I need to read a Spring Boot jar and load all the clases on a ClassLoader.
My problem,in spring boot classes are on "/BOOT-INF/classes" directory and not on the root directory.
Anybody knows how i can load this classes in my ClassLoader?
I try to do this:
private URLClassLoader getURLClassLoaderFromJar(Path jarPath) throws MalformedURLException {
return URLClassLoader
.newInstance(new URL[] { new URL("jar:file:" + jarPath.toAbsolutePath().toString() + "!/") });
}
This load the jar, but no the classes inside /BOOT-INF/classes
Investigating a bit how spring boot loads third party(Liquibase) classes, i would go like this:
Given that you know the package name you want to load
Resource[] scan(ClassLoader loader, String packageName) throws IOException {
ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver(
loader);
String pattern = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX
+ ClassUtils.convertClassNameToResourcePath(packageName) + "/**/*.class";
Resource[] resources = resolver.getResources(pattern);
return resources;
}
void findAllClasses(String packageName, ClassLoader loader) throws ClassNotFoundException {
MetadataReaderFactory metadataReaderFactory = new CachingMetadataReaderFactory(
loader);
try {
Resource[] resources = scan(loader, packageName);
for (Resource resource : resources) {
MetadataReader reader = metadataReaderFactory.getMetadataReader(resource);
ClassUtils.forName(reader.getClassMetadata().getClassName(), loader)
}
} catch (IOException ex) {
throw new IllegalStateException(ex);
}
}
Also use your class loader with loaded jar:
findAllClasses("com.package", getURLClassLoaderFromJar(pathToJar));
This variant is safe to use with Spring Boot packaged
executable JARs
I finally opted for decompress de jar on a temporary directory and create a URLClassloader with this entries:
One to the root directory.
One to the BOOT-INF/classes
And one for every jar in BOOT-INT/lib
Path warDirectory = decompressWar(absolutePathFile);
File rootDir = new File(warDirectory.toAbsolutePath().toString());
File springBootDir = new File(warDirectory.toAbsolutePath().toString() + "/BOOT-INF/classes/");
List<URL> listaURL = new ArrayList<URL>();
listaURL.add(rootDir.toURI().toURL());
listaURL.add(springBootDir.toURI().toURL());
//This scan the BOOT-INF/lib folder and return a List<URL> with all the libraries.
listaURL.addAll(getURLfromSpringBootJar(warDirectory));
URL[] urls = new URL[listaURL.size()];
urls = listaURL.toArray(urls);
cl = new URLClassLoader(urls);
//This explore the JAR and load all the .class fulies to get the className.
resultClassesBean = loadJars(Collections.singletonList(pathJarFile), cl);
if(resultClassesBean != null && resultClassesBean.getListResultClasses() != null && !resultClassesBean.getListResultClasses().isEmpty()) {
for(String clazz : resultClassesBean.getListResultClasses()) {
cl.loadClass(clazz);
}
}
Related
I have a jar file that I load dynamically,
inside it there is in lib/ another jar (external library) that I use in main (import it.xxx.xx).
How do I load also this external library dynamically in classpath?
My code doesn't work:
public static void runOne(String jar, String class_name, Optional<String> test_name,
TestExecutionListener listener) throws Exception {
Launcher launcher = LauncherFactory.create();
ClassLoader loader = URLClassLoader.newInstance(
new URL[] { new File(pathJars+"/"+jar).toURI().toURL() },
ServiceUtil.class.getClassLoader()
);
loader.getClass();
addURL(loader); <--here i want add a jar to classpath!
Class cls=loader.loadClass(class_name);
Constructor constructor = cls.getConstructor();
constructor.newInstance();
LauncherDiscoveryRequest request;
if (test_name.isPresent()) {
Method m = cls.getMethod(test_name.get());
request = LauncherDiscoveryRequestBuilder.request()
.selectors(selectMethod(cls,m))
.build();
}
else{
request = LauncherDiscoveryRequestBuilder.request()
.selectors(selectClass(cls))
.build();
}
TestPlan testPlan = launcher.discover(request);
launcher.registerTestExecutionListeners(listener);
launcher.execute(request);
//launcher.execute(request);
loader=null;
System.gc();
}
public static void addURL(ClassLoader loader) throws IOException {
URL u=loader.getResource("lib/sem-platform-sdk-1.0-SNAPSHOT.jar");
Class[] parameters = new Class[]{URL.class};
URLClassLoader sysloader = (URLClassLoader) ClassLoader.getSystemClassLoader();
Class sysclass = URLClassLoader.class;
try {
Method method = sysclass.getDeclaredMethod("addURL", parameters);
method.setAccessible(true);
method.invoke(sysloader, new Object[]{u});
} catch (Throwable t) {
t.printStackTrace();
throw new IOException("Error, could not add URL to system classloader");
}//end try catch
}//end method
Thanks
This is generally done with a build tool (e.g. maven or gradle). I don't know if you are using one of these. They make life so much easier.
We use Maven with the Apache Shade plugin to do exactly this. Maven has commands to set up the configuration for you automatically, then you add the Shade plugin to the resulting configuration file (pom.xml).
https://maven.apache.org/plugins/maven-shade-plugin/index.html
If I understand your problem correctly, you want the classes loaded from the jar file to be able to access the classes in the nested jar file. You can accomplish this by creating a ClassLoader with one entry for the jar file and another entry for the nested jar file.
Java has a special URL scheme, jar:, for referring to a jar entry directly. (This scheme and syntax is described in the documentation of JarURLConnection.) So you can construct your ClassLoader this way:
URL jarURL = new File(pathJars+"/"+jar).toURI().toURL();
URL semURL = new URL("jar:" + jarURL + "!/"
+ "lib/sem-platform-sdk-1.0-SNAPSHOT.jar");
ClassLoader loader = URLClassLoader.newInstance(
new URL[] { jarURL, semURL },
ServiceUtil.class.getClassLoader()
);
I have two java projects MASTER and PLUGIN. PLUGIN has dependencies to MASTER and its intent is to extend a class found in MASTER, called SCRIPT.
Once I have declared a SCRIPT (myScript), I want to move the .class file to a folder that MASTER can access. I want MASTER to dynamically load and instantiate that class as a SCRIPT.
I've looked for quite a bit and tried different solutions, but I always get a ClassNotFoundException exception.
I would prefer to do this without passing arguments to the JVM at startup.
Is it even possible? This is my current solution: "currentPath" is "etc/etc/myScript.class
try {
OUT.ln("initiating script " + currentPath);
File file = new File(currentPath);
File parent = file.getParentFile();
String name = file.getName().split(".class")[0];
// Convert File to a URL
URL url = parent.toURI().toURL();
URL[] urls = new URL[]{url};
// Create a new class loader with the directory
#SuppressWarnings("resource")
ClassLoader cl = new URLClassLoader(urls);
current = (SCRIPT) cl.loadClass("main.script." + name).newInstance();
} catch (Exception e) {
e.printStackTrace();
throw new RuntimeException("Unable to load script " + currentPath);
}
if the class you want to load is defined within a package like:
main.script.myScript
and you want to load this class from a folder like c:/myclasses,
then you have to put this class to c:/myclasses/main/script/myScript.class
and then instantate the classloader with the basefolder like:
URL[] urls = new URL[]{new URL("file://c:/myclasses")};
ClassLoader cl = new URLClassLoader(urls);
then the class can be loaded by using the qualified class name:
cl.loadClass("main.script.myScript").getDeclaredConstructor().newInstance()
if you want to keep the class at a specific folder without considering the package structure you could do something like this:
public static void main(String[] args) {
try {
File file = new File("etc/etc/myScript.class");
String className = file.getName().split(".class")[0];
String packageName = "main.script.";
byte[] bytes = Files.readAllBytes(Path.of(file.getPath()));
MyClassLoader myClassLoader = new MyClassLoader(Thread.currentThread().getContextClassLoader());
Object o = myClassLoader.getClass(packageName+className, bytes).getDeclaredConstructor().newInstance();
System.out.println(o);
} catch (Exception e) {
e.printStackTrace();
throw new RuntimeException("Unable to load script ");
}
}
public static class MyClassLoader extends ClassLoader {
public MyClassLoader(ClassLoader parent) {
super(parent);
}
public Class<?> getClass(String name, byte[] code) {
return defineClass(name, code, 0, code.length);
}
}
So, I have a main application that should load a jar that contains code and other resources (i.e.: jar files, text files, java properties etc.). I use:
JarFile jar = new JarFile(jar);
Enumeration<JarEntry> entries = jar.entries();
int URLsize = 1;
while (entries.hasMoreElements())
if (entries.nextElement().getName().startsWith("foo/bar/foobar"))
URLsize++;
entries = jar.entries();
URL[] urls = new URL[URLsize];
urls[0] = patch.toURI().toURL();
int count = 1;
while (entries.hasMoreElements())
{
JarEntry nextElement = entries.nextElement();
if (nextElement.getName().startsWith("foo/bar/foobar"))
{
urls[count] = new URL("jar:file:/"+ jar.getAbsolutePath() + "!/" + nextElement.getName());
count++;
}
}
to load the resources of the jar, and an URLClassLoader plus some reflection to get all resources together and execute the jar's main class, like this:
URLClassLoader loader = new URLClassLoader (urls);
Thread.currentThread().setContextClassLoader(loader);
Class<?> jarC = Class.forName ("foo.bar.barfoo.Main", true, loader);
Constructor<?> cons = jarC.getConstructor(String.class, String.class, Properties.class, Properties.class, String[].class);
Object instance = cons.newInstance (systemPath, programPath, config, some_data, args);
Method method = jarC.getMethod ("Main");
method.invoke (instance);
Now the problem is that inside the loaded jar's code when I try to load a bunch of files (resources) from a package inside the jar (e.g.: /foo/bar/foobar) it throws a NullPointerException.
private static InputStream getResourceAsStream(String resource) {
try {
return Thread.currentThread().getContextClassLoader().getResource(resource).openStream();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
That's how I try to get the package that than gets parsed with a BufferedReader and an InputStreamReader to get the names of each resource inside the package.
Okay, maybe a bit too detailed (this is just one way I use the getResourceAsStream method), but I hope I made myself understood, the ContextClassLoader doesn't contain the resources I loaded in the application that runs this jar within itself, so what do I need to do to get those from within the loaded jar?
EDIT: Calling the getResourceAsStream method:
private static List<String> getResourceFiles(String path) throws IOException {
List<String> filenames = new ArrayList<>();
try (
InputStream in = getResourceAsStream(path);
BufferedReader br = new BufferedReader(new InputStreamReader(in))) {
String resource;
while ((resource = br.readLine()) != null) {
filenames.add(resource);
}
}
return filenames;
}
And where the getResourceFiles method is called:
List<String> names = Foo.getResourceFiles("/foo/bar/foobar");
Why do you even do all this? Why not just add URL to JAR to the URLClassLoader?
E.g.
URLClassLoader loader = new URLClassLoader(new File(jar).toURI().toURL());
Also you should probably make that URLClassLoader have your current classloader as parent, e.g.
URLClassLoader loader = new URLClassLoader(new File(jar).toURI().toURL(), Thread.currentThread().getContextClassLoader());
With tomcat 8 I have extend the WebAppClassLoader and add some jar filed from a shared location to the classloader path using addRepository() method. With tomcat 8 addRepository have been removed and new resource implementation have been introduced. I'm still able to use the addUrl method to add jar files. But I would like to implement the new resource based implementation.
I've tried with
DirResourceSet dirResourceSet = new DirResourceSet(getContext().getResources(), "/WEB-INF/lib", "/home/thusitha/lib/runtimes/cxf", "/");
WebResourceRoot webResourceRoot = getContext().getResources();
webResourceRoot.getContext().getResources().addPreResources(dirResourceSet);
But this is not working and still it throws classnotfoundexception
Can someone tell me how to map a directory which contains jars to a particular webapp using Tomcat new resource implementation?
A solution to this problem is to register your resources by overriding the ContextConfig class (org.apache.catalina.startup.ContextConfig). Catalina enters a starting state immediately after it scans your document path for resources. Most of the processing of those resources, such as annotations, is handled by the ContextConfig LifecycleListener. To ensure the resources are added before the context configuration takes place, override the ContextConfig.
final Context currentContext = ctx;
ContextConfig ctxCfg = new ContextConfig() {
#Override
public void lifecycleEvent(LifecycleEvent event) {
if (event.getType().equals(Lifecycle.CONFIGURE_START_EVENT)) {
WebResourceRoot webResourcesRoot = currentContext.getResources();
String baseDir = Platform.getBaseDir(); // Server Base Directory
File libDir = new File(baseDir + File.separator + "lib");
DirResourceSet dirResourceSet = null;
try {
dirResourceSet = new DirResourceSet(webResourcesRoot, "/WEB-INF/lib", libDir.getCanonicalPath(), "/");
} catch (IOException e) {
throw new RuntimeException(e);
}
webResourcesRoot.addPostResources(dirResourceSet);
String[] possibleJars = dirResourceSet.list("/WEB-INF/lib");
for(String libfile : possibleJars) {
WebResource possibleJar = dirResourceSet.getResource("/WEB-INF/lib/"+libfile);
System.err.println(String.format("Loading possible jar %s",possibleJar.getCanonicalPath())); // Just checking...
if (possibleJar.isFile() && possibleJar.getName().endsWith(".jar")) {
WebResourceSet resourceSet = new JarResourceSet(webResourcesRoot, "/WEB-INF/classes", possibleJar.getCanonicalPath(),"/");
webResourcesRoot.addPostResources(resourceSet);
}
}
}
super.lifecycleEvent(event);
}
};
ctx.addLifecycleListener(ctxCfg);
This is an undocumented solution that works on Tomcat 8.0.23. Considering the complexity and difficulty of this I can't say it is a better solution than adding jars directly to ClassLoaders.
the problem is next: i took the base classLoader code from here. but my classLoader is specific from a point, that it must be able to load classes from a filesystem(let's take WinOS), so in classLoader must be some setAdditionalPath() method, which sets a path(a directory on a filesystem), from which we'll load class(only *.class, no jars). here is code, which modifies the loader from a link(you can see, that only loadClass is modified), but it doesn't work properly:
public void setAdditionalPath(String dir) {
if(dir == null) {
throw new NullPointerException("");
}
this.Path = dir;
}
public Loader(){
super(Loader.class.getClassLoader());
}
public Class loadClass(String className) throws ClassNotFoundException {
if(Path.length() != 0) {
File file = new File(Path);
try {
// Convert File to an URL
URL url = file.toURL();
URL[] urls = new URL[]{url};
// Create a new class loader with the directory
ClassLoader cl = new URLClassLoader(urls);
ClassLoader c = cl.getSystemClassLoader();
Class cls = c.loadClass(className);
return cls;
} catch (MalformedURLException e) {
} catch (ClassNotFoundException e) {
}
}
return findClass(Path);
}
I'd grateful if anyone helps :)
You can just use framework provided java.net.URLClassLoader. No need to write your own. It supports loading of classes from directories and JAR files.
Any URL that ends with a '/' is assumed to refer to a directory.
Otherwise, the URL is assumed to refer to a JAR file which will be
opened as needed.
It also supports a parent class loader. If this class loader does not suite your requirements, perhaps you can specify in more detail what you need. And in any case, you can look at the source and derive your own class loader class based on that.
Here is a short working snippet of code that should demostrate how to load a class by name from a URLClassLoader:
ClassLoader systemClassLoader = ClassLoader.getSystemClassLoader();
// This URL for a directory will be searched *recursively*
URL classes =
new URL( "file:///D:/code/myCustomClassesAreUnderThisFolder/" );
ClassLoader custom =
new URLClassLoader( new URL[] { classes }, systemClassLoader );
// this class should be loaded from your directory
Class< ? > clazz = custom.loadClass( "my.custom.class.Name" );
// this class will be loaded as well, because you specified the system
// class loader as the parent
Class< ? > clazzString = custom.loadClass( "java.lang.String" );