Use spring custom annotation scan to find classes that use custom annotations

We often have classes with specified annotations in scanning projects. The following is a method of using spring to scan custom annotations, which is more flexible.

I put the scanned class in the map here, you can put it elsewhere for later use

import lombok.extern.slf4j.Slf4j;
import org.apache.shiro.SecurityUtils;
import org.apache.shiro.session.Session;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;
import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.core.type.classreading.MetadataReaderFactory;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;

import javax.persistence.Table;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * 扫描指定包下带有指定注解的class
 * @author jaffreyen
 * @date 2018/3/5
 */
@Slf4j
public class MyApplicationListener implements ApplicationListener {

    /**
     * Handle an application event.
     *
     * @param event the event to respond to
     */
    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver();
        final String RESOURCE_PATTERN = "/**/*.class";
        // 扫描的包名
        final String BASE_PACKAGE = "com.xxx";
        Map<String,Class<?>> classCache = new HashMap<>();
        try {
            String pattern = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX + ClassUtils.convertClassNameToResourcePath(BASE_PACKAGE)
                    + RESOURCE_PATTERN;
            Resource[] resources = resourcePatternResolver.getResources(pattern);
            MetadataReaderFactory readerFactory = new CachingMetadataReaderFactory(resourcePatternResolver);
            for (Resource resource : resources) {
                if (resource.isReadable()) {
                    MetadataReader reader = readerFactory.getMetadataReader(resource);
                    //扫描到的class
                    String className = reader.getClassMetadata().getClassName();
                    Class<?> clazz = Class.forName(className);
                    //判断是否有指定注解
                    Table annotation = clazz.getAnnotation(Table.class);
                    if(annotation != null){
                        //这个类使用了自定义注解
                        classCache.put(className, clazz);
                    }
                }
            }
        } catch (IOException | ClassNotFoundException e) {
            log.error("读取class失败", e);
        }
    }
}