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PODifferent ZipOutputStream results on different platforms
 

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  1. PODifferent ZipOutputStream results on different platforms
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    <p>I have code that produces a zip output stream and then I send that stream through the response stream of a servlet. When testing in development on my mac everything works fine, however, when I put the code on my server (RHEL) the zip archive seems to be corrupt. When I try to list the contents of the file using jar I get:</p> <p>java.util.zip.ZipException: error in opening zip file</p> <p>But strangely, extracting the archive with jar works (other unarchivers fail, however).</p> <p>To test further, I made sure the contents of the zip file were exactly the same coming from my mac and RHEL. In both cases the size of the zip files were exactly the same, however, the hashes (MD5) were different.</p> <p>As I said, the code to produce the zip file as well as the contents are exactly the same so I have no idea what is going on. I'm fairly sure my zip file creation is correct since it is working on one of the platforms. There is no indication of any problem when generating the zip file on the RHEL server.</p> <p>Thoughts? Thanks for the help.</p> <p>EDIT: Here's the code ...</p> <pre><code>// first add the kml document ZipOutputStream stream = new ZipOutputStream(response.getOutputStream()); stream.putNextEntry(new ZipEntry("doc.kml")); stream.write(kml.getBytes(), 0, kml.length()); stream.closeEntry(); File image = null; byte[] bytes = null; FileInputStream fstream = null; // include the images for each type File images = new File("/tmp/images"); String filename = null; for(Type type: types) { filename = type.getName() + ".png"; image = new File(images, filename); bytes = new byte[(int)image.length()]; fstream = new FileInputStream(image); fstream.read(bytes); stream.putNextEntry(new ZipEntry(filename)); stream.write(bytes); stream.closeEntry(); fstream.close(); } stream.finish(); stream.flush(); stream.close(); </code></pre> <p>EDIT2: The plot thickens, it seems the RHEL zip stream is fine as long as there is only one image in the archive. Hopefully this is enough for google to help me out.</p>
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    1. COwithout code, hard to give much feedback. my _guess_ would be that at some point the data is getting treated as text and maybe you are getting newline conversions. at any point in the client or server are you using Readers or Writers (maybe on the client side download code)?
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      1. PODifferent ZipOutputStream results on different platforms
      1. USjtahlborn
    2. COThe hashes can be different only if the content is different. Your conclusion that "the contents are exactly the same" seems to be unwarranted. a problem can creep in with rubbish characters that get appended or prepended to the zip data stream. Imagine if you had an HTML tag, followed by a bunch of binary zip data. Some zip programs can tolerate that kind of junk, some cannot. This would explain why jar could read your archive, while other tools did not. To diagnose this, trace the HTTP response and look directly at the zip content. Try zipping just one file with no compression.
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      1. PODifferent ZipOutputStream results on different platforms
      1. USCheeso
    3. COjtahlborn-I've updated the post to include the code. Let me know if you have questions. Cheeso-Not sure what to tell you, when I use jar to unzip the files they are indeed the same hash, however, the jar files themselves are not the same hash. Thanks for the help.
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