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。