Jar 没有加载资源文件

Question

I have a project with a folder "src/main/resources" where inside there is the hibernate configuration file, I load it using this line of code

HibernateUtil.class.getResource("/hibernate.cgf.xml").getPath()

From inside the IDE it is working well, but when I create the jar it doesn't file the file.

How can I load it properly in the jar file too?

Thanks

Answer 1

Could you please try this:

ClassLoader classLoader = getClass().getClassLoader();
File file = new File(classLoader.getResource("fileName").getFile());

Answer 2

I cannot say for ceratin that this is the issue without knowing how exactly you use the path extracted by:

HibernateUtil.class.getResource("/hibernate.cgf.xml").getPath()

but I can tell you this:

Run from an IDE the above line of code will return:

/path/to/project/src/main/resources/hibernate.cgf.xml

which is a valid filesystem path. You can then use this path to, for example, create an instance of File class and then use that instance to read the file contents.

However the same line of code run from inside a jar file will return:

file:/path/to/jar/jar_name.jar!/hibernate.cgf.xml

which is not a valid filesystem path. If you create an instance of File class using this path and then try to read the contents of the file you'll get an exception: java.io.FileNotFoundExeption

To read the contents of the file from inside of a jar you should use method Class.getResourceAsStream(String) , which will return an instance of class sun.net.www.protocol.jar.JarURLConnection.JarURLInputStream (or equivalent in non-Oracle or non-OpenJDK Java). You can then use this object to read the contents of the file. For example:

InputStream inputStream = HibernateUtil.class.getResourceAsStream("/hibernate.cgf.xml");
Scanner scanner = new Scanner(inputStream).useDelimiter("\\A");
String fileContents = scanner.hasNext() ? sscanner.next() : "";

Answer 3

Most likely, the file is absent from the jar you create. There's too little information in your question, but I will try a guess:

Your hibernate.cgf.xml resides in the same directory as the Java sourcefles, and you are using a build tool (be it IDE, maven, gradle or an ant script) that expects resources to be stored in a separate directory.

It's easy to check: try to unzip your jar and see if the file is there (use any tool, you can just change the extension from .jar to .zip). I think you will see the file is absent.

Then come back with a question: "how to pack my non-java resources into a jar, using XXX", where XXX will be the name of the techology you are using for building the jar.

Answer 4

Most probably the slash in "/hibernate.cgf.xml" is not needed, if the hibernate.cgf.xml is in the same package as you class HibernateUtil.

You can access the file actually also via the classloader using the full path. Yet you never add to it the first slash.

Here is some code demonstrating how you can access the file using different methods:

public static void main(String[] args) {
    // Accessing via class
    System.out.println(SimpleTests.class.getResource("hibernate.cgf.xml").getPath());
    // Accessing via classloader from the current thread
    String path = Thread.currentThread().getContextClassLoader()
            .getResource("simple/hibernate.cgf.xml").getPath();
    System.out.println(path);
    // Accessing via classloader used by the current class
    System.out.println(SimpleTests.class.getClassLoader().getResource("simple/hibernate.cgf.xml").getPath());
}

In the example above the package 'simple' should be replaced by the package where your hibernate.cgf.xml is. But you should never have the slash at the beginning of the package declaration.