Can we declare spring bean conditionally?

Question

Is there a way we can declare a Spring bean conditionally like:

<bean class="path.to.the.class.MyClass" if="${1+2=3}" /> 

It would be useful instead of having to use profiles. I don't have a specific use-case in mind, but it came to me.

Answer 1

You can use @Conditional from Spring4 or @ConditionalOnProperty from Spring Boot.

1. Using Spring4 (only)

if you are NOT using Spring Boot, this can be overkill.

First, create a Condition class, in which the ConditionContext has access to the Environment:

public class MyCondition implements Condition {     @Override     public boolean matches(ConditionContext context,                            AnnotatedTypeMetadata metadata) {         Environment env = context.getEnvironment();         return null != env                 && "true".equals(env.getProperty("server.host"));     } } 

Then annotate your bean:

@Bean @Conditional(MyCondition.class) public ObservationWebSocketClient observationWebSocketClient() {     //return bean } 

2.Using Spring Boot:

@ConditionalOnProperty(name="server.host", havingValue="localhost") 

And in your abcd.properties file ,

server.host=localhost