Spring Boot @Conditional相关注解解析

墨蓝 2022-06-02 08:47 257阅读 0赞

1.配置类

package com.spring4all.convert;
    
    import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
    import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
    import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression;
    import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Conditional;
    import org.springframework.context.annotation.Configuration;
    
    import com.spring4all.domain.User;
    /**
     * 条件配置类
     * @author Bowin
     *
     */
    @Configuration
    public class EncodingConvertConfiguration {
    
    	/**
    	 * 只有满足Wind8Condition条件之后创建一个bean。
    	 * @return
    	 */
    	@Bean
    	@Conditional(WindowsCondition.class)
    	public EncodingConvert windowsEncodingConvert(){
    		System.out.println("===开始装配:@Conditional===");
    		return new WindowsEncodingConvert();
    	}
    	
    	@Bean
    	@Conditional(LinuxCondition.class)
    	public EncodingConvert LinuxEncodingConvert(){
    		System.out.println("===开始装配:@Conditional===");
    		return new LinuxEncodingConvert();
    	}
    	
    	/**
    	 * @ConditionalOnProperty 表示classpath下有某个属性的时候才装配
    	 * @return
    	 */
    	@Bean 
    	@ConditionalOnProperty(name="runnable-enable",havingValue="false",matchIfMissing=false)
    	public Runnable createRunable(){
    		System.out.println("===开始装配:@ConditionalOnProperty===");
    		return ()->{};
    		
    	}
    	/**
    	 * @ConditionalOnClass 表示classpath下有某个class的时候才装配
    	 * @return
    	 */
    	@Bean 
    	@ConditionalOnClass(EncodingConvertConfiguration.class)
    	public Runnable createRunable2(){
    		System.out.println("===开始装配:@ConditionalOnClass===");
    		return ()->{};
    		
    	}
    	/**
    	 *SpEL表达式结果为true时才装配
    	 * @return
    	 */
    	@Bean
    	@ConditionalOnExpression("${enabled:false}")
    	public Runnable createRunnable3(){
    		System.out.println("===开始装配:@ConditionalOnExpression===");
    		return ()->{};
    	}
    	/**
    	 * @ConditionalOnBean 表示class下存在某个bean的时候装配
    	 * @ConditionalOnMissBean 表示class下不存在某个bean的时候装配
    	 * @return
    	 */
    	@Bean 
    	@ConditionalOnBean(User.class)
    	public User createUserBean(){
    		System.out.println("===开始装配:@ConditionalOnBean===");
    		return new User("a");
    		
    	}
    	
    }

2.接口类

package com.spring4all.convert;
    /**
     * 装换接口
     * @author Bowin
     *
     */
    public interface EncodingConvert{
    
    	public  void print();
    }

3.实现类

package com.spring4all.convert;
    
    public class WindowsEncodingConvert  implements EncodingConvert{
    
    	@Override
    	public void print() {
    		System.out.println("当前操作系统是windows！");
    	}
    
    }

package com.spring4all.convert;
    
    public class LinuxEncodingConvert  implements EncodingConvert{
    
    	@Override
    	public void print() {
    		System.out.println("当前操作系统是Linux！");		
    	}
    
    }

4.具体条件实现类

package com.spring4all.convert;
    
    import org.springframework.context.annotation.Condition;
    import org.springframework.context.annotation.ConditionContext;
    import org.springframework.core.type.AnnotatedTypeMetadata;
    /**
     * windows条件下
     * @author Bowin
     *
     */
    public class WindowsCondition  implements Condition{
    
    	@Override
    	public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
    		return context.getEnvironment().getProperty("os.name").contains("Windows");
    	}
    
    }

package com.spring4all.convert;
    
    import org.springframework.context.annotation.Condition;
    import org.springframework.context.annotation.ConditionContext;
    import org.springframework.core.type.AnnotatedTypeMetadata;
    
    public class LinuxCondition  implements Condition{
    
    	@Override
    	public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
    		return context.getEnvironment().getProperty("os.name").contains("Linux");  
    	}
    
    }

4.测试

package com.spring4all;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.context.ConfigurableApplicationContext;
    
    import com.spring4all.convert.EncodingConvert;
    /**
     * 启动测试
     * @author Bowin
     *
     */
    @SpringBootApplication
    public class Application{
    
        public static void main(String[] args) {
            ConfigurableApplicationContext run = SpringApplication.run(Application.class, args);
            EncodingConvert bean = run.getBean(EncodingConvert.class);
            bean.print();
            
        }
    
    }