CODEWITHSUNDEEP
javareflectionclassloader
amphibient
amphibient

Reputation: 31212

Is it possible to create a ClassLoader that contains a single jar?

I am trying to write a simple code analyzer and, for starters, just want to create an instance of a ClassLoader whose classpath is a single jar file, independent of the classpath of the actual code analyzer application. Then I want to get a listing of all the entries within but then use reflection on each one within the context of the classpath to do some basic code analysis and tabulate the results.

Is it possible to create a ClassLoader that contains a single jar whose listings can be further analyzed using reflection?

For example, create a custom loader:

String clspath = "/my/dir/myjar.jar";

URL clspathURL = null;

try {
    clspathURL = new URL("file:///" + clspath);
} catch(MalformedURLException badURLex) {

}

Then do something to list all the classes it loaded OR (not sure if it loads all the classes available to it upon initialization) if it does not load all the classes, load them

Then be able to do an in memory code analysis using reflection.

Upvotes: 0

Views: 275

Answers (1)

mwhs
mwhs

Reputation: 5978

Getting a list of the files from a jar and loading the class for reflection are two separate things. Use a ZipInputStream for the first and a URLClassLoader for the second task:

 URL jar = ...;

 ClassLoader cl = new URLClassLoader(new URL[]{jar});

 ZipInputStream zip = new ZipInputStream(jar.openStream());
 while(true) {
    ZipEntry e = zip.getNextEntry();
    if (e == null)
      break;
    String nameAsInZip = e.getName():

    if(nameAsInZip.endsWith(".class")) {

       String nameForClassLoader = ....; // transform name for CL

       Class clazz = cl.loadClass(nameForClassLoader);

       // analyze class

    }

 }

Upvotes: 1

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