参考了多篇文章都说明了use-default-filters参数的基本用途,但有些主要点没有说到,这里补充记录下:

<context:component-scan base-package="com.jaamy"  use-default-filters="false">
         <context:include-filter type="annotation"  expression="org.springframework.stereotype.Controller" />
</context:component-scan>

 这个只扫描com.jaamy包下的@Controller,不会扫描@Service、@Repository

 

<context:component-scan base-package="com.jaamy">
         <context:include-filter type="annotation"  expression="org.springframework.stereotype.Controller" />
</context:component-scan>

 这个不但扫描com.jaamy包下的@Controller,同时也会扫描@Service、@Repository,注意这里没有添加use-default-filters参数

 

下面配合源码说明下use-default-filters参数的作用以及和context:include-filter、exclude-filter的关系。

代码中是根据use-default-filters的值来确定是否需要调用registerDefaultFilters来添加默认的filters到includeFilters中,看下面的代码:

org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider

public ClassPathScanningCandidateComponentProvider(boolean useDefaultFilters, Environment environment) {
        if (useDefaultFilters) {
            registerDefaultFilters();
        }
        Assert.notNull(environment, "Environment must not be null");
        this.environment = environment;
    }

 

use-default-filters为true时调用了下面的代码,在includeFilters列表中添加了Component、ManagedBean和Named,因此use-default-filters的值直接影响includeFilters的内容,而includeFilters的容直接影响了要扫描的内容,因此use-default-filters的值是否配置也就决定了整体要扫描的内容。

protected void registerDefaultFilters() {
        this.includeFilters.add(new AnnotationTypeFilter(Component.class));
        ClassLoader cl = ClassPathScanningCandidateComponentProvider.class.getClassLoader();
        try {
            this.includeFilters.add(new AnnotationTypeFilter(
                    ((Class<? extends Annotation>) ClassUtils.forName("javax.annotation.ManagedBean", cl)), false));
            logger.debug("JSR-250 'javax.annotation.ManagedBean' found and supported for component scanning");
        }
        catch (ClassNotFoundException ex) {
            // JSR-250 1.1 API (as included in Java EE 6) not available - simply skip.
        }
        try {
            this.includeFilters.add(new AnnotationTypeFilter(
                    ((Class<? extends Annotation>) ClassUtils.forName("javax.inject.Named", cl)), false));
            logger.debug("JSR-330 'javax.inject.Named' annotation found and supported for component scanning");
        }
        catch (ClassNotFoundException ex) {
            // JSR-330 API not available - simply skip.
        }
    }

 

关于include-filter、exclude-filter的作用主要是用来过滤扫描到的bean是否合法:

首先通过exclude-filter进行黑名单过滤;

然后通过include-filter进行白名单过滤;

否则默认排除。 看下面的代码:

protected boolean isCandidateComponent(MetadataReader metadataReader) throws IOException {
        for (TypeFilter tf : this.excludeFilters) {
            if (tf.match(metadataReader, this.metadataReaderFactory)) {
                return false;
            }
        }
        for (TypeFilter tf : this.includeFilters) {
            if (tf.match(metadataReader, this.metadataReaderFactory)) {
                return isConditionMatch(metadataReader);
            }
        }
        return false;
    }

 

总结:

<context:component-scan base-package="com.jaamy"  use-default-filters="false">
         <context:include-filter type="annotation"  expression="org.springframework.stereotype.Controller" />
</context:component-scan>

针对上面的配置,use-default-filters的作用如下:

use-default-filters不配置或者是配置为true时:

不但要扫描include配置的com.jaamy包下的@Controller,而且还要扫描@Service和@Repository

use-default-filters配置为false时:

只扫描include配置的com.jaamy包下的@Controller,不扫描@Service和@Repository

 

参考地址:http://jinnianshilongnian.iteye.com/blog/1762632

 

posted on 2016-12-22 15:13  jaamy  阅读(1889)  评论(0编辑  收藏  举报