HttpClient 操作工具类

设置post方法的header,增加红色字体部分的配置: 
HttpClient client = new HttpClient(); 
    client.getParams().setBooleanParameter(
     "http.protocol.expect-continue", false); 
   PostMethod method = new PostMethod(url); 
   method.addRequestHeader("Connection", "close");


一。  http 工作 大至 原理 


HTTP工作原理 
1.客户端和服务器。
2.建立连接,客户端向服务器发送一个请求。
3.服务器接受到请求后,向客户端发出响应信息。
4.客户端与服务器断开链接。




请求报文与响应报文。
请求报文格式:
请求行-->通用信息头-->请求头-->实体头-->报文主体
响应报文格式:
状态行-->通用信息头-->相应头-->实体头-->报文主体


android 集成了org.apache.http.client.HttpClient;   可以直接实现简单的htttp  Get 和  Post 操作  但是不支持 多部post 操作 。 要实现 多部分post 操作还需要导 额外 jar包 这里就不介绍了。


实现一个 http 操作  


1 。需要生成一个Http Client 客户端对象 。


2。  生成响应的请求对象  。


3。接受发回的信息  。


4.。解析返回的信息。


直接看  get 请求操作 。

public String httpGet(String url, String params) throws Exception{  
           
        String result=""; //返回信息    
        if (null!=params&&!params.equals(""))    
        {    
            url += "?" + params;    
        }    
        //创建一个httpGet请求  
        HttpGet request=new HttpGet(url);   
        //创建一个htt客户端  
        HttpClient httpClient=new DefaultHttpClient();  
        //接受客户端发回的响应  
        HttpResponse httpResponse=httpClient.execute(request);  
        int statusCode=httpResponse.getStatusLine().getStatusCode();  
        if(statusCode==HttpStatus.SC_OK){  
            //得到客户段响应的实体内容  
            HttpEntity responseHttpEntity=httpResponse.getEntity();  
            //得到输入流  
            InputStream in=responseHttpEntity.getContent();  
            //得到输入流的内容  
            result=getData(in);  
        }  
        Log.d(TAG, statusCode+"");  
        return result;  
    }
post 操作  

几个额外的辅助方法  

/**  
     * 读取返回的信息   
     * @param in  
     * @return  
     */ 
    private String getData(InputStream in) {  
        String result="";  
        StringBuilder sb=new StringBuilder();  
        BufferedReader br = new BufferedReader(new InputStreamReader(in));  
        String line = "";  
        try {  
            while ((line = br.readLine()) != null) {  
                //result = result + line;  
                sb.append(line);  
            }  
            br.close();  
        } catch (Exception e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        } finally {  
            if (result != null) {  
                try {  
                    br.close();  
                } catch (IOException e) {  
                    // TODO Auto-generated catch block  
                    e.printStackTrace();  
                }  
            }  
        }  
        return sb.toString();  
    }
**
     * 输入流转换成字符串
     * @param is: 输入流
     * @return 字符串对象
     */
    private static String InputStreamToString(InputStream is){
        BufferedReader reader = null;
        StringBuffer responseText = null;
        String readerText = null;
        try {
            reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));
            responseText = new StringBuffer();
            readerText = reader.readLine();
            while(readerText != null){
                responseText.append(readerText);
                responseText.append(System.getProperty("line.separator"));
                readerText = reader.readLine();
            }
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return responseText.toString();
    }

/**
     * 将cookie写入指定文件
     * @param cookies: cookie
     * @param fileName: 文件名
     */
    private static void write(Cookie[] cookies, String fileName){
        try {
            String path = System.getProperty("user.home") + "\\" + fileName;
            File file = new File(path);
            BufferedWriter bw = new BufferedWriter(new FileWriter(file));
            for(Cookie c : cookies){
                bw.append(c.toString());
                bw.append(System.getProperty("line.separator"));
            }
            bw.flush();
            bw.close();
            Runtime.getRuntime().exec("explorer " + path + "");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
如何 post json格式的数据,并附加http头,接受返回数据,请看下面的代码:
 
[java] view plaincopy
private void HttpPostData() {  
try {  
    HttpClient httpclient = new DefaultHttpClient();  
    String uri = "http://www.yourweb.com";  
    HttpPost httppost = new HttpPost(uri);   
    //添加http头信息  
    httppost.addHeader("Authorization", "your token"); //认证token  
    httppost.addHeader("Content-Type", "application/json");  
    httppost.addHeader("User-Agent", "imgfornote");  
    //http post的json数据格式:  {"name": "your name","parentId": "id_of_parent"}  
    JSONObject obj = new JSONObject();  
    obj.put("name", "your name");  
    obj.put("parentId", "your parentid");  
    httppost.setEntity(new StringEntity(obj.toString()));     
    HttpResponse response;  
    response = httpclient.execute(httppost);  
    //检验状态码,如果成功接收数据  
    int code = response.getStatusLine().getStatusCode();  
    if (code == 200) {   
        String rev = EntityUtils.toString(response.getEntity());//返回json格式: {"id": "27JpL~j4vsL0LX00E00005","version": "abc"}         
        obj = new JSONObject(rev);  
        String id = obj.getString("id");  
        String version = obj.getString("version");  
    }  
    } catch (ClientProtocolException e) {     
    } catch (IOException e) {     
    } catch (Exception e) {   
    }  
}  
主要用到的类有:org.apache.http.client.HttpClient 、org.apache.http.client.methods.HttpPost 和 org.json.JSONObject
请求行 ,是一个方法符号开头 ,后面跟着请求 URI和协议的版本, 以CRLF作为结尾 . 请求后以空格分隔. 除了作为结尾的 CRLF(回车换行)外,不允许出现单独的CR和LF字符,格式如下: 
 Method Request-URI HTTP-Version CRLF 
例如 :  GET /test.html HTTP/1.1 (CRLF) 
HTTP请求方法 :  GET POST HEAD DELETE PUT 
POST方法用于向服务器发送请求,要求服务器接受附在请求后面的数据.POST方法在表单提交的时候用的最多 . 
例如:  
POST /login.jsp HTTP/1.1 (CRLF) 
Accept:image/gif (CRLF) (...) 
........ 
Host:www.sample.com (CRLF) 
(CRLF) 
username=hell@password=123456  两个(CRLF)之后加上参数 
HEAD方法只是请求消息报头,而不是完整的内容. 通常用于测试超链接的有效性. 


HTTP响应  
HTTP-Version Status-Code Reason-Phrase CRLF 
例如 : HTTP/1.1 200 OK (CRLF) 


状态分类  
1xx 提示信息 
2xx 请求成功 
3xx 重定向 
4xx 客户端错误 
5xx 服务器错误 
HTTP消息有客户端到服务器的请求和服务器到客户端的响应组成. 
消息都是由开始行,消息报头(可选),空行(只有CRLF的行),消息正文(可选)组成. 
对于请求消息,开始行就是请求行,对于响应消息,开始行就是状态行. 
Apache HttpClient 是很方便的 Java 开源的访问 HTTP 资源的组件。网站上的资源不总是能匿名访问的,很多都需要登陆后才能操作,且不说论坛里登陆后才能发言,就是某些稍显敏感的 XML 等信息也是登陆后才能获取到的。


没问题,HttpClient 能让你做到,它提供了 Basic 和 Form-Based 两种验证方式。登陆后获得服务器端发来的 Cookie 作为下一次访问的凭证, 让服务端认为你还是个合法用户。服务端不是用 Session 来维护会话的吗?是的,Session 也要有个载体,Cookie 了。或有时 Java Web 会用 jsessionid 参数在服务端与客户端来回关联 Session 信息,也没问题,HttpClient 同样能胜任。


下面主要说明 Form-Based 的验证方式,Basic 的验证简单列了几行代码,还未实践,具体可参考文后的链接。


看 Form-Based 方式的演示代码,如果登陆时需要一个验证码的话,那只有自己想办法怎么得到这个码了,登陆时谁都想无码:

package cc.unmi.httpclient; 
  
import org.apache.commons.httpclient.Cookie;
import org.apache.commons.httpclient.HttpClient;
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.junit.Test;
  
public class HttpClientLogin {
  
    public static void main(String[] args){
        //登陆 Url
        String loginUrl = "http://localhost/unmi/login.html";
  
        //需登陆后访问的 Url
        String dataUrl = "http://localhost/unmi/user_info.html?userid=123456";
  
        HttpClient httpClient = new HttpClient();
  
        //模拟登陆,按实际服务器端要求选用 Post 或 Get 请求方式
        PostMethod postMethod = new PostMethod(loginUrl);
  
        //设置登陆时要求的信息,一般就用户名和密码,验证码自己处理了
        NameValuePair[] data = {
                new NameValuePair("username", "Unmi"),
                new NameValuePair("password", "123456"),
                new NameValuePair("code", "anyany")
        };
        postMethod.setRequestBody(data);
  
        try {
            //设置 HttpClient 接收 Cookie,用与浏览器一样的策略
            httpClient.getParams().setCookiePolicy(CookiePolicy.BROWSER_COMPATIBILITY);
            httpClient.executeMethod(postMethod);
  
            //获得登陆后的 Cookie
            Cookie[] cookies=httpClient.getState().getCookies();
            String tmpcookies= "";
            for(Cookie c:cookies){
                tmpcookies += c.toString()+";";
            }
  
            //进行登陆后的操作
            GetMethod getMethod = new GetMethod(dataUrl);
  
            //每次访问需授权的网址时需带上前面的 cookie 作为通行证
            getMethod.setRequestHeader("cookie",tmpcookies);
  
            //你还可以通过 PostMethod/GetMethod 设置更多的请求后数据
            //例如,referer 从哪里来的,UA 像搜索引擎都会表名自己是谁,无良搜索引擎除外
            postMethod.setRequestHeader("Referer", "http://unmi.cc");
            postMethod.setRequestHeader("User-Agent","Unmi Spot");
  
            httpClient.executeMethod(getMethod);
  
            //打印出返回数据,检验一下是否成功
            String text = getMethod.getResponseBodyAsString();
            System.out.println(text);
  
        } catch (Exception e) {
            e.printStackTrace();
        }   
    }
}
Basic 验证的简单代码导引,还未亲试:
 
HttpClient client = new HttpClient();
  
// 1
client.getState().setCredentials(
    new AuthScope("unmi.cc", 80, AuthScope.ANY_REALM),
    new UsernamePasswordCredentials("username", "password")
);
  
// 2
client.getParams().setAuthenticationPreemptive(true);
  
// 3
GetMethod getMothod = new GetMethod("http://unmi.cc/twitter");
  
// 4
getMothod.setDoAuthentication( true );
  
// 5
int status = client.executeMethod( getMothod );

ttpClient post方法 解析json数据(向服务器传递,接受服务器传递))
  
  
public class json extends Activity {
    public Context context;
    private TextView textView1;
    public static String URL = "http://webservice.webxml.com.cn/WebServices/WeatherWebService.asmx?wsdl";
    private DefaultHttpClient httpClient;
    StringBuilder result = new StringBuilder();
    private static final int TIMEOUT = 60;
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        HttpParams paramsw = createHttpParams();
        httpClient = new DefaultHttpClient(paramsw);
        HttpPost post = new HttpPost(               "http://webservice.webxml.com.cn/WebServices/WeatherWebService.asmx?wsdl");
        List params = new ArrayList();
        params.add(new BasicNameValuePair("name", "this is post"));
        try {
            //向服务器写json
            JSONObject json = new JSONObject();
            Object email = null;
            json.put("email", email);
            Object pwd = null;
           json.put("password", pwd);
            StringEntity se = new StringEntity( "JSON: " + json.toString());
            se.setContentEncoding(new BasicHeader(HTTP.CONTENT_TYPE, "application/json"));
            post.setEntity(se);
            post.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));
            HttpResponse httpResponse = httpClient.execute(post);
 
            int httpCode = httpResponse.getStatusLine().getStatusCode();
            if (httpCode == HttpURLConnection.HTTP_OK&&httpResponse!=null) {
                Header[] headers = httpResponse.getAllHeaders();
                HttpEntity entity = httpResponse.getEntity();
                Header header = httpResponse.getFirstHeader("content-type");
                //读取服务器返回的json数据(接受json服务器数据)
                InputStream inputStream = entity.getContent();
               InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
                BufferedReader reader = new BufferedReader(inputStreamReader);// 读字符串用的。
                String s;
                while (((s = reader.readLine()) != null)) {
                    result.append(s);
 
                }
                reader.close();// 关闭输入流
                //在这里把result这个字符串个给JSONObject。解读里面的内容。
                JSONObject jsonObject = new JSONObject(result.toString());
                String re_username = jsonObject.getString("username");
                String re_password = jsonObject.getString("password");
                int re_user_id = jsonObject.getInt("user_id");
               setTitle("用户id_"+re_user_id);
                Log.v("url response", "true="+re_username);
                Log.v("url response", "true="+re_password);
 
            } else {
 
                textView1.setText("Error Response" + httpResponse.getStatusLine().toString());
 
            }
        } catch (UnsupportedEncodingException e) {
        } catch (ClientProtocolException e) {
        } catch (IOException e) {
        } catch (JSONException e) {
            e.printStackTrace();
        } finally {
            if (httpClient != null) {
                httpClient.getConnectionManager().shutdown();// 最后关掉链接。
                httpClient = null;
            }
        }
    }
 
    public static final HttpParams createHttpParams() {
        final HttpParams params = new BasicHttpParams();
        HttpConnectionParams.setStaleCheckingEnabled(params, false);
        HttpConnectionParams.setConnectionTimeout(params, TIMEOUT * 1000);
        HttpConnectionParams.setSoTimeout(params, TIMEOUT * 1000);
        HttpConnectionParams.setSocketBufferSize(params, 8192 * 5);
        return params;
    }
}
HttpClient程序包是一个实现了 HTTP 协议的客户端编程工具包,要想熟练的掌握它,必须熟悉 HTTP协议。一个最简单的调用如下:


import java.io.IOException;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.impl.client.DefaultHttpClient; 
public class Test {
    public static void main(String[] args) {
 
       // 核心应用类
       HttpClient httpClient = new DefaultHttpClient();
 
        // HTTP请求
        HttpUriRequest request =
                new HttpGet("http://localhost/index.html");
 
        // 打印请求信息
        System.out.println(request.getRequestLine());
        try {
            // 发送请求,返回响应
            HttpResponse response = httpClient.execute(request);
 
            // 打印响应信息
            System.out.println(response.getStatusLine());
        } catch (ClientProtocolException e) {
            // 协议错误
            e.printStackTrace();
        } catch (IOException e) {
            // 网络异常
            e.printStackTrace();
        }
    }
}
 
如果HTTP服务器正常并且存在相应的服务,则上例会打印出两行结果:
 
    GET http://localhost/index.html HTTP/1.1
    HTTP/1.1 200 OK 
 
核心对象httpClient的调用非常直观,其execute方法传入一个request对象,返回一个response对象。使用 httpClient发出HTTP请求时,系统可能抛出两种异常,分别是ClientProtocolException和IOException。第一种异常的发生通常是协议错误导致,如在构造HttpGet对象时传入的协议不对(例如不小心将”http”写成”htp”),或者服务器端返回的内容不符合HTTP协议要求等;第二种异常一般是由于网络原因引起的异常,如HTTP服务器未启动等。
从实际应用的角度看,HTTP协议由两大部分组成:HTTP请求和HTTP响应。那么HttpClient程序包是如何实现HTTP客户端应用的呢?实现过程中需要注意哪些问题呢?
HTTP请求
 
HTTP 1.1由以下几种请求组成:GET, HEAD, POST, PUT, DELETE, TRACE and OPTIONS, 程序包中分别用HttpGet, HttpHead, HttpPost, HttpPut, HttpDelete, HttpTrace, and HttpOptions 这几个类创建请求。所有的这些类均实现了HttpUriRequest接口,故可以作为execute的执行参数使用。
所有请求中最常用的是GET与POST两种请求,与创建GET请求的方法相同,可以用如下方法创建一个POST请求:
 
HttpUriRequest request = new HttpPost(
        "http://localhost/index.html");
 
 
HTTP请求格式告诉我们,有两个位置或者说两种方式可以为request提供参数:request-line方式与request-body方式。
request-line
 
request-line方式是指在请求行上通过URI直接提供参数。
(1)
我们可以在生成request对象时提供带参数的URI,如:
 
HttpUriRequest request = new HttpGet(
        "http://localhost/index.html?param1=value1¶m2=value2");
 
(2)
另外,HttpClient程序包为我们提供了URIUtils工具类,可以通过它生成带参数的URI,如:
 
URI uri = URIUtils.createURI("http", "localhost", -1, "/index.html",
    "param1=value1¶m2=value2", null);
HttpUriRequest request = new HttpGet(uri);
System.out.println(request.getURI());
 
上例的打印结果如下:
 
    http://localhost/index.html?param1=value1¶m2=value2
 
(3)
需要注意的是,如果参数中含有中文,需将参数进行URLEncoding处理,如:
 
String param = "param1=" + URLEncoder.encode("中国", "UTF-8") + "¶m2=value2";
URI uri = URIUtils.createURI("http", "localhost", 8080,
"/sshsky/index.html", param, null);
System.out.println(uri);
 
上例的打印结果如下:
 
    http://localhost/index.html?param1=%E4%B8%AD%E5%9B%BD¶m2=value2
 
(4)
对于参数的URLEncoding处理,HttpClient程序包为我们准备了另一个工具类:URLEncodedUtils。通过它,我们可以直观的(但是比较复杂)生成URI,如:
 
List params = new ArrayList();
params.add(new BasicNameValuePair("param1", "中国"));
params.add(new BasicNameValuePair("param2", "value2"));
String param = URLEncodedUtils.format(params, "UTF-8");
URI uri = URIUtils.createURI("http", "localhost", 8080,
"/sshsky/index.html", param, null);
System.out.println(uri);
 
上例的打印结果如下:
 
    http://localhost/index.html?param1=%E4%B8%AD%E5%9B%BD¶m2=value2
 
request-body
 
与request-line方式不同,request-body方式是在request-body中提供参数,此方式只能用于POST请求。在 HttpClient程序包中有两个类可以完成此项工作,它们分别是UrlEncodedFormEntity类与MultipartEntity类。这两个类均实现了HttpEntity接口。
(1)
使用最多的是UrlEncodedFormEntity类。通过该类创建的对象可以模拟传统的HTML表单传送POST请求中的参数。如下面的表单:
 

   
   
   

 
我们可以用下面的代码实现:
 
List formParams = new ArrayList();
formParams.add(new BasicNameValuePair("param1", "中国"));
formParams.add(new BasicNameValuePair("param2", "value2"));
HttpEntity entity = new UrlEncodedFormEntity(formParams, "UTF-8");
 
HttpPost request = new HttpPost(“http://localhost/index.html”);
request.setEntity(entity);
 
当然,如果想查看HTTP数据格式,可以通过HttpEntity对象的各种方法取得。如:
 
List formParams = new ArrayList();
formParams.add(new BasicNameValuePair("param1", "中国"));
formParams.add(new BasicNameValuePair("param2", "value2"));
UrlEncodedFormEntity entity = new UrlEncodedFormEntity(formParams, "UTF-8");
 
System.out.println(entity.getContentType());
System.out.println(entity.getContentLength());
System.out.println(EntityUtils.getContentCharSet(entity));
System.out.println(EntityUtils.toString(entity));
 
上例的打印结果如下:
 
    Content-Type: application/x-www-form-urlencoded; charset=UTF-8
    39
    UTF-8
    param1=%E4%B8%AD%E5%9B%BD¶m2=value2 
(2)
除了传统的application/x-www-form-urlencoded表单,我们另一个经常用到的是上传文件用的表单,这种表单的类型为 multipart/form-data。在HttpClient程序扩展包(HttpMime)中专门有一个类与之对应,那就是 MultipartEntity类。此类同样实现了HttpEntity接口。如下面的表单: 
        enctype="multipart/form-data">
   
   
   
   

 
我们可以用下面的代码实现: 
MultipartEntity entity = new MultipartEntity();
entity.addPart("param1", new StringBody("中国", Charset.forName("UTF-8")));
entity.addPart("param2", new StringBody("value2", Charset.forName("UTF-8")));
entity.addPart("param3", new FileBody(new File("C:\\1.txt"))); 
HttpPost request = new HttpPost(“http://localhost/index.html”);
request.setEntity(entity); 
HTTP响应
 
HttpClient程序包对于HTTP响应的处理较之HTTP请求来说是简单多了,其过程同样使用了HttpEntity接口。我们可以从 HttpEntity对象中取出数据流(InputStream),该数据流就是服务器返回的响应数据。需要注意的是,HttpClient程序包不负责解析数据流中的内容。如:
 
HttpUriRequest request = ...;
HttpResponse response = httpClient.execute(request);
 
// 从response中取出HttpEntity对象
HttpEntity entity = response.getEntity();
 
// 查看entity的各种指标
System.out.println(entity.getContentType());
System.out.println(entity.getContentLength());
System.out.println(EntityUtils.getContentCharSet(entity));
 
// 取出服务器返回的数据流
InputStream stream = entity.getContent();
 
// 以任意方式操作数据流stream
// 调用方式 略
 
附注:
 
本文说明的是HttpClient 4.0.1,该程序包(包括依赖的程序包)由以下几个JAR包组成:
 
commons-logging-1.1.1.jar
commons-codec-1.4.jar
httpcore-4.0.1.jar
httpclient-4.0.1.jar
apache-mime4j-0.6.jar
httpmime-4.0.1.jar 
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 


现在Apache已经发布了:HttpCore 4.0-beta3、HttpClient 4.0-beta1。
到此处可以去下载这些源代码:http://hc.apache.org/downloads.cgi
另外,还需要apache-mime4j-0.5.jar 包。

import java.util.ArrayList;
import java.util.List;
import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.params.CookiePolicy;
import org.apache.http.client.params.ClientPNames;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.EntityUtils;
  
public class Test2 {
    public static void main(String[] args) throws Exception {
        DefaultHttpClient httpclient = new DefaultHttpClient();      //实例化一个HttpClient
        HttpResponse response = null;
        HttpEntity entity = null;
        httpclient.getParams().setParameter(
                ClientPNames.COOKIE_POLICY, CookiePolicy.BROWSER_COMPATIBILITY);  //设置cookie的兼容性
        HttpPost httpost = new HttpPost("http://127.0.0.1:8080/pub/jsp/getInfo");           //引号中的参数是:servlet的地址
        List  nvps = new ArrayList ();                     
        nvps.add(new BasicNameValuePair("jqm", "fb1f7cbdaf2bf0a9cb5d43736492640e0c4c0cd0232da9de")); 
        //   BasicNameValuePair("name", "value"), name是post方法里的属性, value是传入的参数值
        nvps.add(new BasicNameValuePair("sqm", "1bb5b5b45915c8"));
        httpost.setEntity(new UrlEncodedFormEntity(nvps, HTTP.UTF_8));            //将参数传入post方法中
        response = httpclient.execute(httpost);                                               //执行
        entity = response.getEntity();                                                             //返回服务器响应
        try{
            System.out.println("----------------------------------------");
            System.out.println(response.getStatusLine());                           //服务器返回状态
            Header[] headers = response.getAllHeaders();                    //返回的HTTP头信息
            for (int i=0; i
HttpClient4.0 学习实例 - 页面获取
 
HttpClient 4.0出来不久,所以网络上面相关的实例教程不多,搜httpclient得到的大部分都是基于原 Commons HttpClient 3.1 (legacy) 包的,官网下载页面:http://hc.apache.org/downloads.cgi,如果大家看了官网说明就明白httpclient4.0是从原包分支出来独立成包的,以后原来那个包中的httpclient不会再升级,所以以后我们是用httpclient新分支,由于4.0与之前的3.1包结构以及接口等都有较大变化,所以网上搜到的实例大部分都是不适合4.0的,当然,我们可以通过那些实例去琢磨4.0的用法,我也是新手,记录下学习过程方便以后检索
 
本实例我们来获取抓取网页编码,内容等信息
 
默认情况下,服务器端会根据客户端的请求头信息来返回服务器支持的编码,像google.cn他本身支持utf-8,gb2312等编码,所以如果你在头部中不指定任何头部信息的话他默认会返回gb2312编码,而如果我们在浏览器中直接访问google.cn,通过httplook,或者firefox 的firebug插件查看返回头部信息的话会发现他返回的是UTF-8编码
 
下面我们还是看实例来解说吧,注释等我也放代码里面解释,放完整代码,方便新手理解
 
本实例将
 
使用的httpclient相关包
httpclient-4.0.jar
httpcore-4.0.1.jar
httpmime-4.0.jar
commons-logging-1.0.4.jar等其它相关包
package com.baihuo.crawler.test; 
import java.util.regex.Matcher;
import java.util.regex.Pattern; 
import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.HttpHost;
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;
  
class HttpClientTest { 
    public final static void main(String[] args) throws Exception { 
        // 初始化,此处构造函数就与3.1中不同
        HttpClient httpclient = new DefaultHttpClient(); 
        HttpHost targetHost = new HttpHost("www.google.cn");
        //HttpGet httpget = new HttpGet("http://www.apache.org/");
        HttpGet httpget = new HttpGet("/"); 
        // 查看默认request头部信息
        System.out.println("Accept-Charset:" + httpget.getFirstHeader("Accept-Charset"));
        // 以下这条如果不加会发现无论你设置Accept-Charset为gbk还是utf-8,他都会默认返回gb2312(本例针对google.cn来说)
        httpget.setHeader("User-Agent", "Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9.1.2)");
        // 用逗号分隔显示可以同时接受多种编码
        httpget.setHeader("Accept-Language", "zh-cn,zh;q=0.5");
        httpget.setHeader("Accept-Charset", "GB2312,utf-8;q=0.7,*;q=0.7");
        // 验证头部信息设置生效
        System.out.println("Accept-Charset:" + httpget.getFirstHeader("Accept-Charset").getValue());
        // Execute HTTP request
        System.out.println("executing request " + httpget.getURI());
        HttpResponse response = httpclient.execute(targetHost, httpget);
        //HttpResponse response = httpclient.execute(httpget); 
        System.out.println("----------------------------------------");
        System.out.println("Location: " + response.getLastHeader("Location"));
        System.out.println(response.getStatusLine().getStatusCode());
        System.out.println(response.getLastHeader("Content-Type"));
        System.out.println(response.getLastHeader("Content-Length"));        
        System.out.println("----------------------------------------");
        // 判断页面返回状态判断是否进行转向抓取新链接
        int statusCode = response.getStatusLine().getStatusCode();
        if ((statusCode == HttpStatus.SC_MOVED_PERMANENTLY) ||
                (statusCode == HttpStatus.SC_MOVED_TEMPORARILY) ||
                (statusCode == HttpStatus.SC_SEE_OTHER) ||
                (statusCode == HttpStatus.SC_TEMPORARY_REDIRECT)) {
            // 此处重定向处理  此处还未验证
            String newUri = response.getLastHeader("Location").getValue();
            httpclient = new DefaultHttpClient();
            httpget = new HttpGet(newUri);
            response = httpclient.execute(httpget);
        } 
        // Get hold of the response entity
        HttpEntity entity = response.getEntity();        
        // 查看所有返回头部信息
        Header headers[] = response.getAllHeaders();
        int ii = 0;
        while (ii < headers.length) {
            System.out.println(headers[ii].getName() + ": " + headers[ii].getValue());
            ++ii;
        }        
        // If the response does not enclose an entity, there is no need
        // to bother about connection release
        if (entity != null) {
            // 将源码流保存在一个byte数组当中,因为可能需要两次用到该流,
            byte[] bytes = EntityUtils.toByteArray(entity);
            String charSet = "";            
            // 如果头部Content-Type中包含了编码信息,那么我们可以直接在此处获取
            charSet = EntityUtils.getContentCharSet(entity); 
            System.out.println("In header: " + charSet);
            // 如果头部中没有,那么我们需要 查看页面源码,这个方法虽然不能说完全正确,因为有些粗糙的网页编码者没有在页面中写头部编码信息
            if (charSet == "") {
                regEx="(?=





你可能感兴趣的:(其他知识,java)