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Relative path to image folder java spring

I have a problem with a relative path to an image folder.
I want to list the images into a folder to add their urls to a list and show them in a jsp.
The code is this:
File carpetaImagenes = new File("../../../../../webapp/resources/img/maquinas/"+seleccion);
List<String> listaUrlImagenes = new ArrayList<String>();
/** Recorremos el directorio de imagenes de la maquina */
for(File imagen : carpetaImagenes.listFiles()){
String imageFileName = imagen.getName();
listaUrlImagenes.add(imageFileName);
}
The result of "carpetaImagenes.listFiles()" is always null. I suppose the path is bad.
Here you can see the image of the folder tree. The class is into "controlador" folder and the images are into "webbapp/resources/img/maquinas/1"
I haeve tried several paths with no luck.
Thank you very much.

User following method getImageList and it should work
relativeFilePath = "img/maquinas/"+seleccion;
This is a relative path from classpath. I assume ../../../../../webapp/resources is your actual folder where everyrthing is deployed .
private List getImageList(String relativeFilePath) {
List<String> listaUrlImagenes = new ArrayList<String>();
try {
InputStream in = getResourceAsStream(relativeFilePath);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String resource;
while ((resource = br.readLine()) != null) {
listaUrlImagenes.add(resource);
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return listaUrlImagenes;
}
private InputStream getResourceAsStream(String resource) {
final InputStream in = ClassLoader cl = this.getClass().getClassLoader().getResourceAsStream(
resource);
return in == null ? getClass().getResourceAsStream(resource) : in;
}
And in spring following should work.
ClassLoader cl = this.getClass().getClassLoader();
ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver(
cl);
Resource[] resources = resolver.getResources("classpath:/img/maquinas/"+seleccion);// or *.png
for (Resource resource : resources) {
listaUrlImagenes.add(resource.getFilename());
}

Finally working!!
File carpetaImagenes = new ClassPathResource("imagenes/maquinas/"+seleccion).getFile();
File[] listaImagenes = carpetaImagenes.listFiles();

Loading classes from a set of files

I have a task to check a set of conditions for unknown set of classes from classpath. I want to scan it for classes, load each of them and perform my checks. Now I have a set of urls to class files and I try to use URLClassLoader. But to load a class I need to specify a fully qualified class name, but I don't have them (I have only file path). I don't think that building class name from class file path is relieble, is it a better way to do it?
Thanks!

I'd just parse the beginning of the class file, looking for "package" keyword and first occurrence of "class" keyword. Then, when you combine those two (packageName + "." + className), it should result in a proper class name.

I started a project once to automatically test classes found on the class path for run time exceptions, by calling constructors and methods reflectively with dodgy arguments like null, 0, 1, -1, "" etc.
That project has a class called Finder wich does roughly what you need:
static List<Class<?>> findClassesForPackage(String packagename, Report report) throws ClassNotFoundException {
// 'classes' will hold a list of directories matching the package name.
// There may be more than one if a package is split over multiple
// jars/paths
List<Class<?>> classes = new ArrayList<Class<?>>();
List<File> directories = new ArrayList<File>();
try {
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
if (classLoader == null) {
throw new ClassNotFoundException("Can't get class loader.");
}
// Ask for all resources for the path
String path = packagename.replace('.', '/');
Enumeration<URL> resources = classLoader.getResources(path);
while (resources.hasMoreElements()) {
URL res = resources.nextElement();
if (res.getProtocol().equalsIgnoreCase("jar")) {
JarURLConnection conn = (JarURLConnection) res.openConnection();
JarFile jar = conn.getJarFile();
for (JarEntry entry : Collections.list(jar.entries())) {
if (entry.getName().startsWith(path) && entry.getName().endsWith(".class")
&& !entry.getName().contains("$")) {
String className = entry.getName().replace("/", ".").substring(0,
entry.getName().length() - 6);
LOG.debug("Adding JAR className " + className);
try {
Class<?> clazz = Class.forName(className);
classes.add(clazz);
report.addClass(className);
} catch (Throwable throwable) {
ParamSet params = new ParamSet();
params.addParamValue(new ParamValue(className, "fully qualified classname"));
report.addError(className, new Error("Class.forName()", params, throwable));
}
}
}
} else
directories.add(new File(URLDecoder.decode(res.getPath(), "UTF-8")));
}
} catch (NullPointerException e) {
throw new ClassNotFoundException(String.format("%s does not appear to be a valid package", packagename), e);
} catch (UnsupportedEncodingException e) {
throw new ClassNotFoundException(String.format("%s does not appear to be a valid package", packagename), e);
} catch (IOException e) {
throw new ClassNotFoundException(String.format("Could not get all resources for %s", packagename), e);
}
List<String> subPackages = new ArrayList<String>();
// For every directory identified capture all the .class files
for (File directory : directories) {
if (directory.exists()) {
// Get the list of the files contained in the package
File[] files = directory.listFiles();
for (File file : files) {
// add .class files to results
String fileName = file.getName();
if (file.isFile() && fileName.endsWith(".class")) {
// removes the .class extension
String className = packagename + '.' + fileName.substring(0, fileName.length() - 6);
LOG.debug("Adding FILE className " + className);
try {
Class<?> clazz = Class.forName(className);
classes.add(clazz);
report.addClass(className);
} catch (Throwable throwable) {
ParamSet params = new ParamSet();
params.addParamValue(new ParamValue(className, "fully qualified classname"));
report.addError(className, new Error("Class.forName()", params, throwable));
}
}
// keep track of subdirectories
if (file.isDirectory()) {
subPackages.add(packagename + "." + fileName);
}
}
} else {
throw new ClassNotFoundException(String.format("%s (%s) does not appear to be a valid package",
packagename, directory.getPath()));
}
}
// check all potential subpackages
for (String subPackage : subPackages) {
classes.addAll(findClassesForPackage(subPackage, report));
}
return classes;
}
You probably have to strip some code that does reporting etc.

Class loading class from jar

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[].

How to clear ResourceBundle cache

This is a webapp running on Tomcat, using Guice. According to the docs we should be able to call ResourceBundle.clearCache(); to clear the ResourceBundle cache and presumably get the latest from the bundle property files.
We have also tried the following:
Class klass = ResourceBundle.getBundle("my.bundle").getClass().getSuperclass();
Field field = klass.getDeclaredField("cacheList");
field.setAccessible(true);
ConcurrentHashMap cache = (ConcurrentHashMap) field.get(null);
cache.clear(); // If i debug here I can see the cache is now empty!
and
ResourceBundle.clearCache(this.class.getClassLoader());
The behavior that I am expecting is:
Start up tomcat and hit a page and it says 'Hello World'
Change the properties file containing 'Hello World' to 'Goodbye Earth'
Clear the cache using a servlet
Hit the page and expect to see 'Goodbye Earth'
So question is, how is ResourceBundle.clearCache() actually working ? And is there some generic file cache we need to clear also ?

This worked for me:
ResourceBundle.clearCache();
ResourceBundle resourceBundle= ResourceBundle.getBundle("YourBundlePropertiesFile");
String value = resourceBundle.getString("your_resource_bundle_key");
Notes:
ResourceBundle.clearCache() is added at Java 1.6
Do not use a static resourceBundle property, use
ResourceBundle.getBundle() method after invoking clearCache()
method.

I do not believe you can effect the reloading of an already created ResourceBundle instance since its internal control class has already been created. You may try this as an alternative for initializing your bundle:
ResourceBundle.getBundle("my.bundle", new ResourceBundle.Control() {
#Override
public long getTimeToLive(String arg0, Locale arg1) {
return TTL_DONT_CACHE;
}
});

I have found this solution (works with tomcat):
use a custom ResourceBundle.Control (because I need UTF8)
add the getTimeToLive as "Perception" description
force the reload flag
the "ResourceBundle.clearCache" doesn't work
How to call :
ResourceBundle bundle = ResourceBundle.getBundle("yourfile", new UTF8Control());
The custom class :
public class UTF8Control extends Control
{
public ResourceBundle newBundle(
String baseName,
Locale locale,
String format,
ClassLoader loader,
boolean reload)
throws IllegalAccessException, InstantiationException, IOException
{
// The below is a copy of the default implementation.
String bundleName = toBundleName(baseName, locale);
String resourceName = toResourceName(bundleName, "properties");
ResourceBundle bundle = null;
InputStream stream = null;
// FORCE RELOAD because needsReload doesn't work and reload is always false
reload = true;
if (reload) {
URL url = loader.getResource(resourceName);
if (url != null) {
URLConnection connection = url.openConnection();
if (connection != null) {
connection.setUseCaches(false);
stream = connection.getInputStream();
}
}
}
else {
stream = loader.getResourceAsStream(resourceName);
}
if (stream != null) {
try {
// Only this line is changed to make it to read properties files as UTF-8.
bundle = new PropertyResourceBundle(new InputStreamReader(stream, "UTF-8"));
}
finally {
stream.close();
}
}
return bundle;
}
// ASK NOT TO CACHE
public long getTimeToLive(String arg0, Locale arg1) {
return TTL_DONT_CACHE;
}
}

maybe this post can solve your problem.

this is one more possibility to clear cache
Class<ResourceBundle> type = ResourceBundle.class;
try {
Field cacheList = type.getDeclaredField("cacheList");
cacheList.setAccessible(true);
((Map<?, ?>) cacheList.get(ResourceBundle.class)).clear();
}
catch (Exception e) {
system.out.print("Failed to clear ResourceBundle cache" + e);
}

This works, iff you can intercept the very first creation of the resource bundle:
while (true) {
ResourceBundle resourceBundle = ResourceBundle.getBundle("SystemMessages", new Locale("hu", "HU"),
new ResourceBundle.Control() {
#Override
public List<String> getFormats(String baseName) {
return ResourceBundle.Control.FORMAT_PROPERTIES;
}
#Override
public ResourceBundle newBundle(String baseName, Locale locale, String format, ClassLoader loader, boolean reload) throws IllegalAccessException, InstantiationException, IOException {
System.err.println(this.toBundleName(baseName, locale) + ": " + format + " - " + reload);
return super.newBundle(baseName, locale, format, loader, reload);
}
#Override
public long getTimeToLive(String baseName, Locale locale) {
long ttl = 1000;
System.err.println(this.toBundleName(baseName, locale) + " - " + ttl + "ms");
return ttl;
}
#Override
public boolean needsReload(String baseName, Locale locale, String format, ClassLoader loader, ResourceBundle bundle, long loadTime) {
System.err.println(baseName + "_" + locale + " - " + new Date(loadTime));
return true;
}
});
System.out.println(resourceBundle.getString("display.first_name") + ": John");
System.out.println(resourceBundle.getString("display.last_name") + ": Doe");
Thread.sleep(5000);
}

Custom class loader for loading dll in applet

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.