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| e-docs > WebLogic Server > Internationalization Guide > Using Message Catalogs with BEA WebLogic Server |
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Internationalization Guide
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Using Message Catalogs with BEA WebLogic Server
The following sections describe message catalogs and how to use them:
Message catalogs are XML files that contain a description of a collection of text messages, each indexed by a unique idenifier. You compile these XML files into classes during the i18ngen utility build process. (Refer to 18ngen Utility for more information). The methods of the resulting classes are the objects used to log messages at runtime.
Message catalogs support multiple locales or languages. For a specific message catalog there is exactly one default version, known as the top-level catalog. Then there are corresponding locale-specific catalogs, one for each additional supported locale. The top-level catalog includes all the information necessary to define the message. The locale-specific catalogs contain only the message ID, the date changed, and the translation of the message for the specific locale.
The message catalog files are defined by an XML document type definition (DTD). The DTDs are stored in the msgcat directory. The location of the msgcat directory may vary, depending upon where you installed WebLogic Server. If you used the default installation path, the msgcat directory is located in the BEA_HOME directory under WL_HOME\samples\server\src\examples\i18n\msgcat.
Two DTDs are included in the WebLogic Server distribution:
The msgcat directory also contains templates that you can use to create top-level and locale-specific message catalogs.
Users may choose to create a single log message catalog for all their logging requirements, or create smaller catalogs based on a subsystem or Java package. We recommend using multiple subsystems because you can focus on specific portions of the log during viewing.
For simple text catalogs, the recommended approach is to create a single catalog for each utility being internationalized. Developers can create site-specific message catalogs using the Message Editor as described in Using the BEA WebLogic Server Message Editor.
All messages and exceptions must be defined in the default, top-level catalog. The WebLogic Server distribution includes a collection of sample catalogs in the WL_HOME\samples\server\src\examples\i18n\msgcat directory.
Note: This directory path may vary, depending on where you chose to install WebLogic Server.
Catalogs that provide different localizations of the base catalogs are defined in msgcat subdirectories named for the locale (for example, msgcat\de for Germany). You might have a top-level catalog named mycat.xml, and a German translation of it called ..\de\mycat.xml. Typically the top-level catalog is English, but English is not required for any catalogs except the installed WebLogic Server catalogs.
Locale designations (for example, de) also have a hierarchy as defined in the java.util.Locale documentation. A locale can include a language, country, and variant. Language is the most common locale designation. Language can be extended with a country code. For instance, en\US, indicates American English. The name of the associated catalog is ..\en\US\mycat.xml. Variants are vendor or browser-specific and are used to introduce minor differences (for example, collation sequences) between two or more locales defined by either language or country.
Choosing Names for Message Catalogs
Because the name of a message catalog file (without the .xml extension) is used to generate runtime class and property names, you should choose the name carefully.
Follow these guidelines for naming message catalogs:
For example, the resulting class names for a catalog named Xyz.xml are XyzLogLocalizer and XyzLogger.
The following considerations also apply to message catalog files:
The message body, message detail, cause, and action sections of a log message can include message arguments, as described by java.text.MessageFormat. Only the message body section in a simple message can include arguments. Arguments are values that can be dynamically set at runtime. These values are passed to routines, such as printing out a message. A message can support up to 10 arguments, numbered 0-9. You can include any subset of these arguments in any text section of the message definition, although the message body should include all of the arguments. You insert message arguments into a message definition during development, and these arguments are replaced by the appropriate message content at runtime when the message is logged.
The following excerpt from an XML log message definition shows how you can use message arguments. The argument number must correspond to one of the arguments specified in the method attribute. Specifically, {0} with the first argument, {1} with the second, and so on.
Listing 2-1 Example of Message Arguments
<messagebody>Unable to open file, {0}.</messagebody>
<messagedetail>
File, {0} does not exist. The server will restore the file
contents from {1}, resulting in the use of default values
for all future requests.
</messagedetail>
<cause>The file was deleted</cause>
<action>
If this error repeats then investigate unauthorized access to
the file system.
</action>An example of a method attribute for the above message is as follows:
-method="logNoFile(String name, String path)"
The message expects two arguments, {0} and {1}:
In addition, the arguments are expected to be strings, or representable as strings. Numeric data is represented as {n,number}. Dates are supported as {n,date}. You must assign a severity level for log messages. Log messages are generated through the generated Logger methods, as defined by the method attribute.
The catalog format for top-level and locale-specific catalog files is slightly different. The top-level catalogs define the textual messages for the base locale. Locale-specific catalogs only provide translations of text defined in the top-level version. Log message catalogs are defined differently from simple text catalogs.
Elements of each of these types of catalogs are described in the following sections:
Elements of a Log Message Catalog
This section provides reference information for the following elements of a log message catalog:
The following table describes the attributes that you can define for the message_catalog element.
The following table describes the attributes that you can define for the log_message element.
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Unique identifier for this log message. Uniqueness should extend across all catalogs. Value must be in range defined by baseid and endid attributes. This is a child element of message_catalog. |
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Date/time stamp used for managing modifications to this message. The date is supplied by utilities that run on the catalogs. The syntax is: |
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Indicates the severity of the log message. Must be one of the following: debug, info, warning, notice, error, critical, alert, or emergency. User catalogs may only use debug, info, warning, and error. |
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Indicates whether to generate a stack trace for Throwable arguments. Possible values are true or false. When the value is true a trace is generated. The syntax is: |
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Method signature for logging this message. Two methods are actually provided: the one specified here and a similar one with an additional Throwable argument. The syntax is the standard Java method signature, without the qualifiers, semicolon, and extensions. Argument types can be any Java primitive or class. Classes must be fully qualified if not in java.lang. Classes must also conform to java.text.MessageFormat conventions. In general, class arguments should have a useful toString() method. Arguments can be any valid name, but should follow the convention of argn where n is 0 thru 9. There can be no more than ten (10) arguments. For each argn there should be at least one corresponding placeholder in the text elements described inOther log_message Catalog Elements Placeholders are of the form {n}, {n,number} or {n,date}. |
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Indicates whether to generate methods to return Loggable objects for each message. The syntax is: |
Other log_message Catalog Elements
The following table describes the child elements of the log_message element.
The following example shows a log message catalog, MyUtilLog.xml, with one log message.
Listing 2-2 Example of a Log Message Catalog
<?xml version="1.0"?>
<!DOCTYPE message_catalog PUBLIC "weblogic-message-catalog-dtd" "http://www.bea.com/servers/wls700/dtd/msgcat.dtd">
<message_catalog
l10n_package="programs.utils"
i18n_package="programs.utils"
subsystem="MYUTIL"
version="1.0"
baseid="600000"
endid="600100"
<log_message
messageid="600001"
severity="warning"
method="logNoAuthorization(String arg0, java.util.Date arg1,
int arg2)"
<messagebody>
Could not open file, {0} on {1,date} after {2,number} attempts.
</messagebody>
<messagedetail>
The configuration for this application will be defaulted to
factory settings. Custom configuration information resides
in file, {0}, created on {1,date}, but is not readable.
</messagedetail>
<cause>
The user is not authorized to use custom configurations. Custom
configuration information resides in file, {0}, created on
{1,date}, but is not readable.The attempt has been logged to
the security log.
</cause>
<action>
The user needs to gain approriate authorization or learn to
live with the default settings.
</action>
</log_message>
</message_catalog>
Elements of a Simple Text Message Catalog
This section provides reference information for the following simple text message catalog elements:
The following table describes the attributes that you can define for the message_catalog element.
The following table describes the attributes that you can define for the message element.
The following table describes the child element of the message element.
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The text associated with the message. This element may contain zero or more placeholders {n} that will be replaced by the appropriate arguments when the log message is localized. |
The following example shows a simple text catalog, MyUtilLabels.xml, with one text definition.
Listing 2-3 Example of a Simple Text Catalog
<?xml version="1.0"?>
<!DOCTYPE message_catalog PUBLIC "weblogic-message-catalog-dtd"
"http://www.bea.com/servers/wls700/dtd/msgcat.dtd">
<message_catalog>
l10n_package="programs.utils"
i18n_package="programs.utils"
subsystem="MYUTIL"
version="1.0"
<message>
messageid="FileMenuTitle"
<messagebody>
File
</messagebody>
</message>
</message_catalog>
Elements of a Locale-Specific Catalog
The locale-specific catalogs are subsets of top-level catalogs. They are maintained in subdirectories named for the locales they represent. The elements and attributes described in the following sections are valid for locale-specific catalogs.
The following table describes the attributes that you can define for the locale_message_catalog element.
The locale-specific catalog uses the attributes defined for the log_message element in the log message catalog so this element does not need to be defined.
Other locale_message_catalog Elements
The locale-specific catalog uses the messagebody, messagedetail, cause, and action catalog elements defined for the log message catalog so these elements do not need to be defined.
The following example shows a French translation of a message that is available in ...\msgcat\fr\MyUtilLabels.xml.
The translated message appears as shown in Listing 2-4.
Listing 2-4 Example of a Message Translated to French
<?xml version="1.0"?>
<!DOCTYPE message_catalog PUBLIC
"weblogic-locale-message-catalog-dtd"
"http://www.bea.com/servers/wls700/dtd/l10n_msgcat.dtd">
<locale_message_catalog
l10n_package="programs.utils"
subsystem="MYUTIL"
version="1.0">
<message>
<messageid="FileMenuTitle">
<messagebody> Fichier </messagebody>
</message>
</locale_message_catalog>
When entering text in the messagebody, messagedetail, cause and action elements, you must use a tool that generates valid Unicode Transformation Format-8 (UTF-8) characters, and have appropriate keyboard mappings installed. UTF-8 is an efficient encoding of Unicode character-strings that optimizes the encoding ASCII characters. Message catalogs always use UTF-8 encoding. The MessageLocalizer utility that is downloaded with WebLogic Server is a tool that can be used to generate valid UTF-8 characters.
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