Class ResourceBundle
- 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
};
}
}
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:
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"));
}
}
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.- Since:
- 1.1
- See Also:
-
Nested Class Summary
Modifier and TypeClassDescriptionstatic class
ResourceBundle.Control
defines a set of callback methods that are invoked by theResourceBundle.getBundle
factory methods during the bundle loading process. -
Field Summary
-
Constructor Summary
-
Method Summary
Modifier and TypeMethodDescriptionstatic final void
Removes all resource bundles from the cache that have been loaded by the caller's module.static final void
clearCache
(ClassLoader loader) Removes all resource bundles from the cache that have been loaded by the given class loader.boolean
containsKey
(String key) Determines whether the givenkey
is contained in thisResourceBundle
or its parent bundles.Returns the base name of this bundle, if known, ornull
if unknown.static final ResourceBundle
Gets a resource bundle using the specified base name, the default locale, and the caller module.static ResourceBundle
Gets a resource bundle using the specified base name and the default locale on behalf of the specified module.static final ResourceBundle
Gets a resource bundle using the specified base name and locale, and the caller module.static ResourceBundle
getBundle
(String baseName, Locale locale, ClassLoader loader) Gets a resource bundle using the specified base name, locale, and class loader.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.static ResourceBundle
Gets a resource bundle using the specified base name and locale on behalf of the specified module.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.static final ResourceBundle
getBundle
(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 Object
Gets an object for the given key from this resource bundle or one of its parents.final String
Gets 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 Object
handleGetObject
(String key) Gets an object for the given key from this resource bundle.Returns aSet
of the keys contained only in thisResourceBundle
.keySet()
Returns aSet
of all keys contained in thisResourceBundle
and its parent bundles.protected void
setParent
(ResourceBundle parent) Sets the parent bundle of this bundle.
-
Field Details
-
parent
The parent bundle of this bundle. The parent bundle is searched bygetObject
when 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, ornull
if unknown. If not null, then this is the value of thebaseName
parameter 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
- ifkey
isnull
MissingResourceException
- 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
- ifkey
isnull
MissingResourceException
- 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'sgetObject
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
- ifkey
isnull
MissingResourceException
- 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 bygetObject
when 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
- ifbaseName
isnull
MissingResourceException
- 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 callinggetBundle(baseName, Locale.getDefault(), this.getClass().getClassLoader(), control);
getClassLoader()
is run with the security privileges ofResourceBundle
. SeegetBundle
for 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
- ifbaseName
orcontrol
isnull
MissingResourceException
- if no resource bundle for the specified base name can be foundIllegalArgumentException
- if the givencontrol
doesn't perform properly (e.g.,control.getCandidateLocales
returns null.) Note that validation ofcontrol
is 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
- ifbaseName
orlocale
isnull
MissingResourceException
- 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
- ifbaseName
ormodule
isnull
SecurityException
- 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
ResourceBundleProvider
for 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
module
is 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. CustomResourceBundleControlProvider
implementations, 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
, ormodule
isnull
SecurityException
- 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 callinggetBundle(baseName, targetLocale, this.getClass().getClassLoader(), control);
getClassLoader()
is run with the security privileges ofResourceBundle
. SeegetBundle
for 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
Locale
inlocales
- Throws:
NullPointerException
- ifbaseName
,locales
orcontrol
isnull
MissingResourceException
- if no resource bundle for the specified base name in any of thelocales
can be found.IllegalArgumentException
- if the givencontrol
doesn't perform properly (e.g.,control.getCandidateLocales
returns null.) Note that validation ofcontrol
is 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:
getBundle(baseName, targetLocale, callerModule);
getBundle(baseName, targetLocale, loader, control);
control
is the default instance ofResourceBundle.Control
unless aControl
instance is provided byResourceBundleControlProvider
SPI. Refer to the description of modifying the default behavior. The following describes the default behavior.Resource Bundle Search and Loading Strategy
getBundle
uses 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 + "_" + language
Candidate 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_de
In 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
Locale
s, 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 ofgetCandidateLocales
for details.getBundle
then 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'getFormats
method, 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,
getBundle
creates a new instance of this class and uses it as the result resource bundle. - Otherwise,
getBundle
attempts 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 ofgetResource
has 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 newPropertyResourceBundle
instance 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
getFallbackLocale
method 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
MissingResourceException
is 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,
getBundle
examines 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
setParent
method 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:
getBundle
caches instantiated resource bundles and might return the same resource bundle instance multiple times.Note:The
baseName
argument 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 accessPropertyResourceBundle
s 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
ResourceBundle
for the ".class" files, syntactically correct ".properties" files). The default locale isLocale("en", "GB")
.Calling
getBundle
with 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
loader
is 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
, orloader
isnull
MissingResourceException
- 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 thegetBundle
factory methods with nocontrol
argument, the givencontrol
specifies how to locate and instantiate resource bundles. Conceptually, the bundle loading process with the givencontrol
is performed in the following steps.- This factory method looks up the resource bundle in the cache for
the specified
baseName
,targetLocale
andloader
. 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.getFormats
method 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.getCandidateLocales
method is called with the target locale to get a list of candidateLocale
s for which resource bundles are searched. - The
control.newBundle
method is called to instantiate aResourceBundle
for 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 thenewBundle
method returns aResourceBundle
instance 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 Locale
format
1 Locale("de", "DE")
java.class
2 Locale("de", "DE")
java.properties
3 Locale("de")
java.class
4 Locale("de")
java.properties
5 Locale("")
java.class
6 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.getFallbackLocale
method 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.newBundle
method. If the time-to-live period of the resource bundle found in the cache has expired, the factory method calls thecontrol.needsReload
method to determine whether the resource bundle needs to be reloaded. If reloading is required, the factory method callscontrol.newBundle
to reload the resource bundle. Ifcontrol.newBundle
returnsnull
, 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.getTimeToLive
for details.The following is an example of the bundle loading process with the default
ResourceBundle.Control
implementation.Conditions:
- Base bundle name:
foo.bar.Messages
- Requested
Locale
:Locale.ITALY
- Default
Locale
:Locale.FRENCH
- Available resource bundles:
foo/bar/Messages_fr.properties
andfoo/bar/Messages.properties
First,
getBundle
tries 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,
getBundle
findsfoo/bar/Messages.properties
, which is put on hold because it's the base bundle.getBundle
callscontrol.getFallbackLocale("foo.bar.Messages", Locale.ITALY)
which returnsLocale.FRENCH
. Next,getBundle
tries 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
getBundle
findsfoo/bar/Messages_fr.properties
and creates aResourceBundle
instance. Then,getBundle
sets up its parent chain from the list of the candidate locales. Onlyfoo/bar/Messages.properties
is found in the list andgetBundle
creates aResourceBundle
instance 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
, orcontrol
isnull
MissingResourceException
- if no resource bundle for the specified base name can be foundIllegalArgumentException
- if the givencontrol
doesn't perform properly (e.g.,control.getCandidateLocales
returns null.) Note that validation ofcontrol
is 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
- ifloader
is 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
- ifkey
isnull
-
getKeys
Returns an enumeration of the keys.- Returns:
- an
Enumeration
of the keys contained in thisResourceBundle
and its parent bundles.
-
containsKey
Determines whether the givenkey
is contained in thisResourceBundle
or its parent bundles.- Parameters:
key
- the resourcekey
- Returns:
true
if the givenkey
is contained in thisResourceBundle
or its parent bundles;false
otherwise.- Throws:
NullPointerException
- ifkey
isnull
- Since:
- 1.6
-
keySet
-
handleKeySet
Returns aSet
of the keys contained only in thisResourceBundle
.The default implementation returns a
Set
of the keys returned by thegetKeys
method except for the ones for which thehandleGetObject
method returnsnull
. Once theSet
has been created, the value is kept in thisResourceBundle
in order to avoid producing the sameSet
in subsequent calls. Subclasses can override this method for faster handling.- Returns:
- a
Set
of the keys contained only in thisResourceBundle
- Since:
- 1.6
-