I am working in a project where I have to load two different property files (for example parent.properties & child.properties ) which are totally have different base name and it should also have inheritance relationship between this two bundle. So that if any keys are not found in child.properties it should get from parent.properties.
When I was analyzing the resource bundle code, I came to know there is method setParent(), this method is used to set which is your parent bundle (something like java super class). For example if we use bundle name called "child_en.properties" the my parent bundle should be "child.properties".
As this method was protected method in ResourceBundle Class, so to use this class I have sub classed my own ResourceBundle class and overridden the setParent Method like below.
public class P4JResourceBundle extends ResourceBundle {
protected void setParent(ResourceBundle parent) {
super.setParent(parent);
}
public void letsChangeParent(String parent){
this.setParent(ResourceBundle.getBundle(parent));
}
public Enumeration getKeys() {
return null;
}
protected Object handleGetObject(String key) {
return null;
}
So after changing the class I have executed with the below method, excepts that it should pick the key from parent.properties file if the key is not present in child.properties file.
public class ResourceBundleExample {
public static void main(String[] args) {
P4JResourceBundle myBundle = new P4JResourceBundle();
myBundle.letsChangeParent("com.passion4java.resourcebundle.parent");
ResourceBundle bundle = myBundle.getBundle("com.passion4java.resourcebundle.child");
System.out.println(bundle.getString("i_am_not_in_child_file"));
}
}
As usual J there is an error thrown saying the key was missing.
Exception in thread "main" java.util.MissingResourceException: Can't find resource for bundle java.util.PropertyResourceBundle, key i_am_not_in_child_file
at java.util.ResourceBundle.getObject(Unknown Source)
at java.util.ResourceBundle.getString(Unknown Source)
at com.passion4java.resourcebundle.ResourceBundleExample.main(ResourceBundleExample.java:11)
So what's wrong?
I tried to debug the code in the resource bundle class and below code surprised me.
public static final ResourceBundle getBundle(String baseName,Locale locale){
return getBundleImpl(baseName, locale, getLoader());
}
private static ResourceBundle getBundleImpl(String baseName, Locale locale,
ClassLoader loader){
if (baseName == null) {
throw new NullPointerException ();
}
String bundleName = baseName;
String localeSuffix = locale.toString();
if (localeSuffix.length() > 0) {
bundleName += "_" + localeSuffix;
} else if (locale.getVariant().length() > 0) {
//new Locale("", "", "VARIANT").toString == ""
bundleName += "___" + locale.getVariant();
}
Locale defaultLocale = Locale.getDefault();
Object lookup = findBundleInCache(loader, bundleName, defaultLocale);
if (lookup == NOT_FOUND) {
throwMissingResourceException(baseName, locale);
} else if (lookup != null) {
return (ResourceBundle )lookup;
}
Object parent = NOT_FOUND; // **********THIS_LINE_OF_CODE**********
try {
//locate the root bundle and work toward the desired child
Object root = findBundle(loader, baseName, defaultLocale, baseName, null);
if (root == null) {
putBundleInCache(loader, baseName, defaultLocale, NOT_FOUND);
root = NOT_FOUND;
}
…cont
As I was setting the value in setParent() of resource bundle to change the parent resource bundle, but when the bundle are created using ResourceBundle.getInstance(), internally it calls getBundleImpl() which set the parent as "NOT_FOUND" direcly.
I was really confused why the code was setting directly rather than using values from the setter method????
As user of this class this implementation really stops customization which users expects.
Please feel free to comment.
