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Juergen Hoeller
2020-06-10 11:19:52 +02:00
parent 7f87eb56d9
commit a045574418
38 changed files with 284 additions and 268 deletions
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src/docs/asciidoc/core/core-expressions.adoc
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@@ -393,8 +393,8 @@ More and more types of expression will be compilable in the future.
[[expressions-beandef]]
== Expressions in bean definitions
SpEL expressions can be used with XML or annotation-based configuration metadata for
defining ``BeanDefinition``s. In both cases the syntax to define the expression is of the
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> }`.
@@ -402,7 +402,8 @@ form `#{ <expression string> }`.
[[expressions-beandef-xml-based]]
=== XML configuration
A property or constructor-arg value can be set using expressions as shown below.
A property or constructor argument value can be set by using expressions, as the following
example shows:
[source,xml,indent=0]
[subs="verbatim"]
@@ -414,10 +415,14 @@ A property or constructor-arg value can be set using expressions as shown below.
</bean>
----
The variable `systemProperties` is predefined, so you can use it in your expressions as
shown below. Note that you do not have to prefix the predefined variable with the `#`
symbol in this context.
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"]
----
@@ -428,8 +433,11 @@ symbol in this context.
</bean>
----
You can also refer to other bean properties by name, for example.
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"]
----
@@ -451,10 +459,10 @@ You can also refer to other bean properties by name, for example.
[[expressions-beandef-annotation-based]]
=== Annotation config
The `@Value` annotation can be placed on fields, methods and method/constructor
parameters to specify a default value.
To specify a default value, you can place the `@Value` annotation on fields, methods,
and method or constructor parameters.
Here is an example to set the default value of a field variable.
The following example sets the default value of a field variable:
[source,java,indent=0]
[subs="verbatim,quotes"]
@@ -475,7 +483,7 @@ Here is an example to set the default value of a field variable.
}
----
The equivalent but on a property setter method is shown below.
The following example shows the equivalent but on a property setter method:
[source,java,indent=0]
[subs="verbatim,quotes"]
@@ -496,7 +504,8 @@ The equivalent but on a property setter method is shown below.
}
----
Autowired methods and constructors can also use the `@Value` annotation.
Autowired methods and constructors can also use the `@Value` annotation, as the following
examples show:
[source,java,indent=0]
[subs="verbatim,quotes"]
@@ -1129,7 +1138,7 @@ The following example shows how to use the Elvis operator:
----
ExpressionParser parser = new SpelExpressionParser();
String name = parser.parseExpression("name?:'Unknown'").getValue(String.class);
String name = parser.parseExpression("name?:'Unknown'").getValue(new Inventor(), String.class);
System.out.println(name); // 'Unknown'
----