ServletContext.getResource从lib中获取资源

Question

I have a jar-file test.jar that is placed within WEB-INF/lib and contains a single file in its root:

/
|- test.jsp

Now i would like to access this file from somewhere in my code:

this.getServletContext().getResource("/test.jsp");

But the result is always null although the documentation of getResource states that the jar-files within WEB-INF/lib are also searched:

http://docs.oracle.com/javaee/6/api/javax/servlet/ServletContext.html#getResource%28java.lang.String%29

Am i missing something or why can't i get the resource?

Answer 1

You already provided the link to the javadoc, quoting the relevant part:

The path must begin with a / and is interpreted as relative to the current context root, or relative to the /META-INF/resources directory of a JAR file inside the web application's /WEB-INF/lib directory.

So it is interpreted as relative to the /META-INF/resources folder in a jar file.

However you indicated with a tag that you are using Tomcat. Tomcat implementation of the ServletContext.getResource() is somewhat different. It doesn't even mention the resource is searched in jar files.

Suggestion: don't put your resources in jar files if you want to access them with ServletContext.getResource() . If you do need to put them into jar files, then instead use the Class.getResource() method, eg put an optionally empty class into the jar file, and use that to access/load the resource, for example:

Jar content:

/
|- SomeClass.class
|- test.jsp

Java code to access test.jsp :

SomeClass.class.getResource("/test.jsp"); // or it can even be "test.jsp"

Answer 2

You can use your thread's class loader to get your file as an InputStream like this:

Thread.currentThread().getContextClassLoader().getResourceAsStream("test.jsp");

The method getResourceAsStream() works for any file in the classpath, whether it's in a directory or inside a JAR.