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Java

Example file download servlet

 /**
     *  Sends a file to the ServletResponse output stream.  Typically
     *  you want the browser to receive a different name than the
     *  name the file has been saved in your local database, since
     *  your local names need to be unique.
     *
     *  @param req The request
     *  @param resp The response
     *  @param filename The name of the file you want to download.
     *  @param original_filename The name the browser should receive.
     */
    private void doDownload( HttpServletRequest req, HttpServletResponse resp,
                             String filename, String original_filename )
        throws IOException
    {
        File                f        = new File(filename);
        int                 length   = 0;
        ServletOutputStream op       = resp.getOutputStream();
        ServletContext      context  = getServletConfig().getServletContext();
        String              mimetype = context.getMimeType( filename );

        //
        //  Set the response and go!
        //
        //
        resp.setContentType( (mimetype != null) ? mimetype : "application/octet-stream" );
        resp.setContentLength( (int)f.length() );
        resp.setHeader( "Content-Disposition", "attachment; filename=\"" + original_filename + "\"" );

        //
        //  Stream to the requester.
        //
        byte[] bbuf = new byte[BUFSIZE];
        DataInputStream in = new DataInputStream(new FileInputStream(f));

        while ((in != null) && ((length = in.read(bbuf)) != -1))
        {
            op.write(bbuf,0,length);
        }

        in.close();
        op.flush();
        op.close();
    }
https://snipt.net/embed/014efe4a0518362bc6cb89f3e6792f28/
/raw/014efe4a0518362bc6cb89f3e6792f28/
014efe4a0518362bc6cb89f3e6792f28
java
Java
45
2019-08-21T18:06:36
True
False
False
/api/public/snipt/19806/
example-file-download-servlet
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><a href="#L-1"> 1</a> <a href="#L-2"> 2</a> <a href="#L-3"> 3</a> <a href="#L-4"> 4</a> <a href="#L-5"> 5</a> <a href="#L-6"> 6</a> <a href="#L-7"> 7</a> <a href="#L-8"> 8</a> <a href="#L-9"> 9</a> <a href="#L-10">10</a> <a href="#L-11">11</a> <a href="#L-12">12</a> <a href="#L-13">13</a> <a href="#L-14">14</a> <a href="#L-15">15</a> <a href="#L-16">16</a> <a href="#L-17">17</a> <a href="#L-18">18</a> <a href="#L-19">19</a> <a href="#L-20">20</a> <a href="#L-21">21</a> <a href="#L-22">22</a> <a href="#L-23">23</a> <a href="#L-24">24</a> <a href="#L-25">25</a> <a href="#L-26">26</a> <a href="#L-27">27</a> <a href="#L-28">28</a> <a href="#L-29">29</a> <a href="#L-30">30</a> <a href="#L-31">31</a> <a href="#L-32">32</a> <a href="#L-33">33</a> <a href="#L-34">34</a> <a href="#L-35">35</a> <a href="#L-36">36</a> <a href="#L-37">37</a> <a href="#L-38">38</a> <a href="#L-39">39</a> <a href="#L-40">40</a> <a href="#L-41">41</a> <a href="#L-42">42</a> <a href="#L-43">43</a> <a href="#L-44">44</a></pre></div></td><td class="code"><div class="highlight"><pre><span></span><span id="L-1"><a name="L-1"></a> <span class="cm">/**</span> </span><span id="L-2"><a name="L-2"></a><span class="cm"> * Sends a file to the ServletResponse output stream. Typically</span> </span><span id="L-3"><a name="L-3"></a><span class="cm"> * you want the browser to receive a different name than the</span> </span><span id="L-4"><a name="L-4"></a><span class="cm"> * name the file has been saved in your local database, since</span> </span><span id="L-5"><a name="L-5"></a><span class="cm"> * your local names need to be unique.</span> </span><span id="L-6"><a name="L-6"></a><span class="cm"> *</span> </span><span id="L-7"><a name="L-7"></a><span class="cm"> * @param req The request</span> </span><span id="L-8"><a name="L-8"></a><span class="cm"> * @param resp The response</span> </span><span id="L-9"><a name="L-9"></a><span class="cm"> * @param filename The name of the file you want to download.</span> </span><span id="L-10"><a name="L-10"></a><span class="cm"> * @param original_filename The name the browser should receive.</span> </span><span id="L-11"><a name="L-11"></a><span class="cm"> */</span> </span><span id="L-12"><a name="L-12"></a> <span class="kd">private</span> <span class="kt">void</span> <span class="nf">doDownload</span><span class="o">(</span> <span class="n">HttpServletRequest</span> <span class="n">req</span><span class="o">,</span> <span class="n">HttpServletResponse</span> <span class="n">resp</span><span class="o">,</span> </span><span id="L-13"><a name="L-13"></a> <span class="n">String</span> <span class="n">filename</span><span class="o">,</span> <span class="n">String</span> <span class="n">original_filename</span> <span class="o">)</span> </span><span id="L-14"><a name="L-14"></a> <span class="kd">throws</span> <span class="n">IOException</span> </span><span id="L-15"><a name="L-15"></a> <span class="o">{</span> </span><span id="L-16"><a name="L-16"></a> <span class="n">File</span> <span class="n">f</span> <span class="o">=</span> <span class="k">new</span> <span class="n">File</span><span class="o">(</span><span class="n">filename</span><span class="o">);</span> </span><span id="L-17"><a name="L-17"></a> <span class="kt">int</span> <span class="n">length</span> <span class="o">=</span> <span class="mi">0</span><span class="o">;</span> </span><span id="L-18"><a name="L-18"></a> <span class="n">ServletOutputStream</span> <span class="n">op</span> <span class="o">=</span> <span class="n">resp</span><span class="o">.</span><span class="na">getOutputStream</span><span class="o">();</span> </span><span id="L-19"><a name="L-19"></a> <span class="n">ServletContext</span> <span class="n">context</span> <span class="o">=</span> <span class="n">getServletConfig</span><span class="o">().</span><span class="na">getServletContext</span><span class="o">();</span> </span><span id="L-20"><a name="L-20"></a> <span class="n">String</span> <span class="n">mimetype</span> <span class="o">=</span> <span class="n">context</span><span class="o">.</span><span class="na">getMimeType</span><span class="o">(</span> <span class="n">filename</span> <span class="o">);</span> </span><span id="L-21"><a name="L-21"></a> </span><span id="L-22"><a name="L-22"></a> <span class="c1">//</span> </span><span id="L-23"><a name="L-23"></a> <span class="c1">// Set the response and go!</span> </span><span id="L-24"><a name="L-24"></a> <span class="c1">//</span> </span><span id="L-25"><a name="L-25"></a> <span class="c1">//</span> </span><span id="L-26"><a name="L-26"></a> <span class="n">resp</span><span class="o">.</span><span class="na">setContentType</span><span class="o">(</span> <span class="o">(</span><span class="n">mimetype</span> <span class="o">!=</span> <span class="kc">null</span><span class="o">)</span> <span class="o">?</span> <span class="n">mimetype</span> <span class="o">:</span> <span class="s">&quot;application/octet-stream&quot;</span> <span class="o">);</span> </span><span id="L-27"><a name="L-27"></a> <span class="n">resp</span><span class="o">.</span><span class="na">setContentLength</span><span class="o">(</span> <span class="o">(</span><span class="kt">int</span><span class="o">)</span><span class="n">f</span><span class="o">.</span><span class="na">length</span><span class="o">()</span> <span class="o">);</span> </span><span id="L-28"><a name="L-28"></a> <span class="n">resp</span><span class="o">.</span><span class="na">setHeader</span><span class="o">(</span> <span class="s">&quot;Content-Disposition&quot;</span><span class="o">,</span> <span class="s">&quot;attachment; filename=\&quot;&quot;</span> <span class="o">+</span> <span class="n">original_filename</span> <span class="o">+</span> <span class="s">&quot;\&quot;&quot;</span> <span class="o">);</span> </span><span id="L-29"><a name="L-29"></a> </span><span id="L-30"><a name="L-30"></a> <span class="c1">//</span> </span><span id="L-31"><a name="L-31"></a> <span class="c1">// Stream to the requester.</span> </span><span id="L-32"><a name="L-32"></a> <span class="c1">//</span> </span><span id="L-33"><a name="L-33"></a> <span class="kt">byte</span><span class="o">[]</span> <span class="n">bbuf</span> <span class="o">=</span> <span class="k">new</span> <span class="kt">byte</span><span class="o">[</span><span class="n">BUFSIZE</span><span class="o">];</span> </span><span id="L-34"><a name="L-34"></a> <span class="n">DataInputStream</span> <span class="n">in</span> <span class="o">=</span> <span class="k">new</span> <span class="n">DataInputStream</span><span class="o">(</span><span class="k">new</span> <span class="n">FileInputStream</span><span class="o">(</span><span class="n">f</span><span class="o">));</span> </span><span id="L-35"><a name="L-35"></a> </span><span id="L-36"><a name="L-36"></a> <span class="k">while</span> <span class="o">((</span><span class="n">in</span> <span class="o">!=</span> <span class="kc">null</span><span class="o">)</span> <span class="o">&amp;&amp;</span> <span class="o">((</span><span class="n">length</span> <span class="o">=</span> <span class="n">in</span><span class="o">.</span><span class="na">read</span><span class="o">(</span><span class="n">bbuf</span><span class="o">))</span> <span class="o">!=</span> <span class="o">-</span><span class="mi">1</span><span class="o">))</span> </span><span id="L-37"><a name="L-37"></a> <span class="o">{</span> </span><span id="L-38"><a name="L-38"></a> <span class="n">op</span><span class="o">.</span><span class="na">write</span><span class="o">(</span><span class="n">bbuf</span><span class="o">,</span><span class="mi">0</span><span class="o">,</span><span class="n">length</span><span class="o">);</span> </span><span id="L-39"><a name="L-39"></a> <span class="o">}</span> </span><span id="L-40"><a name="L-40"></a> </span><span id="L-41"><a name="L-41"></a> <span class="n">in</span><span class="o">.</span><span class="na">close</span><span class="o">();</span> </span><span id="L-42"><a name="L-42"></a> <span class="n">op</span><span class="o">.</span><span class="na">flush</span><span class="o">();</span> </span><span id="L-43"><a name="L-43"></a> <span class="n">op</span><span class="o">.</span><span class="na">close</span><span class="o">();</span> </span><span id="L-44"><a name="L-44"></a> <span class="o">}</span> </span></pre></div> </td></tr></table>
java, servlet