HttpClient 4.0的使用详解

HttpClient   2012-02-10 08:41:36 发布
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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();   

    }

}

扩展阅读

HttpClient4.1 使用示例
HttpClient工具类
java之httpClient 3.x、AsyncHttpClient1.9.x使用总结
网络爬虫入门(二)模拟提交以及HttpClient修正
httpclient4.3.x模拟post及get请求

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