1.定义注解

@Target({ ElementType.TYPE })@Retention(RetentionPolicy.RUNTIME)@Documented@Componentpublic @interface Interface {    /**     * 别名数组     * @return String[]，默认空字符串     */    String[] value() default "";}

2.扫描注解注册bean的处理

public class CustomerInterfaceRegistryPostProcessor implements PriorityOrdered, BeanDefinitionRegistryPostProcessor {    private final static Logger LOG = LoggerFactory.getLogger(CustomerInterfaceRegistryPostProcessor.class);    @Override    public int getOrder() {        return Ordered.LOWEST_PRECEDENCE;    }        @Override    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {        if (LOG.isDebugEnabled()) {            LOG.debug("postProcessBeanFactory");        }                //搜索被Interface注解的类。key为bean的id，value为bean的实例。        //beanFactory.getBeansWithAnnotation返回时通过getBean方法将bean的实例化，如果bean中autowired注解的属性没有实例化就会注入null        //Map
    
      map = beanFactory.getBeansWithAnnotation(Interface.class);        String[] ary = beanFactory.getBeanNamesForAnnotation(Interface.class);        if (ary!=null && ary.length>0) {            for (String beanName : ary) {                                //通过Spring的beanName获取bean的类型                Class
      cls = beanFactory.getType(beanName);                if (cls.getAnnotations()!=null && cls.getAnnotations().length>0) {                    for (Annotation annotation : cls.getAnnotations()) {                        if (annotation instanceof Interface) {                            Interface intfc = (Interface) annotation;                                                        //将全限定名注册为别名                            this.registerAlias(beanFactory, beanName, cls.getName());                                                        //其他别名注册                            for (String row : intfc.value()) {                                this.registerAlias(beanFactory, beanName, row);                            }                        }                    }                }            }        }    }    @Override    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {        if (LOG.isDebugEnabled()) {            LOG.debug("postProcessBeanDefinitionRegistry");        }    }        /**     * 为bean注册别名     * 注意：如果别名与bean的ID冲突，放弃别名注册     * @param factory ConfigurableListableBeanFactory     * @param beanName bean的ID     * @param value Interface的value     */    private void registerAlias(ConfigurableListableBeanFactory factory, String beanId, String value) {        //防止别名覆盖bean的ID        if (factory.containsBeanDefinition(value)) {            if (LOG.isDebugEnabled()) {                LOG.debug("[failed] because value=" + value + " is existed");            }            return;        }        else {            if (LOG.isDebugEnabled()) {                LOG.debug("[success] beanId=" + beanId + ", value=" + value);            }            factory.registerAlias(beanId, value);        }    }}
    

3.配置spring

好了，通过自定义注解集成Component，实现bean被spring发现并注册完成了。

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如果不想让自定义注解集成Component可以实现吗？答案是肯定可以的，就是要自定义类扫描，这部分代码我是参考MyBatis的原理实现的。

1.定义注解（去除@Component）

@Target({ ElementType.TYPE })@Retention(RetentionPolicy.RUNTIME)@Documentedpublic @interface Interface {    /**     * 别名数组     * @return String[]，默认空字符串     */    String[] value() default "";}

2.自定义类扫描

public class CustomerClassPathBeanDefinitionScanner extends ClassPathBeanDefinitionScanner {    public CustomerClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, boolean useDefaultFilters) {        super(registry, useDefaultFilters);    }        /**     * 扫描包路径，通过include和exclude等过滤条件，返回符合条件的bean定义     * 由于这个方法在父类是protected，所以只能通过继承类获取结果     * @param basePackages 需要扫描的包路径     */    public Set
    
      doScan(String... basePackages) {        return super.doScan(basePackages);    }}
    

3.扫描注解注册bean的处理

public class CustomerInterfaceRegistryPostProcessor implements PriorityOrdered, BeanDefinitionRegistryPostProcessor {    private final static Logger LOG = LoggerFactory.getLogger(CustomerInterfaceRegistryPostProcessor.class);    /**     * 搜索条件：Interface注解     */    private String annotation;    /**     * 搜索条件：扫描包路径数组     */    private String[] basePackage;        public CustomerInterfaceRegistryPostProcessor() {        super();        this.annotation = Interface.class.getName();        this.basePackage = new String[] {"net.zhust.spring", "net.zhust.common"};    }    public CustomerInterfaceRegistryPostProcessor(String annotation, String[] basePackage) {        super();        this.annotation = annotation;        this.basePackage = basePackage;    }    @Override    public int getOrder() {        return Ordered.LOWEST_PRECEDENCE;    }        private Set
    
      getBeanDefinitionHolderSet(String...basePackages) {        Set
     
       result = null;        BeanDefinitionRegistry registry = new SimpleBeanDefinitionRegistry();        BondeClassPathBeanDefinitionScanner scanner = new BondeClassPathBeanDefinitionScanner(registry, false);        final String annotationType = this.annotation;        //配置过滤条件        TypeFilter includeFilter = new TypeFilter(){            @Override            public boolean match(MetadataReader arg0, MetadataReaderFactory arg1) throws IOException {                boolean result = false;                //拥有annotationInterface指定的注解的类（非抽象）                if (arg0.getClassMetadata().isConcrete() && arg0.getAnnotationMetadata().hasAnnotation(annotationType)) {                    result = true;                }                return result;            }                    };        scanner.addIncludeFilter(includeFilter);                result = scanner.doScan(basePackages);        return result;    }        @Override    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {        if (LOG.isDebugEnabled()) {            LOG.debug("postProcessBeanFactory");        }                DefaultListableBeanFactory dlbf = (DefaultListableBeanFactory) beanFactory;        Set
      
        beans = this.getBeanDefinitionHolderSet(this.basePackage);        for (BeanDefinitionHolder bdh : beans) {            //获取bean的类型(经测试此时，bean可以操作)            try {                Class
        cls = Class.forName(bdh.getBeanDefinition().getBeanClassName());                cls.getInterfaces();                if (cls.getAnnotations()!=null && cls.getAnnotations().length>0) {                    for (Annotation annotation : cls.getAnnotations()) {                        if (annotation instanceof Interface) {                            Interface intfc = (Interface) annotation;                            //将全限定名注册为别名                            this.registerAlias(beanFactory, bdh.getBeanName(), cls.getName());                                                        //其他别名注册                            for (String row : intfc.value()) {                                this.registerAlias(beanFactory, bdh.getBeanName(), row);                            }                                                        //如果不做registerBeanDefinition，那么bean内的注解会无效(如Autowired)                            RootBeanDefinition rbd = new RootBeanDefinition(cls);                            dlbf.registerBeanDefinition(bdh.getBeanName(), rbd);                        }                    }                }            }            catch(Exception ex) {                ex.printStackTrace();            }        }    }    @Override    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {        if (LOG.isDebugEnabled()) {            LOG.debug("postProcessBeanDefinitionRegistry");        }    }        /**     * 为bean注册别名     * 注意：如果别名与bean的ID冲突，放弃别名注册     * @param factory ConfigurableListableBeanFactory     * @param beanName bean的ID     * @param value Interface的value     */    private void registerAlias(ConfigurableListableBeanFactory factory, String beanId, String value) {        //防止别名覆盖bean的ID        if (factory.containsBeanDefinition(value)) {            if (LOG.isDebugEnabled()) {                LOG.debug("[failed] because value=" + value + " is existed");            }            return;        }        else {            if (LOG.isDebugEnabled()) {                LOG.debug("[success] beanId=" + beanId + ", value=" + value);            }            factory.registerAlias(beanId, value);        }    }}
      
     
    

4.配置spring

    
    	
     		
      		
      			
       				
        
         net.zhust.spring
        				
        
         net.zhust.common
        			
       		
      	
     	
     
    

好了，就那么简单！