Simplest way to serve static data from outside the application server in a Java web application

Question

I have a Java web application running on Tomcat  I want to load static images that will be shown both on the Web UI and in PDF files generated by the application  Also new images will be added and saved by uploading via the Web UI  It s not a problem to do this by having the static data stored within the web container but storing and loading them from outside the web container is giving me headache  I d prefer not to use a separate web server like Apache for serving the static data at this point  I also don t like the idea of storing the images in binary in a database  I ve seen some suggestions like having the image directory being a symbolic link pointing to a directory outside the web container  but will this approach work both on Windows and  nix environments  Some suggest writing a filter or a servlet for handling the image serving but those suggestions have been very vague and high-level without pointers to more detailed information on how to accomplish this

User · Answer

This is story from my workplace  - We try to upload multiply images and document files use Struts 1 and Tomcat 7 x  - We try to write uploaded files to file system  filename and full path to database records  - We try to separate file folders outside web app directory       The below solution is pretty simple  effective for requirement       In file META-INF context xml file with the following content   Example  my application run at http   localhost 8080 ABC  my application   project named ABC    this is also full content of file context xml    lt  xml version  1 0  encoding  UTF-8   gt   lt Context path   ABC  aliases   images D  images  docs D  docs   gt     works with Tomcat version 7 or later   Result  We have been created 2 alias  For example  we save images at  D  images foo jpg and view from link or using image tag     lt img src  http   localhost 8080 ABC images foo jsp  alt  Foo  height  142  width  142  gt    or    lt img src   images foo jsp  alt  Foo  height  142  width  142  gt     I use Netbeans 7 x  Netbeans seem auto create file WEB-INF context xml

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Add to server xml       lt Context docBase  c  dirtoshare  path   dir    gt    Enable dir file listing parameter in web xml          lt init-param gt           lt param-name gt listings lt  param-name gt           lt param-value gt true lt  param-value gt       lt  init-param gt

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if anyone not able to resolve his problem with accepted answer  then note these below considerations    no need to mention localhost  lt port gt  with  lt img gt  src attribute  make sure you are running this project outside eclipse  because eclipse creates context docBase entry on its own inside its local server xml file

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Read the InputStream of a file and write it to ServletOutputStream for sending binary data to the client    Local file You can read a file directly using FileInputStream  path image png    Mongo DataBase file s you can get InputStream using GridFS       WebServlet   files URLStream   public class URLStream extends HttpServlet       private static final long serialVersionUID   1L       public URLStream             super               protected void service HttpServletRequest request  HttpServletResponse response  throws ServletException  IOException           File source   new File  D   SVN Commit PNG            long start   System nanoTime             InputStream image   new FileInputStream source              String fileID   request getParameter  id            System out println  Requested File ID     fileID              Mongo DB GridFS - https   stackoverflow com a 33544285 5081877         image   outputImageFile getInputStream               if  image    null                 BufferedInputStream bin   null              BufferedOutputStream bout   null              ServletOutputStream sos   response getOutputStream                try                   bin   new BufferedInputStream  image                    bout   new BufferedOutputStream  sos                    int ch  0                    while  ch bin read     -1                        bout write ch                                   finally                   bin close                    image close                    bout close                    sos close                             else               PrintWriter writer   response getWriter                writer append  Something went wrong with your request                 System out println  Image not available                       System out println  Time taken by Stream Copy      System nanoTime  -start                  Result the URL directly to the src attibute      lt img src  http   172 0 0 1 8080 ServletApp files URLStream id 5a575be200c117cc2500003b  alt  mongodb File   gt   lt img src  http   172 0 0 1 8080 ServletApp files URLStream  alt  local file   gt    lt video controls  controls  src  http   172 0 0 1 8080 ServletApp files URLStream  gt  lt  video gt

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I did it even simpler  Problem  A CSS file had url links to img folder   Gets 404    I looked at url  http   tomcatfolder port img blablah png  which does not exist  But  that is really pointing to the ROOT app in Tomcat     So I just copied the img folder from my webapp into that ROOT app   Works     Not recommended for production  of course  but this is for an internal tool dev app

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You can do it by putting your images on a fixed path  for example   var images  or c  images   add a setting in your application settings  represented in my example by the Settings class   and load them like that  in a HttpServlet of yours   String filename   Settings getValue  images path     request getParameter  imageName   FileInputStream fis   new FileInputStream filename    int b   0  while   b   fis read       -1            response getOutputStream   write b       Or if you want to manipulate the image   String filename   Settings getValue  images path     request getParameter  imageName   File imageFile   new File filename   BufferedImage image   ImageIO read imageFile   ImageIO write image   image png   response getOutputStream       then the html code would be  lt img src  imageServlet imageName myimage png    gt   Of course you should think of serving different content types -  image jpeg   for example based on the file extension  Also you should provide some caching   In addition you could use this servlet for quality rescaling of your images  by providing width and height parameters as arguments  and using image getScaledInstance w  h  Image SCALE SMOOTH   considering performance  of course

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If you decide to dispatch to FileServlet then you will also need allowLinking  true  in context xml in order to allow FileServlet to traverse the symlinks   See http   tomcat apache org tomcat-6 0-doc config context html

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I ve seen some suggestions like having the image directory being a symbolic link pointing to a directory outside the web container  but will this approach work both on Windows and  nix environments   If you adhere the  nix filesystem path rules  i e  you use exclusively forward slashes as in  path to files   then it will work on Windows as well without the need to fiddle around with ugly File separator string-concatenations  It would however only be scanned on the same working disk as from where this command is been invoked  So if Tomcat is for example installed on C  then the  path to files would actually point to C  path to files  If the files are all located outside the webapp  and you want to have Tomcat s DefaultServlet to handle them  then all you basically need to do in Tomcat is to add the following Context element to  conf server xml inside  lt Host gt  tag   lt Context docBase  quot  path to files quot  path  quot  files quot    gt   This way they ll be accessible through http   example com files      For Tomcat-based servers such as JBoss EAP 6 x or older  the approach is basically the same  see also here  GlassFish Payara configuration example can be found here and WildFly configuration example can be found here  If you want to have control over reading writing files yourself  then you need to create a Servlet for this which basically just gets an InputStream of the file in flavor of for example FileInputStream and writes it to the OutputStream of the HttpServletResponse  On the response  you should set the Content-Type header so that the client knows which application to associate with the provided file  And  you should set the Content-Length header so that the client can calculate the download progress  otherwise it will be unknown  And  you should set the Content-Disposition header to attachment if you want a Save As dialog  otherwise the client will attempt to display it inline  Finally just write the file content to the response output stream  Here s a basic example of such a servlet   WebServlet  quot  files   quot   public class FileServlet extends HttpServlet         Override     protected void doGet HttpServletRequest request  HttpServletResponse response          throws ServletException  IOException               String filename   URLDecoder decode request getPathInfo   substring 1    quot UTF-8 quot            File file   new File  quot  path to files quot   filename           response setHeader  quot Content-Type quot   getServletContext   getMimeType filename            response setHeader  quot Content-Length quot   String valueOf file length              response setHeader  quot Content-Disposition quot    quot inline  filename   quot  quot    file getName      quot   quot  quot            Files copy file toPath    response getOutputStream               When mapped on an url-pattern of for example  files    then you can call it by http   example com files image png  This way you can have more control over the requests than the DefaultServlet does  such as providing a default image  i e  if   file exists    file   new File  quot  path to files quot    quot 404 gif quot   or so   Also using the request getPathInfo   is preferred above request getParameter   because it is more SEO friendly and otherwise IE won t pick the correct filename during Save As  You can reuse the same logic for serving files from database  Simply replace new FileInputStream   by ResultSet getInputStream    Hope this helps  See also   Recommended way to save uploaded files in a servlet application Abstract template for a static resource servlet  supporting HTTP cache  How to retrieve and display images from a database in a JSP page  How to stream audio video files such as MP3  MP4  AVI  etc using a Servlet

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If you want to work with JAX-RS  e g  RESTEasy  try this    Path   pic   public Response get  QueryParam  url   final String url        String picUrl   URLDecoder decode url   UTF-8         return Response ok sendPicAsStream picUrl                header HttpHeaders CONTENT TYPE   image jpg                build       private StreamingOutput sendPicAsStream String picUrl        return output - gt            try  InputStream is    new URL picUrl   openStream                  ByteStreams copy is  output                        using javax ws rs core Response and com google common io ByteStreams

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Requirement   Accessing the static Resources  images videos   etc    from outside of WEBROOT directory or from local disk  Step 1    Create a folder under webapps of tomcat server   let us say the folder name is myproj  Step 2   Under myproj create a WEB-INF folder under this create a simple web xml  code under web xml   lt web-app gt   lt  web-app gt    Directory Structure for the above two steps  c  programfile apachesoftwarefoundation tomcat     webapps                                                                                                                            ---myproj                                                                                                                                    ---WEB-INF                                                                                                                                            ---web xml   Step 3  Now create a xml file with name myproj xml under the following location  c  programfile apachesoftwarefoundation tomcat conf catalina localhost   CODE in myproj xml    lt Context path   myproj images  docBase  e  myproj   crossContext  false  debug  0  reloadable  true  privileged  true    gt       Step 4   4 A  Now create a folder with name myproj in E drive of your hard disk and create a new   folder with name images and place some images in images folder  e myproj images    Let us suppose myfoto jpg is placed under e  myproj images myfoto jpg  4 B  Now create a folder with name WEB-INF in e  myproj WEB-INF and create a web xml in WEB-INF folder  Code in web xml   lt web-app gt   lt  web-app gt    Step 5  Now create  a  html document with name index html and place under e  myproj  CODE under index html                                                       Welcome to Myproj                                  The Directory Structure for the above Step 4 and Step 5 is as follows   E  myproj      --index html            --images            ----myfoto jpg            --WEB-INF            --web xml   Step 6  Now start the apache tomcat server  Step 7  open the browser and type the url as follows  http   localhost 8080 myproj       then u display the content which is provided in index html  Step 8  To Access the Images under your local hard disk  outside of webroot   http   localhost 8080 myproj images myfoto jpg

[tomcat] Simplest way to serve static data from outside the application server in a Java web application

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