HttpClient4获取抓取网页编码，内容等信息

public static void worm() throws Exception{
		    // 初始化，此处构造函数就与3.1中不同
            HttpClient httpclient = new DefaultHttpClient();
		    HttpHost targetHost = new HttpHost("www.baidu.com");
	        //HttpGet httpget = new HttpGet("http://www.apache.org/");
	        HttpGet httpget = new HttpGet("/");
	 
	        // 查看默认request头部信息
	        System.out.println("Accept-Charset:" + httpget.getFirstHeader("Accept-Charset"));
	        // 以下这条如果不加会发现无论你设置Accept-Charset为gbk还是utf-8，他都会默认返回gb2312（本例针对google.cn来说）
	        httpget.setHeader("User-Agent", "Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9.1.2)");
	        // 用逗号分隔显示可以同时接受多种编码
	        httpget.setHeader("Accept-Language", "zh-cn,zh;q=0.5");
	        httpget.setHeader("Accept-Charset", "GB2312,utf-8;q=0.7,*;q=0.7");
	        // 验证头部信息设置生效
	        System.out.println("Accept-Charset:" + httpget.getFirstHeader("Accept-Charset").getValue());
	 
	        // Execute HTTP request
	        System.out.println("executing request " + httpget.getURI());
	        HttpResponse response = httpclient.execute(targetHost, httpget);
	        //HttpResponse response = httpclient.execute(httpget);
	 
	        System.out.println("----------------------------------------");
	        System.out.println("Location: " + response.getLastHeader("Location"));
	        System.out.println(response.getStatusLine().getStatusCode());
	        System.out.println(response.getLastHeader("Content-Type"));
	        System.out.println(response.getLastHeader("Content-Length"));
	        
	        System.out.println("----------------------------------------");
	 
	        // 判断页面返回状态判断是否进行转向抓取新链接
	        int statusCode = response.getStatusLine().getStatusCode();
	        if ((statusCode == HttpStatus.SC_MOVED_PERMANENTLY) ||
	                (statusCode == HttpStatus.SC_MOVED_TEMPORARILY) ||
	                (statusCode == HttpStatus.SC_SEE_OTHER) ||
	                (statusCode == HttpStatus.SC_TEMPORARY_REDIRECT)) {
	            // 此处重定向处理  此处还未验证
	            String newUri = response.getLastHeader("Location").getValue();
	            httpclient = new DefaultHttpClient();
	            httpget = new HttpGet(newUri);
	            response = httpclient.execute(httpget);
	        }
	 
	        // Get hold of the response entity
	        HttpEntity entity = response.getEntity();
	        
	        // 查看所有返回头部信息
	        Header headers[] = response.getAllHeaders();
	        int ii = 0;
	        while (ii < headers.length) {
	            System.out.println(headers[ii].getName() + ": " + headers[ii].getValue());
	            ++ii;
	        }
	        
	        // If the response does not enclose an entity, there is no need
	        // to bother about connection release
	        if (entity != null) {
	            // 将源码流保存在一个byte数组当中，因为可能需要两次用到该流，
	            byte[] bytes = EntityUtils.toByteArray(entity);
	            String charSet = "";
	            
	            // 如果头部Content-Type中包含了编码信息，那么我们可以直接在此处获取
	            charSet = EntityUtils.getContentCharSet(entity);
	 
	            System.out.println("In header: " + charSet);
	            // 如果头部中没有，那么我们需要 查看页面源码，这个方法虽然不能说完全正确，因为有些粗糙的网页编码者没有在页面中写头部编码信息
	            if (charSet == "") {
	                String regEx="(?=<meta).*?(?<=charset=[\\'|\\\"]?)([[a-z]|[A-Z]|[0-9]|-]*)";
	                Pattern p=Pattern.compile(regEx, Pattern.CASE_INSENSITIVE);
	                Matcher m=p.matcher(new String(bytes));  // 默认编码转成字符串，因为我们的匹配中无中文，所以串中可能的乱码对我们没有影响
	                boolean result=m.find();
	                if (m.groupCount() == 1) {
	                    charSet = m.group(1);
	                } else {
	                    charSet = "";
	                }
	            }
	            System.out.println("Last get: " + charSet);
	            // 至此，我们可以将原byte数组按照正常编码专成字符串输出（如果找到了编码的话）
	            System.out.println("Encoding string is: " + new String(bytes, charSet));
	        }
	 
	        httpclient.getConnectionManager().shutdown();  
	}