THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
...
I
...
have
...
been
...
using
...
Wicket
...
for
...
about
...
one
...
and
...
a
...
half
...
years
...
(and
...
followed
...
it
...
about
...
a
...
year
...
longer),
...
and
...
only
...
recently
...
I
...
realized
...
the
...
tremendous
...
flexibility
...
of
...
Wicket.
...
The
...
core
...
developers
...
keep
...
introducing
...
major
...
features
...
by
...
replacing
...
large
...
and
...
small
...
parts
...
of
...
the
...
core,
...
without
...
changing
...
much
...
of
...
the
...
existing
...
programming
...
interface.
...
It
...
doesn't
...
stop
...
there
...
though.
...
Any
...
good
...
developer
...
can
...
do
...
the
...
same
...
with
...
relatively
...
little
...
effort.
...
On
...
occasion
...
I
...
replaced
...
important
...
parts
...
of
...
the
...
core
...
myself,
...
just
...
because
...
I
...
wanted
...
it
...
a
...
little
...
bit
...
different.
...
Upcoming
...
release
...
1.4
...
is
...
all
...
about
...
introducing
...
the
...
long
...
awaited
...
generic
...
models.
...
But
...
the
...
...
...
...
...
...
contain another little gem. Created by non-core
...
developer
...
John
...
Ray:
...
child
...
components
...
within
...
a
...
wicket:message
...
element.
...
But
...
before
...
I
...
explain
...
what
...
that
...
means,
...
lets
...
first
...
look
...
at
...
your
...
internationalization
...
options
...
in
...
Wicket.
...
This
...
article
...
requires
...
you
...
to
...
have
...
a
...
very
...
basic
...
grasp
...
of
...
Wicket
...
(what
...
the
...
application
...
class
...
is,
...
how
...
wicket:id
...
is
...
used,
...
and
...
simple
...
components
...
like
...
Panel
...
and
...
Label).
...
A
...
bit
...
of
...
knowledge
...
on
...
Java
...
properties
...
helps
...
as
...
well.
...
Simple
...
texts:
...
wicket:message
...
element,
...
and
...
wicket:message
...
attribute
...
A
...
simple
...
web
...
page
...
easily
...
contains
...
dozens
...
of
...
texts
...
that
...
need
...
i18n.
...
It
...
would
...
be
...
cumbersome
...
to
...
have
...
to
...
put
...
a
...
wicket:id
...
on
...
all
...
of
...
these,
...
and
...
then
...
add
...
a
...
Label
...
to
...
each.
...
Instead
...
you
...
can
...
use
...
the
...
wicket:message
...
element
...
in
...
the
...
HTML
...
file
...
directly.
...
For
...
example
...
in
...
MyPanel.html:
| Code Block |
|---|
<wicket:message key="helloworld">Hello</wicket:message> |
The
...
key
...
(helloworld)
...
is
...
used
...
to
...
lookup
...
the
...
message
...
in
...
the
...
property
...
files.
...
The
...
default
...
text
...
(Hello)
...
is
...
used
...
when
...
the
...
message
...
could
...
not
...
be
...
found.
...
The
...
property
...
files
...
are
...
(MyPanel.properties):
| Code Block |
|---|
helloworld: Hello world |
And
...
for
...
Dutch(MyPanel_nl.properties):
| Code Block |
|---|
helloworld: Hallo wereld |
The
...
ouput
...
with
...
an
...
English
...
locale:
...
Hello
...
world
...
You
...
can
...
do
...
the
...
same
...
for
...
HTML
...
attributes.
...
For
...
example:
| Code Block |
|---|
<input type="submit" value="Default text" wicket:message="value:helloworld"/> |
Would
...
result
...
in:
| Code Block |
|---|
<input type="submit" value="Hello world"/> |
If
...
there
...
are
...
multiple
...
attributes
...
to
...
translate,
...
add
...
them
...
prepended
...
with
...
a
...
comma:
| Code Block |
|---|
<input type="submit" value="Default text" wicket:message="value:helloworld,title:hellotitle"/> h3.Wicket |
Wicket's
...
locale
...
selection
...
As
...
usual
...
in
...
Java
...
i18n
...
systems,
...
messages
...
are
...
looked
...
up
...
by
...
locale.
...
The
...
locale
...
is
...
automatically
...
extracted
...
from
...
the
...
HTTP
...
request,
...
but
...
can
...
also
...
be
...
explicitly
...
set
...
with
...
getSession().setLocale(Locale.US).
...
If
...
you
...
need
...
to
...
override
...
the
...
locale
...
for
...
a
...
specific
...
component,
...
override
...
getLocale()
...
on
...
that
...
component
...
and
...
it
...
will
...
be
...
used
...
by
...
that
...
component
...
and
...
its
...
children.
...
If
...
a
...
client
...
does
...
not
...
provide
...
a
...
preferred
...
Locale,
...
Java's
...
default
...
Locale
...
is
...
used.
...
See
...
...
and
...
...
for
...
more
...
information.
...
Finding
...
the
...
message
...
Another
...
extremely
...
powerful
...
concept
...
is
...
how
...
the
...
message
...
is
...
looked
...
up
...
in
...
the
...
property
...
files.
...
Normally
...
a
...
properties
...
file
...
with
...
the
...
same
...
name
...
as
...
the
...
current
...
component
...
is
...
used.
...
E.g.
...
if
...
you
...
are
...
working
...
within
...
the
...
component
...
SummaryPanel,
...
the
...
message
...
is
...
looked
...
up
...
in
...
the
...
file
...
SummaryPanel_nl_NL.properties
...
(for
...
Dutch,
...
Netherlands
...
locale).
...
If
...
that
...
fails
...
(either
...
because
...
the
...
file
...
does
...
not
...
exist,
...
or
...
because
...
it
...
does
...
not
...
contain
...
the
...
message),
...
file
...
SummaryPanel_nl.properties,
...
and
...
then
...
SummaryPanel.properties
...
are
...
investigated.
...
This
...
is
...
all
...
just
...
like
...
Java's
...
resource
...
bundles
...
work.
...
But
...
of
...
course
...
Wicket
...
goes
...
further.
...
If
...
the
...
message
...
is
...
still
...
not
...
found,
...
the
...
property
...
files
...
of
...
the
...
parent
...
class
...
are
...
investigated,
...
and
...
again,
...
and
...
again,
...
all
...
the
...
way
...
up
...
to
...
java.lang.Object.
...
For
...
each
...
class
...
all
...
locale
...
variants
...
are
...
searched
...
for.
...
Components are reusable, but in order to make it really reusable you should be able to override the messages depending on where the component is used. This is facilitated by first looking up the message (following the algorithm above) for every parent in the component hierarchy (aka page hierarchy). Every component can override the messages of its child components, so the search starts at the page's properties and then trickles down to the component that uses it (yes, its top-down). In order to make overrides specific to a certain child component, you can prefix the message key with the component id of the child. See ComponentStringResourceLoader for more details.
If no message was found in the page hierarchy, another search starts which will look at your application class and its super classes. So Wicket first looks at MyApplication.properties (provided MyApplication is the name of your application) and then up the class hierarchy, passing org.apache.wicket.Application,
...
up
...
to
...
java.lang.Object.
...
This is how Wicket provides its many default i18n texts.
This might sound complicated, but in practice you simply have one properties file per page and some more for components that are reused over multiple pages. For smaller applications you can even put everything in one properties file. These rules work so well that you just do what you think is correct and it almost always just is.
One note on the location of the properties files: like HTML files, they must be in the same package, and the same classloader as the component they are associated with. In practice they live next to each other in the same directory.
If you want Wicket to get its resources from somewhere else (e.g. from a database), you can implement the interface org.apache.wicket.resource.loader.IStringResourceLoader
...
and
...
configure
...
this
...
in
...
the
...
init()
...
method
...
of
...
your
...
application
...
class.
...
References:
...
ExtensionResourceNameIterator,
...
ComponentStringResourceLoader,
...
and
...
for
...
real
...
control
...
freaks
...
the
...
new
...
...
Reloading
...
and
...
caching
...
When
...
Wicket
...
is
...
started
...
in
...
development
...
mode,
...
changed
...
properties
...
files
...
are
...
detected
...
and
...
reloaded.
...
To
...
properly
...
make
...
use
...
of
...
this
...
feature
...
from
...
an
...
IDE,
...
you
...
should
...
run
...
Wicket
...
directly
...
from
...
the
...
compiled
...
sources,
...
for
...
example
...
with
...
the
...
Start
...
file,
...
included
...
in
...
every
...
QuickStart.
...
In
...
Eclipse
...
you
...
just
...
save
...
the
...
properties
...
file,
...
in
...
IntelliJ
...
you
...
must
...
do
...
a
...
make
...
(Ctrl-F9)
...
before
...
changes
...
are
...
picked
...
up.
...
In
...
production
...
mode,
...
resolved
...
properties
...
are
...
heavily
...
cached
...
for
...
performance.
...
(Same
...
applies
...
to
...
html
...
files.)
...
Putting
...
dynamic
...
values
...
in
...
the
...
messages
...
As
...
soon
...
as
...
you
...
need
...
to
...
add
...
values
...
to
...
the
...
messages,
...
you
...
also
...
need
...
to
...
add
...
some
...
Java
...
code.
...
The
...
java
...
code
...
provides
...
the
...
vales,
...
but
...
the
...
rest
...
of
...
the
...
text
...
still
...
comes
...
from
...
the
...
properties
...
file.
...
One
...
of
...
the
...
nice
...
things
...
here
...
is
...
how
...
Wicket
...
leverages
...
java
...
bean
...
properties.
...
Here
...
is
...
a
...
complete
...
example.
...
Not
...
many
...
frameworks
...
make
...
this
...
so
...
easy!
...
MyPanel.properties:
| Code Block |
|---|
summ: You, and ${otherCount} others, reviewed '${title}' \ and rated it ${rate}. |
MyPanel.html:
| Code Block |
|---|
<span wicket:id="summary">Text that will be replaced.</span> |
MyPanel.java:
| Code Block |
|---|
// Summary has getters for otherCount, title, etc. Summary summary = ...; add(new Label("summary", new StringResourceModel( "summ", this, new Model(summary)))); |
Resulting
...
in
...
something
...
like:
| Code Block |
|---|
<span>You, and 5 others, reviewed 'Wicket in Action' and rated it excellent.</span> h3.Property based message key It goes further: do you know a framework that can do this? MyPanel.properties: summ.short: Thanks! summ.long: You, and ${otherCount} others, reviewed '${title}' \ and rated it ${rate}. Thanks! MyPanel.html: <span wicket:id="summary">Text that will be replaced.</span> MyPanel.java: // summary.getMsgPrefs().getStyle() returns "short" or "long" add(new Label("summary", new StringResourceModel( "summ.${msgPrefs.style}", this, Action' and rated it excellent.</span> |
Property based message key
It goes further: do you know a framework that can do this?
MyPanel.properties:
| Code Block |
|---|
summ.short: Thanks!
summ.long: You, and ${otherCount} others, reviewed '${title}' and rated it ${rate}. Thanks! |
MyPanel.html:
| Code Block |
|---|
<span wicket:id="summary">Text that will be replaced.</span> |
MyPanel.java:
| Code Block |
|---|
// summary.getMsgPrefs().getStyle() returns "short" or "long"
add(new Label("summary", new StringResourceModel("summ.${msgPrefs.style}", this, new Model(summary)))); |
And more!
The Java property syntax is also still available (e.g. like {0,Date}, {2,number,###.##} etc.)? You can find all forms in the javadocs of StringResourceModel.
The Component class has convenience method which you may find useful:
| Code Block |
|---|
add(new Label("summary", getString("summ.${msgPrefs.style}", new Model(summary)))); |
Putting wicket components into the message
If you want to translate a components text containing additional Wicket components (e.g. Links) you can use wicket:message-tag in combination with a container around it. Example a form component label related to a checkbox (label for) containing a link:
Java:
| Code Block |
|---|
final FormComponentLabel termsAndConditionsCheckLabel = new FormComponentLabel("termsAndConditionsCheckLabel", acceptedTerms);
form.add(termsAndConditionsCheckLabel);
final Link terms = new Link("terms") {
@Override
public void onClick() {
setResponsePage(TermsOfUsePage.class);
}
};
termsAndConditionsCheckLabel.add(terms);
final Label termsOfUse = new Label("terms_of_use", new ResourceModel("terms_of_use"));
termsOfUse.setRenderBodyOnly(true);
terms.add(termsOfUse);
|
Markup (HTML):
| Code Block |
|---|
<label wicket:id="termsAndConditionsCheckLabel">
<wicket:message key="termsAndConditionsCheckLabel">I am 18 years old and agree with the <a href="#" wicket:id="terms"><span wicket:id="terms_of_use">terms of use</span></a> and conditions.</wicket:message>
</label>
|
Messages (in ....properties.xml):
| Code Block |
|---|
<entry key="termsAndConditionsCheckLabel">I am 18 years old and agree with the ${terms_of_use} and conditions.</entry>
<entry key="terms_of_use">Terms of Use</entry>
|
The trouble with property files
Now this is all nice, but there is one problem you will frequently encountered while using string resources. In this problem you have a sentence that contains one or more dynamically constructed parts (for example some links). The order of these dynamic parts is potentially different for each locale. In the previous example, we may want to link to an information page on the title, and on the word 'others' open a modal window with a list of people.
If you try this with Wicket 1.3 (or any other Java framework I know of that uses resource bundles) you'll find that there is actually no pure way to do this. I know of 3 workarounds, but neither is very attractive. Lets review them. The first way is to split the texts before, after and between the dynamic components. This works good enough, but varying the order of the components is not possible unless you so something clever on the Java side, or have multiple HTML files. The latter is also workaround number 2: for each locale use a separate HTML file with the translation directly included (note: Wicket uses the same rules to lookup HTML files as it does for property files, e.g. MyPanel_nl.html just works like you expect it to). However, having more then one HTML file per component often leads to maintenance horror as changes must be synchronized over many files. The third workaround is to add placeholders to the message text that later are replaced by some HTML. That HTML is either hand written (in which case you may wonder why you started with Wicket at all), or you need to do some serious Wicket hacking to get components to render to a StringBuffer.
Now lets do this with Wicket 1.4-m1:
MyPanel.properties:
| Code Block |
|---|
new Model(summary)))); And more! The Java property syntax is also still available (e.g. like {0,Date}, {2,number,###.##} etc.)? You can find all forms in the javadocs of StringResourceModel. h3.The trouble with property files Now this is all nice, but there is one problem you will frequently encountered while using string resources. In this problem you have a sentence that contains one or more dynamically constructed parts (for example some links). The order of these dynamic parts is potentially different for each locale. In the previous example, we may want to link to an information page on the title, and on the word 'others' open a modal window with a list of people. If you try this with Wicket 1.3 (or any other Java framework I know of that uses resource bundles) you'll find that there is actually no pure way to do this. I know of 3 workarounds, but neither is very attractive. Lets review them. The first way is to split the texts before, after and between the dynamic components. This works good enough, but varying the order of the components is not possible unless you so something clever on the Java side, or have multiple HTML files. The latter is also workaround number 2: for each locale use a separate HTML file with the translation directly included (note: Wicket uses the same rules to lookup HTML files as it does for property files, e.g. MyPanel_nl.html just works like you expect it to). However, having more then one HTML file per component often leads to maintenance horror as changes must be synchronized over many files. The third workaround is to add placeholders to the message text that later are replaced by some HTML. That HTML is either hand written (in which case you may wonder why you started with Wicket at all), or you need to do some serious Wicket hacking to get components to render to a StringBuffer. Now lets do this with Wicket 1.4-m1: MyPanel.properties: summ: You, and ${othersLink}, reviewed ${titleLink} \ and rated it ${rate}. others: ${otherCount} others |
MyPanel.html:
| Code Block |
|---|
<wicket:message key="summ">Text that will be replaced. <span wicket:id="rate">rate</span> <a href="#" wicket:id="titleLink"> <span wicket:id="titleLabel">label</span></a> <a href="#" wicket:id="othersLink"> <span wicket:id="othersLabel">label<</span></a> </wicket:message> |
MyPanel.java:
| Code Block |
|---|
// Note, we directly add the embedded components // rate, othersLink and titleLink add(new Label("rate", new PropertyModel(summary, "rate"))); Link othLink = new Link("othersLink") { .... } add(othLink); othLink.add(new Label("othersLabel", new StringResourceModel( "others", this, new Model(summary)))); ExternalLink titleLink = new ExternalLink( "titleLink", summary.getTitleUrl()); add(titleLink); titleLink.add(new Label("titleLabel", new PropertyModel(summary, "title"))); |
The
...
html
...
file
...
contains
...
a
...
wicket:message
...
element
...
with
...
some
...
embedded
...
components.
...
All
...
text
...
within
...
the
...
element
...
is
...
removed
...
and
...
replaced
...
by
...
the
...
text
...
from
...
the
...
properties
...
file.
...
Labels
...
like
...
${othersLink}
...
are
...
replaced
...
by
...
the
...
rendered
...
component
...
of
...
the
...
same
...
wicket:id.
...
That
...
component
...
must
...
be
...
embedded
...
in
...
the
...
wicket:message
...
element.
...
Note
...
that
...
the
...
order
...
of
...
the
...
components
...
is
...
irrelevant.
...
Also
...
note
...
that
...
you
...
will
...
not
...
see
...
any
...
reference
...
to
...
the
...
wicket:message
...
element
...
in
...
the
...
java
...
code.
...
If
...
you
...
want
...
runnable
...
code
...
you
...
can
...
download
...
the
...
...
...
...
(a
...
Maven
...
2
...
project
...
based
...
on
...
...
...
See
...
below
...
for
...
instructions.
...
Getting
...
string
...
resources
...
from
...
code
...
Despite
...
all
...
of
...
the
...
above,
...
there
...
always
...
remain
...
some
...
cases
...
in
...
which
...
you
...
need
...
direct
...
access
...
to
...
the
...
messages.
...
Luckily
...
Wicket
...
provides
...
access
...
through
...
the
...
...
You
...
can
...
get
...
the
...
localizer
...
from
...
any
...
component
...
with
...
getLocalizer().
...
Again,
...
see
...
the
...
...
...
...
for
...
an
...
example.
...
Encoding
...
troubles
...
Fairly
...
unknown
...
to
...
beginning
...
programmers
...
is
...
that
...
you
...
are
...
only
...
allowed
...
to
...
use
...
ISO-8859-1
...
encoding
...
in
...
java
...
properties
...
files.
...
If
...
you
...
live
...
in
...
Europe
...
this
...
is
...
a
...
fairly
...
annoying
...
as
...
many
...
languages
...
have
...
characters
...
that
...
are
...
not
...
known
...
to
...
ISO-8859-1
...
(for
...
example
...
the
...
euro
...
symbol
...
€).
...
The
...
simple
...
workaround
...
is
...
escaping:
...
cree\u00EBr
...
instead
...
of
...
creeër.
...
(I
...
always
...
use
...
...
...
to
...
look
...
up
...
the
...
ISO
...
codepoint.)
...
But
...
imagine
...
you
...
are
...
making
...
a
...
site
...
in
...
Thai!
...
Luckily
...
Wicket
...
can
...
also
...
read
...
XML
...
property
...
files.
...
Here
...
is
...
a
...
fragment
...
of
...
the
...
Thai
...
properties
...
that
...
comes
...
with
...
Wicket:
| Code Block |
|---|
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd"> <properties> <entry key="Required">ข้อมูลใน ${label} เป็นที่ต้องการ.</entry> </properties> |
Nice!
...
Sample
...
code
...
To
...
test
...
the
...
code
...
in
...
this
...
article
...
I
...
created
...
a
...
...
...
...
Unzip
...
it,
...
and
...
run
...
mvn
...
jetty:run
...
to
...
start
...
it.
...
When
...
it
...
is
...
started
...
access
...
it
...
on
...
http://localhost:8080/i18ntest.
...
Changing
...
resource
...
settings
...
Finally,
...
if
...
you
...
need
...
more
...
power,
...
you
...
can
...
change
...
all
...
of
...
Wicket's
...
settings
...
in
...
the
...
init()
...
method
...
of
...
your
...
application.
...
Call
...
...
to
...
get
...
a
...
...
instance.
...
Let
...
look
...
at
...
some
...
of
...
the
...
options.
...
ThrowExceptionOnMissingResource:
...
this
...
will
...
make
...
Wicket
...
throw
...
an
...
exception
...
when
...
a
...
resource
...
is
...
missing.
...
At
...
first
...
this
...
may
...
seem
...
a
...
convenient
...
way
...
to
...
test
...
that
...
you
...
listed
...
all
...
messages
...
in
...
a
...
properties
...
file.
...
However,
...
many
...
standard
...
Wicket
...
components
...
use
...
defaults
...
as
...
fall
...
back,
...
so
...
this
...
option
...
is
...
mostly
...
useless.
...
Alternatively,
...
watch
...
for
...
warnings
...
in
...
the
...
log.
...
...
this
...
will
...
make
...
Wicket
...
use
...
the
...
default
...
value
...
(e.g.
...
the
...
text
...
within
...
the
...
wicket:message
...
element)
...
when
...
the
...
resource
...
is
...
not
...
found
...
in
...
a
...
properties
...
file.
...
Setting
...
this
...
to
...
true
...
(the
...
default)
...
may
...
hide
...
errors
...
for
...
a
...
long
...
time,
...
but
...
setting
...
this
...
false
...
will
...
make
...
your
...
site
...
not
...
work
...
if
...
you
...
made
...
an
...
error.
...
Choose
...
carefully.
...
There
...
are
...
many
...
more
...
options
...
that
...
allow
...
you
...
to
...
change
...
what,
...
when
...
and
...
how
...
properties
...
are
...
loaded.
...
I
...
have
...
never
...
found
...
a
...
use
...
for
...
these,
...
but
...
they
...
are
...
there
...
if
...
you
...
need
...
them.
...
Conclusion
As you have seen in this article, Wicket provides simple ways to do everything around internationalization, and some more less simple ways to completely customize this for the rare case you need it. Furthermore, the new Wicket 1.4 release will make it a lot better with support for componenta embedded in a wicket:message element. You can download the example to see everything in action.
Update 20080526
Incorperated the comment from Stefan Fußenegger on what happens if the user gives no preferred locale.