程序包 cn.taketoday.context.condition

Annotation Interface ConditionalOnProperty

@Retention(RUNTIME)
@Conditional(cn.taketoday.context.condition.OnPropertyCondition.class)
@Target({TYPE,METHOD})
public @interface ConditionalOnProperty

@Conditional that checks if the specified properties have a specific value. By default the properties must be present in the Environment and not equal to false. The havingValue() and matchIfMissing() attributes allow further customizations.

The havingValue() attribute can be used to specify the value that the property should have. The table below shows when a condition matches according to the property value and the havingValue() attribute:

Having values

Property Value	havingValue=""	havingValue="true"	havingValue="false"	havingValue="foo"
"true"	yes	yes	no	no
"false"	no	no	yes	no
"foo"	yes	no	no	yes

If the property is not contained in the Environment at all, the matchIfMissing() attribute is consulted. By default missing attributes do not match.

This condition cannot be reliably used for matching collection properties. For example, in the following configuration, the condition matches if today.example.values is present in the Environment but does not match if today.example.values[0] is present.

 @ConditionalOnProperty(prefix = "today", name = "example.values")
 class ExampleAutoConfiguration {
 }
 

It is better to use a custom condition for such cases.

作者:

Maciej Walkowiak, Stephane Nicoll, Phillip Webb, TODAY
2019-06-18 15:06

可选元素概要

可选元素

修饰符和类型	可选元素	说明
String	havingValue	The string representation of the expected value for the properties.
boolean	matchIfMissing	Specify if the condition should match if the property is not set.
String[]	name	The name of the properties to test.
String	prefix	A prefix that should be applied to each property.
String[]	value	Alias for name().

元素详细资料

value

String[] value

Alias for name().

返回:

the names

默认值:

{}

prefix

String prefix

A prefix that should be applied to each property. The prefix automatically ends with a dot if not specified. A valid prefix is defined by one or more words separated with dots (e.g. "acme.system.feature").

返回:

the prefix

默认值:

""

name

String[] name

The name of the properties to test. If a prefix has been defined, it is applied to compute the full key of each property. For instance if the prefix is app.config and one value is my-value, the full key would be app.config.my-value

Use the dashed notation to specify each property, that is all lower case with a "-" to separate words (e.g. my-long-property).

返回:

the names

默认值:

{}

havingValue

String havingValue

The string representation of the expected value for the properties. If not specified, the property must not be equal to false.

返回:

the expected value

默认值:

""

matchIfMissing

boolean matchIfMissing

Specify if the condition should match if the property is not set. Defaults to false.

返回:

if the condition should match if the property is missing

默认值:

false