public class TestResourceBundle {
private static final Path frZoo = Paths.get("./src/Zoo_fr.properties");
private static final Path enZoo = Paths.get("./src/Zoo_en.properties");
private static void createFiles() {
try {
Files.createFile(frZoo);
Files.createFile(enZoo);
try (BufferedWriter enWriter = Files.newBufferedWriter(enZoo);
BufferedWriter frWriter = Files.newBufferedWriter(frZoo);) {
enWriter.write("hello=Hello\nopen=The zoo is open");
frWriter.write("hello=Bonjour\nopen=Le zoo est ouvert");
}
} catch (IOException e) {
e.printStackTrace();
}
}
private static void createBundle() {
Locale us = new Locale("en", "US");
Locale france = new Locale("fr", "FR");
ResourceBundle usBundle = ResourceBundle.getBundle("Zoo", us);
ResourceBundle frBundle = ResourceBundle.getBundle("Zoo", france);
System.out.println(usBundle.getString("hello"));
System.out.println(frBundle.getString("hello"));
}
}
In the main function, if I run the following, it will throw java.util.MissingResourceException
public static void main(String[] args) {
createFiles();
createBundle();
}
but if I run these two functions separately (in two programs), it works and does not have any problem.
First run
public static void main(String[] args) {
createFiles();
// createBundle();
}
then run the following, in this case, it works
public static void main(String[] args) {
// createFiles();
createBundle();
}
I don't know why, please help
The problem is that you are trying to load a bundle that is not present in the classpath the application knows about.
When you call ResourceBundle.getBundle it will try to load the resource bundle from the application classpath. But the application classpath was already defined at the application startup, so your brand new files are not listed there.
Two options I can think of: Load the bundle from a file input stream or, define your own classloader to load the files.
1. Load the bundle from a File Input Stream
Create a new PropertyResourceBundle from a FileInputStream that loads each file directly.
Warning: Stream closing and exception handling omitted for brevity.
FileInputStream enFileStream = new FileInputStream("./src/Zoo_en.properties");
FileInputStream frFileStream = new FileInputStream("./src/Zoo_fr.properties");
ResourceBundle usBundle = new PropertyResourceBundle(enFileStream);
ResourceBundle frBundle = new PropertyResourceBundle(frFileStream);
2. Create a URL ClassLoader to load the new files
This is a more scalable approach. Create a new URLClassLoader and use that class loader as an argument for getBundle.
Warning: Stream closing and exception handling omitted for brevity.
File bundleRootPath = new File("./src");
URL[] urls = new URL[]{bundleRootPath.toURI().toURL()};
ClassLoader classLoader = new URLClassLoader(urls);
ResourceBundle usBundle = ResourceBundle.getBundle("Zoo", us, classLoader);
ResourceBundle frBundle = ResourceBundle.getBundle("Zoo", france, classLoader);
Hope that helps.
Related
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 the following code snippet, I am trying to load some class files into my project to create an object. Unfortunately, it seems that something is missing, because there are no classes loaded. What is it?
private static void myClassloader() throws Exception
{
File file = new File(pathGeneratedClasses);
try
{
#SuppressWarnings("deprecation")
URL url = file.toURL();
URL[] urls = new URL[]{url};
ClassLoader sqlQuery = new URLClassLoader(urls);
Class myClass = sqlQuery.loadClass("de.cimt.jaxb.JaxCodeGen");
}
catch (Exception e)
{
System.out.println(e.toString());
}
}
sqlQuery.loadClass() will be returning the class you requested for, try assigning the returned value to something.
If no class is found then ClassNotFoundException will be thrown.
I need develop a "launcher" for a java application. This launcher need be able to:
check if main application is up-to-date;
if not, download a update;
run this application and self terminate.
Something like this:
public final class Launcher {
public static void main(String[] args) throws Exception {
String jarName = args[0];
if (jarHasUpdate(jarName)
refreshJar(jarName);
executeJar(jarName);
}
}
What better way of develop the step 3?
I'm trying 2 distinct ways:
1- Run another instance of Java
With the code:
Runtime.getRuntime().exec("java -jar mainApp.jar");
Problem: the launcher still running until mainApp have finished.
2- Using ClassLoader to load .jar at runtime
Like this:
public final class Launcher {
#SuppressWarnings({ "unchecked", "rawtypes" })
public static void main(String[] args) throws Exception {
if (args.length < 2) {
System.out.println("Invalid number of arguments.");
System.exit(1);
}
Refresh.refreshFile(args[0]);
// args[0] .jar name
// args[1] class with main function
File file = new File(args[0]);
try (URLClassLoader cl = new URLClassLoader(new URL[] { file.toURI().toURL() });) {
Class cls = cl.loadClass(args[1]);
Method method = cls.getDeclaredMethod("main", new Class[] { String[].class });
Object params = new String[] {};
method.invoke(cls, params);
}
}
}
Problem: if "mainApp.jar" has dependencies, this isn't loaded.
Frankly, I do not know even it is possible or not.
But what I am trying to do is just like below.
I made a class file from ClassFile.java via javac command in terminal.
Then I want to get an instance from .java file or .class file.
Next, I made another project in eclipse, As you guess this project path and upper file path are completely different. For instance, ClassFile.java/class file can be located in '~/Downloads' folder, the other hand, new eclipse project can be in '~/workspace/'.
So I read file which referred in step 1 by FileInputStream.
From here, I just paste my code.
public class Main {
private static final String CLASS_FILE_PATH =
"/Users/juneyoungoh/Downloads/ClassFile.class";
private static final String JAVA_FILE_PATH =
"/Users/juneyoungoh/Downloads/ClassFile.java";
private static Class getClassFromFile(File classFile) throws Exception {
System.out.println("get class from file : [" + classFile.getCanonicalPath() + " ]");
Object primativeClz = new Object();
ObjectInputStream ois = null;
ois = new ObjectInputStream(new FileInputStream(classFile));
primativeClz = ois.readObject();
ois.close();
return primativeClz.getClass();
}
public static void main(String[] args) throws Exception {
getClassInfo(getClassFromFile(new File(CLASS_FILE_PATH)));
}
}
just like your assumption, this code has errors.
For example, it shows :
java.io.StreamCurruptedException: invalid stream header : CAFEBABE
this there any way to get object instance from .class file or .java file?
P.S.
I wish do not use extra libraries.
private static final String CLASS_FOLDER =
"/Users/juneyoungoh/Downloads/";
private static Class getClassFromFile(String fullClassName) throws Exception {
URLClassLoader loader = new URLClassLoader(new URL[] {
new URL("file://" + CLASS_FOLDER)
});
return loader.loadClass(fullClassName);
}
public static void main( String[] args ) throws Exception {
System.out.println((getClassFromFile("ClassFile"));
}