java应用集锦9:httpclient4.2.2的几个常用方法，登录之后访问页面问题，下载文件

转账注明出处：http://renjie120.iteye.com/blog/1727933

在工作中要用到android，然后进行网络请求的时候，打算使用httpClient。

总结一下httpClient的一些基本使用。

版本是4.2.2。

使用这个版本的过程中，百度很多，结果都是出现的org.apache.commons.httpclient.这个包名，而不是我这里的org.apache.http.client.HttpClient----------前者版本是 Commons HttpClient 3.x ，不是最新的版本HttpClient 4.×。

官网上面：

Commons HttpClient 3.x codeline is at the end of life. All users of Commons HttpClient 3.x are strongly encouraged to upgrade to HttpClient 4.1.  

1.基本的get

public void getUrl(String url, String encoding)
            throws ClientProtocolException, IOException {
        // 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("内容编码是：" + entity.getContentEncoding());
            System.out.println("内容类型是：" + entity.getContentType());
            // 得到返回的主体内容.
            InputStream instream = entity.getContent();
            try {
                BufferedReader reader = new BufferedReader(
                        new InputStreamReader(instream, encoding));
                System.out.println(reader.readLine());
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                instream.close();
            }
        }

        // 关闭连接.
        client.getConnectionManager().shutdown();
    }

2.基本的Post

   下面的params参数，是在表单里面提交的参数。

public void postUrlWithParams(String url, Map params, String encoding)
            throws Exception {
        DefaultHttpClient httpclient = new DefaultHttpClient();
        try {

            HttpPost httpost = new HttpPost(url);
            // 添加参数
            List<NameValuePair> nvps = new ArrayList<NameValuePair>();
            if (params != null && params.keySet().size() > 0) {
                Iterator iterator = params.entrySet().iterator();
                while (iterator.hasNext()) {
                    Map.Entry entry = (Entry) iterator.next();
                    nvps.add(new BasicNameValuePair((String) entry.getKey(),
                            (String) entry.getValue()));
                }
            }

            httpost.setEntity(new UrlEncodedFormEntity(nvps, Consts.UTF_8));

            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();
            if (cookies.isEmpty()) {
                System.out.println("None");
            } else {
                for (int i = 0; i < cookies.size(); i++) {
                    System.out.println("- " + cookies.get(i).toString());
                }
            }

        } finally {
            // 关闭请求
            httpclient.getConnectionManager().shutdown();
        }
    }

3。打印页面输出的小代码片段

private static void dump(HttpEntity entity, String encoding)
            throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(
                entity.getContent(), encoding));
        System.out.println(br.readLine());
    }

4.常见的登录session问题，需求:使用账户，密码登录系统之后，然后再访问页面不出错。

特别注意，下面的httpclient对象要使用一个，而不要在第二次访问的时候，重新new一个。至于如何保存这个第一步经过了验证的 httpclient，有很多种方法实现。单例，系统全局变量（android 下面的Application），ThreadLocal变量等等。

       以及下面创建的httpClient要使用ThreadSafeClientConnManager对象！

   public String getSessionId(String url, Map params, String encoding,

        String url2) throws Exception {
    DefaultHttpClient httpclient = new DefaultHttpClient(
            new ThreadSafeClientConnManager());
    try {

        HttpPost httpost = new HttpPost(url);
        // 添加参数
        List<NameValuePair> nvps = new ArrayList<NameValuePair>();
        if (params != null && params.keySet().size() > 0) {
            Iterator iterator = params.entrySet().iterator();
            while (iterator.hasNext()) {
                Map.Entry entry = (Entry) iterator.next();
                nvps.add(new BasicNameValuePair((String) entry.getKey(),
                        (String) entry.getValue()));
            }
        }
        // 设置请求的编码格式
        httpost.setEntity(new UrlEncodedFormEntity(nvps, 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));
    } finally {
        // 关闭请求
        httpclient.getConnectionManager().shutdown();
    }
    return "";
}

5.下载文件，例如mp3等等。

//第一个参数，网络连接；第二个参数，保存到本地文件的地址
public void getFile(String url, String fileName) {
        HttpClient httpClient = new DefaultHttpClient();
        HttpGet get = new HttpGet(url);
        try {
            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;
                    }
                }
            };

            byte[] charts = httpClient.execute(get, handler);
            FileOutputStream out = new FileOutputStream(fileName);
            out.write(charts);
            out.close();

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            httpClient.getConnectionManager().shutdown();
        }
    }

6.创建一个多线程环境下面可用的httpClient

（原文：http://blog.csdn.net/jiaoshi0531/article/details/6459468）

              HttpParams params = new BasicHttpParams();
//设置允许链接的做多链接数目
ConnManagerParams.setMaxTotalConnections(params, 200);
//设置超时时间.
ConnManagerParams.setTimeout(params, 10000);
//设置每个路由的最多链接数量是20
ConnPerRouteBean connPerRoute = new ConnPerRouteBean(20);
//设置到指定主机的路由的最多数量是50
HttpHost localhost = new HttpHost("127.0.0.1",80);
connPerRoute.setMaxForRoute(new HttpRoute(localhost), 50);
ConnManagerParams.setMaxConnectionsPerRoute(params, connPerRoute);
//设置链接使用的版本
HttpProtocolParams.setVersion(params, HttpVersion.HTTP_1_1);
//设置链接使用的内容的编码
HttpProtocolParams.setContentCharset(params,
        HTTP.DEFAULT_CONTENT_CHARSET);
//是否希望可以继续使用.
HttpProtocolParams.setUseExpectContinue(params, true);

SchemeRegistry schemeRegistry = new SchemeRegistry();
schemeRegistry.register(new Scheme("http",PlainSocketFactory.getSocketFactory(),80));
schemeRegistry.register(new Scheme("https",SSLSocketFactory.getSocketFactory(),443));
ClientConnectionManager cm = new ThreadSafeClientConnManager(params,schemeRegistry);
httpClient = new DefaultHttpClient(cm, params);

7.实用的一个对象，http上下文，可以从这个对象里面取到一次请求相关的信息，例如request，response，代理主机等。

public static void getUrl(String url, String encoding)
            throws ClientProtocolException, IOException {
        // 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());
            dump(entity, encoding);
        }
    }

 输出结果大致如下：

socket超时时间：0
最终请求的目标:money.finance.sina.com.cn:-1
是否发送完毕:true
请求的版本:HTTP/1.1
请求的头信息:
Host--money.finance.sina.com.cn
Connection--Keep-Alive
User-Agent--Apache-HttpClient/4.2.2 (java 1.5)
请求的链接:/corp/go.php/vFD_BalanceSheet/stockid/600031/ctrl/part/displaytype/4.phtml
返回结果内容编码是：null
返回结果内容类型是：Content-Type: text/html

8.设置代理

             //String  hostIp代理主机ip,int port  代理端口
tpHost proxy = new HttpHost(hostIp, port);
// 设置代理主机.
tpclient.getParams().setParameter(ConnRoutePNames.DEFAULT_PROXY,
proxy);

9.设置保持链接时间

//在服务端设置一个保持持久连接的特性.
        //HTTP服务器配置了会取消在一定时间内没有活动的链接，以节省系统的持久性链接资源.
        httpClient.setKeepAliveStrategy(new ConnectionKeepAliveStrategy() {
            public long getKeepAliveDuration(HttpResponse response,
                    HttpContext context) {
                HeaderElementIterator it = new BasicHeaderElementIterator(
                        response.headerIterator(HTTP.CONN_KEEP_ALIVE));
                while (it.hasNext()) {
                    HeaderElement he = it.nextElement();
                    String param = he.getName();
                    String value = he.getValue();
                    if (value != null && param.equalsIgnoreCase("timeout")) {
                        try {
                            return Long.parseLong(value) * 1000;
                        } catch (Exception e) {

                        }
                    }
                }
                HttpHost target = (HttpHost)context.getAttribute(ExecutionContext.HTTP_TARGET_HOST);
                if("www.baidu.com".equalsIgnoreCase(target.getHostName())){
                    return 5*1000;
                }
                else
                    return 30*1000;
            }
        });

转账注明出处：http://renjie120.iteye.com/blog/1727933