使用HttpClient进行网络处理的基本步骤如下：

1、通过get的方式获取到Response对象。

CloseableHttpClient httpClient = HttpClients.createDefault();

HttpGet httpGet = new HttpGet("http://www.baidu.com/");

CloseableHttpResponse response = httpClient.execute(httpGet);

2、获取Response对象的Entity。

HttpEntity entity = response.getEntity();

注：HttpClient将Response的正文及Request的POST/PUT方法中的正文均封装成一个HttpEntity对象。可以通过entity.getContenType()，entity.getContentLength()等方法获取到正文的相关信息。但最重要的方法是通过getContent()获取到InputStream对象。

3、通过Entity获取到InputStream对象，然后对返回内容进行处理。

is = entity.getContent();

sc = new Scanner(is);

// String filename = path.substring(path.lastIndexOf(‘/‘)+1);

String filename = "2.txt";

os = new PrintWriter(filename);

while (sc.hasNext()) {

os.write(sc.nextLine());

}

使用HtppClient下载一个网页的完整代码如下：

package com.ljh.test;

import java.io.IOException;

import java.io.InputStream;

import java.io.PrintWriter;

import java.io.Writer;

import java.util.Scanner;

import org.apache.http.HttpEntity;

import org.apache.http.HttpStatus;

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;

public class DownloadWebPage{

public static void downloadPagebyGetMethod() throws IOException {

// 1、通过HttpGet获取到response对象

CloseableHttpClient httpClient = HttpClients.createDefault();

HttpGet httpGet = new HttpGet("http://www.baidu.com/");

CloseableHttpResponse response = httpClient.execute(httpGet);

InputStream is = null;

Scanner sc = null;

Writer os = null;

if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {

try {

// 2、获取response的entity。

HttpEntity entity = response.getEntity();

// 3、获取到InputStream对象，并对内容进行处理

is = entity.getContent();

sc = new Scanner(is);

// String filename = path.substring(path.lastIndexOf(‘/‘)+1);

String filename = "2.txt";

os = new PrintWriter(filename);

while (sc.hasNext()) {

os.write(sc.nextLine());

}

} catch (ClientProtocolException e) {

e.printStackTrace();

} finally {

if (sc != null) {

sc.close();

}

if (is != null) {

is.close();

}

if (os != null) {

os.close();

}

if (response != null) {

response.close();

}

}

}

}

public static void main(String[] args) {

try {

downloadPagebyGetMethod();

} catch (IOException e) {

e.printStackTrace();

}

}

}

注意：直接将HttpGet改为HttpPost，返回的结果有误，百度返回302状态，即重定向，新浪返回拒绝访问。怀疑大多网站均不允许POST方法直接访问网站。

原文：http://blog.csdn.net/enson16855/article/details/26244147