- Direct Known Subclasses:
ListResourceBundle,PropertyResourceBundle
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:
- be easily localized, or translated, into different languages
- handle multiple locales at once
- be easily modified later to support even more locales
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:
public class MyResources extends ListResourceBundle {
protected Object[][] getContents() {
return new Object[][] {
// LOCALIZE THE SECOND STRING OF EACH ARRAY (e.g., "OK")
{"OkKey", "OK"},
{"CancelKey", "Cancel"},
// END OF MATERIAL TO LOCALIZE
};
}
}
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"));
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 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 implementation of a ResourceBundle subclass must be thread-safe
if it's simultaneously used by multiple threads. The default implementations
of the non-abstract methods in this class, and the methods in the direct
known concrete subclasses ListResourceBundle and
PropertyResourceBundle are thread-safe.
Resource Bundles and Named Modules
Resource bundles can be deployed in modules in the following ways:Resource bundles together with an application
Resource bundles can be deployed together with an application in the same module. In that case, the resource bundles are loaded by code in the module by calling thegetBundle(String)
or getBundle(String, Locale) method.
Resource bundles as service providers
Resource bundles can be deployed in one or more service provider modules and they can be located usingServiceLoader.
A service interface or class must be
defined. The caller module declares that it uses the service, the service
provider modules declare that they provide implementations of the service.
Refer to ResourceBundleProvider for developing resource bundle
services and deploying resource bundle providers.
The module obtaining the resource bundle can be a resource bundle
provider itself; in which case this module only locates the resource bundle
via service provider mechanism.
A resource bundle provider can
provide resource bundles in any format such XML which replaces the need
of ResourceBundle.Control.
Resource bundles in other modules and class path
Resource bundles in a named module may be encapsulated so that it cannot be located by code in other modules. Resource bundles in unnamed modules and class path are open for any module to access. Resource bundle follows the resource encapsulation rules as specified inModule.getResourceAsStream(String).
The getBundle factory methods with no Control parameter
locate and load resource bundles from
service providers.
It may continue the search as if calling Module.getResourceAsStream(String)
to find the named resource from a given module and calling
ClassLoader.getResourceAsStream(String); refer to
the specification of the getBundle method for details.
Only non-encapsulated resource bundles of "java.class"
or "java.properties" format are searched.
If the caller module is a resource bundle provider, it does not fall back to the class loader search.
In cases where the getBundle factory method is called from a context
where there is no caller frame on the stack (e.g. when called directly from
a JNI attached thread), the caller module is default to the unnamed module for the
system class loader.
Resource bundles in automatic modules
A common format of resource bundles is in .properties file format. Typically.properties resource bundles
are packaged in a JAR file. Resource bundle only JAR file can be readily
deployed as an automatic module. For example, if the JAR file contains the
entry "p/q/Foo_ja.properties" and no .class entry,
when resolved and defined as an automatic module, no package is derived
for this module. This allows resource bundles in .properties
format packaged in one or more JAR files that may contain entries
in the same directory and can be resolved successfully as
automatic modules.
ResourceBundle.Control
TheResourceBundle.Control class provides information necessary
to perform the bundle loading process by the getBundle
factory methods that take a ResourceBundle.Control
instance. You can implement your own subclass in order to enable
non-standard resource bundle formats, change the search strategy, or
define caching parameters. Refer to the descriptions of the class and the
getBundle
factory method for details.
ResourceBundle.Control is designed for an application deployed
in an unnamed module, for example to support resource bundles in
non-standard formats or package localized resources in a non-traditional
convention. ResourceBundleProvider is the replacement for
ResourceBundle.Control when migrating to modules.
UnsupportedOperationException will be thrown when a factory
method that takes the ResourceBundle.Control parameter is called.
For the getBundle factory
methods that take no ResourceBundle.Control instance, their default behavior of resource bundle loading
can be modified with custom ResourceBundleControlProvider implementations.
If any of the
providers provides a ResourceBundle.Control for the given base name, that ResourceBundle.Control will be used instead of the default ResourceBundle.Control. If there is
more than one service provider for supporting the same base name,
the first one returned from ServiceLoader will be used.
A custom ResourceBundle.Control implementation is ignored by named modules.
Cache Management
Resource bundle instances created by thegetBundle factory
methods are cached by default, and the factory methods return the same
resource bundle instance multiple times if it has been
cached. getBundle clients may clear the cache, manage the
lifetime of cached resource bundle instances using time-to-live values,
or specify not to cache resource bundle instances. Refer to the
descriptions of the getBundle factory method, clearCache, ResourceBundle.Control.getTimeToLive, and ResourceBundle.Control.needsReload for details.
Example
The following is a very simple example of aResourceBundle
subclass, MyResources, that manages two resources (for a larger number of
resources you would probably use a Map).
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).
// 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;
}
public Enumeration<String> getKeys() {
return Collections.enumeration(keySet());
}
// Overrides handleKeySet() so that the getKeys() implementation
// can rely on the keySet() value.
protected Set<String> handleKeySet() {
return new HashSet<String>(Arrays.asList("okKey", "cancelKey"));
}
}
// 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;
}
protected Set<String> handleKeySet() {
return new HashSet<String>(Arrays.asList("cancelKey"));
}
}
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:
- 1.1
- See Also:
-
Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionstatic classResourceBundle.Controldefines a set of callback methods that are invoked by theResourceBundle.getBundlefactory methods during the bundle loading process. -
Field Summary
Fields -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionstatic final voidRemoves all resource bundles from the cache that have been loaded by the caller's module.static final voidclearCache(ClassLoader loader) Removes all resource bundles from the cache that have been loaded by the given class loader.booleancontainsKey(String key) Determines whether the givenkeyis contained in thisResourceBundleor its parent bundles.Returns the base name of this bundle, if known, ornullif unknown.static final ResourceBundleGets a resource bundle using the specified base name, the default locale, and the caller module.static ResourceBundleGets a resource bundle using the specified base name and the default locale on behalf of the specified module.static final ResourceBundleGets a resource bundle using the specified base name and locale, and the caller module.static ResourceBundlegetBundle(String baseName, Locale locale, ClassLoader loader) Gets a resource bundle using the specified base name, locale, and class loader.static ResourceBundlegetBundle(String baseName, Locale targetLocale, ClassLoader loader, ResourceBundle.Control control) Returns a resource bundle using the specified base name, target locale, class loader and control.static ResourceBundleGets a resource bundle using the specified base name and locale on behalf of the specified module.static final ResourceBundlegetBundle(String baseName, Locale targetLocale, ResourceBundle.Control control) Returns a resource bundle using the specified base name, target locale and control, and the caller's class loader.static final ResourceBundlegetBundle(String baseName, ResourceBundle.Control control) Returns a resource bundle using the specified base name, the default locale and the specified control.abstract Enumeration<String> getKeys()Returns an enumeration of the keys.Returns the locale of this resource bundle.final ObjectGets an object for the given key from this resource bundle or one of its parents.final StringGets a string for the given key from this resource bundle or one of its parents.final String[]getStringArray(String key) Gets a string array for the given key from this resource bundle or one of its parents.protected abstract ObjecthandleGetObject(String key) Gets an object for the given key from this resource bundle.Returns aSetof the keys contained only in thisResourceBundle.keySet()Returns aSetof all keys contained in thisResourceBundleand its parent bundles.protected voidsetParent(ResourceBundle parent) Sets the parent bundle of this bundle.
-
Field Details
-
parent
The parent bundle of this bundle. The parent bundle is searched bygetObjectwhen this bundle does not contain a particular resource.
-
-
Constructor Details
-
ResourceBundle
public ResourceBundle()Sole constructor. (For invocation by subclass constructors, typically implicit.)
-
-
Method Details
-
getBaseBundleName
Returns the base name of this bundle, if known, ornullif unknown. If not null, then this is the value of thebaseNameparameter that was passed to theResourceBundle.getBundle(...)method when the resource bundle was loaded.- Returns:
- The base name of the resource bundle, as provided to and expected
by the
ResourceBundle.getBundle(...)methods. - Since:
- 1.8
- See Also:
-
getString
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(key);- Parameters:
key- the key for the desired string- Returns:
- the string for the given key
- Throws:
NullPointerException- ifkeyisnullMissingResourceException- if no object for the given key can be foundClassCastException- if the object found for the given key is not a string
-
getStringArray
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(key);- Parameters:
key- the key for the desired string array- Returns:
- the string array for the given key
- Throws:
NullPointerException- ifkeyisnullMissingResourceException- if no object for the given key can be foundClassCastException- if the object found for the given key is not a string array
-
getObject
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 usinghandleGetObject. If not successful, and the parent resource bundle is not null, it calls the parent'sgetObjectmethod. 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- ifkeyisnullMissingResourceException- if no object for the given key can be found
-
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
Sets the parent bundle of this bundle. The parent bundle is searched bygetObjectwhen this bundle does not contain a particular resource.- Parameters:
parent- this bundle's parent bundle.
-
getBundle
Gets a resource bundle using the specified base name, the default locale, and the caller module. Calling this method is equivalent to callinggetBundle(baseName, Locale.getDefault(), callerModule);- 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- ifbaseNameisnullMissingResourceException- if no resource bundle for the specified base name can be found- See Also:
-
getBundle
Returns a resource bundle using the specified base name, the default locale and the specified control. Calling this method is equivalent to callingexcept thatgetBundle(baseName, Locale.getDefault(), this.getClass().getClassLoader(), control);getClassLoader()is run with the security privileges ofResourceBundle. SeegetBundlefor the complete description of the resource bundle loading process with aResourceBundle.Control.- Parameters:
baseName- the base name of the resource bundle, a fully qualified class namecontrol- the control which gives information for the resource bundle loading process- Returns:
- a resource bundle for the given base name and the default locale
- Throws:
NullPointerException- ifbaseNameorcontrolisnullMissingResourceException- if no resource bundle for the specified base name can be foundIllegalArgumentException- if the givencontroldoesn't perform properly (e.g.,control.getCandidateLocalesreturns null.) Note that validation ofcontrolis performed as needed.UnsupportedOperationException- if this method is called in a named module- Since:
- 1.6
-
getBundle
Gets a resource bundle using the specified base name and locale, and the caller module. Calling this method is equivalent to callinggetBundle(baseName, locale, callerModule);- Parameters:
baseName- the base name of the resource bundle, a fully qualified class namelocale- the locale for which a resource bundle is desired- Returns:
- a resource bundle for the given base name and locale
- Throws:
NullPointerException- ifbaseNameorlocaleisnullMissingResourceException- if no resource bundle for the specified base name can be found- See Also:
-
getBundle
Gets a resource bundle using the specified base name and the default locale on behalf of the specified module. This method is equivalent to callinggetBundle(baseName, Locale.getDefault(), module);- Parameters:
baseName- the base name of the resource bundle, a fully qualified class namemodule- the module for which the resource bundle is searched- Returns:
- a resource bundle for the given base name and the default locale
- Throws:
NullPointerException- ifbaseNameormoduleisnullSecurityException- if a security manager exists and the caller is not the specified module and doesn't haveRuntimePermission("getClassLoader")MissingResourceException- if no resource bundle for the specified base name can be found in the specified module- Since:
- 9
- See Also:
-
getBundle
Gets a resource bundle using the specified base name and locale on behalf of the specified module.Resource bundles in named modules may be encapsulated. When the resource bundle is loaded from a service provider, the caller module must have an appropriate uses clause in its module descriptor to declare that the module uses of
ResourceBundleProviderfor the named resource bundle. Otherwise, it will load the resource bundles that are local in the given module as if callingModule.getResourceAsStream(String)or that are visible to the class loader of the given module as if callingClassLoader.getResourceAsStream(String). When the resource bundle is loaded from the specified module, it is subject to the encapsulation rules specified byModule.getResourceAsStream.If the given
moduleis an unnamed module, then this method is equivalent to callinggetBundle(baseName, targetLocale, module.getClassLoader()to load resource bundles that are visible to the class loader of the given unnamed module. CustomResourceBundleControlProviderimplementations, if present, will only be invoked if the specified module is an unnamed module.- Parameters:
baseName- the base name of the resource bundle, a fully qualified class nametargetLocale- the locale for which a resource bundle is desiredmodule- the module for which the resource bundle is searched- Returns:
- a resource bundle for the given base name and locale in the module
- Throws:
NullPointerException- ifbaseName,targetLocale, ormoduleisnullSecurityException- if a security manager exists and the caller is not the specified module and doesn't haveRuntimePermission("getClassLoader")MissingResourceException- if no resource bundle for the specified base name and locale can be found in the specifiedmodule- Since:
- 9
- See Also:
-
getBundle
public static final ResourceBundle getBundle(String baseName, Locale targetLocale, ResourceBundle.Control control) Returns a resource bundle using the specified base name, target locale and control, and the caller's class loader. Calling this method is equivalent to callingexcept thatgetBundle(baseName, targetLocale, this.getClass().getClassLoader(), control);getClassLoader()is run with the security privileges ofResourceBundle. SeegetBundlefor the complete description of the resource bundle loading process with aResourceBundle.Control.- Parameters:
baseName- the base name of the resource bundle, a fully qualified class nametargetLocale- the locale for which a resource bundle is desiredcontrol- the control which gives information for the resource bundle loading process- Returns:
- a resource bundle for the given base name and a
Localeinlocales - Throws:
NullPointerException- ifbaseName,localesorcontrolisnullMissingResourceException- if no resource bundle for the specified base name in any of thelocalescan be found.IllegalArgumentException- if the givencontroldoesn't perform properly (e.g.,control.getCandidateLocalesreturns null.) Note that validation ofcontrolis performed as needed.UnsupportedOperationException- if this method is called in a named module- Since:
- 1.6
-
getBundle
Gets a resource bundle using the specified base name, locale, and class loader.When this method is called from a named module and the given loader is the class loader of the caller module, this is equivalent to calling:
otherwise, this is equivalent to calling:getBundle(baseName, targetLocale, callerModule);wheregetBundle(baseName, targetLocale, loader, control);controlis the default instance ofResourceBundle.Controlunless aControlinstance is provided byResourceBundleControlProviderSPI. Refer to the description of modifying the default behavior. The following describes the default behavior.Resource Bundle Search and Loading Strategy
getBundleuses the base name, the specified locale, and the default locale (obtained fromLocale.getDefault) to generate a sequence of candidate bundle names. If the specified locale's language, script, country, and variant are all empty strings, then the base name is the only candidate bundle name. Otherwise, a list of candidate locales is generated from the attribute values of the specified locale (language, script, country and variant) and appended to the base name. Typically, this will look like the following:baseName + "_" + language + "_" + script + "_" + country + "_" + variant baseName + "_" + language + "_" + script + "_" + country baseName + "_" + language + "_" + script baseName + "_" + language + "_" + country + "_" + variant baseName + "_" + language + "_" + country baseName + "_" + languageCandidate bundle names where the final component is an empty string are omitted, along with the underscore. For example, if country is an empty string, the second and the fifth candidate bundle names above would be omitted. Also, if script is an empty string, the candidate names including script are omitted. For example, a locale with language "de" and variant "JAVA" will produce candidate names with base name "MyResource" below.
MyResource_de__JAVA MyResource_deIn the case that the variant contains one or more underscores ('_'), a sequence of bundle names generated by truncating the last underscore and the part following it is inserted after a candidate bundle name with the original variant. For example, for a locale with language "en", script "Latn, country "US" and variant "WINDOWS_VISTA", and bundle base name "MyResource", the list of candidate bundle names below is generated:MyResource_en_Latn_US_WINDOWS_VISTA MyResource_en_Latn_US_WINDOWS MyResource_en_Latn_US MyResource_en_Latn MyResource_en_US_WINDOWS_VISTA MyResource_en_US_WINDOWS MyResource_en_US MyResource_en
Note: For some
Locales, the list of candidate bundle names contains extra names, or the order of bundle names is slightly modified. See the description of the default implementation ofgetCandidateLocalesfor details.getBundlethen iterates over the candidate bundle names to find the first one for which it can instantiate an actual resource bundle. It uses the default controls'getFormatsmethod, which generates two bundle names for each generated name, the first a class name and the second a properties file name. For each candidate bundle name, it attempts to create a resource bundle:- First, it attempts to load a class using the generated class name.
If such a class can be found and loaded using the specified class
loader, is assignment compatible with ResourceBundle, is accessible from
ResourceBundle, and can be instantiated,
getBundlecreates a new instance of this class and uses it as the result resource bundle. - Otherwise,
getBundleattempts to locate a property resource file using the generated properties file name. It generates a path name from the candidate bundle name by replacing all "." characters with "/" and appending the string ".properties". It attempts to find a "resource" with this name usingClassLoader.getResource. (Note that a "resource" in the sense ofgetResourcehas nothing to do with the contents of a resource bundle, it is just a container of data, such as a file.) If it finds a "resource", it attempts to create a newPropertyResourceBundleinstance from its contents. If successful, this instance becomes the result resource bundle.
This continues until a result resource bundle is instantiated or the list of candidate bundle names is exhausted. If no matching resource bundle is found, the default control's
getFallbackLocalemethod is called, which returns the current default locale. A new sequence of candidate locale names is generated using this locale and searched again, as above.If still no result bundle is found, the base name alone is looked up. If this still fails, a
MissingResourceExceptionis thrown.Once a result resource bundle has been found, its parent chain is instantiated. If the result bundle already has a parent (perhaps because it was returned from a cache) the chain is complete.
Otherwise,
getBundleexamines the remainder of the candidate locale list that was used during the pass that generated the result resource bundle. (As before, candidate bundle names where the final component is an empty string are omitted.) When it comes to the end of the candidate list, it tries the plain bundle name. With each of the candidate bundle names it attempts to instantiate a resource bundle (first looking for a class and then a properties file, as described above).Whenever it succeeds, it calls the previously instantiated resource bundle's
setParentmethod with the new resource bundle. This continues until the list of names is exhausted or the current bundle already has a non-null parent.Once the parent chain is complete, the bundle is returned.
Note:
getBundlecaches instantiated resource bundles and might return the same resource bundle instance multiple times.Note:The
baseNameargument should be a fully qualified class name. However, for compatibility with earlier versions, Java SE Runtime Environments do not verify this, and so it is possible to accessPropertyResourceBundles by specifying a path name (using "/") instead of a fully qualified class name (using ".").The following class and property files are provided:
- MyResources.class
- MyResources.properties
- MyResources_fr.properties
- MyResources_fr_CH.class
- MyResources_fr_CH.properties
- MyResources_en.properties
- MyResources_es_ES.class
ResourceBundlefor the ".class" files, syntactically correct ".properties" files). The default locale isLocale("en", "GB").Calling
getBundlewith the locale arguments below will instantiate resource bundles as follows:Locale Resource bundle Locale("fr", "CH") MyResources_fr_CH.class, parent MyResources_fr.properties, parent MyResources.class Locale("fr", "FR") MyResources_fr.properties, parent MyResources.class Locale("de", "DE") MyResources_en.properties, parent MyResources.class Locale("en", "US") MyResources_en.properties, parent MyResources.class Locale("es", "ES") MyResources_es_ES.class, parent MyResources.class The file MyResources_fr_CH.properties is never used because it is hidden by the MyResources_fr_CH.class. Likewise, MyResources.properties is also hidden by MyResources.class.
- API Note:
- If the caller module is a named module and the given
loaderis the caller module's class loader, this method is equivalent togetBundle(baseName, locale); otherwise, it may not find resource bundles from named modules. UsegetBundle(String, Locale, Module)to load resource bundles on behalf on a specific module instead. - Parameters:
baseName- the base name of the resource bundle, a fully qualified class namelocale- the locale for which a resource bundle is desiredloader- the class loader from which to load the resource bundle- Returns:
- a resource bundle for the given base name and locale
- Throws:
NullPointerException- ifbaseName,locale, orloaderisnullMissingResourceException- if no resource bundle for the specified base name can be found- Since:
- 1.2
- See Also:
- First, it attempts to load a class using the generated class name.
If such a class can be found and loaded using the specified class
loader, is assignment compatible with ResourceBundle, is accessible from
ResourceBundle, and can be instantiated,
-
getBundle
public static ResourceBundle getBundle(String baseName, Locale targetLocale, ClassLoader loader, ResourceBundle.Control control) Returns a resource bundle using the specified base name, target locale, class loader and control. Unlike thegetBundlefactory methods with nocontrolargument, the givencontrolspecifies how to locate and instantiate resource bundles. Conceptually, the bundle loading process with the givencontrolis performed in the following steps.- This factory method looks up the resource bundle in the cache for
the specified
baseName,targetLocaleandloader. If the requested resource bundle instance is found in the cache and the time-to-live periods of the instance and all of its parent instances have not expired, the instance is returned to the caller. Otherwise, this factory method proceeds with the loading process below. - The
control.getFormatsmethod is called to get resource bundle formats to produce bundle or resource names. The strings"java.class"and"java.properties"designate class-based and property-based resource bundles, respectively. Other strings starting with"java."are reserved for future extensions and must not be used for application-defined formats. Other strings designate application-defined formats. - The
control.getCandidateLocalesmethod is called with the target locale to get a list of candidateLocales for which resource bundles are searched. - The
control.newBundlemethod is called to instantiate aResourceBundlefor the base bundle name, a candidate locale, and a format. (Refer to the note on the cache lookup below.) This step is iterated over all combinations of the candidate locales and formats until thenewBundlemethod returns aResourceBundleinstance or the iteration has used up all the combinations. For example, if the candidate locales areLocale("de", "DE"),Locale("de")andLocale("")and the formats are"java.class"and"java.properties", then the following is the sequence of locale-format combinations to be used to callcontrol.newBundle.Index Localeformat1 Locale("de", "DE")java.class2 Locale("de", "DE")java.properties3 Locale("de")java.class4 Locale("de")java.properties5 Locale("")java.class6 Locale("")java.properties - If the previous step has found no resource bundle, proceed to
Step 6. If a bundle has been found that is a base bundle (a bundle
for
Locale("")), and the candidate locale list only containedLocale(""), return the bundle to the caller. If a bundle has been found that is a base bundle, but the candidate locale list contained locales other than Locale(""), put the bundle on hold and proceed to Step 6. If a bundle has been found that is not a base bundle, proceed to Step 7. - The
control.getFallbackLocalemethod is called to get a fallback locale (alternative to the current target locale) to try further finding a resource bundle. If the method returns a non-null locale, it becomes the next target locale and the loading process starts over from Step 3. Otherwise, if a base bundle was found and put on hold in a previous Step 5, it is returned to the caller now. Otherwise, a MissingResourceException is thrown. - At this point, we have found a resource bundle that's not the base bundle. If this bundle set its parent during its instantiation, it is returned to the caller. Otherwise, its parent chain is instantiated based on the list of candidate locales from which it was found. Finally, the bundle is returned to the caller.
During the resource bundle loading process above, this factory method looks up the cache before calling the
control.newBundlemethod. If the time-to-live period of the resource bundle found in the cache has expired, the factory method calls thecontrol.needsReloadmethod to determine whether the resource bundle needs to be reloaded. If reloading is required, the factory method callscontrol.newBundleto reload the resource bundle. Ifcontrol.newBundlereturnsnull, the factory method puts a dummy resource bundle in the cache as a mark of nonexistent resource bundles in order to avoid lookup overhead for subsequent requests. Such dummy resource bundles are under the same expiration control as specified bycontrol.All resource bundles loaded are cached by default. Refer to
control.getTimeToLivefor details.The following is an example of the bundle loading process with the default
ResourceBundle.Controlimplementation.Conditions:
- Base bundle name:
foo.bar.Messages - Requested
Locale:Locale.ITALY - Default
Locale:Locale.FRENCH - Available resource bundles:
foo/bar/Messages_fr.propertiesandfoo/bar/Messages.properties
First,
getBundletries loading a resource bundle in the following sequence.- class
foo.bar.Messages_it_IT - file
foo/bar/Messages_it_IT.properties - class
foo.bar.Messages_it - file
foo/bar/Messages_it.properties - class
foo.bar.Messages - file
foo/bar/Messages.properties
At this point,
getBundlefindsfoo/bar/Messages.properties, which is put on hold because it's the base bundle.getBundlecallscontrol.getFallbackLocale("foo.bar.Messages", Locale.ITALY)which returnsLocale.FRENCH. Next,getBundletries loading a bundle in the following sequence.- class
foo.bar.Messages_fr - file
foo/bar/Messages_fr.properties - class
foo.bar.Messages - file
foo/bar/Messages.properties
getBundlefindsfoo/bar/Messages_fr.propertiesand creates aResourceBundleinstance. Then,getBundlesets up its parent chain from the list of the candidate locales. Onlyfoo/bar/Messages.propertiesis found in the list andgetBundlecreates aResourceBundleinstance that becomes the parent of the instance forfoo/bar/Messages_fr.properties.- Parameters:
baseName- the base name of the resource bundle, a fully qualified class nametargetLocale- the locale for which a resource bundle is desiredloader- the class loader from which to load the resource bundlecontrol- the control which gives information for the resource bundle loading process- Returns:
- a resource bundle for the given base name and locale
- Throws:
NullPointerException- ifbaseName,targetLocale,loader, orcontrolisnullMissingResourceException- if no resource bundle for the specified base name can be foundIllegalArgumentException- if the givencontroldoesn't perform properly (e.g.,control.getCandidateLocalesreturns null.) Note that validation ofcontrolis performed as needed.UnsupportedOperationException- if this method is called in a named module- Since:
- 1.6
- This factory method looks up the resource bundle in the cache for
the specified
-
clearCache
public static final void clearCache()Removes all resource bundles from the cache that have been loaded by the caller's module.- Since:
- 1.6
- See Also:
-
clearCache
Removes all resource bundles from the cache that have been loaded by the given class loader.- Parameters:
loader- the class loader- Throws:
NullPointerException- ifloaderis null- Since:
- 1.6
- See Also:
-
handleGetObject
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- ifkeyisnull
-
getKeys
Returns an enumeration of the keys.- Returns:
- an
Enumerationof the keys contained in thisResourceBundleand its parent bundles.
-
containsKey
Determines whether the givenkeyis contained in thisResourceBundleor its parent bundles.- Parameters:
key- the resourcekey- Returns:
trueif the givenkeyis contained in thisResourceBundleor its parent bundles;falseotherwise.- Throws:
NullPointerException- ifkeyisnull- Since:
- 1.6
-
keySet
Returns aSetof all keys contained in thisResourceBundleand its parent bundles.- Returns:
- a
Setof all keys contained in thisResourceBundleand its parent bundles. - Since:
- 1.6
-
handleKeySet
Returns aSetof the keys contained only in thisResourceBundle.The default implementation returns a
Setof the keys returned by thegetKeysmethod except for the ones for which thehandleGetObjectmethod returnsnull. Once theSethas been created, the value is kept in thisResourceBundlein order to avoid producing the sameSetin subsequent calls. Subclasses can override this method for faster handling.- Returns:
- a
Setof the keys contained only in thisResourceBundle - Since:
- 1.6
-