Use of Spring @Conditional annotations

Spring boot is powerful because it uses the new features of the Spring 4 framework: @Conditional annotations, which enable some configurations only if certain conditions are met.

Here's how to use condition

First write a class

Package com.test.spring;

Import org.springframework.context.annotation.Condition;
Import Org.springframework.context.annotation.ConditionContext;
Import Org.springframework.core.type.AnnotatedTypeMetadata;

public class Mycondition implements Condition
{
	/**
	 * Write your own logic here, only return true to enable configuration */
	 public
	Boolean Matches (Conditioncontext context, annotatedtypemetadata Metadata)
	{
		return true;
	}
}

The next step is to use the

Package com.test.spring;

Import java.io.Serializable;

Import Org.springframework.context.annotation.Bean;
Import org.springframework.context.annotation.Conditional;
Import org.springframework.context.annotation.Configuration;

@Configuration
@Conditional (mycondition.class) Public
class Config
{
	@Bean
	public Serializable createserializable ()
	{
		System.out.println ("======000");
		Return "";
	}
}

@Conditional (Mycondition.class)

This code can be labeled on the class, indicating that all @bean under the class are enabled for configuration

can also be labeled on the method, just enable configuration for the method

In addition to your own custom condition, Spring provides a lot of condition for us

@ConditionalOnBean (a bean is instantiated only if an object exists in the current context)
@ConditionalOnClass (a class is located on the classpath to instantiate a bean)
@ConditionalOnExpression (a bean is instantiated only when the expression is true)
@ConditionalOnMissingBean (a bean is instantiated only if an object does not exist in the current context)
@ConditionalOnMissingClass (a bean is instantiated only if it does not exist on a class path)
@ConditionalOnNotWebApplication (not web App)