HttpClient学习系列 — 学习总结 |我的资源库露水湾

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Java 代码

// 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Java 代码

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 Java 代码

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 Java 代码

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：Java 代码

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 Java 代码

// 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 Java 代码

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);