java.util
Class ResourceBundle

java.lang.Object sample code for java.lang.Object definition code for java.lang.Object 
  extended by java.util.ResourceBundle
Direct Known Subclasses:
ListResourceBundle sample code for java.util.ListResourceBundle definition code for java.util.ListResourceBundle , PropertyResourceBundle sample code for java.util.PropertyResourceBundle definition code for java.util.PropertyResourceBundle

public abstract class ResourceBundle
extends Object sample code for java.lang.Object definition code for java.lang.Object

Resource bundles contain locale-specific objects. When your program needs a locale-specific resource, a String for example, your program can load it from the resource bundle that is appropriate for the current user's locale. In this way, you can write program code that is largely independent of the user's locale isolating most, if not all, of the locale-specific information in resource bundles.

This allows you to write programs that can:

Resource bundles belong to families whose members share a common base name, but whose names also have additional components that identify their locales. For example, the base name of a family of resource bundles might be "MyResources". The family should have a default resource bundle which simply has the same name as its family - "MyResources" - and will be used as the bundle of last resort if a specific locale is not supported. The family can then provide as many locale-specific members as needed, for example a German one named "MyResources_de".

Each resource bundle in a family contains the same items, but the items have been translated for the locale represented by that resource bundle. For example, both "MyResources" and "MyResources_de" may have a String that's used on a button for canceling operations. In "MyResources" the String may contain "Cancel" and in "MyResources_de" it may contain "Abbrechen".

If there are different resources for different countries, you can make specializations: for example, "MyResources_de_CH" contains objects for the German language (de) in Switzerland (CH). If you want to only modify some of the resources in the specialization, you can do so.

When your program needs a locale-specific object, it loads the ResourceBundle class using the getBundle sample code for java.util.ResourceBundle.getBundle(java.lang.String, java.util.Locale) definition code for java.util.ResourceBundle.getBundle(java.lang.String, java.util.Locale) method:

 ResourceBundle myResources =
      ResourceBundle.getBundle("MyResources", currentLocale);
 

Resource bundles contain key/value pairs. The keys uniquely identify a locale-specific object in the bundle. Here's an example of a ListResourceBundle that contains two key/value pairs:

 public class MyResources extends ListResourceBundle {
      public Object[][] getContents() {
              return contents;
      }
      static final Object[][] contents = {
      // LOCALIZE THIS
              {"OkKey", "OK"},
              {"CancelKey", "Cancel"},
      // END OF MATERIAL TO LOCALIZE
      };
 }
 
Keys are always Strings. In this example, the keys are "OkKey" and "CancelKey". In the above example, the values are also Strings--"OK" and "Cancel"--but they don't have to be. The values can be any type of object.

You retrieve an object from resource bundle using the appropriate getter method. Because "OkKey" and "CancelKey" are both strings, you would use getString to retrieve them:

 button1 = new Button(myResources.getString("OkKey"));
 button2 = new Button(myResources.getString("CancelKey"));
 
The getter methods all require the key as an argument and return the object if found. If the object is not found, the getter method throws a MissingResourceException.

Besides getString, ResourceBundle also provides a method for getting string arrays, getStringArray, as well as a generic getObject method for any other type of object. When using getObject, you'll have to cast the result to the appropriate type. For example:

 int[] myIntegers = (int[]) myResources.getObject("intList");
 

The Java 2 platform provides two subclasses of ResourceBundle, ListResourceBundle and PropertyResourceBundle, that provide a fairly simple way to create resources. As you saw briefly in a previous example, ListResourceBundle manages its resource as a List of key/value pairs. PropertyResourceBundle uses a properties file to manage its resources.

If ListResourceBundle or PropertyResourceBundle do not suit your needs, you can write your own ResourceBundle subclass. Your subclasses must override two methods: handleGetObject and getKeys().

The following is a very simple example of a ResourceBundle subclass, MyResources, that manages two resources (for a larger number of resources you would probably use a Hashtable). Notice that you don't need to supply a value if a "parent-level" ResourceBundle handles the same key with the same value (as for the okKey below).

Example:

 // default (English language, United States)
 public class MyResources extends ResourceBundle {
     public Object handleGetObject(String key) {
         if (key.equals("okKey")) return "Ok";
         if (key.equals("cancelKey")) return "Cancel";
         return null;
     }
 }

 // German language
 public class MyResources_de extends MyResources {
     public Object handleGetObject(String key) {
         // don't need okKey, since parent level handles it.
         if (key.equals("cancelKey")) return "Abbrechen";
         return null;
     }
 }
 
You do not have to restrict yourself to using a single family of ResourceBundles. For example, you could have a set of bundles for exception messages, ExceptionResources (ExceptionResources_fr, ExceptionResources_de, ...), and one for widgets, WidgetResource (WidgetResources_fr, WidgetResources_de, ...); breaking up the resources however you like.

Since:
JDK1.1
See Also:
ListResourceBundle sample code for java.util.ListResourceBundle definition code for java.util.ListResourceBundle , PropertyResourceBundle sample code for java.util.PropertyResourceBundle definition code for java.util.PropertyResourceBundle , MissingResourceException sample code for java.util.MissingResourceException definition code for java.util.MissingResourceException

Field Summary
protected  ResourceBundle sample code for java.util.ResourceBundle definition code for java.util.ResourceBundle parent sample code for java.util.ResourceBundle.parent definition code for java.util.ResourceBundle.parent
          The parent bundle of this bundle.
 
Constructor Summary
ResourceBundle sample code for java.util.ResourceBundle.ResourceBundle() definition code for java.util.ResourceBundle.ResourceBundle() ()
          Sole constructor.
 
Method Summary
static ResourceBundle sample code for java.util.ResourceBundle definition code for java.util.ResourceBundle getBundle sample code for java.util.ResourceBundle.getBundle(java.lang.String) definition code for java.util.ResourceBundle.getBundle(java.lang.String) (String sample code for java.lang.String definition code for java.lang.String  baseName)
          Gets a resource bundle using the specified base name, the default locale, and the caller's class loader.
static ResourceBundle sample code for java.util.ResourceBundle definition code for java.util.ResourceBundle getBundle sample code for java.util.ResourceBundle.getBundle(java.lang.String, java.util.Locale) definition code for java.util.ResourceBundle.getBundle(java.lang.String, java.util.Locale) (String sample code for java.lang.String definition code for java.lang.String  baseName, Locale sample code for java.util.Locale definition code for java.util.Locale  locale)
          Gets a resource bundle using the specified base name and locale, and the caller's class loader.
static ResourceBundle sample code for java.util.ResourceBundle definition code for java.util.ResourceBundle getBundle sample code for java.util.ResourceBundle.getBundle(java.lang.String, java.util.Locale, java.lang.ClassLoader) definition code for java.util.ResourceBundle.getBundle(java.lang.String, java.util.Locale, java.lang.ClassLoader) (String sample code for java.lang.String definition code for java.lang.String  baseName, Locale sample code for java.util.Locale definition code for java.util.Locale  locale, ClassLoader sample code for java.lang.ClassLoader definition code for java.lang.ClassLoader  loader)
          Gets a resource bundle using the specified base name, locale, and class loader.
abstract  Enumeration sample code for java.util.Enumeration definition code for java.util.Enumeration <String sample code for java.lang.String definition code for java.lang.String > getKeys sample code for java.util.ResourceBundle.getKeys() definition code for java.util.ResourceBundle.getKeys() ()
          Returns an enumeration of the keys.
 Locale sample code for java.util.Locale definition code for java.util.Locale getLocale sample code for java.util.ResourceBundle.getLocale() definition code for java.util.ResourceBundle.getLocale() ()
          Returns the locale of this resource bundle.
 Object sample code for java.lang.Object definition code for java.lang.Object getObject sample code for java.util.ResourceBundle.getObject(java.lang.String) definition code for java.util.ResourceBundle.getObject(java.lang.String) (String sample code for java.lang.String definition code for java.lang.String  key)
          Gets an object for the given key from this resource bundle or one of its parents.
 String sample code for java.lang.String definition code for java.lang.String getString sample code for java.util.ResourceBundle.getString(java.lang.String) definition code for java.util.ResourceBundle.getString(java.lang.String) (String sample code for java.lang.String definition code for java.lang.String  key)
          Gets a string for the given key from this resource bundle or one of its parents.
 String sample code for java.lang.String definition code for java.lang.String [] getStringArray sample code for java.util.ResourceBundle.getStringArray(java.lang.String) definition code for java.util.ResourceBundle.getStringArray(java.lang.String) (String sample code for java.lang.String definition code for java.lang.String  key)
          Gets a string array for the given key from this resource bundle or one of its parents.
protected abstract  Object sample code for java.lang.Object definition code for java.lang.Object handleGetObject sample code for java.util.ResourceBundle.handleGetObject(java.lang.String) definition code for java.util.ResourceBundle.handleGetObject(java.lang.String) (String sample code for java.lang.String definition code for java.lang.String  key)
          Gets an object for the given key from this resource bundle.
protected  void setParent sample code for java.util.ResourceBundle.setParent(java.util.ResourceBundle) definition code for java.util.ResourceBundle.setParent(java.util.ResourceBundle) (ResourceBundle sample code for java.util.ResourceBundle definition code for java.util.ResourceBundle  parent)
          Sets the parent bundle of this bundle.
 
Methods inherited from class java.lang.Object sample code for java.lang.Object definition code for java.lang.Object
clone sample code for java.lang.Object.clone() definition code for java.lang.Object.clone() , equals sample code for java.lang.Object.equals(java.lang.Object) definition code for java.lang.Object.equals(java.lang.Object) , finalize sample code for java.lang.Object.finalize() definition code for java.lang.Object.finalize() , getClass sample code for java.lang.Object.getClass() definition code for java.lang.Object.getClass() , hashCode sample code for java.lang.Object.hashCode() definition code for java.lang.Object.hashCode() , notify sample code for java.lang.Object.notify() definition code for java.lang.Object.notify() , notifyAll sample code for java.lang.Object.notifyAll() definition code for java.lang.Object.notifyAll() , toString sample code for java.lang.Object.toString() definition code for java.lang.Object.toString() , wait sample code for java.lang.Object.wait() definition code for java.lang.Object.wait() , wait sample code for java.lang.Object.wait(long) definition code for java.lang.Object.wait(long) , wait sample code for java.lang.Object.wait(long, int) definition code for java.lang.Object.wait(long, int)
 

Field Detail

parent sample code for java.util.ResourceBundle.parent

protected ResourceBundle sample code for java.util.ResourceBundle definition code for java.util.ResourceBundle  parent
The parent bundle of this bundle. The parent bundle is searched by getObject sample code for java.util.ResourceBundle.getObject(java.lang.String) definition code for java.util.ResourceBundle.getObject(java.lang.String) when this bundle does not contain a particular resource.

Constructor Detail

ResourceBundle sample code for java.util.ResourceBundle() definition code for java.util.ResourceBundle()

public ResourceBundle()
Sole constructor. (For invocation by subclass constructors, typically implicit.)

Method Detail

getString sample code for java.util.ResourceBundle.getString(java.lang.String) definition code for java.util.ResourceBundle.getString(java.lang.String)

public final String sample code for java.lang.String definition code for java.lang.String  getString(String sample code for java.lang.String definition code for java.lang.String  key)
Gets a string for the given key from this resource bundle or one of its parents. Calling this method is equivalent to calling
(String) getObject sample code for java.util.ResourceBundle.getObject(java.lang.String) definition code for java.util.ResourceBundle.getObject(java.lang.String) (key).

Parameters:
key - the key for the desired string
Returns:
the string for the given key
Throws:
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if key is null
MissingResourceException sample code for java.util.MissingResourceException definition code for java.util.MissingResourceException - if no object for the given key can be found
ClassCastException sample code for java.lang.ClassCastException definition code for java.lang.ClassCastException - if the object found for the given key is not a string

getStringArray sample code for java.util.ResourceBundle.getStringArray(java.lang.String) definition code for java.util.ResourceBundle.getStringArray(java.lang.String)

public final String sample code for java.lang.String definition code for java.lang.String [] getStringArray(String sample code for java.lang.String definition code for java.lang.String  key)
Gets a string array for the given key from this resource bundle or one of its parents. Calling this method is equivalent to calling
(String[]) getObject sample code for java.util.ResourceBundle.getObject(java.lang.String) definition code for java.util.ResourceBundle.getObject(java.lang.String) (key).

Parameters:
key - the key for the desired string array
Returns:
the string array for the given key
Throws:
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if key is null
MissingResourceException sample code for java.util.MissingResourceException definition code for java.util.MissingResourceException - if no object for the given key can be found
ClassCastException sample code for java.lang.ClassCastException definition code for java.lang.ClassCastException - if the object found for the given key is not a string array

getObject sample code for java.util.ResourceBundle.getObject(java.lang.String) definition code for java.util.ResourceBundle.getObject(java.lang.String)

public final Object sample code for java.lang.Object definition code for java.lang.Object  getObject(String sample code for java.lang.String definition code for java.lang.String  key)
Gets an object for the given key from this resource bundle or one of its parents. This method first tries to obtain the object from this resource bundle using handleGetObject sample code for java.util.ResourceBundle.handleGetObject(java.lang.String) definition code for java.util.ResourceBundle.handleGetObject(java.lang.String) . If not successful, and the parent resource bundle is not null, it calls the parent's getObject method. If still not successful, it throws a MissingResourceException.

Parameters:
key - the key for the desired object
Returns:
the object for the given key
Throws:
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if key is null
MissingResourceException sample code for java.util.MissingResourceException definition code for java.util.MissingResourceException - if no object for the given key can be found

getLocale sample code for java.util.ResourceBundle.getLocale() definition code for java.util.ResourceBundle.getLocale()

public Locale sample code for java.util.Locale definition code for java.util.Locale  getLocale()
Returns the locale of this resource bundle. This method can be used after a call to getBundle() to determine whether the resource bundle returned really corresponds to the requested locale or is a fallback.

Returns:
the locale of this resource bundle

setParent sample code for java.util.ResourceBundle.setParent(java.util.ResourceBundle) definition code for java.util.ResourceBundle.setParent(java.util.ResourceBundle)

protected void setParent(ResourceBundle sample code for java.util.ResourceBundle definition code for java.util.ResourceBundle  parent)
Sets the parent bundle of this bundle. The parent bundle is searched by getObject sample code for java.util.ResourceBundle.getObject(java.lang.String) definition code for java.util.ResourceBundle.getObject(java.lang.String) when this bundle does not contain a particular resource.

Parameters:
parent - this bundle's parent bundle.

getBundle sample code for java.util.ResourceBundle.getBundle(java.lang.String) definition code for java.util.ResourceBundle.getBundle(java.lang.String)

public static final ResourceBundle sample code for java.util.ResourceBundle definition code for java.util.ResourceBundle  getBundle(String sample code for java.lang.String definition code for java.lang.String  baseName)
Gets a resource bundle using the specified base name, the default locale, and the caller's class loader. Calling this method is equivalent to calling
getBundle(baseName, Locale.getDefault(), this.getClass().getClassLoader()),
except that getClassLoader() is run with the security privileges of ResourceBundle. See getBundle sample code for java.util.ResourceBundle.getBundle(java.lang.String, java.util.Locale, java.lang.ClassLoader) definition code for java.util.ResourceBundle.getBundle(java.lang.String, java.util.Locale, java.lang.ClassLoader) for a complete description of the search and instantiation strategy.

Parameters:
baseName - the base name of the resource bundle, a fully qualified class name
Returns:
a resource bundle for the given base name and the default locale
Throws:
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if baseName is null
MissingResourceException sample code for java.util.MissingResourceException definition code for java.util.MissingResourceException - if no resource bundle for the specified base name can be found

getBundle sample code for java.util.ResourceBundle.getBundle(java.lang.String, java.util.Locale) definition code for java.util.ResourceBundle.getBundle(java.lang.String, java.util.Locale)

public static final ResourceBundle sample code for java.util.ResourceBundle definition code for java.util.ResourceBundle  getBundle(String sample code for java.lang.String definition code for java.lang.String  baseName,
                                             Locale sample code for java.util.Locale definition code for java.util.Locale  locale)
Gets a resource bundle using the specified base name and locale, and the caller's class loader. Calling this method is equivalent to calling
getBundle(baseName, locale, this.getClass().getClassLoader()),
except that getClassLoader() is run with the security privileges of ResourceBundle. See getBundle sample code for java.util.ResourceBundle.getBundle(java.lang.String, java.util.Locale, java.lang.ClassLoader) definition code for java.util.ResourceBundle.getBundle(java.lang.String, java.util.Locale, java.lang.ClassLoader) for a complete description of the search and instantiation strategy.

Parameters:
baseName - the base name of the resource bundle, a fully qualified class name
locale - the locale for which a resource bundle is desired
Returns:
a resource bundle for the given base name and locale
Throws:
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if baseName or locale is null
MissingResourceException sample code for java.util.MissingResourceException definition code for java.util.MissingResourceException - if no resource bundle for the specified base name can be found

getBundle sample code for java.util.ResourceBundle.getBundle(java.lang.String, java.util.Locale, java.lang.ClassLoader) definition code for java.util.ResourceBundle.getBundle(java.lang.String, java.util.Locale, java.lang.ClassLoader)

public static ResourceBundle sample code for java.util.ResourceBundle definition code for java.util.ResourceBundle  getBundle(String sample code for java.lang.String definition code for java.lang.String  baseName,
                                       Locale sample code for java.util.Locale definition code for java.util.Locale  locale,
                                       ClassLoader sample code for java.lang.ClassLoader definition code for java.lang.ClassLoader  loader)
Gets a resource bundle using the specified base name, locale, and class loader.

Conceptually, getBundle uses the following strategy for locating and instantiating resource bundles:

getBundle uses the base name, the specified locale, and the default locale (obtained from Locale.getDefault sample code for java.util.Locale.getDefault() definition code for java.util.Locale.getDefault() ) to generate a sequence of candidate bundle names. If the specified locale's language, country, and variant are all empty strings, then the base name is the only candidate bundle name. Otherwise, the following sequence is generated from the attribute values of the specified locale (language1, country1, and variant1) and of the default locale (language2, country2, and variant2):

Candidate bundle names where the final component is an empty string are omitted. For example, if country1 is an empty string, the second candidate bundle name is omitted.

getBundle then iterates over the candidate bundle names to find the first one for which it can instantiate an actual resource bundle. For each candidate bundle name, it attempts to create a resource bundle:

If no result resource bundle has been found, a MissingResourceException is thrown.

Once a result resource bundle has been found, its parent chain is instantiated. getBundle iterates over the candidate bundle names that can be obtained by successively removing variant, country, and language (each time with the preceding "_") from the bundle name of the result resource bundle. As above, candidate bundle names where the final component is an empty string are omitted. With each of the candidate bundle names it attempts to instantiate a resource bundle, as described above. Whenever it succeeds, it calls the previously instantiated resource bundle's setParent sample code for java.util.ResourceBundle.setParent(java.util.ResourceBundle) definition code for java.util.ResourceBundle.setParent(java.util.ResourceBundle) method with the new resource bundle, unless the previously instantiated resource bundle already has a non-null parent.

Implementations of getBundle may cache instantiated resource bundles and return the same resource bundle instance multiple times. They may also vary the sequence in which resource bundles are instantiated as long as the selection of the result resource bundle and its parent chain are compatible with the description above.

The baseName argument should be a fully qualified class name. However, for compatibility with earlier versions, Sun's Java 2 runtime environments do not verify this, and so it is possible to access PropertyResourceBundles by specifying a path name (using "/") instead of a fully qualified class name (using ".").

Example: The following class and property files are provided: MyResources.class, MyResources_fr_CH.properties, MyResources_fr_CH.class, MyResources_fr.properties, MyResources_en.properties, MyResources_es_ES.class. The contents of all files are valid (that is, public non-abstract subclasses of ResourceBundle for the ".class" files, syntactically correct ".properties" files). The default locale is Locale("en", "GB").

Calling getBundle with the shown locale argument values instantiates resource bundles from the following sources:

The file MyResources_fr_CH.properties is never used because it is hidden by MyResources_fr_CH.class.

Parameters:
baseName - the base name of the resource bundle, a fully qualified class name
locale - the locale for which a resource bundle is desired
loader - the class loader from which to load the resource bundle
Returns:
a resource bundle for the given base name and locale
Throws:
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if baseName, locale, or loader is null
MissingResourceException sample code for java.util.MissingResourceException definition code for java.util.MissingResourceException - if no resource bundle for the specified base name can be found
Since:
1.2

handleGetObject sample code for java.util.ResourceBundle.handleGetObject(java.lang.String) definition code for java.util.ResourceBundle.handleGetObject(java.lang.String)

protected abstract Object sample code for java.lang.Object definition code for java.lang.Object  handleGetObject(String sample code for java.lang.String definition code for java.lang.String  key)
Gets an object for the given key from this resource bundle. Returns null if this resource bundle does not contain an object for the given key.

Parameters:
key - the key for the desired object
Returns:
the object for the given key, or null
Throws:
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if key is null

getKeys sample code for java.util.ResourceBundle.getKeys() definition code for java.util.ResourceBundle.getKeys()

public abstract Enumeration sample code for java.util.Enumeration definition code for java.util.Enumeration <String sample code for java.lang.String definition code for java.lang.String > getKeys()
Returns an enumeration of the keys.