Accessing properties file in a JSF application programmatically

by

The Class#getResourceAsStream() can take a path which is relative to the location of the Class which you’re using there as starting point. So, for example, if the class is located in the com.example package and you request the path foo/filename.properties, then it will actually load the com/example/foo/filename.properties file. But if you use /foo/filename.properties, then it will actually load foo/filename.properties from the classpath root.

So, your code

java.util.Properties prop = new java.util.Properties();
String path = "localization/stat_codes.properties";
InputStream foo = prop.getClass().getResourceAsStream(path);

will actually look for java/util/localization/stat_codes.properties file.

But in applications with a complex multiple classloader hierarchy, the one classloader isn’t the other. The classloader which loaded the core Java classes does not necessarily have knowledge about files which are in the webapp’s /WEB-INF/classes. So prefixing the path with / will not necessarily be the solution, it would still return null.

If you can guarantee that the current class is visible by the same classloader as the properties files (because they’re in the same sub-root of the classpath, e.g. /WEB-INF/classes, then you should indeed use

String path = "/localization/stat_codes.properties";
InputStream foo = this.getClass().getResourceAsStream(path);

But if at some point, the properties files will be externalized because of more easy maintenance/editing during runtime so that you don’t need to rebuild/redeploy/restart the webapp whenever you want to edit the files, then the above line of code will likely fail as well. The externalized location would be only accessible by a different classloader. The canonical solution is to use the thread’s context classloader as starting point instead, it has access to all resources in the classpath.

String path = "localization/stat_codes.properties";
ClassLoader loader = Thread.currentThread().getContextClassLoader();
InputStream foo = loader.getResourceAsStream(path);

(note that this one cannot take a path starting with /, it’s always relative to the common root)

See also:

More Related Contents:

  1. What is the JSF resource library for and how should it be used?
  2. How to reference CSS / JS / image resource in Facelets template?
  3. Internationalization in JSF, when to use message-bundle and resource-bundle?
  4. Localization in JSF, how to remember selected locale per session instead of per request/view
  5. Obtaining Facelets templates/files from an external filesystem or database
  6. String concatenation in EL for dynamic ResourceBundle key
  7. Read resource bundle properties in a managed bean
  8. How and when should I load the model from database for h:dataTable
  9. Get JSF managed bean by name in any Servlet related class
  10. Conditionally displaying JSF components
  11. How to save uploaded file in JSF
  12. Invoke JSF managed bean action on page load
  13. How do PrimeFaces Selectors as in update=”@(.myClass)” work?
  14. Packaging Facelets files (templates, includes, composites) in a JAR
  15. Default action to execute when pressing enter in a form
  16. What URL to use to link / navigate to other JSF pages
  17. How to compare a char property in EL
  18. internationalization in JSF with ResourceBundle entries which are loaded from database
  19. PrimeFaces CSS skin not showing in login page, also JavaScript undefined errors
  20. How to write a file to resource/images folder of the app?
  21. Creating master-detail table and dialog, how to reuse same dialog for create and edit
  22. h:outputText seems to trim whitespace, how do I preserve whitespace?
  23. What is the function of @this exactly?
  24. How to conditionally render an f:selectItem tag?
  25. Customize primefaces chart
  26. How to use EL in PrimeFaces oncomplete attribute which is updated during action method
  27. How to include a pop-up dialog box in subflow
  28. Uses of javax.faces.PROJECT_STAGE
  29. Redirect in @PostConstruct causes IllegalStateException
  30. Pass method argument/parameter to composite-component action attribute

Leave a Comment