如何检查网站是否已更新并发送电子邮件？

Question

嗨，我知道在Firefox上有一个网站检查器扩展，将通过Firefox通知网站是否已更新。

是否有任何代码片段用于执行相同的功能？我想通过电子邮件通知进行网站更新。

Answer 1

通过在您的URL对象上调用openConnection()来使用HttpUrlConnection。

getResponseCode()会在您从连接中读取后给您HTTP响应。

例如

URL u = new URL ("http://www.example.com/"); 
    HttpURLConnection huc = (HttpURLConnection) u.openConnection(); 
    huc.setRequestMethod ("GET"); 
    huc.connect() ; 
    OutputStream os = huc.getOutputStream () ; 
    int code = huc.getResponseCode () ; 

（未测试！）

Answer 2

这做工作持续了页面内容的最后SHA2哈希和对每5秒一个持久化比较当前的哈希值。顺便说一下，exmaple依赖apache编解码器库进行sha2操作。

import org.apache.commons.codec.digest.*; 

import java.io.*; 
import java.net.*; 
import java.util.*; 

/** 
* User: jhe 
*/ 
public class UrlUpdatedChecker { 

    static Map<String, String> checkSumDB = new HashMap<String, String>(); 

    public static void main(String[] args) throws IOException, InterruptedException { 

     while (true) { 
      String url = "http://www.stackoverflow.com"; 

      // query last checksum from map 
      String lastChecksum = checkSumDB.get(url); 

      // get current checksum using static utility method 
      String currentChecksum = getChecksumForURL(url); 

      if (currentChecksum.equals(lastChecksum)) { 
       System.out.println("it haven't been updated"); 
      } else { 
       // persist this checksum to map 
       checkSumDB.put(url, currentChecksum); 
       System.out.println("something in the content have changed..."); 

       // send email you can check: http://www.javacommerce.com/displaypage.jsp?name=javamail.sql&id=18274 
      } 

      Thread.sleep(5000); 
     } 
    } 

    private static String getChecksumForURL(String spec) throws IOException { 
     URL u = new URL(spec); 
     HttpURLConnection huc = (HttpURLConnection) u.openConnection(); 
     huc.setRequestMethod("GET"); 
     huc.setDoOutput(true); 
     huc.connect(); 
     return DigestUtils.sha256Hex(huc.getInputStream()); 
    } 
}