如何使用 pentaho 水壶查看 http 标头

Posted 2023-04-18

【中文标题】如何使用 pentaho 水壶查看 http 标头

【英文标题】：How to see an http header with pentaho kettle

【发布时间】：2013-08-12 12:10:45

【问题描述】：

有什么方法可以查看 http 调用的响应标头吗？ 我会更具体。我需要查看资源（由网络上的 URL 指向）何时被修改。知道最后修改的日期，我决定是否下载它。我认为这样做的一种方法是查看 http 调用的标头。有什么建议么 ？

【问题讨论】：

不是 Web 开发人员，除了使用 javascript 步骤并检查代码中的标头之外，我不知道其他方法。无论如何，这是 Kettle/ETL 工具的常见问题，我很想知道您找到什么解决方案。

【参考方案1】：

这将使用用户定义的 Java 类轻松完成。在这里，您是一个 Class 示例，期望在上一步中输入一个名为 picture（图片的 url）的输入行。现在使用以下代码添加您的用户定义的 java 类：

import java.util.*;
import java.lang.System.*;
import java.net.*;
import java.io.*;
import java.text.*;
import java.util.Date;
import java.util.Calendar;


public boolean processRow(StepMetaInterface smi, StepDataInterface sdi) throws KettleException, Exception


  //First, get a row from the default input hop
  Object[] r = getRow();

  //If the row object is null, we are done processing.
  if (r == null) 
      setOutputDone();
      return false;
  



String filesSavePath = getParameter("filesSavePath")+"/tmp/pictures";
//remove "file://" from filesSavePath, otherwise gives a file io exception, file not found
filesSavePath =  filesSavePath.replace("file://","");

String picture = get(Fields.In, "picture").getString(r);

//get the last chunk of picture as filename to save in disk
String filePictureName = picture.substring(picture.lastIndexOf('/') + 1);
String fileFullPath = filesSavePath+ "/"+ filePictureName;

//lets get the headers from picture
try   

    boolean fileExists = new File(fileFullPath).isFile();

    //if picture do not exists save it
    if(fileExists != true)
        saveImage(picture, fileFullPath);
        System.out.println("new picture saved = " + filePictureName);
        System.out.println("*******************************");
    

    //if file exists compare date last modified file from header, younger than yesterday.
    //if true save it.
    else
        //get the last-modified header
        URL url = new URL(picture);
        URLConnection conn = url.openConnection();

        long lastModified = conn.getLastModified();         

        //get last-modified date
        Date lastModifiedDate = new Date(lastModified);

        //get yesterday date
        Calendar cal = Calendar.getInstance();
        cal.add(Calendar.DATE, -1);
        Date yesterdayDate = cal.getTime();


        //today just for testing
        //Date today = new Date();
        //boolean  dateCompare = today.after(yesterdayDate);


        boolean  dateCompare = lastModifiedDate.after(yesterdayDate);           

        //if true save it!
        if(dateCompare == true)
            saveImage(picture, fileFullPath);
            System.out.println("new picture saved(last modified after yesterday) = " + filePictureName);
        


        System.out.println("picture = " + picture);
        System.out.println("last modified after yesterday = " + dateCompare);
        System.out.println("last modified = " + lastModifiedDate);
        //System.out.println("today = " + today);
        System.out.println("yesterday date = " + yesterdayDate);
        System.out.println("*******************************");
    



 
catch (Exception e) 
System.out.println("error: " + e);
String fullStackTrace = org.apache.commons.lang.exception.ExceptionUtils.getFullStackTrace(e);
System.out.println("fullStackTrace: " + fullStackTrace);



return true;









    private static void saveImage(String imageUrl, String destinationFile) throws IOException 
    URL url = new URL(imageUrl);
    InputStream is = url.openStream();
    OutputStream os = new FileOutputStream(destinationFile);

    byte[] b = new byte[2048];
    int length;

    while ((length = is.read(b)) != -1) 
        os.write(b, 0, length);
    

    is.close();
    os.close();