客户端HttpClient4处理 Servlet Gzip后的内容

亦凉 2021-05-12 11:55 451阅读 0赞

1、服务器端servlet代码：

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		response.setHeader("Cache-Control", "no-cache");
    		response.setContentType("text/html;charset=UTF-8");
    
    		String str = "中文测试this is a test!";
    
    		if (isGzipSupport(request)) {// 支持gzip
    			response.setHeader("Content-Encoding", "gzip");
    			OutputStream os = response.getOutputStream();
    			GZIPOutputStream gs = new GZIPOutputStream(os);
    			gs.write(str.getBytes("UTF-8"));// 解决中文乱码问题
    			gs.finish();
    			gs.close();
    			os.close();
    		} else {
    			PrintWriter out = response.getWriter();
    			out.write(str);
    			out.flush();
    			out.close();
    		}
    	}
    	
    	/**
         * 判断客户端是否要求进行gzip压缩处理
         * @param request
         * @return
         */
        private boolean isGzipSupport(HttpServletRequest request) {
            String headEncoding = request.getHeader("accept-encoding");
            return (headEncoding != null && (headEncoding.indexOf("gzip") != -1));
        }

通过判断http的header中accept-encoding 是否为gzip（表明客户端支持gzip解压，服务端可以使用gzip进行数据压缩），对返回的数据进行gzip压缩。

部署后，浏览器上访问可以得到如下内容：

中文测试this is a test!

通过抓包可以发现：

![Center][]

浏览器默认发送的request请求中会携带aeecpt-encoding gzip信息（现代浏览器都支持gzip解压）

2、客户端代码：

package nc.edu.nuc.utils;
    
    import java.io.IOException;
    import java.nio.charset.Charset;
    
    import org.apache.http.Header;
    import org.apache.http.HeaderElement;
    import org.apache.http.HttpEntity;
    import org.apache.http.HttpException;
    import org.apache.http.HttpRequest;
    import org.apache.http.HttpRequestInterceptor;
    import org.apache.http.HttpResponse;
    import org.apache.http.HttpResponseInterceptor;
    import org.apache.http.HttpStatus;
    import org.apache.http.client.ClientProtocolException;
    import org.apache.http.client.HttpClient;
    import org.apache.http.client.entity.GzipDecompressingEntity;
    import org.apache.http.client.methods.HttpGet;
    import org.apache.http.client.methods.HttpPost;
    import org.apache.http.entity.StringEntity;
    import org.apache.http.impl.client.CloseableHttpClient;
    import org.apache.http.impl.client.DefaultHttpClient;
    import org.apache.http.protocol.HttpContext;
    import org.apache.http.util.EntityUtils;
    
    
    @SuppressWarnings("deprecation")
    public class HttpInterceptorUtil {
    	private static DefaultHttpClient httpclient = new DefaultHttpClient();  
    	
    	static {
    		httpclient.addRequestInterceptor(new HttpRequestInterceptor() {
    			public void process(final HttpRequest request, final HttpContext arg1)
    					throws HttpException, IOException {
    				if (!request.containsHeader("Accept-Encoding")) {
    					request.addHeader("Accept-Encoding", "gzip");
    				}
    			}
    		});
    		
    		/*httpclient.addResponseInterceptor(new HttpResponseInterceptor() {  
    	           public void process(  
    	                   final HttpResponse response,   
    	                   final HttpContext context) throws HttpException, IOException {  
    	               HttpEntity entity = response.getEntity();  
    	               Header ceheader = entity.getContentEncoding();  
    	               if (ceheader != null) {  
    	                   HeaderElement[] codecs = ceheader.getElements();  
    	                   for (int i = 0; i < codecs.length; i++) {  
    	                       if (codecs[i].getName().equalsIgnoreCase("gzip")) {  
    	                           response.setEntity(  
    	                                   new GzipDecompressingEntity(response.getEntity()));   
    	                           return;  
    	                       }  
    	                   }  
    	               }  
    	           }  
    	             
    	       });  */
    	}
    
    
    	public static void main(String...strings) throws ClientProtocolException, IOException {
    		HttpGet httpget = new HttpGet("http://localhost:8080/WebTest/SendAndGzipServlet");   
            
    	       // Execute HTTP request  
    	       System.out.println("executing request " + httpget.getURI());  
    	       HttpResponse response = httpclient.execute(httpget);  
    	  
    	       System.out.println("----------------------------------------");  
    	       System.out.println(response.getStatusLine());  
    	       System.out.println(response.getLastHeader("Content-Encoding"));  
    	       System.out.println(response.getLastHeader("Content-Length"));  
    	       System.out.println("----------------------------------------");  
    	  
    	       HttpEntity entity = response.getEntity();  
    	         
    	       if (entity != null) {  
    	           String content = EntityUtils.toString(entity);  
    	           System.out.println(content);  
    	           System.out.println("----------------------------------------");  
    	           System.out.println("Uncompressed size: "+content.length());  
    	       }  
    	  
    	       // When HttpClient instance is no longer needed,   
    	       // shut down the connection manager to ensure  
    	       // immediate deallocation of all system resources  
    	       httpclient.getConnectionManager().shutdown();
    	}
    }

1）httpClient支持拦截器，我们队client添加了request和response两个拦截器，request拦截器目的是在http header中添加content-encoding gzip信息，方便告诉服务端可以使用gzip压缩，客户端支持解压；response拦截器目的是对gzip数据进行解压。

2）如果把response拦截器注释掉，返回的数据就是乱码：

executing request http://localhost:8080/WebTest/SendAndGzipServlet
    ----------------------------------------
    HTTP/1.1 200 OK
    Content-Encoding: gzip
    Content-Length: 46
    ----------------------------------------
    ?

[Center]: /images/20210511/5defa73dba5547bbb95884e245bcc913.png