HttpClient实现HelloWorld

HttpClient 这个框架主要用来请求第三方服务器，然后获取到网页，得到我们需要的数据

搞个简单实例，让大家体验一把

创建一个Maven项目 在pom.xml贴上依赖

<dependency>    <groupId>org.apache.httpcomponents</groupId>    <artifactId>httpclient</artifactId>    <version>4.5.3</version></dependency>

第一种：

package com.gcx.demo.HelloWorld2;import java.io.IOException;import org.apache.http.HttpEntity;import org.apache.http.client.ClientProtocolException;import org.apache.http.client.methods.CloseableHttpResponse;import org.apache.http.client.methods.HttpGet;import org.apache.http.impl.client.CloseableHttpClient;import org.apache.http.impl.client.HttpClients;import org.apache.http.util.EntityUtils;public class App2 {public static void main(String[] args) {//创建一个httpclient 实例CloseableHttpClient httpClient=HttpClients.createDefault();//创见HttpGet实例HttpGet httpGet=new HttpGet("https://www.baidu.com");CloseableHttpResponse execute=null;//执行这个实例try { execute = httpClient.execute(httpGet); //获取返回的实体 HttpEntity entity = execute.getEntity(); System.out.println("网页内容:"+EntityUtils.toString(entity,"utf-8"));} catch (ClientProtocolException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}finally{try {execute.close();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}}

输出：

这里得到了百度首页源码，当然要获得具体数据的话，要用到Jsoup，后面文章在做详述

第二种(简化下)：

package com.gcx.demo.HelloWorld2;import java.io.IOException;import org.apache.http.HttpEntity;import org.apache.http.client.ClientProtocolException;import org.apache.http.client.methods.CloseableHttpResponse;import org.apache.http.client.methods.HttpGet;import org.apache.http.impl.client.CloseableHttpClient;import org.apache.http.impl.client.HttpClients;import org.apache.http.util.EntityUtils;/** * Hello world! * */public class App {    public static void main( String[] args ) throws ClientProtocolException, IOException{    //创建HttpClient实例    CloseableHttpClient httpClient=HttpClients.createDefault();    //创建httpget实例    HttpGet httpGet=new HttpGet("http://www.baidu.com");    //执行这个实例    CloseableHttpResponse response = httpClient.execute(httpGet);    //获取返回实体    HttpEntity entity = response.getEntity();    System.out.println("网页内容:"+EntityUtils.toString(entity,"utf-8"));        response.close();            }}

但是实际开发的话，我们对于每一种异常的抛出，catch里都需要做一些业务上的操作，所以以后用的话，还是第一种，假如爬虫任务很简单，容易爬取，并且量小，那就第二种。还是要根据具体情况而定