How to write/read file inside WebContent

General
1

Hello,
Does anyone know how to write/read file inside WebContent folder? (application folder)
I want to put a file there (text or xml), and then the application will read that file.
I tried System.getProperty(“user.dir”) inside Eclipse, and it returns my home folder.

Faizal

2

Hello,

As an opening statement, I would point out that this is not a Vaadin specific question, but a general java Web/J2EE question.

You basically have two fundamental choices : if you place the file in WEB-INF\classes or WEB-INF\lib, the file is not visible to the outside world. If you place the file anywhere else inside the web application directory (WebContent) but outside of the WebContent\WEB-INF, the file could be accessible to the end user.

WebContent
   super-secret.properties
   WEB-INF
       classes
           hidden.properties

If the web application were deployed to /example, and the user accessed http://theserver/example/super-secret.properties - the file would be downloaded to the end user[1]
. The J2EE spec mandates, I believe, that files in the WEB-INF folder (and below) are not accessible to the front end.

Personally, I would recommend that the file be placed on the classpath. That way, you can use ClassLoader.html#getResourceAsStream to open an input stream. That sounds very complicated, but in fact it’s not (no error checking included):

  ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
    InputStream stream = classLoader.getResourceAsStream("hidden.properties");

    if (stream == null) {
      // File not nound
    } else {
      Properties p = new Properties();
      p.load(stream);
    }

How do you get the file into the classpath? Simply add it to the root of your source directory. The Eclipse compiler will (almost certainly - Eclipse people tell me if I’m wrong) copy the .properties file to the root of the WebContent\WEB-INF\classes directory, and thus it is simply on the class path.

There are ways to access files in the WebContent directory, but they require a bit more setting up - you need access to the ServletContext, and then you can use ServletContext#getResourceAsStream e.g.


 ServletContext context = ... // This is the tricky bit, depends on where you are calling from
 InputStream stream = context.getResourceAsStream("/super-secret.properties")
  if (stream == null) {
      // File not nound
    } else {
      Properties p = new Properties();
      p.load(stream);
    }

Sorry this is so long - but it’s not as simple a question as you might imagine.

In short - I recommend using the classpath/classloader method. It’s more secure, and it’ll also work in non web environments.

Cheers,

Charles

[1]
This may not happen in a Vaadin application, actually, because of how the default servlet mapping is. The fundamental principle is right, though.

3

Hello show me example for save xml file, which is read from classloader inputstream. I need save to this file via same access

4

Don’t write to your webcontent folder. What if you upgrade your .war?

Store your stuff somewhere else on the filesystem or use a database or something.