Solved

Running Zipping Program from within JSP

Posted on 2003-11-13
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Last Modified: 2010-04-01
Ok, here is the situation.  We have a website linked to a massive database (USDA).  Through the website the user can pair down this data to get a more refined data set.  For example, The user can see the reported losses report by corn farmers in Kansas for 2000 through 2003.  We want to allow the user to no only see the data in the browser, but to be able to save and download the data as a Comma Seperated Value (CSV) file.  Saving the file is failry simple and we have that worked out.  These files are huge, so we want to zip them after they are created to make downloads faster.  The only problem is I can't get teyh command line version of any zipping program (winzip, winrar, etc..) to run from inside JSP code.  Here is the code, please help if you have any ideas.

// the file is already created
Runtime rt = Runtime.getRuntime();
Process p = null;
try {
String[] cmd = {"winrar.exe A", "d:\\tomcat4\\webapps\\dashboard\\down.zip d:\\tomcat4\\webapps\\dashboard\\data.csv"};
 p = rt.exec(cmd);
p.waitFor();
} catch (Exception e)
{
e.printStackTrace();
}
0
Comment
Question by:sjno
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3 Comments
 
LVL 2

Accepted Solution

by:
dyanet earned 250 total points
ID: 9740753
Two other solutions for you:
1. use java.util.zip package to compress the files. Use FileInputStream to read the file in and ZipOutputStream to write it the output file.  You can probably do that while you are creating the CSV file for the first time.
2. If you are running behind Apache, investigate and see if mod_gzip will solve your problem.  Most modern browsers support compressed content and Apache will automatically compress the file to achieve the desired goal - less use of bandwidth.
0
 

Expert Comment

by:u9707118
ID: 9741619
Here is a pure java solution that I have written for my project.
You can play around with the 'BUFFER' size for performance.


import java.util.ArrayList;
import java.util.zip.*;
import java.io.*;

static final int BUFFER = 2048;
byte data[] = new byte[BUFFER];          

FileOutputStream dest = new FileOutputStream("c:\\mydata\\myZipFile.zip");
ZipOutputStream out = new ZipOutputStream(new BufferedOutputStream(dest));
BufferedInputStream origin;
ArrayList filenameList = new ArrayList();

filenameList.add("mycsvfile1.csv");
filenameList.add("mycsvfile2.csv");
//etc..

for (int counter=0; counter<filenameList.size(); counter++) {
            FileInputStream fi = new FileInputStream((String)filenameList.get(counter));
            origin = new BufferedInputStream(fi, BUFFER);
            ZipEntry entry = new ZipEntry((String)filenameList.get(counter)); //creates entry containing file
               
            entry.setMethod(ZipOutputStream.DEFLATED); //sets method to compressed
            out.putNextEntry(entry); //adds entry to zip file
       
            //write data to zip file
            int count;
            while((count = origin.read(data, 0, BUFFER)) != -1) {
                out.write(data, 0, count);
            }//end while
            origin.close();          
                 
}//end for
out.close();




Hey presto you have a compressed zip file that you can spit back to your user.

Hope this helps,

Damian
0
 

Author Comment

by:sjno
ID: 9742085
If I knew how to split points I would but since dyanet answered first they gets the points I guess.
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