使用Apache中的HttpClient的实例CloseableHttpClient的一个例子

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Apache的HttpClient可以被用于从客户端发送HTTP请求到服务器端,下面给出一个用HttpClient执行GET和POST请求的操作方法

使用maven构建依赖包:

            <!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient -->            <dependency>                <groupId>org.apache.httpcomponents</groupId>                <artifactId>httpclient</artifactId>                <version>${httpclient.version}</version>            </dependency>

注意此httpClient包从4.4开始SSLContexts类就被移去了,我在使用4.3.1版本.其中的jar列表如下: jar包列表

使用Apache的HttpClient发送GET和POST请求的步骤如下:
1. 使用帮助类HttpClients创建CloseableHttpClient对象.
2. 基于要发送的HTTP请求类型创建HttpGet或者HttpPost实例.
3. 使用addHeader方法添加请求头部,诸如User-Agent, Accept-Encoding等参数.
4. 对于POST请求,创建NameValuePair列表,并添加所有的表单参数.然后把它填充进HttpPost实体.
5. 通过执行此HttpGet或者HttpPost请求获取CloseableHttpResponse实例
6. 从此CloseableHttpResponse实例中获取状态码,错误信息,以及响应页面等等.
7. 最后关闭HttpClient资源.

下面给出示例代码:

package com.journaldev.utils;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.util.ArrayList;import java.util.List;import org.apache.http.HttpEntity;import org.apache.http.NameValuePair;import org.apache.http.client.entity.UrlEncodedFormEntity;import org.apache.http.client.methods.CloseableHttpResponse;import org.apache.http.client.methods.HttpGet;import org.apache.http.client.methods.HttpPost;import org.apache.http.impl.client.CloseableHttpClient;import org.apache.http.impl.client.HttpClients;import org.apache.http.message.BasicNameValuePair;public class ApacheHttpClientExample {    private static final String USER_AGENT = "Mozilla/5.0";    private static final String GET_URL = "http://localhost:9090/SpringMVCExample";    private static final String POST_URL = "http://localhost:9090/SpringMVCExample/home";    public static void main(String[] args) throws IOException {        sendGET();        System.out.println("GET DONE");        sendPOST();        System.out.println("POST DONE");    }    private static void sendGET() throws IOException {        CloseableHttpClient httpClient = HttpClients.createDefault();        HttpGet httpGet = new HttpGet(GET_URL);        httpGet.addHeader("User-Agent", USER_AGENT);        CloseableHttpResponse httpResponse = httpClient.execute(httpGet);        System.out.println("GET Response Status:: "                + httpResponse.getStatusLine().getStatusCode());        BufferedReader reader = new BufferedReader(new InputStreamReader(                httpResponse.getEntity().getContent()));        String inputLine;        StringBuffer response = new StringBuffer();        while ((inputLine = reader.readLine()) != null) {            response.append(inputLine);        }        reader.close();        // print result        System.out.println(response.toString());        httpClient.close();    }    private static void sendPOST() throws IOException {        CloseableHttpClient httpClient = HttpClients.createDefault();        HttpPost httpPost = new HttpPost(POST_URL);        httpPost.addHeader("User-Agent", USER_AGENT);        List<NameValuePair> urlParameters = new ArrayList<NameValuePair>();        urlParameters.add(new BasicNameValuePair("userName", "Pankaj Kumar"));        HttpEntity postParams = new UrlEncodedFormEntity(urlParameters);        httpPost.setEntity(postParams);        CloseableHttpResponse httpResponse = httpClient.execute(httpPost);        System.out.println("POST Response Status:: "                + httpResponse.getStatusLine().getStatusCode());        BufferedReader reader = new BufferedReader(new InputStreamReader(                httpResponse.getEntity().getContent()));        String inputLine;        StringBuffer response = new StringBuffer();        while ((inputLine = reader.readLine()) != null) {            response.append(inputLine);        }        reader.close();        // print result        System.out.println(response.toString());        httpClient.close();    }}

输出结果如下所示 :

GET Response Status:: 200<html><head>    <title>Home</title></head><body><h1>    Hello world!  </h1><P>  The time on the server is March 7, 2015 1:01:22 AM IST. </p></body></html>GET DONEPOST Response Status:: 200<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>User Home Page</title></head><body><h3>Hi Pankaj Kumar</h3></body></html>POST DONE

参考网址:看这里

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