org.springframework.context.support

Class ReloadableResourceBundleMessageSource

java.lang.Object

org.springframework.context.support.MessageSourceSupport

org.springframework.context.support.AbstractMessageSource

org.springframework.context.support.ReloadableResourceBundleMessageSource

All Implemented Interfaces:

Aware, HierarchicalMessageSource, MessageSource, ResourceLoaderAware

public class ReloadableResourceBundleMessageSource
extends AbstractMessageSource
implements ResourceLoaderAware

Spring-specific MessageSource implementation that accesses resource bundles using specified basenames, participating in the Spring ApplicationContext's resource loading.

In contrast to the JDK-based ResourceBundleMessageSource, this class uses Properties instances as its custom data structure for messages, loading them via a PropertiesPersister strategy from Spring Resource handles. This strategy is not only capable of reloading files based on timestamp changes, but also of loading properties files with a specific character encoding. It will detect XML property files as well.

In contrast to ResourceBundleMessageSource, this class supports reloading of properties files through the "cacheSeconds" setting, and also through programmatically clearing the properties cache. Since application servers typically cache all files loaded from the classpath, it is necessary to store resources somewhere else (for example, in the "WEB-INF" directory of a web app). Otherwise changes of files in the classpath will not be reflected in the application.

Note that the base names set as "basenames" property are treated in a slightly different fashion than the "basenames" property of ResourceBundleMessageSource. It follows the basic ResourceBundle rule of not specifying file extension or language codes, but can refer to any Spring resource location (instead of being restricted to classpath resources). With a "classpath:" prefix, resources can still be loaded from the classpath, but "cacheSeconds" values other than "-1" (caching forever) will not work in this case.

This MessageSource implementation is usually slightly faster than ResourceBundleMessageSource, which builds on ResourceBundle - in the default mode, i.e. when caching forever. With "cacheSeconds" set to 1, message lookup takes about twice as long - with the benefit that changes in individual properties files are detected with a maximum delay of 1 second. Higher "cacheSeconds" values usually do not make a significant difference.

This MessageSource can easily be used outside of an ApplicationContext: It will use a DefaultResourceLoader as default, simply getting overridden with the ApplicationContext's resource loader if running in a context. It does not have any other specific dependencies.

Thanks to Thomas Achleitner for providing the initial implementation of this message source!

Author:

Juergen Hoeller

See Also:

setCacheSeconds(int), setBasenames(java.lang.String...), setDefaultEncoding(java.lang.String), setFileEncodings(java.util.Properties), setPropertiesPersister(org.springframework.util.PropertiesPersister), setResourceLoader(org.springframework.core.io.ResourceLoader), DefaultPropertiesPersister, DefaultResourceLoader, ResourceBundleMessageSource, ResourceBundle

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	ReloadableResourceBundleMessageSource.PropertiesHolder PropertiesHolder for caching.

Field Summary

Fields inherited from class org.springframework.context.support.MessageSourceSupport

logger

Constructor Summary

Constructors

Constructor and Description
ReloadableResourceBundleMessageSource()

Method Summary

Modifier and Type	Method and Description
protected List<String>	calculateAllFilenames(String basename, Locale locale) Calculate all filenames for the given bundle basename and Locale.
protected List<String>	calculateFilenamesForLocale(String basename, Locale locale) Calculate the filenames for the given bundle basename and Locale, appending language code, country code, and variant code.
void	clearCache() Clear the resource bundle cache.
void	clearCacheIncludingAncestors() Clear the resource bundle caches of this MessageSource and all its ancestors.
protected ReloadableResourceBundleMessageSource.PropertiesHolder	getMergedProperties(Locale locale) Get a PropertiesHolder that contains the actually visible properties for a Locale, after merging all specified resource bundles.
protected ReloadableResourceBundleMessageSource.PropertiesHolder	getProperties(String filename) Get a PropertiesHolder for the given filename, either from the cache or freshly loaded.
protected Properties	loadProperties(Resource resource, String filename) Load the properties from the given resource.
protected Properties	newProperties() Template method for creating a plain new Properties instance.
protected ReloadableResourceBundleMessageSource.PropertiesHolder	refreshProperties(String filename, ReloadableResourceBundleMessageSource.PropertiesHolder propHolder) Refresh the PropertiesHolder for the given bundle filename.
protected MessageFormat	resolveCode(String code, Locale locale) Resolves the given message code as key in the retrieved bundle files, using a cached MessageFormat instance per message code.
protected String	resolveCodeWithoutArguments(String code, Locale locale) Resolves the given message code as key in the retrieved bundle files, returning the value found in the bundle as-is (without MessageFormat parsing).
void	setBasename(String basename) Set a single basename, following the basic ResourceBundle convention of not specifying file extension or language codes, but in contrast to ResourceBundleMessageSource referring to a Spring resource location: e.g.
void	setBasenames(String... basenames) Set an array of basenames, each following the basic ResourceBundle convention of not specifying file extension or language codes, but in contrast to ResourceBundleMessageSource referring to a Spring resource location: e.g.
void	setCacheSeconds(int cacheSeconds) Set the number of seconds to cache loaded properties files.
void	setConcurrentRefresh(boolean concurrentRefresh) Specify whether to allow for concurrent refresh behavior, i.e.
void	setDefaultEncoding(String defaultEncoding) Set the default charset to use for parsing properties files.
void	setFallbackToSystemLocale(boolean fallbackToSystemLocale) Set whether to fall back to the system Locale if no files for a specific Locale have been found.
void	setFileEncodings(Properties fileEncodings) Set per-file charsets to use for parsing properties files.
void	setPropertiesPersister(PropertiesPersister propertiesPersister) Set the PropertiesPersister to use for parsing properties files.
void	setResourceLoader(ResourceLoader resourceLoader) Set the ResourceLoader to use for loading bundle properties files.
String	toString()

Methods inherited from class org.springframework.context.support.AbstractMessageSource

getCommonMessages, getDefaultMessage, getMessage, getMessage, getMessage, getMessageFromParent, getMessageInternal, getParentMessageSource, isUseCodeAsDefaultMessage, resolveArguments, setCommonMessages, setParentMessageSource, setUseCodeAsDefaultMessage

Methods inherited from class org.springframework.context.support.MessageSourceSupport

createMessageFormat, formatMessage, isAlwaysUseMessageFormat, renderDefaultMessage, setAlwaysUseMessageFormat

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

ReloadableResourceBundleMessageSource

public ReloadableResourceBundleMessageSource()

Method Detail

setBasename

public void setBasename(String basename)

Set a single basename, following the basic ResourceBundle convention of not specifying file extension or language codes, but in contrast to ResourceBundleMessageSource referring to a Spring resource location: e.g. "WEB-INF/messages" for "WEB-INF/messages.properties", "WEB-INF/messages_en.properties", etc.

XML properties files are also supported: .g. "WEB-INF/messages" will find and load "WEB-INF/messages.xml", "WEB-INF/messages_en.xml", etc as well.

Parameters:

basename - the single basename

See Also:

setBasenames(java.lang.String...), ResourceEditor, ResourceBundle

setBasenames

public void setBasenames(String... basenames)

Set an array of basenames, each following the basic ResourceBundle convention of not specifying file extension or language codes, but in contrast to ResourceBundleMessageSource referring to a Spring resource location: e.g. "WEB-INF/messages" for "WEB-INF/messages.properties", "WEB-INF/messages_en.properties", etc.

XML properties files are also supported: .g. "WEB-INF/messages" will find and load "WEB-INF/messages.xml", "WEB-INF/messages_en.xml", etc as well.

The associated resource bundles will be checked sequentially when resolving a message code. Note that message definitions in a previous resource bundle will override ones in a later bundle, due to the sequential lookup.

Parameters:

basenames - an array of basenames

See Also:

setBasename(java.lang.String), ResourceBundle

setDefaultEncoding

public void setDefaultEncoding(String defaultEncoding)

Set the default charset to use for parsing properties files. Used if no file-specific charset is specified for a file.

Default is none, using the java.util.Properties default encoding: ISO-8859-1.

Only applies to classic properties files, not to XML files.

Parameters:

defaultEncoding - the default charset

See Also:

setFileEncodings(java.util.Properties), PropertiesPersister.load(java.util.Properties, java.io.InputStream)

setFileEncodings

public void setFileEncodings(Properties fileEncodings)

Set per-file charsets to use for parsing properties files.

Only applies to classic properties files, not to XML files.

Parameters:

fileEncodings - Properties with filenames as keys and charset names as values. Filenames have to match the basename syntax, with optional locale-specific appendices: e.g. "WEB-INF/messages" or "WEB-INF/messages_en".

See Also:

setBasenames(java.lang.String...), PropertiesPersister.load(java.util.Properties, java.io.InputStream)

setFallbackToSystemLocale

public void setFallbackToSystemLocale(boolean fallbackToSystemLocale)

Set whether to fall back to the system Locale if no files for a specific Locale have been found. Default is "true"; if this is turned off, the only fallback will be the default file (e.g. "messages.properties" for basename "messages").

Falling back to the system Locale is the default behavior of java.util.ResourceBundle. However, this is often not desirable in an application server environment, where the system Locale is not relevant to the application at all: Set this flag to "false" in such a scenario.

setCacheSeconds

public void setCacheSeconds(int cacheSeconds)

Set the number of seconds to cache loaded properties files.

• Default is "-1", indicating to cache forever (just like java.util.ResourceBundle).
• A positive number will cache loaded properties files for the given number of seconds. This is essentially the interval between refresh checks. Note that a refresh attempt will first check the last-modified timestamp of the file before actually reloading it; so if files don't change, this interval can be set rather low, as refresh attempts will not actually reload.
• A value of "0" will check the last-modified timestamp of the file on every message access. Do not use this in a production environment!

setConcurrentRefresh

public void setConcurrentRefresh(boolean concurrentRefresh)

Specify whether to allow for concurrent refresh behavior, i.e. one thread locked in a refresh attempt for a specific cached properties file whereas other threads keep returning the old properties for the time being, until the refresh attempt has completed.

Default is "true": This behavior is new as of Spring Framework 4.1, minimizing contention between threads. If you prefer the old behavior, i.e. to fully block on refresh, switch this flag to "false".

See Also:

setCacheSeconds(int)

setPropertiesPersister

public void setPropertiesPersister(PropertiesPersister propertiesPersister)

Set the PropertiesPersister to use for parsing properties files.

The default is a DefaultPropertiesPersister.

See Also:

DefaultPropertiesPersister

setResourceLoader

public void setResourceLoader(ResourceLoader resourceLoader)

Set the ResourceLoader to use for loading bundle properties files.

The default is a DefaultResourceLoader. Will get overridden by the ApplicationContext if running in a context, as it implements the ResourceLoaderAware interface. Can be manually overridden when running outside of an ApplicationContext.

Specified by:

setResourceLoader in interface ResourceLoaderAware

Parameters:

resourceLoader - ResourceLoader object to be used by this object

See Also:

DefaultResourceLoader, ResourceLoaderAware

resolveCodeWithoutArguments

protected String resolveCodeWithoutArguments(String code,
                                             Locale locale)

Resolves the given message code as key in the retrieved bundle files, returning the value found in the bundle as-is (without MessageFormat parsing).

Overrides:

resolveCodeWithoutArguments in class AbstractMessageSource

Parameters:

code - the code of the message to resolve

locale - the Locale to resolve the code for (subclasses are encouraged to support internationalization)

Returns:

the message String, or null if not found

See Also:

AbstractMessageSource.resolveCode(java.lang.String, java.util.Locale), MessageFormat

resolveCode

protected MessageFormat resolveCode(String code,
                                    Locale locale)

Resolves the given message code as key in the retrieved bundle files, using a cached MessageFormat instance per message code.

Specified by:

resolveCode in class AbstractMessageSource

Parameters:

code - the code of the message to resolve

locale - the Locale to resolve the code for (subclasses are encouraged to support internationalization)

Returns:

the MessageFormat for the message, or null if not found

See Also:

AbstractMessageSource.resolveCodeWithoutArguments(String, java.util.Locale)

getMergedProperties

protected ReloadableResourceBundleMessageSource.PropertiesHolder getMergedProperties(Locale locale)

Get a PropertiesHolder that contains the actually visible properties for a Locale, after merging all specified resource bundles. Either fetches the holder from the cache or freshly loads it.

Only used when caching resource bundle contents forever, i.e. with cacheSeconds < 0. Therefore, merged properties are always cached forever.

calculateAllFilenames

protected List<String> calculateAllFilenames(String basename,
                                             Locale locale)

Calculate all filenames for the given bundle basename and Locale. Will calculate filenames for the given Locale, the system Locale (if applicable), and the default file.

Parameters:

basename - the basename of the bundle

locale - the locale

Returns:

the List of filenames to check

See Also:

setFallbackToSystemLocale(boolean), calculateFilenamesForLocale(java.lang.String, java.util.Locale)

calculateFilenamesForLocale

protected List<String> calculateFilenamesForLocale(String basename,
                                                   Locale locale)

Calculate the filenames for the given bundle basename and Locale, appending language code, country code, and variant code. E.g.: basename "messages", Locale "de_AT_oo" -> "messages_de_AT_OO", "messages_de_AT", "messages_de".

Follows the rules defined by Locale.toString().

Parameters:

basename - the basename of the bundle

locale - the locale

Returns:

the List of filenames to check

getProperties

protected ReloadableResourceBundleMessageSource.PropertiesHolder getProperties(String filename)

Get a PropertiesHolder for the given filename, either from the cache or freshly loaded.

Parameters:

filename - the bundle filename (basename + Locale)

Returns:

the current PropertiesHolder for the bundle

refreshProperties

protected ReloadableResourceBundleMessageSource.PropertiesHolder refreshProperties(String filename,
                                                                                   ReloadableResourceBundleMessageSource.PropertiesHolder propHolder)

Refresh the PropertiesHolder for the given bundle filename. The holder can be null if not cached before, or a timed-out cache entry (potentially getting re-validated against the current last-modified timestamp).

Parameters:

filename - the bundle filename (basename + Locale)

propHolder - the current PropertiesHolder for the bundle

loadProperties

protected Properties loadProperties(Resource resource,
                                    String filename)
                             throws IOException

Load the properties from the given resource.

Parameters:

resource - the resource to load from

filename - the original bundle filename (basename + Locale)

Returns:

the populated Properties instance

Throws:

IOException - if properties loading failed

newProperties

protected Properties newProperties()

Template method for creating a plain new Properties instance. The default implementation simply calls Properties.Properties().

Allows for returning a custom Properties extension in subclasses. Overriding methods should just instantiate a custom Properties subclass, with no further initialization or population to be performed at that point.

Returns:

a plain Properties instance

Since:

4.2

clearCache

public void clearCache()

Clear the resource bundle cache. Subsequent resolve calls will lead to reloading of the properties files.

clearCacheIncludingAncestors

public void clearCacheIncludingAncestors()

Clear the resource bundle caches of this MessageSource and all its ancestors.

See Also:

clearCache()

toString

public String toString()

Overrides:

toString in class Object