getResourceAsStream returns null

Question

I\'m loading a text file from within a package in a compiled JAR of my Java project. The relevant directory structure is as follows:

/src/initialization/Life         


        

Answer 1

Don't use absolute paths, make them relative to the 'resources' directory in your project. Quick and dirty code that displays the contents of MyTest.txt from the directory 'resources'.

@Test
public void testDefaultResource() {
    // can we see default resources
    BufferedInputStream result = (BufferedInputStream) 
         Config.class.getClassLoader().getResourceAsStream("MyTest.txt");
    byte [] b = new byte[256];
    int val = 0;
    String txt = null;
    do {
        try {
            val = result.read(b);
            if (val > 0) {
                txt += new String(b, 0, val);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } 
    } while (val > -1);
    System.out.println(txt);
}

Answer 2

@Emracool... I'd suggest you an alternative. Since you seem to be trying to load a *.txt file. Better to use FileInputStream() rather then this annoying getClass().getClassLoader().getResourceAsStream() or getClass().getResourceAsStream(). At least your code will execute properly.

Answer 3

Make sure your resource directory (e.g. "src") is in your classpath (make sure it's a source directory in your build path in eclipse).

Make sure clazz is loaded from the main classloader.

Then, to load src/initialization/Lifepaths.txt, use

clazz.getResourceAsStream("/initialization/Lifepaths.txt");

Why: clazz.getResourcesAsStream(foo) looks up foo from within the classpath of clazz, relative to the directory clazz lives in. The leading "/" makes it load from the root of any directory in the classpath of clazz.

Unless you're in a container of some kind, like Tomcat, or are doing something with ClassLoaders directly, you can just treat your eclipse/command line classpath as the only classloader classpath.

Answer 4

if you are using Maven make sure your packing is 'jar' not 'pom'.

<packaging>jar</packaging>

Answer 5

What worked for me is I placed the file under

src/main/java/myfile.log

and

InputStream is = getClass().getClassLoader().getResourceAsStream("myfile.log");
        
        if (is == null) {
            throw new FileNotFoundException("Log file not provided");
        }

Answer 6

The default JVM classloader will use parent-classloader to load resources first: .

Lifepaths.class.getClass()'s classloader is bootstrap classloader, so getResourceAsStream will search $JAVA_HOME only, regardless of user provided classpath. Obviously, Lifepaths.txt is not there.

Lifepaths.class 's classloader is system classpath classloader, so getResourceAsStream will search user-defined classpath and Lifepaths.txt is there.

When using java.lang.Class#getResourceAsStream(String name), name which is not start with '/' will be added with package name as prefix. If you want avoid this, please using java.lang.ClassLoader#getResourceAsStream. For example:

ClassLoader loader = Thread.currentThread().getContextClassLoader();
String resourceName = "Lifepaths.txt";
InputStream resourceStream = loader.getResourceAsStream(resourceName);