httpClient 学习总结

最新推荐文章于 2023-08-28 14:32:33 发布

听风暖

最新推荐文章于 2023-08-28 14:32:33 发布

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本文链接：https://blog.youkuaiyun.com/qq_26431469/article/details/50468719

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httpClient 常用功能

1．读取网页(HTTP/HTTPS)内容

/**
* 最简单的HTTP客户端,用来演示通过GET或者POST方式访问某个页面
*/
public class SimpleClient {
   public static void main(String[] args) throws IOException {
       HttpClient client = new HttpClient();   //创建一个客户端
       // 使用 GET 方法，如果服务器需要通过 HTTPS 连接，那只需要将下面 URL 中的 http 换成 https
       HttpMethod method = new GetMethod("http://java.sun.com");
       // 使用POST方法
       // HttpMethod method = new PostMethod("http://java.sun.com");
       client.executeMethod(method);

       // 打印服务器返回的状态
       System.out.println(method.getStatusLine());
       // 打印返回的信息
       System.out.println(method.getResponseBodyAsString());
       // 释放连接
       method.releaseConnection();
   }
}

首先创建一个HTTP客户端(HttpClient)的实例，然后选择提交的方法是GET或者POST，最后在HttpClient实例上执行提交的方法，最后从所选择的提交方法中读取服务器反馈回来的结果。这就是使用HttpClient的基本流程。

2、使用POST方式提交数据(httpClient3)

第一种：模拟上传url文件(该方式也适合做普通post请求):

/**
     * 上传url文件到指定URL
     * @param fileUrl 上传图片url
     * @param postUrl 上传路径及参数,注意有些中文参数需要使用预先编码 eg : URLEncoder.encode(appName, "UTF-8")
     * @return
     * @throws IOException
     */
    public static String doUploadFile(String postUrl) throws IOException {
        if(StringUtils.isEmpty(postUrl))
            return null;
        String response = "";
        PostMethod postMethod = new PostMethod(postUrl);
        try {
            HttpClient client = new HttpClient();
            client.getHttpConnectionManager().getParams()
                    .setConnectionTimeout(50000);// 设置连接时间
            int status = client.executeMethod(postMethod);
            if (status == HttpStatus.SC_OK) {
                InputStream inputStream = postMethod.getResponseBodyAsStream();
                BufferedReader br = new BufferedReader(new InputStreamReader(
                        inputStream));
                StringBuffer stringBuffer = new StringBuffer();
                String str = "";
                while ((str = br.readLine()) != null) {
                    stringBuffer.append(str);
                }
                response = stringBuffer.toString();
            } else {
                response = "fail";
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 释放连接
            postMethod.releaseConnection();
        }
        return response;
    }

第二种：模拟文件上传到指定位置

/**
     * 上传文件到指定URL
     * @param file
     * @param url
     * @return
     * @throws IOException
     */
    public static String doUploadFile(File file, String url) throws IOException {
        String response = "";
        if (!file.exists()) {
            return "file not exists";
        }
        PostMethod postMethod = new PostMethod(url);
        try {
            //----------------------------------------------
            // FilePart：用来上传文件的类,file即要上传的文件
            FilePart fp = new FilePart("file", file);
            Part[] parts = { fp };

            // 对于MIME类型的请求，httpclient建议全用MulitPartRequestEntity进行包装
            MultipartRequestEntity mre = new MultipartRequestEntity(parts,
                    postMethod.getParams());
            postMethod.setRequestEntity(mre);
            //---------------------------------------------
            HttpClient client = new HttpClient();
            client.getHttpConnectionManager().getParams()
                    .setConnectionTimeout(50000);// 由于要上传的文件可能比较大 , 因此在此设置最大的连接超时时间
            int status = client.executeMethod(postMethod);
            if (status == HttpStatus.SC_OK) {
                InputStream inputStream = postMethod.getResponseBodyAsStream();
                BufferedReader br = new BufferedReader(new InputStreamReader(
                        inputStream));
                StringBuffer stringBuffer = new StringBuffer();
                String str = "";
                while ((str = br.readLine()) != null) {
                    stringBuffer.append(str);
                }
                response = stringBuffer.toString();
            } else {
                response = "fail";
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 释放连接
            postMethod.releaseConnection();
        }
        return response;
    }

3．处理页面重定向

下面的代码片段演示如何处理页面的重定向

client.executeMethod(post);
System.out.println(post.getStatusLine().toString());
post.releaseConnection();
// 检查是否重定向
int statuscode = post.getStatusCode();
if ((statuscode == HttpStatus.SC_MOVED_TEMPORARILY) || (statuscode == HttpStatus.SC_MOVED_PERMANENTLY) || 
(statuscode ==HttpStatus.SC_SEE_OTHER) || (statuscode == HttpStatus.SC_TEMPORARY_REDIRECT)) {
// 读取新的 URL 地址 
   Header header=post.getResponseHeader("location");
   if (header!=null){
      Stringnewuri=header.getValue();
      if((newuri==null)||(newuri.equals("")))
         newuri="/";
         GetMethodredirect=newGetMethod(newuri);
         client.executeMethod(redirect);
         System.out.println("Redirect:"+redirect.getStatusLine().toString());
         redirect.releaseConnection();
   }else 
    System.out.println("Invalid redirect");
}
4． 模拟登录开心网
本小节应该说是HTTP客户端编程中最常碰见的问题，很多网站的内容都只是对注册用户可见的，这种情况下就必须要求使用正确的用户名和口令登录成功后，方可浏览到想要的页面。因为HTTP协议是无状态的，也就是连接的有效期只限于当前请求，请求内容结束后连接就关闭了。在这种情况下为了保存用户的登录信息必须使用到Cookie机制。以JSP/Servlet为例，当浏览器请求一个JSP或者是Servlet的页面时，应用服务器会返回一个参数，名为jsessionid（因不同应用服务器而异），值是一个较长的唯一字符串的Cookie，这个字符串值也就是当前访问该站点的会话标识。浏览器在每访问该站点的其他页面时候都要带上jsessionid这样的Cookie信息，应用服务器根据读取这个会话标识来获取对应的会话信息。
对于需要用户登录的网站，一般在用户登录成功后会将用户资料保存在服务器的会话中，这样当访问到其他的页面时候，应用服务器根据浏览器送上的Cookie中读取当前请求对应的会话标识以获得对应的会话信息，然后就可以判断用户资料是否存在于会话信息中，如果存在则允许访问页面，否则跳转到登录页面中要求用户输入帐号和口令进行登录。这就是一般使用JSP开发网站在处理用户登录的比较通用的方法。
这样一来，对于HTTP的客户端来讲，如果要访问一个受保护的页面时就必须模拟浏览器所做的工作，首先就是请求登录页面，然后读取Cookie值；再次请求登录页面并加入登录页所需的每个参数；最后就是请求最终所需的页面。当然在除第一次请求外其他的请求都需要附带上Cookie信息以便服务器能判断当前请求是否已经通过验证。说了这么多，可是如果你使用httpclient的话，你甚至连一行代码都无需增加，你只需要先传递登录信息执行登录过程，然后直接访问想要的页面，跟访问一个普通的页面没有任何区别，因为类HttpClient已经帮你做了所有该做的事情了，太棒了！下面的例子实现了模拟登陆开心网并向自己好友发送消息的功能。
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import org.apache.commons.httpclient.Cookie;
import org.apache.commons.httpclient.Header;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpStatus;
import org.apache.commons.httpclient.NameValuePair;
import org.apache.commons.httpclient.cookie.CookiePolicy;
import org.apache.commons.httpclient.methods.GetMethod;
import org.apache.commons.httpclient.methods.PostMethod;
import org.apache.commons.httpclient.params.HttpClientParams;
import org.apache.commons.httpclient.params.HttpMethodParams;

class Login {
    public static String loginurl = "https://security.kaixin001.com/login/login_post.php";
    static Cookie[] cookies = {};

    static HttpClient httpClient = new HttpClient();
    
    static String email = "xxx@qq.com";//你的email
    static String psw = "xxx";//你的密码
    // 消息发送的action
    String url = "http://www.kaixin001.com/home/";

    public static void getUrlContent()
            throws Exception {

        HttpClientParams httparams = new HttpClientParams();
        httparams.setSoTimeout(30000);
        httpClient.setParams(httparams);

        httpClient.getHostConfiguration().setHost("www.kaixin001.com", 80);

        httpClient.getParams().setParameter(
                HttpMethodParams.HTTP_CONTENT_CHARSET, "UTF-8");

        PostMethod login = new PostMethod(loginurl);
        login.addRequestHeader("Content-Type",
                "application/x-www-form-urlencoded; charset=UTF-8");

        NameValuePair Email = new NameValuePair("loginemail", email);// 邮箱
        NameValuePair password = new NameValuePair("password", psw);// 密码
        // NameValuePair code = new NameValuePair( "code"
        // ,"????");//有时候需要验证码，暂时未解决

        NameValuePair[] data = { Email, password };
        login.setRequestBody(data);

        httpClient.executeMethod(login);
        int statuscode = login.getStatusCode();
        System.out.println(statuscode + "-----------");
        String result = login.getResponseBodyAsString();
        System.out.println(result+"++++++++++++");

        cookies = httpClient.getState().getCookies();
        System.out.println("==========Cookies============");
        int i = 0;
        for (Cookie c : cookies) {
            System.out.println(++i + ":   " + c);
        }
        httpClient.getState().addCookies(cookies);

        // 当state为301或者302说明登陆页面跳转了，登陆成功了
        if ((statuscode == HttpStatus.SC_MOVED_TEMPORARILY)
                || (statuscode == HttpStatus.SC_MOVED_PERMANENTLY)
                || (statuscode == HttpStatus.SC_SEE_OTHER)
                || (statuscode == HttpStatus.SC_TEMPORARY_REDIRECT)) {
            // 读取新的 URL 地址
            Header header = login.getResponseHeader("location");
            // 释放连接
            login.releaseConnection();
            System.out.println("获取到跳转header>>>" + header);
            if (header != null) {
                String newuri = header.getValue();
                if ((newuri == null) || (newuri.equals("")))
                    newuri = "/";
                GetMethod redirect = new GetMethod(newuri);
                // 
                redirect.setRequestHeader("Cookie", cookies.toString());
                httpClient.executeMethod(redirect);
                System.out.println("Redirect:"
                        + redirect.getStatusLine().toString());
                redirect.releaseConnection();

            } else
                System.out.println("Invalid redirect");
        } else {
            // 用户名和密码没有被提交，当登陆多次后需要验证码的时候会出现这种未提交情况
            System.out.println("用户没登陆");
            System.exit(1);
        }

    }

    public static void sendMsg() throws Exception {
        // 登录后发消息
        System.out.println("*************发消息***********");

        String posturl = "http://www.kaixin001.com/msg/post.php";
        PostMethod poster = new PostMethod(posturl);

        poster.addRequestHeader("Content-Type",
                "application/x-www-form-urlencoded; charset=UTF-8");
        poster.setRequestHeader("Cookie", cookies.toString());

        NameValuePair uids = new NameValuePair("uids", "89600585");// 发送的好友对象的id,此处换成你的好友id
        NameValuePair content = new NameValuePair("content", "你好啊!");// 需要发送的信息的内容
        NameValuePair liteeditor_0 = new NameValuePair("liteeditor_0", "你好啊!");// 需要发送的信息的内容
        NameValuePair texttype = new NameValuePair("texttype", "plain");
        NameValuePair send_separate = new NameValuePair("send_separate", "0");
        NameValuePair service = new NameValuePair("service", "0");
        NameValuePair[] msg = { uids, content, texttype, send_separate, service,liteeditor_0 };

        poster.setRequestBody(msg);
        httpClient.executeMethod(poster);

        String result = poster.getResponseBodyAsString();
        System.out.println(result+"++++++++++++");
        //System.out.println(StreamOut(result, "iso8859-1"));
        int statuscode = poster.getStatusCode();
        System.out.println(statuscode + "-----------");
        if(statuscode == 301 || statuscode == 302){
            // 读取新的 URL 地址
            Header header = poster.getResponseHeader("location");
            System.out.println("获取到跳转header>>>" + header);
            if (header != null) {
                String newuri = header.getValue();
                if ((newuri == null) || (newuri.equals("")))
                    newuri = "/";
                GetMethod redirect = new GetMethod(newuri);
                // 
                redirect.setRequestHeader("Cookie", cookies.toString());
                httpClient.executeMethod(redirect);
                System.out.println("Redirect:"
                        + redirect.getStatusLine().toString());
                redirect.releaseConnection();

            } else
                System.out.println("Invalid redirect");
        }
        
            poster.releaseConnection();
    }

    public static String StreamOut(InputStream txtis, String code)
            throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(txtis,
                code));
        String tempbf;
        StringBuffer html = new StringBuffer(100);
        while ((tempbf = br.readLine()) != null) {
            html.append(tempbf + "\n");
        }
        return html.toString();

    }
}
5． 提交XML格式参数
提交XML格式的参数很简单，仅仅是一个提交时候的ContentType问题，下面的例子演示从文件文件中读取XML信息并提交给服务器的过程，该过程可以用来测试Web服务。
import java.io.File; 
import java.io.FileInputStream; 
import org.apache.commons.httpclient.HttpClient; 
import org.apache.commons.httpclient.methods.EntityEnclosingMethod; 
import org.apache.commons.httpclient.methods.PostMethod;
/** 
 *用来演示提交XML格式数据的例子
*/
public class PostXMLClient {

   public static void main(String[] args) throws Exception {
      File input = new File(“test.xml”);
      PostMethod post = new PostMethod(“http://localhost:8080/httpclient/xml.jsp”);

      // 设置请求的内容直接从文件中读取
      post.setRequestBody( new FileInputStream(input)); 
      if (input.length() < Integer.MAX_VALUE)
         post.setRequestContentLength(input.length());
      else
         post.setRequestContentLength(EntityEnclosingMethod.CONTENT_LENGTH_CHUNKED);

      // 指定请求内容的类型
      post.setRequestHeader( "Content-type" , "text/xml; charset=GBK" );
      HttpClient httpclient = new HttpClient();
      int result = httpclient.executeMethod(post);
      System.out.println( "Response status code: " + result);
      System.out.println( "Response body: " );
      System.out.println(post.getResponseBodyAsString()); 
      post.releaseConnection(); 
   } 
}