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