如何找到带有自定义批注@Foo的所有bean？

Z时代
2024-01-10
分类：问答

我有这个春天的配置：

@Lazy
@Configuration
public class MyAppConfig {
    @Foo @Bean
    public IFooService service1() { return new SpecialFooServiceImpl(); }
}

如何获得所有带有注释的bean的列表@Foo？

注意：@Foo是我定义的自定义注释。它不是“官方” Spring注释之一。

[编辑]按照Avinash T.的建议，我编写了这个测试案例：

import static org.junit.Assert.*;
import java.lang.annotation.ElementType;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.annotation.Retention;
import java.lang.reflect.Method;
import java.util.Map;
import org.junit.Test;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Lazy;
public class CustomAnnotationsTest {
    @Test
    public void testFindByAnnotation() throws Exception {
        AnnotationConfigApplicationContext appContext = new AnnotationConfigApplicationContext( CustomAnnotationsSpringCfg.class );
        Method m = CustomAnnotationsSpringCfg.class.getMethod( "a" );
        assertNotNull( m );
        assertNotNull( m.getAnnotation( Foo.class ) );
        BeanDefinition bdf = appContext.getBeanFactory().getBeanDefinition( "a" );
        // Is there a way to list all annotations of bdf?
        Map<String, Object> beans = appContext.getBeansWithAnnotation( Foo.class );
        assertEquals( "[a]", beans.keySet().toString() );
    }
    @Retention( RetentionPolicy.RUNTIME )
    @Target( ElementType.METHOD )
    public static @interface Foo {
    }
    public static class Named {
        private final String name;
        public Named( String name ) {
            this.name = name;
        }
        @Override
        public String toString() {
            return name;
        }
    }
    @Lazy
    @Configuration
    public static class CustomAnnotationsSpringCfg {
        @Foo @Bean public Named a() { return new Named( "a" ); }
             @Bean public Named b() { return new Named( "b" ); }
    }
}

但是失败了org.junit.ComparisonFailure: expected:<[[a]]> but was:<[[]]>。为什么？

回答：

一对夫妇spring专家的帮助下，我找到了一个解决方案：source的属性BeanDefinition可以AnnotatedTypeMetadata。这个接口有一个getAnnotationAttributes()我可以用来获取bean方法的注释的方法：

public List<String> getBeansWithAnnotation( Class<? extends Annotation> type, Predicate<Map<String, Object>> attributeFilter ) {
    List<String> result = Lists.newArrayList();
    ConfigurableListableBeanFactory factory = applicationContext.getBeanFactory();
    for( String name : factory.getBeanDefinitionNames() ) {
        BeanDefinition bd = factory.getBeanDefinition( name );
        if( bd.getSource() instanceof AnnotatedTypeMetadata ) {
            AnnotatedTypeMetadata metadata = (AnnotatedTypeMetadata) bd.getSource();
            Map<String, Object> attributes = metadata.getAnnotationAttributes( type.getName() );
            if( null == attributes ) {
                continue;
            }
            if( attributeFilter.apply( attributes ) ) {
                result.add( name );
            }
        }
    }
    return result;
}