从WAR文件读取文件时出现问题

Question

I have a war file with the below structure.

--js
  --sum.js
--WEB-INF
  --classes
    ---com
       -----test
           -----MyTest.class
--home.html

I am trying to read the js file in my MyTest.class file,But I am getting exception while reading it. I tried most of the solutions already mentioned in the stack.

I have tried

1)

String path = Thread.currentThread().getContextClassLoader().getResource("js/sum.js").getPath();
        File f = new File(path);
        System.out.println(f.getAbsolutePath());

First line is throwing nullpointer exception

2)

InputStream in =MyNashHornTest.class.getClassLoader().getResourceAsStream("/js/sum.js");
        BufferedReader br = new BufferedReader(new InputStreamReader(in));

Second line is throwing null pointer exception

3)

InputStream in =MyNashHornTest.class.getClassLoader().getResourceAsStream("../../../../js/sum.js");
        BufferedReader br = new BufferedReader(new InputStreamReader(in));

Second line is throwing null pointer exception

Please help me to resolve this issue.

Answer 1

For war files, don't use the servlet container's classloader, but use the ServletContext instead.

This method allows servlet containers to make a resource available to a servlet from any location, without using a class loader.

ServletContext context = getServletContext();
InputStream is = context.getResourceAsStream("/yourfilename.txt");

It is recommended to keep it under the /WEB-INF directory if you don't want browers being able to access it.

The path must begin with a « / » and is interpreted as relative to the current context root. This method returns null if no resource exists at the specified path. For example ServletContext.getResourceAsStream(« WEB-INF/resources/yourfilename.cnf ») will return a nul exception, so be careful !

Why null pointer comes??

The path must begin with a "/" and is interpreted as relative to the current context root. This method returns null if no resource exists at the specified path. For example, using a path that doesn't start with a slash, You will get a null return value.

Details Description is given here: How to use ServletContext.getResourceAsStream(java.lang.String path)?

Resource Link:

HOW TO: Read a file from jar and war files (java and webapp archive) ?

Answer 2

You can get resources from the class path with ClassLoader.getResource or from the web root directory with ServletContext.getResource .

In a war, you use the former to access ressources stored under WEB-INF/classes , or in jars under WEB-INF/lib , and the former for what lies directly at the root of the web application.