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Use code includes and tabs in SpEL documentation

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See gh-22171
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Sébastien Deleuze
2024-04-08 11:53:56 +02:00
parent 62db2680f5
commit 94050b3638
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framework-docs/modules/ROOT/pages/core/expressions/beandef.adoc
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[[expressions-beandef]]
= Expressions in Bean Definitions
You can use SpEL expressions with XML-based or annotation-based configuration metadata for
defining `BeanDefinition` instances. In both cases, the syntax to define the expression is of the
form `#{ <expression string> }`.
[[expressions-beandef-xml-based]]
== XML Configuration
A property or constructor argument value can be set by using expressions, as the following
example shows:
[source,xml,indent=0,subs="verbatim"]
----
<bean id="numberGuess" class="org.spring.samples.NumberGuess">
<property name="randomNumber" value="#{ T(java.lang.Math).random() * 100.0 }"/>
<!-- other properties -->
</bean>
----
You can use SpEL expressions with configuration metadata for defining bean instances. In both
cases, the syntax to define the expression is of the form `#{ <expression string> }`.
All beans in the application context are available as predefined variables with their
common bean name. This includes standard context beans such as `environment` (of type
`org.springframework.core.env.Environment`) as well as `systemProperties` and
`systemEnvironment` (of type `Map<String, Object>`) for access to the runtime environment.
The following example shows access to the `systemProperties` bean as a SpEL variable:
[source,xml,indent=0,subs="verbatim"]
----
<bean id="taxCalculator" class="org.spring.samples.TaxCalculator">
<property name="defaultLocale" value="#{ systemProperties['user.region'] }"/>
<!-- other properties -->
</bean>
----
Note that you do not have to prefix the predefined variable with the `#` symbol here.
You can also refer to other bean properties by name, as the following example shows:
[source,xml,indent=0,subs="verbatim"]
----
<bean id="numberGuess" class="org.spring.samples.NumberGuess">
<property name="randomNumber" value="#{ T(java.lang.Math).random() * 100.0 }"/>
<!-- other properties -->
</bean>
<bean id="shapeGuess" class="org.spring.samples.ShapeGuess">
<property name="initialShapeSeed" value="#{ numberGuess.randomNumber }"/>
<!-- other properties -->
</bean>
----
[[expressions-beandef-annotation-based]]
== Annotation Configuration
To specify a default value, you can place the `@Value` annotation on fields, methods,
and method or constructor parameters.
and method or constructor parameters (or XML equivalent).
The following example sets the default value of a field:
[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes",role="primary"]
----
public class FieldValueTestBean {
include-code::./FieldValueTestBean[tag=snippet,indent=0]
@Value("#{ systemProperties['user.region'] }")
private String defaultLocale;
public void setDefaultLocale(String defaultLocale) {
this.defaultLocale = defaultLocale;
}
public String getDefaultLocale() {
return this.defaultLocale;
}
}
----
Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
----
class FieldValueTestBean {
@Value("#{ systemProperties['user.region'] }")
var defaultLocale: String? = null
}
----
======
Note that you do not have to prefix the predefined variable with the `#` symbol here.
The following example shows the equivalent but on a property setter method:
[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes",role="primary"]
----
public class PropertyValueTestBean {
private String defaultLocale;
@Value("#{ systemProperties['user.region'] }")
public void setDefaultLocale(String defaultLocale) {
this.defaultLocale = defaultLocale;
}
public String getDefaultLocale() {
return this.defaultLocale;
}
}
----
Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
----
class PropertyValueTestBean {
@Value("#{ systemProperties['user.region'] }")
var defaultLocale: String? = null
}
----
======
include-code::./PropertyValueTestBean[tag=snippet,indent=0]
Autowired methods and constructors can also use the `@Value` annotation, as the following
examples show:
[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes",role="primary"]
----
public class SimpleMovieLister {
private MovieFinder movieFinder;
private String defaultLocale;
@Autowired
public void configure(MovieFinder movieFinder,
@Value("#{ systemProperties['user.region'] }") String defaultLocale) {
this.movieFinder = movieFinder;
this.defaultLocale = defaultLocale;
}
// ...
}
----
Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
----
class SimpleMovieLister {
private lateinit var movieFinder: MovieFinder
private lateinit var defaultLocale: String
@Autowired
fun configure(movieFinder: MovieFinder,
@Value("#{ systemProperties['user.region'] }") defaultLocale: String) {
this.movieFinder = movieFinder
this.defaultLocale = defaultLocale
}
// ...
}
----
======
[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes",role="primary"]
----
public class MovieRecommender {
private String defaultLocale;
private CustomerPreferenceDao customerPreferenceDao;
public MovieRecommender(CustomerPreferenceDao customerPreferenceDao,
@Value("#{systemProperties['user.country']}") String defaultLocale) {
this.customerPreferenceDao = customerPreferenceDao;
this.defaultLocale = defaultLocale;
}
// ...
}
----
Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
----
class MovieRecommender(private val customerPreferenceDao: CustomerPreferenceDao,
@Value("#{systemProperties['user.country']}") private val defaultLocale: String) {
// ...
}
----
======
include-code::./SimpleMovieLister[tag=snippet,indent=0]
include-code::./MovieRecommender[tag=snippet,indent=0]
You can also refer to other bean properties by name, as the following example shows:
include-code::./ShapeGuess[tag=snippet,indent=0]