public abstract classResourceBundleextendsObject
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 aString
that's used on a button for canceling operations. In "MyResources" theString
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 theResourceBundle
class using thegetBundle
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 aListResourceBundle
that contains two key/value pairs:
Keys are alwayspublic 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 alsoString
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 usegetString
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
. BesidesgetString
,ResourceBundle
also provides a method for getting string arrays,getStringArray
, as well as a genericgetObject
method for any other type of object. When usinggetObject
, 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 ofResourceBundle
,ListResourceBundle
andPropertyResourceBundle
, 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.
IfListResourceBundle
orPropertyResourceBundle
do not suit your needs, you can write your ownResourceBundle
subclass. Your subclasses must override two methods:handleGetObject
andgetKeys()
.
The implementation of aResourceBundle
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 subclassesListResourceBundle
andPropertyResourceBundle
are thread-safe.
ResourceBundle.Control
class provides information necessary to perform the bundle loading process by thegetBundle
factory methods that take aResourceBundle.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 thegetBundle
factory method for details.For thegetBundle
factory methods that take noResourceBundle.Control
instance, their default behavior of resource bundle loading can be modified withinstalledResourceBundleControlProvider
implementations. Any installed providers are detected at theResourceBundle
class loading time. If any of the providers provides aResourceBundle.Control
for the given base name, thatResourceBundle.Control
will be used instead of the defaultResourceBundle.Control
. If there is more than one service provider installed for supporting the same base name, the first one returned fromServiceLoader
will be used.
getBundle
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 thegetBundle
factory method,clearCache
,ResourceBundle.Control.getTimeToLive
, andResourceBundle.Control.needsReload
for details.ResourceBundle
subclass,MyResources
, that manages two resources (for a larger number of resources you would probably use aMap
). 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).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; } 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.ListResourceBundle
,PropertyResourceBundle
,MissingResourceException
Modifier and Type | Class | Description |
---|---|---|
static class | ResourceBundle.Control | ResourceBundle.Control defines a set of callback methods that are invoked by theResourceBundle.getBundle factory methods during the bundle loading process. |
Modifier and Type | Field | Description |
---|---|---|
protectedResourceBundle | parent | The parent bundle of this bundle. |
Constructor | Description |
---|---|
ResourceBundle() | Sole constructor. |
Modifier and Type | Method | Description |
---|---|---|
static void | clearCache() | Removes all resource bundles from the cache that have been loaded using the caller's class loader. |
static void | clearCache(ClassLoader loader) | Removes all resource bundles from the cache that have been loaded using the given class loader. |
boolean | containsKey(String key) | Determines whether the given key is contained in thisResourceBundle or its parent bundles. |
String | getBaseBundleName() | Returns the base name of this bundle, if known, or null if unknown. |
staticResourceBundle | getBundle(String baseName) | Gets a resource bundle using the specified base name, the default locale, and the caller's class loader. |
staticResourceBundle | getBundle(String baseName,Locale locale) | Gets a resource bundle using the specified base name and locale, and the caller's class loader. |
staticResourceBundle | getBundle(String baseName,Locale locale,ClassLoader loader) | Gets a resource bundle using the specified base name, locale, and class loader. |
staticResourceBundle | 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. |
staticResourceBundle | 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. |
staticResourceBundle | getBundle(String baseName,ResourceBundle.Control control) | Returns a resource bundle using the specified base name, the default locale and the specified control. |
abstractEnumeration<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 abstractObject | handleGetObject(String key) | Gets an object for the given key from this resource bundle. |
protectedSet<String> | handleKeySet() | Returns a Set of the keys containedonly in thisResourceBundle . |
Set<String> | keySet() | Returns a Set of all keys contained in thisResourceBundle and its parent bundles. |
protected void | setParent(ResourceBundle parent) | Sets the parent bundle of this bundle. |
protected ResourceBundle parent
getObject
when this bundle does not contain a particular resource.public ResourceBundle()
public String getBaseBundleName()
null
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.ResourceBundle.getBundle(...)
methods.getBundle(java.lang.String, java.util.Locale, java.lang.ClassLoader)
public final String getString(String key)
(String)getObject
(key)
.
key
- the key for the desired stringNullPointerException
- ifkey
isnull
MissingResourceException
- if no object for the given key can be foundClassCastException
- 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 arrayNullPointerException
- 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 arraypublic final Object getObject(String key)
handleGetObject
. 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.key
- the key for the desired objectNullPointerException
- ifkey
isnull
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(), this.getClass().getClassLoader())
,
except thatgetClassLoader()
is run with the security privileges ofResourceBundle
. SeegetBundle
for a complete description of the search and instantiation strategy.baseName
- the base name of the resource bundle, a fully qualified class nameNullPointerException
- ifbaseName
isnull
MissingResourceException
- if no resource bundle for the specified base name can be foundpublic static final ResourceBundle getBundle(String baseName,ResourceBundle.Control control)
getBundle(baseName, Locale.getDefault(), this.getClass().getClassLoader(), control),except that
getClassLoader()
is run with the security privileges ofResourceBundle
. SeegetBundle
for the complete description of the resource bundle loading process with aResourceBundle.Control
.baseName
- the base name of the resource bundle, a fully qualified class namecontrol
- the control which gives information for the resource bundle loading processNullPointerException
- 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.public static final ResourceBundle getBundle(String baseName,Locale locale)
getBundle(baseName, locale, this.getClass().getClassLoader())
,
except thatgetClassLoader()
is run with the security privileges ofResourceBundle
. SeegetBundle
for a complete description of the search and instantiation strategy.baseName
- the base name of the resource bundle, a fully qualified class namelocale
- the locale for which a resource bundle is desiredNullPointerException
- ifbaseName
orlocale
isnull
MissingResourceException
- if no resource bundle for the specified base name can be foundpublic static final ResourceBundle getBundle(String baseName,Locale targetLocale,ResourceBundle.Control control)
getBundle(baseName, targetLocale, this.getClass().getClassLoader(), control),except that
getClassLoader()
is run with the security privileges ofResourceBundle
. SeegetBundle
for the complete description of the resource bundle loading process with aResourceBundle.Control
.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 processLocale
inlocales
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.public static ResourceBundle getBundle(String baseName,Locale locale,ClassLoader loader)
This method behaves the same as callinggetBundle(String, Locale, ClassLoader, Control)
passing a default instance ofResourceBundle.Control
unless anotherResourceBundle.Control
is provided with theResourceBundleControlProvider
SPI. Refer to the description ofmodifying the default behavior.
The following describes the default behavior.
getBundle
uses the base name, the specified locale, and the default locale (obtained fromLocale.getDefault
) to generate a sequence ofcandidate 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_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 someLocale
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 caninstantiate 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:
getBundle
creates a new instance of this class and uses it as theresult resource bundle.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 theresult 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'sgetFallbackLocale
method is called, which returns the current default locale. A new sequence of candidate locale names is generated using this locale and and searched again, as above.
If still no result bundle is found, the base name alone is looked up. If this still fails, aMissingResourceException
is thrown.
Once a result resource bundle has been found, itsparent 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'ssetParent
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:ThebaseName
argument should be a fully qualified class name. However, for compatibility with earlier versions, Sun's 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.classThe 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 isLocale("en", "GB")
.CallinggetBundle
with the locale arguments below will instantiate resource bundles as follows:
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.
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 bundleNullPointerException
- ifbaseName
,locale
, orloader
isnull
MissingResourceException
- if no resource bundle for the specified base name can be foundpublic static ResourceBundle getBundle(String baseName,Locale targetLocale,ClassLoader loader,ResourceBundle.Control control)
getBundle
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.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.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 andproperty-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.control.getCandidateLocales
method is called with the target locale to get a list ofcandidateLocale
s for which resource bundles are searched.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
.Locale | format |
Locale("de", "DE") | java.class |
Locale("de", "DE") | java.properties |
Locale("de") | java.class |
Locale("de") | java.properties |
Locale("") | java.class |
Locale("") | java.properties |
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.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.During the resource bundle loading process above, this factory method looks up the cache before calling thecontrol.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 tocontrol.getTimeToLive
for details.
The following is an example of the bundle loading process with the defaultResourceBundle.Control
implementation.
Conditions:
foo.bar.Messages
Locale
:Locale.ITALY
Locale
:Locale.FRENCH
foo/bar/Messages_fr.properties
andfoo/bar/Messages.properties
First,getBundle
tries loading a resource bundle in the following sequence.
foo.bar.Messages_it_IT
foo/bar/Messages_it_IT.properties
foo.bar.Messages_it
foo/bar/Messages_it.properties
foo.bar.Messages
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.
foo.bar.Messages_fr
foo/bar/Messages_fr.properties
foo.bar.Messages
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
.
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 processNullPointerException
- 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.public static final void clearCache()
ResourceBundle.Control.getTimeToLive(String,Locale)
public static final void clearCache(ClassLoader loader)
loader
- the class loaderNullPointerException
- ifloader
is nullResourceBundle.Control.getTimeToLive(String,Locale)
protected abstract Object handleGetObject(String key)
key
- the key for the desired objectNullPointerException
- ifkey
isnull
public abstract Enumeration<String> getKeys()
Enumeration
of the keys contained in thisResourceBundle
and its parent bundles.public boolean containsKey(String key)
key
is contained in thisResourceBundle
or its parent bundles.key
- the resourcekey
true
if the givenkey
is contained in thisResourceBundle
or its parent bundles;false
otherwise.NullPointerException
- ifkey
isnull
public Set<String> keySet()
Set
of all keys contained in thisResourceBundle
and its parent bundles.Set
of all keys contained in thisResourceBundle
and its parent bundles.protected Set<String> handleKeySet()
Set
of the keys containedonly in thisResourceBundle
.The default implementation returns aSet
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.
Set
of the keys contained only in thisResourceBundle