Class Finder & Scanner

Finding one or many classes or resources on the classpath is often needed. Jodd provides two powerful tools: ClassFinder and, its subclass, ClassScanner.

ClassFinder

ClassFinder contains main logic (based on FindFile) for finding classes (and resources) on classpath or simply on set of files. ClassFinder scans JARs (including those linked via manifest file) and filter founded entities. When matched class or resource (i.e. entry) is found, callback method is fired.

For scanning just files and folders, see file finder.

ClassFinder can be fine tuned using following properties:

• systemJars - list of system jars (i.e. wildcard templates), that are always excluded. It is a static property. By default, system jars are already set to exclude common JDK jars on Mac, Linux and Windows.
• excludeJars - list of excluded jars (i.e. wildcard templates) that will be excluded, if specified.
• includeJars - list of jars that has to be included.
• excludeEntries - list of exclude entry wildcard paths.
• includeEntries - list of included entries.
• includeResources - if set to true, all files on the classpath will be scanned, not only classes.
• ignoreException - specifies if exception should be thrown on scanning errors or simply ignored.

Rules for include* and exclude* are powered by our powerful InExRules engine.

Besides these properties, user can change the filtering behavior by overriding methods acceptJar() and acceptEntry().

Scanning is invoked by calling one of scanUrls or scanPaths methods. Note that all these methods are protected, because ClassFinder is designed to be used as a base scanning class for custom scanners.

For every founded class file (or a resource), onEntry method is fired. It gets an instance of EntryData - class that wraps currently founded class or a resource. ClassFinder may also open input stream of an entry by using openInputStream method. Now you can read it's actual content. Once opened, InputStream does not have to be closed in callback method, since ClassFinder does that for you.

ClassFinder is used internally by many Jodd frameworks, for automatic configurations. It usually reads classes on classpath and scans them for some annotations.

ClassScanner

For somewhat convenient and quick work you can use ClassScanner. It extends ClassFinder and just offers few scanning methods as public methods. Here is the usage example:

    ClassScanner cs = new ClassScanner() {
        @Override
        protected void onEntry(EntryData entryData) {
            InputStream inputStream = entryData.openInputStream();
            byte[] bytes = StreamUtil.readAvailableBytes(inputStream);
            System.out.println("---> " +
                entryData.getName() + ':' + entryData.getArchiveName()
                + "\t\t" + bytes.length);
        }
    };
    cs.includeResources(true);
    cs.scan("/some/classpath");

Simple, right! Here is another example how you can e.g. list all resources of some webjar:

    URL url = ClassLoaderUtil.getResourceUrl(
        "/META-INF/resources/webjars/jquery");

    File containerFile = FileUtil.toContainerFile(url);

    ClassScanner classScanner = new ClassScanner() {
        @Override
        protected void onEntry(EntryData entryData) throws Exception {
            System.out.println(entryData.getName());
        }
    };

    classScanner.setIncludeResources(true);
    classScanner.scan(containerFile);

Easy as that :)