3、使用HttpClient進行網路處理的基本步驟

（1）通過get的方式獲取到Response物件。

CloseableHttpClient httpClient = HttpClients.createDefault();  
HttpGet httpGet = new HttpGet("http://www.baidu.com/");  
CloseableHttpResponse response = httpClient.execute(httpGet);  

注意，必需要加上http://的字首，否則會報：Target host is null異常。

注：HttpClient將Response的正文及Request的POST/PUT方法中的正文均封裝成一個HttpEntity物件。可以通過entity.getContenType()，entity.getContentLength()等方法獲取到正文的相關資訊。但最重要的方法是通過getContent()獲取到InputStream物件。

（3）通過Entity獲取到InputStream物件，然後對返回內容進行處理。

package com.test.demo;

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.HttpClient;
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 GetPostDemo {
	
	public static void main(String args[]){
		
		CloseableHttpClient httpclient = HttpClients.createDefault();
		HttpGet httpGet = new HttpGet("http://v.polyv.net/uc/cata/list?cataid=1");  
		try {
			CloseableHttpResponse response = httpclient.execute(httpGet);
			System.out.println("----------------"+response);
			
			/**
			 * 注：HttpClient將Response的正文及Request的POST/PUT方法中的正文均封裝成一個HttpEntity物件。
			 * 可以通過entity.getContenType()，entity.getContentLength()等方法獲取到正文的相關資訊。
			 * 但最重要的方法是通過getContent()獲取到InputStream物件。
			 */
			HttpEntity entity3 = response.getEntity(); 
			System.out.println("----------------"+entity3);
			System.out.println("----------------"+entity3.getContentType());
			System.out.println("----------------"+entity3.getContentLength());
			System.out.println("----------------"+entity3.getContent());
			
			
			InputStream is = null;  
	        Scanner sc = null;  
	        Writer os = null;  
	        if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {  
	            try {  
	                // 2、獲取response的entity。  
	                HttpEntity entity = response.getEntity();  
	  
	                // 3、獲取到InputStream物件，並對內容進行處理  
	                is = entity.getContent();  
	                sc = new Scanner(is);  
	                // String filename = path.substring(path.lastIndexOf('/')+1);  
	                //String filename = "d:\\2.txt";  
	                //os = new PrintWriter(filename); 
	                String contentStr="";
	                while (sc.hasNext()) {  
	                    //os.write(sc.nextLine());
	                	
	                	contentStr=contentStr+sc.nextLine();
	                	//System.out.println("------"+sc.nextLine());
	                }  
	  
	                System.out.println("------"+contentStr);
	            } 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();  
	                }  
	            }  
	        }  
	  
	    
			
		} catch (ClientProtocolException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} 
		
		
		
		
		
		
	}


}