密碼等候后，后續根據第一次請求的URL獲取的Cookie，把這些Cookie添加到第二次請求的Cookie中

Java代碼 ?

DefaultHttpClient?httpclient?=?new?DefaultHttpClient();??

????????HttpPost?httpost?=?new?HttpPost(url);??

????????//?添加參數??

????????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();??

????????//?打印獲取值??

????????System.out.println(Arrays.toString(response.getAllHeaders()));??

????????System.out.println(EntityUtils.toString(entity));??

???

????????//?第二次請求，使用上一次請求的Cookie??

????????DefaultHttpClient?httpclient2?=?new?DefaultHttpClient();??

????????HttpPost?httpost2?=?new?HttpPost("http://my.ifeng.com/?_c=index&_a=my");??

????????//?獲取上一次請求的Cookie??

????????CookieStore?cookieStore2?=?httpclient2.getCookieStore();??

????????//?下一次的Cookie的值，將使用上一次請求??

????????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));??

獲取訪問上下文：

Java代碼 ?

HttpClient?httpclient?=?new?DefaultHttpClient();??

//?設置為get取連接的方式.??

HttpGet?get?=?new?HttpGet(url);??

HttpContext?localContext?=?new?BasicHttpContext();??

//?得到返回的response.第二個參數，是上下文，很好的一個參數！??

httpclient.execute(get,?localContext);??

//?從上下文中得到HttpConnection對象??

HttpConnection?con?=?(HttpConnection)?localContext??

????????.getAttribute(ExecutionContext.HTTP_CONNECTION);??

System.out.println("socket超時時間："?+?con.getSocketTimeout());??

//?從上下文中得到HttpHost對象??

HttpHost?target?=?(HttpHost)?localContext??

????????.getAttribute(ExecutionContext.HTTP_TARGET_HOST);??

System.out.println("最終請求的目標:"?+?target.getHostName()?+?":"??

????????+?target.getPort());??

//?從上下文中得到代理相關信息.??

HttpHost?proxy?=?(HttpHost)?localContext??

????????.getAttribute(ExecutionContext.HTTP_PROXY_HOST);??

if?(proxy?!=?null)??

????System.out.println("代理主機的目標:"?+?proxy.getHostName()?+?":"??

????????????+?proxy.getPort());??

System.out.println("是否發送完畢:"??

????????+?localContext.getAttribute(ExecutionContext.HTTP_REQ_SENT));??

//?從上下文中得到HttpRequest對象??

HttpRequest?request?=?(HttpRequest)?localContext??

????????.getAttribute(ExecutionContext.HTTP_REQUEST);??

System.out.println("請求的版本:"?+?request.getProtocolVersion());??

Header[]?headers?=?request.getAllHeaders();??

System.out.println("請求的頭信息:?");??

for?(Header?h?:?headers)?{??

????System.out.println(h.getName()?+?"--"?+?h.getValue());??

}??

System.out.println("請求的鏈接:"?+?request.getRequestLine().getUri());??

//?從上下文中得到HttpResponse對象??

HttpResponse?response?=?(HttpResponse)?localContext??

????????.getAttribute(ExecutionContext.HTTP_RESPONSE);??

HttpEntity?entity?=?response.getEntity();??

if?(entity?!=?null)?{??

????System.out.println("返回結果內容編碼是："?+?entity.getContentEncoding());??

????System.out.println("返回結果內容類型是："?+?entity.getContentType());??

}??

連接池和代理：

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

? ?里面還有一條如何設置代理

Java代碼 ?

????????//?HttpParams???

????????HttpParams?httpParams??=?new?BasicHttpParams();????

????????//?HttpConnectionParams?設置連接參數??

?????????//?設置連接超時時間????

????????HttpConnectionParams.setConnectionTimeout(httpParams,?30000);????

????????//?設置讀取超時時間????

????????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);??

????????//?設置最大連接數????

????????cm.setMaxTotal(200);??

????????//?設置每個路由默認最大連接數????

????????cm.setDefaultMaxPerRoute(20);??

//??????//?設置代理和代理最大路由??

//??????HttpHost?localhost?=?new?HttpHost("locahost",?80);??

//??????cm.setMaxPerRoute(new?HttpRoute(localhost),?50);??

????????//?設置代理，??

????????HttpHost?proxy?=?new?HttpHost("10.36.24.3",?60001);??

????????httpParams.setParameter(ConnRoutePNames.DEFAULT_PROXY,??proxy);??

??????????

????????HttpClient?httpClient?=?new?DefaultHttpClient(cm,?httpParams);??

自動重連

? ?如果某次請求請求失敗，可以自動重連

Java代碼 ?

DefaultHttpClient?httpClient?=?new?DefaultHttpClient();??

????????????//?可以自動重連??

????????????HttpRequestRetryHandler?requestRetryHandler2?=?new?HttpRequestRetryHandler()?{????

????????????????//?自定義的恢復策略????

????????????????public?synchronized?boolean?retryRequest(IOException?exception,?int?executionCount,?HttpContext?context)?{????

????????????????????//?設置恢復策略，在發生異常時候將自動重試3次????

????????????????????if?(executionCount?>?3)?{??????

????????????????????????//?超過最大次數則不需要重試??????

????????????????????????return?false;??????

????????????????????}??????

????????????????????if?(exception?instanceof?NoHttpResponseException)?{??????

????????????????????????//?服務停掉則重新嘗試連接??????

????????????????????????return?true;??????

????????????????????}??????

????????????????????if?(exception?instanceof?SSLHandshakeException)?{??????

????????????????????????//?SSL異常不需要重試??????

????????????????????????return?false;??????

????????????????????}?????

????????????????????HttpRequest?request?=?(HttpRequest)?context.getAttribute(ExecutionContext.HTTP_REQUEST);????

????????????????????boolean?idempotent?=?(request?instanceof?HttpEntityEnclosingRequest);????

????????????????????if?(!idempotent)?{????

????????????????????????//?請求內容相同則重試????

????????????????????????return?true;????

????????????????????}????

????????????????????return?false;????

????????????????}????

????????????};???

????????????httpClient.setHttpRequestRetryHandler(requestRetryHandler2);???

使用自定義ResponseHandler處理返回的請求

Java代碼 ?

HttpClient?httpClient?=?new?DefaultHttpClient();??

HttpGet?get?=?new?HttpGet(url);??

????//?定義一個類處理URL返回的結果??

????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決定??

????byte[]?charts?=?httpClient.execute(get,?handler);??

????FileOutputStream?out?=?new?FileOutputStream(fileName);??

????out.write(charts);??

????out.close();??

????httpClient.getConnectionManager().shutdown();??

參考文獻

HttpClient官網? ?api 下載 ?
HttpClient官方pdf ?
httpclient4.2.2的幾個常用方法，登錄之后訪問頁面問題，下載文件?

轉載于:https://www.cnblogs.com/yaowen/p/5446861.html

總結

以上是生活随笔為你收集整理的HttpClient学习系列 -- 学习总结的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。

上一篇： 0429 Scrum团队成立与第6-7章
下一篇：实验9：Problem D: 从点到面