How to load a resource bundle from a file resource in Java?

Question

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:

1. Create a subclass of java.util.ResourceBundle.Control
2. 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.