public void launch(String[] args) throws Exception {
final URLClassLoader ucl = (URLClassLoader) getClass().getClassLoader();
classLoader = new CustomClassLoader(ucl.getURLs());
Thread.currentThread().setContextClassLoader(classLoader);
Class<?> mainClass = Class.forName("Main", false, classLoader);
System.out.println(mainClass.getClassLoader().getClass().getName()); //Debug
Method mainMethod = mainClass.getDeclaredMethod("main", new Class[] {String[].class});
mainMethod.invoke(null, (Object) args);
}
When This Code Is Started the Debug Line Prints "sun.misc.Launcher$AppClassLoader"
How would I fix this?
I have to retrieve the value of all fields in a class loaded from a jar.
So I need an instance to do that :
field.get(gameClassInstance);
for each field.
Here the code that load the class and try to create an instance :
private Loader() throws IOException, ClassNotFoundException, InstantiationException, IllegalAccessException {
File jarFile = new File(System.getProperty("user.dir")+File.separator+"games"+File.separator+gameName+".jar");
// Create the URLClassLoader
URL url = jarFile.toURI().toURL();
URL[] urls = new URL[]{url};
URLClassLoader cl = new URLClassLoader(urls);
// Search the class
JarFile jar = new JarFile(jarFile.toString());
Enumeration<JarEntry> e = jar.entries();
while (e.hasMoreElements()) {
JarEntry je = (JarEntry) e.nextElement();
if(je.isDirectory() || !je.getName().endsWith(".class")){
continue;
}
if (je.getName().contains(gameName)){
String className = je.getName().substring(0,je.getName().length()-6); // Remove ".class"
className = className.replace('/', '.');
gameClass = cl.loadClass(className);
gameClassInstance = gameClass.newInstance(); // Create an instance of the class
}
}
jar.close();
cl.close();
}
Here the loaded class :
public class Solitaire {
public Board board = new Board("Board1", "");
public Layout layout = new Layout();
public Player player = new Player();
public Solitaire() {
}
}
There is a StackOverflowError at the line where I create an instance.
I found the solution to my problem, I just make the fields static and retrieve them with field.get(null)
This is the common approach with working with loading class dynamically:
try {
File file = new File(JAR_FILE);
String classToLoad = "com.mycompany.MyClass";
URL jarUrl = new URL("jar", "","file:" + file.getAbsolutePath()+"!/");
URLClassLoader loader = new URLClassLoader(new URL[] {jarUrl}, Thread.currentThread().getContextClassLoader());
Class c = loader.loadClass(classToLoad);
} catch (Exception e) {
e.printStackTrace();
}
However, I need an approach where:
We don't need to create a File (as the jar I am trying to process is a byte array[] when fetched)
Or we won't need to create a temporary file from byte[] array (as AppEngine, the platform I work with does not allow to create temporary files)
You will have to create your own class loader.
Something like this, basic idea in pseudo code:
class MyClassLoader extends ClassLoader {
public Class findClass(String name) {
byte[] b = loadClassData(name);
return defineClass(name, b, 0, b.length);
}
private byte[] loadClassData(String name) {
JarInputStream jis = new JarInputStream(new ByteArrayInputStream(bytearrayJarData));
JarEntry entry = jis.getNextJarEntry();
while (entry != null) {
//compare entry to requested class
// if match, return Byte data
// else entry = jis.getNextJarEntry();
}
return null; // nothing found
}
}
Write your own ClassLoader and override findClass(). There you can use defineClass() to load your byte[].
To address the .dll file loading/unloading issue with applets. I am loading, following this tutorial, .dll files using a custom class loader as :
1- Class Loader (Copied from tutorial)
public class CustomClassLoader extends ClassLoader {
private static final String CLASS_NAME = CustomClassLoader.class.getName();
private Map<String, Class<?>> classes;
public CustomClassLoader() {
super(CustomClassLoader.class.getClassLoader());
classes = new HashMap<String, Class<?>>();
}
public String toString() {
return CustomClassLoader.class.getName();
}
#Override
public Class<?> findClass(String name) throws ClassNotFoundException {
if (classes.containsKey(name)) {
return classes.get(name);
}
String path = name.replace('.', File.separatorChar) + ".class";
byte[] b = null;
try {
b = loadClassData(path);
} catch (IOException e) {
throw new ClassNotFoundException("Class not found at path: " + new File(name).getAbsolutePath(), e); **
}
Class<?> c = defineClass(name, b, 0, b.length);
resolveClass(c);
classes.put(name, c);
return c;
}
private byte[] loadClassData(String name) throws IOException {
String methodName = CLASS_NAME + ".loadClassData";
byte buff[] = null;
try {
File file = new File(name);
int size = (int) file.length();
buff = new byte[size];
DataInputStream in = new DataInputStream(new FileInputStream(name));
in.readFully(buff);
in.close();
} catch (IOException e) {
throw new IOException(e.getMessage());
}
return buff;
}
}
2- A class to load .dll files
public class DllLoader {
private static final String CLASS_NAME = AppletReload.class.getName();
static String javaHome = System.getProperty("java.io.tmpdir");
private static String dllPath = javaHome + Constant.SMARTCARD_JACSPCSC_DLL_NAME;
private static String dllPath1 = javaHome + Constant.SMARTCARD_RXTXSERIAL_DLL_NAME;
public DllLoader() {
}
static {
try {
System.load(dllPath);
Logger.write(LoggerConstant.TRACE, "JACSPCSC Dll loaded from the path: " + dllPath, "Dll Loader");
System.load(dllPath1);
Logger.write(LoggerConstant.TRACE, "RXTXSERIAL Dll loaded from the path: " + dllPath1, "Dll Loader");
} catch (Exception e) {
// Log exception;
}
}
}
And this is how I am using this class loader:
cl = new CustomClassLoader();
ca = cl.findClass("com.DllLoader");
a = ca.newInstance();
The motivation behind loading .dll using custom class loader is that it would guarantee the unloading as well and this is what most of the answers to question on .dll loading/unloading suggest. But in my case, loadClassData() (a function in my classLoader) thows this exception:
loadClassData,Error: com\DllLoader.class (The system cannot find the path specified)
java.io.FileNotFoundException: com\DllLoader.class (The system cannot find the path specified)
and the absolute path of file is show logged as:
**C:\Program Files\Mozilla Firefox\com.DllLoader
I think this is where its searching for the file, and .jar file of applet isn't located here.
I would appreciate if anyone can point out mistake I am making or tell how can I guide browser to look for class file in correct folder.
P.S: Kindly note that a answer to seemingly duplicate question don't solve this problem.
I have a file called mybundle.txt in c:/temp -
c:/temp/mybundle.txt
How do I load this file into a java.util.ResourceBundle? The file is a valid resource bundle.
This does not seem to work:
java.net.URL resourceURL = null;
String path = "c:/temp/mybundle.txt";
java.io.File fl = new java.io.File(path);
try {
resourceURL = fl.toURI().toURL();
} catch (MalformedURLException e) {
}
URLClassLoader urlLoader = new URLClassLoader(new java.net.URL[]{resourceURL});
java.util.ResourceBundle bundle = java.util.ResourceBundle.getBundle( path ,
java.util.Locale.getDefault(), urlLoader );
As long as you name your resource bundle files correctly (with a .properties extension), then this works:
File file = new File("C:\\temp");
URL[] urls = {file.toURI().toURL()};
ClassLoader loader = new URLClassLoader(urls);
ResourceBundle rb = ResourceBundle.getBundle("myResource", Locale.getDefault(), loader);
where "c:\temp" is the external folder (NOT on the classpath) holding the property files, and "myResource" relates to myResource.properties, myResource_fr_FR.properties, etc.
Credit to http://www.coderanch.com/t/432762/java/java/absolute-path-bundle-file
When you say it's "a valid resource bundle" - is it a property resource bundle? If so, the simplest way of loading it probably:
try (FileInputStream fis = new FileInputStream("c:/temp/mybundle.txt")) {
return new PropertyResourceBundle(fis);
}
1) Change the extension to properties (ex. mybundle.properties.)
2) Put your file into a jar and add it to your classpath.
3) Access the properties using this code:
ResourceBundle rb = ResourceBundle.getBundle("mybundle");
String propertyValue = rb.getString("key");
From the JavaDocs for ResourceBundle.getBundle(String baseName):
baseName - the base name of the
resource bundle, a fully qualified
class name
What this means in plain English is that the resource bundle must be on the classpath and that baseName should be the package containing the bundle plus the bundle name, mybundle in your case.
Leave off the extension and any locale that forms part of the bundle name, the JVM will sort that for you according to default locale - see the docs on java.util.ResourceBundle for more info.
For JSF Application
To get resource bundle prop files from a given file path to use them in a JSF app.
Set the bundle with URLClassLoader for a class that extends
ResourceBundle to load the bundle from the file path.
Specify the class at basename property of loadBundle tag.
<f:loadBundle basename="Message" var="msg" />
For basic implementation of extended RB please see the sample at Sample Customized Resource Bundle
/* Create this class to make it base class for Loading Bundle for JSF apps */
public class Message extends ResourceBundle {
public Messages (){
File file = new File("D:\\properties\\i18n");
ClassLoader loader=null;
try {
URL[] urls = {file.toURI().toURL()};
loader = new URLClassLoader(urls);
ResourceBundle bundle = getBundle("message", FacesContext.getCurrentInstance().getViewRoot().getLocale(), loader);
setParent(bundle);
} catch (MalformedURLException ex) { }
}
.
.
.
}
Otherwise, get the bundle from getBundle method but locale from others source like Locale.getDefault(), the new (RB)class may not require in this case.
If, like me, you actually wanted to load .properties files from your filesystem instead of the classpath, but otherwise keep all the smarts related to lookup, then do the following:
Create a subclass of java.util.ResourceBundle.Control
Override the newBundle() method
In this silly example, I assume you have a folder at C:\temp which contains a flat list of ".properties" files:
public class MyControl extends Control {
#Override
public ResourceBundle newBundle(String baseName, Locale locale, String format, ClassLoader loader, boolean reload)
throws IllegalAccessException, InstantiationException, IOException {
if (!format.equals("java.properties")) {
return null;
}
String bundleName = toBundleName(baseName, locale);
ResourceBundle bundle = null;
// A simple loading approach which ditches the package
// NOTE! This will require all your resource bundles to be uniquely named!
int lastPeriod = bundleName.lastIndexOf('.');
if (lastPeriod != -1) {
bundleName = bundleName.substring(lastPeriod + 1);
}
InputStreamReader reader = null;
FileInputStream fis = null;
try {
File file = new File("C:\\temp\\mybundles", bundleName);
if (file.isFile()) { // Also checks for existance
fis = new FileInputStream(file);
reader = new InputStreamReader(fis, Charset.forName("UTF-8"));
bundle = new PropertyResourceBundle(reader);
}
} finally {
IOUtils.closeQuietly(reader);
IOUtils.closeQuietly(fis);
}
return bundle;
}
}
Note also that this supports UTF-8, which I believe isn't supported by default otherwise.
This worked for me very well. And it doesn't reload the bundle everytime. I tried to take some stats to load and reload the bundle from external file location.
File file = new File("C:\\temp");
URL[] urls = {file.toURI().toURL()};
ClassLoader loader = new URLClassLoader(urls);
ResourceBundle rb = ResourceBundle.getBundle("myResource", Locale.getDefault(), loader);
where "c:\temp" is the external folder (NOT on the classpath) holding the property files, and "myResource" relates to myResource.properties, myResource_fr_FR.properties, etc.
Note: If you have the same bundle name on your classpath then it will be picked up by default using this constructor of URLClassLoader.
Credit to http://www.coderanch.com/t/432762/java/java/absolute-path-bundle-file
Find some of the stats below, all time in ms.
I am not worried about the initial load time as that could be something with my workspace or code that I am trying to figure out but what I am trying to show is the reload took way lesser telling me its coming from memory.
Here some of the stats:
Initial Locale_1 load took 3486
Reload Locale_1 took 24
Reload Locale_1 took 23
Reload Locale_1 took 22
Reload Locale_1 took 15
Initial Locale_2 load took 870
Reload Locale_2 took 22
Reload Locale_2 took 18
Initial Locale_3 load took 2298
Reload Locale_3 took 8
Reload Locale_3 took 4
I would prefer to use the resourceboundle class to load the properties - just to get it done in one line instead of 5 lines code through stream, Properties class and load().
FYI ....
public void init(ServletConfig servletConfig) throws ServletException {
super.init(servletConfig);
try {
/*** Type1 */
Properties props = new Properties();
String fileName = getServletContext().getRealPath("WEB-INF/classes/com/test/my.properties");
// stream = Thread.currentThread().getContextClassLoader().getResourceAsStream(fileName);
// stream = ClassLoader.getSystemResourceAsStream("WEB-INF/class/com/test/my.properties");
InputStream stream = getServletContext().getResourceAsStream("/WEB-INF/classes/com/test/my.properties");
// props.load(new FileInputStream(fileName));
props.load(stream);
stream.close();
Iterator keyIterator = props.keySet().iterator();
while(keyIterator.hasNext()) {
String key = (String) keyIterator.next();
String value = (String) props.getProperty(key);
System.out.println("key:" + key + " value: " + value);
}
/*** Type2: */
// Just get it done in one line by rb instead of 5 lines to load the properties
// WEB-INF/classes/com/test/my.properties file
// ResourceBundle rb = ResourceBundle.getBundle("com.test.my", Locale.ENGLISH, getClass().getClassLoader());
ResourceBundle rb = ResourceBundle.getBundle("com.ibm.multitool.customerlogs.ui.nl.redirect");
Enumeration<String> keys = rb.getKeys();
while(keys.hasMoreElements()) {
String key = keys.nextElement();
System.out.println(key + " - " + rb.getObject(key));
}
} catch (IOException e) {
e.printStackTrace();
throw new ServletException("Error loading config.", e);
} catch (Exception e) {
e.printStackTrace();
throw new ServletException("Error loading config.", e);
}
}
I think that you want the file's parent to be on the classpath, not the actual file itself.
Try this (may need some tweaking):
String path = "c:/temp/mybundle.txt";
java.io.File fl = new java.io.File(path);
try {
resourceURL = fl.getParentFile().toURL();
} catch (MalformedURLException e) {
e.printStackTrace();
}
URLClassLoader urlLoader = new URLClassLoader(new java.net.URL[]{resourceURL});
java.util.ResourceBundle bundle = java.util.ResourceBundle.getBundle("mybundle.txt",
java.util.Locale.getDefault(), urlLoader );
The file name should have .properties extension and the base directory should be in classpath. Otherwise it can also be in a jar which is in classpath
Relative to the directory in classpath the resource bundle can be specified with / or . separator. "." is preferred.
If you wanted to load message files for different languages, just use the
shared.loader=
of catalina.properties...
for more info, visit http://theswarmintelligence.blogspot.com/2012/08/use-resource-bundle-messages-files-out.html
This works for me:
File f = new File("some.properties");
Properties props = new Properties();
FileInputStream fis = null;
try {
fis = new FileInputStream(f);
props.load(fis);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (fis != null) {
try {
fis.close();
fis = null;
} catch (IOException e2) {
e2.printStackTrace();
}
}
}
public class One {
private static One one = null;
Map<String, String> configParameter = Collections.synchronizedMap(new HashMap<String, String>());
private One() {
ResourceBundle rb = ResourceBundle.getBundle("System", Locale.getDefault());
Enumeration en = rb.getKeys();
while (en.hasMoreElements()) {
String key = (String) en.nextElement();
String value = rb.getString(key);
configParameter.put(key, value);
}
}
public static One getInstance() {
if (one == null) {
one= new One();
}
return one;
}
public Map<String, String> getParameter() {
return configParameter;
}
public static void main(String[] args) {
String string = One.getInstance().getParameter().get("subin");
System.out.println(string);
}
}
ResourceBundle rb = ResourceBundle.getBundle("service"); //service.properties
System.out.println(rb.getString("server.dns")); //server.dns=http://....