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java.lang.Objectjava.util.ResourceBundle
@TransactionType(value=SUPPORTS) public abstract class ResourceBundle
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
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:
Keys are alwayspublic class MyResources extends ListResourceBundle { public Object[][] getContents() { return contents; } static final Object[][] contents = { // LOCALIZE THIS { "OkKey", "OK" }, { "CancelKey", "Cancel" }, // END OF MATERIAL TO LOCALIZE }; }
String
s. In this example, the
keys are "OkKey" and "CancelKey". In the above example, the values are also
String
s--"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:
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 abutton1 = new Button(myResources.getString("OkKey")); button2 = new Button(myResources.getString("CancelKey"));
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 platform provides one subclass of ResourceBundle
,
ListResourceBundle
,
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.
If ListResourceBundle
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:
You do not have to restrict yourself to using a single family of// 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; } }
ResourceBundle
s. 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.
This Java Card class is a subset of the CDC 1.1 ResourceBundle class. Some interfaces, methods and/or variables have been pruned, and/or other methods simplified, in an effort to reduce the size of this class and/or eliminate dependencies on unsupported features.
ListResourceBundle
,
MissingResourceException
Field Summary | |
---|---|
protected ResourceBundle |
parent
The parent bundle of this bundle. |
Constructor Summary | |
---|---|
ResourceBundle()
Sole constructor. |
Method Summary | |
---|---|
static ResourceBundle |
getBundle(String baseName)
Gets a resource bundle using the specified base name and the default locale. |
static ResourceBundle |
getBundle(String baseName,
Locale locale)
Gets a resource bundle using the specified base name and locale. |
abstract Enumeration<String> |
getKeys()
Returns an enumeration of the keys. |
Locale |
getLocale()
Returns the locale of this resource bundle. |
Object |
getObject(String key)
Gets an object for the given key from this resource bundle or one of its parents. |
String |
getString(String key)
Gets a string for the given key from this resource bundle or one of its parents. |
String[] |
getStringArray(String key)
Gets a string array for the given key from this resource bundle or one of its parents. |
protected abstract Object |
handleGetObject(String key)
Gets an object for the given key from this resource bundle. |
protected void |
setParent(ResourceBundle parent)
Sets the parent bundle of this bundle. |
Methods inherited from class java.lang.Object |
---|
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
---|
protected ResourceBundle parent
getObject
when this bundle does not contain a
particular resource.
Constructor Detail |
---|
public ResourceBundle()
Method Detail |
---|
public final String getString(String key)
(String) getObject
(key)
.
key
- the key for the desired string
NullPointerException
- if key
is null
MissingResourceException
- if no object for the given key can be found
ClassCastException
- if the object found for the given key is not a stringpublic final String[] getStringArray(String key)
(String[]) getObject
(key)
.
key
- the key for the desired string array
NullPointerException
- if key
is null
MissingResourceException
- if no object for the given key can be found
ClassCastException
- if the object found for the given key is not a string
arraypublic final Object getObject(String key)
handleGetObject
.
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.
key
- the key for the desired object
NullPointerException
- if key
is null
MissingResourceException
- if no object for the given key can be foundpublic Locale getLocale()
protected void setParent(ResourceBundle parent)
getObject
when this bundle does not contain a
particular resource.
parent
- this bundle's parent bundle.public static final ResourceBundle getBundle(String baseName)
getBundle(baseName, Locale.getDefault())
. See
getBundle
for a complete description of the search and instantiation strategy.
baseName
- the base name of the resource bundle, a fully qualified class
name
NullPointerException
- if baseName
is null
MissingResourceException
- if no resource bundle for the specified base name can be
foundpublic static ResourceBundle getBundle(String baseName, Locale locale)
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
) to generate a
sequence of candidate bundle names. If the specified locale's
language and country 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
and country1) and of the default locale (language2 and country2):
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:
getBundle
creates
a new instance of this class and uses it as the result
resource bundle.
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 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
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.
Example: The following class and property files are
provided: MyResources.class,
MyResources_fr_CH.class,
MyResources_es_ES.class. The contents of all
files are valid (that is, public non-abstract subclasses of
ResourceBundle for the ".class" files. The default locale is
Locale("en", "GB")
.
Calling getBundle
with the shown locale argument values
instantiates resource bundles from the following sources:
baseName
- the base name of the resource bundle, a fully qualified class
namelocale
- the locale for which a resource bundle is desired
NullPointerException
- if baseName
or locale
is null
MissingResourceException
- if no resource bundle for the specified base name can be
foundprotected abstract Object handleGetObject(String key)
key
- the key for the desired object
NullPointerException
- if key
is null
public abstract Enumeration<String> getKeys()
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