Java Utililty Methods ClassPath

String calculateClassPath(ClassLoader cl)
calculate local file based class path for class loader if possible (servlet classes must be located there)

StringBuffer classPath = new StringBuffer();
boolean jspFound = false, servletFound = false;
while (cl != null) {
 if (cl instanceof URLClassLoader) {
 boolean addClasses = false;
 if (jspFound == false) {
 jspFound = ((URLClassLoader) cl).findResource("javax/servlet/jsp/JspPage.class") != null;
 addClasses |= jspFound;
...

URLClassLoader createClassLoader(List classpathElements, String... paths)
create Class Loader

List<URL> urls = new ArrayList<>();
for (String path : paths) {
 URL url = pathToUrl(path);
 urls.add(url);
for (Object object : classpathElements) {
 if (object != null) {
 String path = object.toString();
...

ClassLoader createClassLoader(List libs, boolean useSystemClassPath)
create Class Loader

List<URL> urls = new ArrayList<>(libs.size());
libs.forEach(lib -> {
 try {
 urls.add((new File(lib)).toURI().toURL());
 } catch (MalformedURLException e) {
 throw new RuntimeException("The file wasn't readable: " + lib, e);
});
...

URL[] createClassPath(File file)
create Class Path

URL[] urls = null;
if ((file.exists()) && (file.isDirectory())) {
 String[] jars = file.list(new FilenameFilter() {
 public boolean accept(File dir, String name) {
 if (name.endsWith(".jar")) {
 return true;
 return false;
...

void dumpClasspath(ClassLoader loader)
dump Classpath

System.out.println("Classloader " + loader + ":");
if (loader instanceof URLClassLoader) {
 URLClassLoader ucl = (URLClassLoader) loader;
 System.out.println("\t" + Arrays.toString(ucl.getURLs()));
} else
 System.out.println("\t(cannot display components as not a URLClassLoader)");
if (loader.getParent() != null)
 dumpClasspath(loader.getParent());
...

boolean existsInClasspath(Class clazz, String fileName)
exists In Classpath

URL dirURL = clazz.getResource("/" + fileName);
return dirURL != null;

boolean existsInClasspath(final String fileName)
exists In Classpath

return getResourceFromClasspath(fileName) != null;

void fillClassPath(ClassLoader cl, StringBuffer classpath)
Walk the classloader hierarchy and add to the classpath

while (cl != null) {
 if (cl instanceof URLClassLoader) {
 URL[] urls = ((URLClassLoader) cl).getURLs();
 for (int i = 0; (urls != null) && i < urls.length; i++) {
 String path = urls[i].getPath();
 if (path.length() >= 3 && path.charAt(0) == '/' && path.charAt(2) == ':')
 path = path.substring(1);
 classpath.append(URLDecoder.decode(path));
...

List findClassPaths()
find Class Paths

List<URL> list = new ArrayList<URL>();
String classpath = System.getProperty("java.class.path");
StringTokenizer tokenizer = new StringTokenizer(classpath, File.pathSeparator);
while (tokenizer.hasMoreTokens()) {
 String path = tokenizer.nextToken();
 File fp = new File(path);
 if (!fp.exists())
 throw new RuntimeException("File in java.class.path does not exist: " + fp);
...

URL[] findClassPaths()
Uses the java.class.path system property to obtain a list of URLs that represent the CLASSPATH

List<URL> list = new ArrayList<URL>();
String classpath = System.getProperty("java.class.path");
StringTokenizer tokenizer = new StringTokenizer(classpath, File.pathSeparator);
while (tokenizer.hasMoreTokens()) {
 String path = tokenizer.nextToken();
 File fp = new File(path);
 if (!fp.exists())
 throw new RuntimeException("File in java.class.path does not exist: " + fp);
...