I have a project that is generating a .war file as a build artifact.
I want to load this .war into the JVM so that I can parse the runtime annotations it contains, but I am having trouble with loading the classes.
I have the following snippet of code to fetch class names from a JarFile:
public static Set<String> getClassNamesFromJarFile(JarFile jarFile) throws IOException {
Set<String> classNames = new HashSet<>();
Enumeration<JarEntry> e = jarFile.entries();
while (e.hasMoreElements()) {
JarEntry jarEntry = e.nextElement();
if (jarEntry.getName().endsWith(".class")) {
String className = jarEntry.getName()
.replace("/", ".");
className = className.substring(0, className.length() - 6);
classNames.add(className);
}
}
return classNames;
}
And I use this snippet for getting the JarFile:
protected static JarFile getJarFile(String jarFileUrl) throws IOException {
try {
return new JarFile(new URI(jarFileUrl.replaceAll(" ", " ")).getSchemeSpecificPart());
} catch (URISyntaxException ex) {
return new JarFile(jarFileUrl.substring("file:".length()));
}
}
Then, on my main, I have the following code:
public static void main(String[] args) throws IOException {
String warpath = "C:\\User\\Me\\Desktop\\someWarFile.war";
// Fetch JarFile
JarFile jar = getJarFile("file:" warpath);
// Load .war into the JVM
URL url = new File(warpath).toURI().toURL();
URLClassLoader child = new URLClassLoader(
new URL[]{url},
Object.class.getClassLoader()
);
// Get class names in the .war
Set<String> classes = getClassNamesFromJarFile(jar);
// Try to get classes from name
for (String className : classes) {
try {
System.out.println("CLASS FOUND: " className);
Class<?> actualClass= Class.forName(className, true, child);
} catch(Error | Exception e) {
System.out.println("ERROR: " e);
}
}
}
For every class I get the output:
...
CLASS FOUND: WEB-INF.classes.com.some.company.project.state.ProjectStateProvider$1
ERROR: java.lang.NoClassDefFoundError: com/some/company/project/state/ProjectStateProvider$1 (wrong name: WEB-INF/classes/com/some/company/project/state/ProjectStateProvider$1)
CLASS FOUND: WEB-INF.classes.com.some.company.configuration.rest.JsonProvider
ERROR: java.lang.NoClassDefFoundError: com/some/company/configuration/rest/JsonProvider (wrong name: WEB-INF/classes/com/some/company/configuration/rest/JsonProvider)
...
I have tried removing the WEB-INF. and the WEB-INF.classes. prefixes from the className, I have also tried adding .class to the className and every combination of the previous solutions, but I just get a java.lang.ClassNotFoundException.
How do I reference classes loaded from the .war like the WEB-INF.classes.com.some.company.project.state.ProjectStateProvider$1 class for example?
CodePudding user response：
I'm using this code, and it works fine:
private void reloadJar(final File pJarFile) throws InstantiationException, IllegalAccessException, MalformedURLException, IOException {
try (final URLClassLoader classLoader = new URLClassLoader(new URL[] { pJarFile.toURI().toURL() }); //
final JarFile file = new JarFile(pJarFile);) {
final Plugin plugin = new Plugin(pJarFile, classLoader);
final Enumeration<JarEntry> entries = file.entries();
while (entries.hasMoreElements()) {
final JarEntry jarEntry = entries.nextElement();
if (!isClassFile(jarEntry)) {
plugin.addNonClassfile(jarEntry);
continue;
}
try {
final String id = getClassName(jarEntry);
final Class<?> cls = classLoader.loadClass(id);
if (JcUClass.isSubclassOf(cls, KittenPluginIf.class)) {
final KittenPluginIf inst = (KittenPluginIf) cls.newInstance();
plugin.setPlugin(inst);
} else if (JcUClass.isSubclassOf(cls, KittenPageIf.class)) {
final KittenPageIf inst = (KittenPageIf) cls.newInstance();
plugin.addPage(inst);
} else {
plugin.addUtilityClass(jarEntry);
}
} catch (final ClassNotFoundException e2) {
plugin.addClassNotFoundEntry(jarEntry);
}
}
if (plugin.isValid()) mPlugins.add(plugin);
}
}
static private boolean isClassFile(final ZipEntry entry) {
return !entry.isDirectory() && entry.getName().endsWith(".class");
}
static private String getClassName(final ZipEntry entry) {
final String className = entry.getName().replace('/', '.'); // including ".class"
return className.substring(0, className.length() - ".class".length());
}
You have to remove some code that contains some custom classes of mine, but this outlines the procedure easily.
The other thing that you have to be aware of: those classes in the .jar or .war file have to be normal javac compiled classes, or any other builder that outputs default java class binaries, like EclipseBuild.
CodePudding user response：
OK. I've changed the getClassNamesFromJarFile method slightly:
public static Set<String> getClassNamesFromJarFile(
JarFile file, String pfx, String sfx) {
Set<String> result = new HashSet<>();
Enumeration<JarEntry> enm = file.entries();
while (enm.hasMoreElements()) {
JarEntry e = enm.nextElement();
String path = e.getName();
if (path.startsWith(pfx) && path.endsWith(sfx)) {
path = path.substring(pfx.length(), path.length()-sfx.length());
path = path.replace('/', '.');
result.add(path);
}
}
return result;
}
Then:
public static void main(String[] args) throws IOException {
String warpath = "C:\\User\\Me\\Desktop\\someWarFile.war";
// Fetch JarFile
JarFile jar = new JarFile(warpath);
// Load .war into the JVM
URL url = new URL("jar:file:" warpath "!/WEB-INF/classes/");
URLClassLoader child = new URLClassLoader(
new URL[]{url},
Object.class.getClassLoader()
);
// Get class names in the .war
Set<String> classes = getClassNamesFromJarFile(jar, "WEB-INF/classes/", ".class");
// Try to get classes from name
for (String className : classes) {
try {
System.out.println("CLASS FOUND: " className);
Class<?> actualClass= Class.forName(className, true, child);
} catch(Error | Exception e) {
System.out.println("ERROR: " e);
}
}
}
UPDATE:
Now the classes will not load if they depend on other classes not in the classpath. For instance, if the war contains jar files in WEB-INF/lib, you need to add them to the URLClassLoader. You should also make available the jar of the servlet API.