Android之Http沟通——4.Android HTTP索取信息:HttpClient

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本节介绍:

他谈到了部分HttpURLConnection。本节HttpClient该，Apache为我们提供HttpClient(简单的Http客户端),只是毕竟不是亲儿子。HttpClient在API 21版本号后就给Google弃用了。而我们实际开发中。非常多页面都不是通过一个简单的URL就能够訪问的，可能须要登陆或者相关权限才干够訪问，这就涉及到了Session,Cookie等的问题了；当然我们能够用HttpURLConnection来实现，可是有点麻烦。而用HttpClient能够简单点。HttpClient用于接收/发送Http请求/响应。但不缓存server响应，不执行HTML页面潜入的JS代码，不会对页面内容进行不论什么解析。处理；要改掉废话太多的习惯，SO简化博文，開始本节内容吧：

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HttpClient使用流程:

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基本流程:

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HttpClient使用演示样例:

1.发送GET请求

嗯，就写个简单的发送GET请求的代码吧:

package com.example.httpclientdemo;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.view.View.OnClickListener;
import android.webkit.WebView;
import android.widget.Button;

public class MainActivity extends Activity implements OnClickListener {

    private Button btnGet;
    private WebView wView;
    public static final int SHOW_DATA = 0X123;
    private String detail = "";

    private Handler handler = new Handler() {
        public void handleMessage(Message msg) {
            if(msg.what == SHOW_DATA)
            {
                wView.loadDataWithBaseURL("",detail, "text/html","UTF-8","");
            }
        };
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
        setView();
    }

    private void initView() {
        btnGet = (Button) findViewById(R.id.btnGet);
        wView = (WebView) findViewById(R.id.wView);
    }

    private void setView() {
        btnGet.setOnClickListener(this);
        wView.getSettings().setDomStorageEnabled(true);
    }
    @Override
    public void onClick(View v) {
        if (v.getId() == R.id.btnGet) {
            GetByHttpClient();
        }
    }
    private void GetByHttpClient() {
        new Thread()
        {
            public void run() 
            {
                    try {
                        HttpClient httpClient = new DefaultHttpClient();
                        HttpGet httpGet = new HttpGet("http://www.w3cschool.cc/python/python-tutorial.html");
                        HttpResponse httpResponse = httpClient.execute(httpGet);
                        if (httpResponse.getStatusLine().getStatusCode() == 200) {
                            HttpEntity entity = httpResponse.getEntity();
                            detail = EntityUtils.toString(entity, "utf-8");
                            handler.sendEmptyMessage(SHOW_DATA);
                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
            };
        }.start();
    }

}

另外。假设是带有參数的GET请求的话，我们能够把參数放到List集合中，在对參数进行URL编码:
然后和URL拼接

List<BasicNameValuePair> params = new LinkedList<BasicNameValuePair>();  
params.add(new BasicNameValuePair("user", "猪小弟"));  
params.add(new BasicNameValuePair("pawd", "123"));
String param = URLEncodedUtils.format(params, "UTF-8"); 
HttpGet httpGet = new HttpGet("http://www.baidu.com"+"?"+param);

接着贴下执行截图:

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2.发送POST请求

POST请求比GET略微复杂一点。创建完HttpPost对象后，通过NameValuePair集合来存储等待提交
的參数。并将參数传递到UrlEncodedFormEntity中，最后调用setEntity(entity)完毕，
HttpClient.execute(HttpPost)就可以。这里就不写样例了。临时没找到Post的站点，又不想
自己写个Servlet。So,直接贴核心代码吧~

核心代码:

    private void PostByHttpClient(final String url)
    {
        new Thread()
        {
            public void run() 
            {
                try{
                    HttpClient httpClient = new DefaultHttpClient();
                    HttpPost httpPost = new HttpPost(url);
                    List<NameValuePair> params = new ArrayList<NameValuePair>();
                    params.add(new BasicNameValuePair("user", "猪大哥"));
                    params.add(new BasicNameValuePair("pawd", "123"));
                    UrlEncodedFormEntity entity = new UrlEncodedFormEntity(params,"UTF-8");
                    httpPost.setEntity(entity);
                    HttpResponse httpResponse =  httpClient.execute(httpPost);
                    if (httpResponse.getStatusLine().getStatusCode() == 200) {
                        HttpEntity entity2 = httpResponse.getEntity();
                        detail = EntityUtils.toString(entity2, "utf-8");
                        handler.sendEmptyMessage(SHOW_DATA);
                    }
                }catch(Exception e){e.printStackTrace();}
            };
        }.start();
    }

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3.胡说八道

事实上关于HttpClient的样例有非常多。比方笔者以前用它来抓学校教务系统上学生的课程表:
这就涉及到Cookie，模拟登陆的东西，说到抓数据(爬虫)。一般我们是搭配着JSoup来解析
抓到数据的，有兴趣能够自己查阅相关文档。至于笔者的毕设，代码非常烂的说。兴许有时间
整理在公布出来吧。这里贴下模拟登陆教务系统部分的代码。大家能够体会下HttpClient：

//获得链接,模拟登录的实现:
    public int getConnect(String user, String key) throws Exception {
        // 先发送get请求 获取cookie值和__ViewState值
        HttpGet getLogin = new HttpGet(true_url);
        // 第一步:基本的HTML:
        String loginhtml = "";
        HttpResponse loginResponse = new DefaultHttpClient().execute(getLogin);
        if (loginResponse.getStatusLine().getStatusCode() == 200) {
            HttpEntity entity = loginResponse.getEntity();
            loginhtml = EntityUtils.toString(entity);
            // 获取响应的cookie值
            cookie = loginResponse.getFirstHeader("Set-Cookie").getValue();
            System.out.println("cookie= " + cookie);
        }

        // 第二步:模拟登录
        // 发送Post请求,禁止重定向
        HttpPost httpPost = new HttpPost(true_url);
        httpPost.getParams().setParameter(ClientPNames.HANDLE_REDIRECTS, false);

        // 设置Post提交的头信息的參数
        httpPost.setHeader("User-Agent",
                "Mozilla/5.0 (Windows NT 6.3; WOW64; Trident/7.0; rv:11.0) like Gecko");
        httpPost.setHeader("Referer", true_url);
        httpPost.setHeader("Cookie", cookie);

        // 设置请求数据
        List<NameValuePair> params = new ArrayList<NameValuePair>();

        params.add(new BasicNameValuePair("__VIEWSTATE",
                getViewState(loginhtml)));// __VIEWSTATE參数，假设变化能够动态抓取获取
        params.add(new BasicNameValuePair("Button1", ""));
        params.add(new BasicNameValuePair("hidPdrs", ""));
        params.add(new BasicNameValuePair("hidsc", ""));
        params.add(new BasicNameValuePair("lbLanguage", ""));
        params.add(new BasicNameValuePair("RadioButtonList1", "%D1%A7%C9%FA"));
        params.add(new BasicNameValuePair("txtUserName", user));
        params.add(new BasicNameValuePair("TextBox2", key));
        params.add(new BasicNameValuePair("txtSecretCode", "")); // ( ╯□╰ )逗比正方,居然不须要验证码

        // 设置编码方式,响应请求,获取响应状态码:
        httpPost.setEntity(new UrlEncodedFormEntity(params, "gb2312"));
        HttpResponse response = new DefaultHttpClient().execute(httpPost);
        int Status = response.getStatusLine().getStatusCode();
        if(Status == 200)return Status;
        System.out.println("Status= " + Status);

        // 重定向状态码为302
        if (Status == 302 || Status == 301) {
            // 获取头部信息中Location的值
            location = response.getFirstHeader("Location").getValue();
            System.out.println(location);
            // 第三步:获取管理信息的主页面
            // Get请求
            HttpGet httpGet = new HttpGet(ip_url + location);// 带上location地址訪问
            httpGet.setHeader("Referer", true_url);
            httpGet.setHeader("Cookie", cookie);

            // 主页的html
            mainhtml = "";
            HttpResponse httpResponseget = new DefaultHttpClient()
                    .execute(httpGet);
            if (httpResponseget.getStatusLine().getStatusCode() == 200) {
                HttpEntity entity = httpResponseget.getEntity();
                mainhtml = EntityUtils.toString(entity);
            }

        }
        return Status;
    }

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总结:

好的，本节关于HttpClient就到这里吧，内容还是比較简单的~
下节我们将使用retrofit来封装我们的HTTP请求。敬请期待~
对了，关于Android里简单的网络技术能够參考小猪之前写过的入门系列:
小猪的Android入门之路 day 8 part 3

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