Using @Conditional with @Configuration in Spring

Using @Conditional with @Configuration in Spring allows us to group @Bean objects loaded on a specific condition without resorting to using @Profile and too many @Bean/@Conditional.

Requirements

We used the following items for this post.

Spring Boot 2.0.4.RELEASE
JDK 8
IntelliJ IDEA

Grouping Beans into Two in Spring

1. All-English Configuration

The @Configuration class contains all beans that give out String values in English. For example, consider the following codes.

package com.turreta.conditionalconfiguration.conditionalconfiguration;

import com.turreta.conditionalconfiguration.conditionalconfiguration.condition.EnglishLanguageCondition;

import com.turreta.conditionalconfiguration.conditionalconfiguration.credits.CreditsEnglish;

import com.turreta.conditionalconfiguration.conditionalconfiguration.helloworld.HelloWorldEnglish;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Conditional;

import org.springframework.context.annotation.Configuration;

@Configuration

@Conditional(EnglishLanguageCondition.class)

public class AllEnglishConfiguration

{

@Bean

public CreditsEnglish creditsEnglish()

{

return new CreditsEnglish();

}

@Bean

public HelloWorldEnglish helloWorldEnglish()

{

return new HelloWorldEnglish();

}

The Condition implementation for this is as follows:

package com.turreta.conditionalconfiguration.conditionalconfiguration.condition;

import org.springframework.context.annotation.Condition;

import org.springframework.context.annotation.ConditionContext;

import org.springframework.core.type.AnnotatedTypeMetadata;

public class EnglishLanguageCondition implements Condition

{

@Override

public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata)

{

// Don't check for actual value

String lang = conditionContext.getEnvironment().getProperty("english");

return lang != null;

}

2. All-German Configuration

This @Configuration class contains all beans that give out String values in the German language. Consider the following codes.

package com.turreta.conditionalconfiguration.conditionalconfiguration;

import com.turreta.conditionalconfiguration.conditionalconfiguration.condition.GermanLanguageCondition;

import com.turreta.conditionalconfiguration.conditionalconfiguration.credits.CreditsGerman;

import com.turreta.conditionalconfiguration.conditionalconfiguration.helloworld.HelloWorldGerman;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Conditional;

import org.springframework.context.annotation.Configuration;

@Configuration

@Conditional(GermanLanguageCondition.class)

public class AllGermanConfiguration

{

@Bean

public CreditsGerman creditsGerman()

{

return new CreditsGerman();

}

@Bean

public HelloWorldGerman helloWorldGerman()

{

return new HelloWorldGerman();

}

The Condition implementation for this is as follows:

package com.turreta.conditionalconfiguration.conditionalconfiguration.condition;

import org.springframework.context.annotation.Condition;

import org.springframework.context.annotation.ConditionContext;

import org.springframework.core.type.AnnotatedTypeMetadata;

public class GermanLanguageCondition implements Condition

{

@Override

public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata)

{

// Don't check for actual value

String lang = conditionContext.getEnvironment().getProperty("german");

return lang != null;

}

Test @Conditional and @Configuration in Spring

To toggle between languages, we explicitly set either one of the system properties – “English” or “German” – and run within the IDE.

package com.turreta.conditionalconfiguration.conditionalconfiguration;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.context.ConfigurableApplicationContext;

@SpringBootApplication

public class ConditionalconfigurationApplication

{

public static void main(String[] args)

{

System.setProperty("german", "any value");

//System.setProperty("english", "any value");

final ConfigurableApplicationContext context = SpringApplication

.run(ConditionalconfigurationApplication.class, args);

System.out.println(context.getBean(HelloWorld.class).getGreeting());

System.out.println(context.getBean(Credits.class).getCredits());

}

Then, we can test our codes by switching between languages using a property. For example, when we want to display a message in German, we could use the “German” system property, which is equivalent to -Dgerman="any value".