7.1.4 Android HTTP请求方式:HttpClient

本节引言：

在上一节中我们对HttpURLConnection进行了学习，本节到第二种方式：HttpClient，尽管被Google弃用了，但是我们我们平时也可以拿HttpClient来抓下包，配合Jsoup解析网页效果更佳！HttpClient用于接收/发送Http请求/响应，但不缓存服务器响应，不执行HTML页面潜入的JS代码，不会对页面内容进行任何解析，处理！开始本节内容！

1.HttpClient使用流程

基本流程：

2.HttpClient使用示例

1）使用HttpClient发送GET请求

直接贴下简单的发送Get请求的代码：

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();    }}

运行截图

另外，如果是带有参数的GET请求的话，我们可以将参数放到一个List集合中，再对参数进行URL编码，最后和URL拼接下就好了：

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);

2）使用HttpClient发送POST请求

POST请求比GET稍微复杂一点，创建完HttpPost对象后，通过NameValuePair集合来存储等待提交的参数，并将参数传递到UrlEncodedFormEntity中，最后调用setEntity(entity)完成，HttpClient.execute(HttpPost)即可；这里就不写例子了，暂时没找到Post的网站，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();}

3.HttpClient抓数据示例(教务系统数据抓取)

其实关于HttpClient的例子有很多，比如笔者曾经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，有兴趣可以自己查阅相关资料，这里贴下笔者毕设app里获取网页部分的关键代码！大家可以体会下：

HttpClient可以通过下述代码获取与设置Cookie：HttpResponse loginResponse = new DefaultHttpClient().execute(getLogin);获得Cookie:cookie = loginResponse.getFirstHeader("Set-Cookie").getValue();请求时带上Cookie:httpPost.setHeader("Cookie", cookie);

//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:主要的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提交的头信息的参数    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参数，如果变化可以动态抓取获取    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,竟然不需要验证码    // 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地址访问        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;}

4.使用HttpPut发送Put请求

示例代码如下：

public static int PutActCode(String actCode, String licPlate, Context mContext) {    int resp = 0;    String cookie = (String) SPUtils.get(mContext, "session", "");    HttpPut httpPut = new HttpPut(PUTACKCODE_URL);    httpPut.setHeader("Cookie", cookie);    try {        List<NameValuePair> params = new ArrayList<NameValuePair>();        params.add(new BasicNameValuePair("activation_code", actCode));        params.add(new BasicNameValuePair("license_plate", licPlate));        httpPut.setEntity(new UrlEncodedFormEntity(params, "UTF-8"));        HttpResponse course_response = new DefaultHttpClient().execute(httpPut);        if (course_response.getStatusLine().getStatusCode() == 200) {            HttpEntity entity2 = course_response.getEntity();            JSONObject jObject = new JSONObject(EntityUtils.toString(entity2));            resp = Integer.parseInt(jObject.getString("status_code"));            return resp;        }    } catch (Exception e) {        e.printStackTrace();    }    return resp;}

本节小结：

好的，本节关于Android HTTP的第二种请求方式:HttpClient就到这里，下节开始我们来学习XML以及Json的解析，本节就到这里，谢谢~

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