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    <p>Basically you just need to construct a new <code>ZipOutputStream</code> around <code>response.getOutputStream()</code> and then add every <code>InputStream</code> from the DB as new <code>ZipEntry</code>. To improve performance, you can wrap the <code>response.getOutputStream()</code> in a <code>BufferedOutputStream</code> beforehand and the <code>InputStream</code> in a <code>BufferedInputStream</code> and use a <code>byte[]</code> buffer.</p> <p>Here's a basic example:</p> <pre><code>package com.example; import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.IOException; import java.io.InputStream; import java.util.zip.ZipEntry; import java.util.zip.ZipOutputStream; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class ZipFileServlet extends HttpServlet { private static final int DEFAULT_BUFFER_SIZE = 10240; // 10KB. private YourFileDAO yourFileDAO = YourDAOFactory.getYourFileDAO(); @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String[] fileIds = request.getParameterValues("fileId"); response.setContentType("application/zip"); response.setHeader("Content-Disposition", "attachment; filename=\"allfiles.zip\""); ZipOutputStream output = null; byte[] buffer = new byte[DEFAULT_BUFFER_SIZE]; try { output = new ZipOutputStream(new BufferedOutputStream(response.getOutputStream(), DEFAULT_BUFFER_SIZE)); for (String fileId : fileIds) { YourFileItem item = yourFileDAO.find(fileId); if (item == null) continue; // Handle yourself. The fileId may be wrong/spoofed. InputStream input = null; try { input = new BufferedInputStream(item.getInputStream(), DEFAULT_BUFFER_SIZE); output.putNextEntry(new ZipEntry(item.getName())); for (int length = 0; (length = input.read(buffer)) &gt; 0;) { output.write(buffer, 0, length); } output.closeEntry(); } finally { if (input != null) try { input.close(); } catch (IOException logOrIgnore) { /**/ } } } } finally { if (output != null) try { output.close(); } catch (IOException logOrIgnore) { /**/ } } } } </code></pre> <p>which can be invoked by a form like this:</p> <pre><code>&lt;form action="zipFile" method="post"&gt; &lt;input type="checkbox" name="fileId" value="1"&gt; foo.exe&lt;br&gt; &lt;input type="checkbox" name="fileId" value="2"&gt; bar.pdf&lt;br&gt; &lt;input type="checkbox" name="fileId" value="3"&gt; waa.doc&lt;br&gt; &lt;input type="checkbox" name="fileId" value="4"&gt; baz.html&lt;br&gt; &lt;input type="submit" value="download zip"&gt; &lt;/form&gt; </code></pre> <p>That said, do in <strong>no way</strong> use <code>ByteArrayInputStream/ByteArrayOutputStream</code> as some here may suggest. Those are namely backed by a raw <code>byte[]</code>. You may risk that that your application breaks when the size of all of the files (from all concurrent users!) together inside bytearrays is larger than the available server memory. You already have a stream from the DB and a stream to the response. Just pipe them through a small byte buffer in a read/write loop. You don't need to get hold of the entire inputstream in a (under the hood) massive byte buffer and then write it away to the outputstream.</p>
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    1. COI am sorry that it took so long for me to reply. I have some business that I have to take care. When I read your code, you have YourFileDAO and YourDAOFactory, I dont seem to have those classes. Are they your classes that you created?
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    2. COThose are just fictive DAO (data access objects) classes/methods with self-explaining names. If your data access layer code is well designed, you should already have them. If not, I'd suggest to head here: http://balusc.blogspot.com/2008/07/dao-tutorial-data-layer.html
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    3. COThank you. I have read your blog. Excellent works.I just want to check if my understanding are accurate 1. yourFileItem is a class that contain information about the file, e.g name, fileID... 2. item.getInputStream() -- I am kind of confuse on this. Can u help me out on this? I am guessing that we are create an InputStream to retrieve the blob file on database. Please forgive my ignorance!!!
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