HttpClient 4.0的使用详解

fmms 11年前

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。对于HTTP协议来说,无非就是用户请求数据,服务器端响应用户请求,并将内容结果返回给用户。HTTP1.1由以下几种请求组成:GET,HEAD, POST, PUT, DELETE, TRACE ,OPTIONS,因此对应到HttpClient程序包中分别用HttpGet,HttpHead, HttpPost, HttpPut, HttpDelete, HttpTrace, HttpOptions 这几个类来创建请求。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。

HTTP请求

当然在所有请求中最常用的还是GET与POST两种请求,创建请求的方式如下: 

HttpUriRequest request = newHttpPost("http://localhost/index.html");

HttpUriRequest request = newHttpGet(“http://127.0.0.1:8080/index.html”);

HTTP请求格式告诉我们,有两种方式可以为request提供参数:request-line方式与request-body方式。

Ø  request-line方式是指在请求行上通过URI直接提供参数。

(1)可以在生成request对象时提供带参数的URI,如:

HttpUriRequest request = newHttpGet("http://localhost/index.html?param1=value1&param2=value2");

(2)HttpClient程序包还提供了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&param2=value2", null);

HttpUriRequest request = newHttpGet(uri);

System.out.println(request.getURI());

上例的实例结果如下:

 http://localhost/index.html?param1=value1&param2=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") +"&param2=value2";

URI uri =URIUtils.createURI("http", "localhost", 8080,"/sshsky/index.html",param, null);

System.out.println(uri);

 上例的实例结果如下:

  http://localhost/index.html?param1=%E4%B8%AD%E5%9B%BD&param2=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 = newArrayList();    params.add(newBasicNameValuePair("param1", "中国"));    params.add(newBasicNameValuePair("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);

 上例的实例结果如下:

  http://localhost/index.html?param1=%E4%B8%AD%E5%9B%BD&param2=value2

Ø  request-body方式是指在请求的request-body中提供参数

与 request-line方式不同,request-body方式是在request-body中提供参数,此方式只能用于进行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)UrlEncodedFormEntity类,故名思意该类主要用于form表单提交。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:

<formaction="http://localhost/index.html" method="POST">        <inputtype="text" name="param1" value="中国"/>        <inputtype="text" name="param2" value="value2"/>        <inupttype="submit" value="submit"/>    </form>

即可以通过下面的代码实现:

List formParams = newArrayList();    formParams.add(newBasicNameValuePair("param1", "中国"));    formParams.add(newBasicNameValuePair("param2", "value2"));    HttpEntity entity = newUrlEncodedFormEntity(formParams, "UTF-8");    HttpPost request = newHttpPost(“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 = newArrayList();    formParams.add(newBasicNameValuePair("param1", "中国"));    formParams.add(newBasicNameValuePair("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));

上例的实例结果如下:

   Content-Type: application/x-www-form-urlencoded; charset=UTF-8

    39

    UTF-8

   param1=%E4%B8%AD%E5%9B%BD&param2=value2 

(2)除了传统的application/x-www-form-urlencoded表单,还有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:

<formaction="http://localhost/index.html" method="POST"           enctype="multipart/form-data">        <inputtype="text" name="param1" value="中国"/>        <inputtype="text" name="param2" value="value2"/>        <inputtype="file" name="param3"/>        <inupttype="submit" value="submit"/>    </form>

可以用下面的代码实现:

MultipartEntity entity = newMultipartEntity();    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 = newHttpPost(“http://localhost/index.html”);    request.setEntity(entity);

HTTP响应 

HttpClient 程序包对于HTTP响应的处理较请求来说简单多了,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();

或者采用如下的接口方式httpClient.execute(request,new ResponseHandler<T> response)进行调用,它的返回值直接对应的即为用户自己想获取的数据的类型及值。

具体实例解析,通过下述方法,即可获取到指定url的页面内容。

public static String executeStringByGet(String url, final Charset charset) {            String result = "";            HttpClient client = new DefaultHttpClient();            HttpGet get = new HttpGet(url);                       try {                result = client.execute(get, new ResponseHandler<String>() {                    @Override                    public String handleResponse(HttpResponse response) throws ClientProtocolException, IOException {                        HttpEntity entity = response.getEntity();                        if(entity != null) {                            if(response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {                                return new String(EntityUtils.toByteArray(entity), charset.getValue());                            }                        }                        return "";                    }                });            } catch (Exception e) {                e.printStackTrace();            }                 return result;        }

HttpClient接口的详细使用:

package com.wow.common.test;         import java.io.IOException;    import java.util.regex.Matcher;    import java.util.regex.Pattern;         import org.apache.http.Header;    import org.apache.http.HttpEntity;    import org.apache.http.HttpResponse;    import org.apache.http.HttpStatus;    import org.apache.http.client.ClientProtocolException;    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;         /**     * 类HttpClientTest.java的实现描述:TODO 类实现描述     * @author zheng.zhaoz 2012-2-9 下午07:33:18     */    public class HttpClientTest {             public static void main(String[] args) {            HttpClient httpClient = new DefaultHttpClient();            //創建一個httpGet方法            HttpGet httpGet = new HttpGet("http://www.cnblogs.com/loveyakamoz/archive/2011/07/21/2113252.html");                       //設置httpGet的參數信息            httpGet.setHeader("Accept", "Accept text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8");            httpGet.setHeader("Accept-Charset", "GB2312,utf-8;q=0.7,*;q=0.7");            httpGet.setHeader("Accept-Encoding", "gzip, deflate");            httpGet.setHeader("Accept-Language", "zh-cn,zh;q=0.5");            httpGet.setHeader("Connection", "keep-alive");            httpGet.setHeader("Cookie", "__utma=226521935.73826752.1323672782.1325068020.1328770420.6;");            httpGet.setHeader("Host", "www.cnblogs.com");            httpGet.setHeader("refer", "http://www.baidu.com/s?tn=monline_5_dg&bs=httpclient4+MultiThreadedHttpConnectionManager");            httpGet.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.1; rv:6.0.2) Gecko/20100101 Firefox/6.0.2");            System.out.println("Accept-Charset: " + httpGet.getFirstHeader("Accept-Charset"));            System.out.println("Execute request: " + httpGet.getURI());                       HttpResponse response = null;            try {                response = httpClient.execute(httpGet);            } catch (ClientProtocolException e) {                e.printStackTrace();            } catch (IOException e) {                e.printStackTrace();            }                       //输出响应的所有头信息            if(response != null) {                Header headers[] = response.getAllHeaders();                int i = 0;                while (i < headers.length) {                    System.out.println(headers[i].getName() + ":  " + headers[i].getValue());                    i++;                }                if(response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {                    try {                        HttpEntity entity = response.getEntity();                        // 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,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 == "") {                            String regEx="(?=<meta).*?(?<=charset=[\\'|\\\"]?)([[a-z]|[A-Z]|[0-9]|-]*)";                            Pattern p=Pattern.compile(regEx, Pattern.CASE_INSENSITIVE);                            Matcher m=p.matcher(new String(bytes));  // 默认编码转成字符串,因为我们的匹配中无中文,所以串中可能的乱码对我们没有影响                            boolean result = m.find();                            if (m.groupCount() == 1) {                                charSet = m.group(1);                            } else {                                charSet = "";                            }                        }                        System.out.println("Last get: " + charSet);                        // 可以将原byte数组按照正常编码专成字符串输出(如果找到了编码的话)                        System.out.println("Encoding string is: " + new String(bytes, charSet));                    } catch (IOException e) {                        e.printStackTrace();                    }                }            }            //關閉聯接            httpClient.getConnectionManager().shutdown();           }    }