一、设置请求头消息 User-Agent模拟浏览器

   1.当使用第一节的代码 来 访问推酷的时候,会返回给我们如下信息:


网页内容:<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<p>系统检测亲不是真人行为,因系统资源限制,我们只能拒绝你的请求。如果你有疑问,可以通过微博 http://weibo.com/tuicool2012/ 联系我们。</p>
</body>
</html>


  这是因为网站做了限制,限制别人爬。解决方式可以设置请求头消息 User-Agent模拟浏览器。代码如下:


/**
* 抓取网页信息使用 get请求
* @param args
* @throws IOException
* @throws ClientProtocolException
*/
public static void main(String[] args) throws ClientProtocolException, IOException {
// 创建httpClient实例
CloseableHttpClient httpClient = HttpClients.createDefault();
// 创建httpGet实例
HttpGet httpGet = new HttpGet("http://www.tuicool.com");
httpGet.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Firefox/45.0");
CloseableHttpResponse response = httpClient.execute(httpGet);
if(response != null){
HttpEntity entity = response.getEntity(); // 获取网页内容
String result = EntityUtils.toString(entity, "UTF-8");
System.out.println("网页内容:" + result);
}
if(response != null){
response.close();
}
if(httpClient != null){
httpClient.close();
}
}


   给HttpGet方法设置头消息,即可模拟浏览器访问。

二、获取响应内容Content-Type  

   使用  entity.getContentType().getValue()  来获取Content-Type,代码如下:


public static void main(String[] args) throws ClientProtocolException, IOException {
// 创建httpClient实例
CloseableHttpClient httpClient = HttpClients.createDefault();
// 创建httpGet实例
HttpGet httpGet = new HttpGet("http://www.tuicool.com");
httpGet.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Firefox/45.0");
CloseableHttpResponse response = httpClient.execute(httpGet);
if(response != null){
HttpEntity entity = response.getEntity(); // 获取网页内容
System.out.println("Content-Type:" + entity.getContentType().getValue()); // 获取Content-Type
}
if(response != null){
response.close();
}
if(httpClient != null){
httpClient.close();
}
}


三、获取响应状态

  200 -- 正常

  403 -- 拒绝

  500 -- 服务器报错

  400 -- 未找到页面

  使用 response.getStatusLine().getStatusCode() 获取响应状态,代码如下:


public static void main(String[] args) throws ClientProtocolException, IOException {
// 创建httpClient实例
CloseableHttpClient httpClient = HttpClients.createDefault();
// 创建httpGet实例
HttpGet httpGet = new HttpGet("http://www.tuicool.com");
httpGet.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Firefox/45.0");
CloseableHttpResponse response = httpClient.execute(httpGet);
if(response != null){
int state = response.getStatusLine().getStatusCode();
System.out.println("响应状态:" + state);
}
if(response != null){
response.close();
}
if(httpClient != null){
httpClient.close();
}
}