Class MessageFormatter
- java.lang.Object
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- com.ibm.icu.message2.MessageFormatter
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@Deprecated public class MessageFormatter extends java.lang.Object
Deprecated.This API is for technology preview only.Overview of
MessageFormatter
In ICU4J, the
MessageFormatter
class is the next iteration ofMessageFormat
. This new version will build on the lessons learned from using MessageFormat for 25 years in various environments, when used directly or as a base for other public APIs.The effort to design a succesor to
MessageFormat
will result in a specification referred to as MessageFormat 2.0. The reasoning for this effort is shared in the “Why MessageFormat needs a successor” document.MessageFormat 2.0 will be more modular and easier to port and backport. It will also provide extension points via interfaces to allow users to supply new formatters and selectors without having to modify the specification. ICU will eventually include support for new formatters, such as intervals, relative time, lists, measurement units, personal names, and more, as well as the ability for users to supply their own custom implementations. These will potentially support use cases like grammatical gender, inflection, markup regimes (such as those require for text-to-speech), and other complex message management needs.
The MessageFormat Working Group, which develops the new data model, semantics, and syntax, is hosted on GitHub. The current specification for the syntax and data model can be found here.
This technical preview implements enough functions for
MessageFormatter
to be useful in many situations, but the final set of functions and the parameters accepted by those functions is not yet finalized.Examples
Basic usage
import static org.junit.Assert.assertEquals; import java.util.Date; import java.util.HashMap; import java.util.Locale; import java.util.Map; import com.ibm.icu.message2.MessageFormatter; @Test public void testMf2() { final Locale enGb = Locale.forLanguageTag("en-GB"); Map
arguments = new HashMap<>(); arguments.put("name", "John"); arguments.put("exp", new Date(1679971371000L)); // March 27, 2023, 7:42:51 PM MessageFormatter mf2 = MessageFormatter.builder() .setPattern("{Hello {$name}, your card expires on {$exp :datetime skeleton=yMMMdE}!}") .setLocale(enGb) .build(); assertEquals( "Hello John, your card expires on Mon, 27 Mar 2023!", mf2.formatToString(arguments)); } Placeholder examples
Code to set runtime value for placeholder Examples of placeholder in message pattern arguments.put("name", "John")
}$name~
arguments.put("exp", new Date(…))
}$exp :datetime skeleton=yMMMdE~
}$exp :datetime datestyle=full~
arguments.put("val", 3.141592653)
}$val~
}$val :number skeleton=(.####)~
No argument for fixed values known at build time }(123456789.531) :number~
Plural selection message
@Test public void testMf2Selection() { final String message = "match {$count :plural}\n" + " when one {You have one notification.}\n" + " when * {You have {$count} notifications.}\n"; final Locale enGb = Locale.forLanguageTag("en-GB"); Map
arguments = new HashMap<>(); MessageFormatter mf2 = MessageFormatter.builder() .setPattern(message) .setLocale(enGb) .build(); arguments.put("count", 1); assertEquals( "You have one notification.", mf2.formatToString(arguments)); arguments.put("count", 42); assertEquals( "You have 42 notifications.", mf2.formatToString(arguments)); } Built-in formatter functions
The tech preview implementation comes with formatters for numbers (
number
), date / time (datetime
), plural selectors (plural
andselectordinal
), and general selector (select
), very similar to what MessageFormat offers.The ICU test code covers most features, and has examples of how to make custom placeholder formatters; you can look for classes that implement
com.ibm.icu.message2.FormatterFactory
(they are namedCustom*Test.java
).Functions currently implemented
These are the functions interpreted right now:
datetime
Similar to MessageFormat's date
andtime
.datestyle
andtimestyle
Similar toargStyle : short | medium | long | full
.
Same values are accepted, but we can use both in one placeholder, for example{$due :datetime datestyle=full timestyle=long}
.pattern
Similar toargStyle = argStyleText
.
This is bad i18n practice, and will probably be dropped.
This is included just to support migration to MessageFormat 2.skeleton
Same asargStyle = argSkeletonText
.
These are the date/time skeletons as supported bySimpleDateFormat
.number
Similar to MessageFormat's number
.skeleton
These are the number skeletons as supported byNumberFormatter
.minimumFractionDigits
Only implemented to be able to pass the unit tests from the ECMA tech preview implementation, which prefers options bags to skeletons.
TBD if the final function will support skeletons, option backs, or both.offset
Used to support plural with an offset.identity
Returns the direct string value of the argument (calling toString()
).plural
Similar to MessageFormat's plural
.skeleton
These are the number skeletons as supported byNumberFormatter
.
Can also be indirect, from a local variable of typenumber
(recommended).offset
Used to support plural with an offset.
Can also be indirect, from a local variable of typenumber
(recommended).selectordinal
Similar to MessageFormat's selectordinal
.
For now it accepts the same parameters asplural
, although there is no use case for them.
TBD if this will be merged intoplural
(with somekind
option) or not.select
Literal match, same as MessageFormat's select
.
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
MessageFormatter.Builder
Deprecated.This API is for technology preview only.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods Modifier and Type Method Description static MessageFormatter.Builder
builder()
Deprecated.This API is for technology preview only.FormattedMessage
format(java.util.Map<java.lang.String,java.lang.Object> arguments)
Deprecated.This API is for technology preview only.java.lang.String
formatToString(java.util.Map<java.lang.String,java.lang.Object> arguments)
Deprecated.This API is for technology preview only.Mf2DataModel
getDataModel()
Deprecated.This API is for technology preview only.java.util.Locale
getLocale()
Deprecated.This API is for technology preview only.java.lang.String
getPattern()
Deprecated.This API is for technology preview only.
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Method Detail
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builder
@Deprecated public static MessageFormatter.Builder builder()
Deprecated.This API is for technology preview only.Creates a builder.- Returns:
- the Builder.
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getLocale
@Deprecated public java.util.Locale getLocale()
Deprecated.This API is for technology preview only.Get the locale to use for all the formatting and selections in the currentMessageFormatter
.- Returns:
- the locale.
-
getPattern
@Deprecated public java.lang.String getPattern()
Deprecated.This API is for technology preview only.Get the pattern (the serialized message in MessageFormat 2 syntax) of the currentMessageFormatter
.If the
MessageFormatter
was created from anMf2DataModel
the this string is generated from that model.- Returns:
- the pattern.
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getDataModel
@Deprecated public Mf2DataModel getDataModel()
Deprecated.This API is for technology preview only.Give public access to the message data model.This data model is similar to the functionality we have today in
MessagePatternUtil
maybe even a bit more higher level.We can also imagine a model where one parses the string syntax, takes the data model, modifies it, and then uses that modified model to create a
MessageFormatter
.- Returns:
- the data model.
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formatToString
@Deprecated public java.lang.String formatToString(java.util.Map<java.lang.String,java.lang.Object> arguments)
Deprecated.This API is for technology preview only.Formats a map of objects by iterating over the MessageFormat's pattern, with the plain text “as is” and the arguments replaced by the formatted objects.- Parameters:
arguments
- a map of objects to be formatted and substituted.- Returns:
- the string representing the message with parameters replaced.
- Throws:
java.lang.IllegalArgumentException
- when something goes wrong (for example wrong argument type, or null arguments, etc.)
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format
@Deprecated public FormattedMessage format(java.util.Map<java.lang.String,java.lang.Object> arguments)
Deprecated.This API is for technology preview only.Not yet implemented: formats a map of objects by iterating over the MessageFormat's pattern, with the plain text “as is” and the arguments replaced by the formatted objects.- Parameters:
arguments
- a map of objects to be formatted and substituted.- Returns:
- the
FormattedMessage
class representing the message with parameters replaced.
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