java扫描包(包含自己写的包或者jar中的包)及子包下的所有类

不管是在Spring还是Mybatis中，我们都需要配置一个包路径进行扫描类对象。

在Spring中，我们需要配置包路径，让Spring容器能扫描包下面的Bean组件。在mybatis中，我们需要配置mapper包路径，以扫描mapper接口，并生成对应的Bean实例。

现在，我参照spring的部分源码，来写一个工具类扫描包及子包下的所有类。

package com.company.handler;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
import org.springframework.beans.factory.support.GenericBeanDefinition;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ResourceLoaderAware;
import org.springframework.core.env.Environment;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.core.io.support.ResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternUtils;
import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.core.type.classreading.MetadataReaderFactory;
import org.springframework.stereotype.Component;
import org.springframework.util.ClassUtils;

import java.io.IOException;
import java.util.LinkedHashSet;
import java.util.Set;

/**
 * 用于Spring动态注入自定义接口
 * @author lichuang
 */
@Component
public class ServiceBeanDefinitionScanner implements ResourceLoaderAware,ApplicationContextAware {

    private static final String DEFAULT_RESOURCE_PATTERN = "**/*.class";

    private MetadataReaderFactory metadataReaderFactory;

    /**
     * 根据包路径获取包及子包下的所有类
     * @param basePackage basePackage
     * @return Set> Set>
     */
    private Set> scannerPackages(String basePackage) {
        Set> set = new LinkedHashSet<>();
        String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
                resolveBasePackage(basePackage) + '/' + DEFAULT_RESOURCE_PATTERN;
        try {
            Resource[] resources = this.resourcePatternResolver.getResources(packageSearchPath);
            for (Resource resource : resources) {
                if (resource.isReadable()) {
                    MetadataReader metadataReader = this.metadataReaderFactory.getMetadataReader(resource);
                    String className = metadataReader.getClassMetadata().getClassName();
                    Class clazz;
                    try {
                        clazz = Class.forName(className);
                        set.add(clazz);
                    } catch (ClassNotFoundException e) {
                        e.printStackTrace();
                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return set;
    }

    protected String resolveBasePackage(String basePackage) {
        return ClassUtils.convertClassNameToResourcePath(this.getEnvironment().resolveRequiredPlaceholders(basePackage));
    }


    private ResourcePatternResolver resourcePatternResolver;

    private ApplicationContext applicationContext;

    @Override
    public void setResourceLoader(ResourceLoader resourceLoader) {
        this.resourcePatternResolver = ResourcePatternUtils.getResourcePatternResolver(resourceLoader);
        this.metadataReaderFactory = new CachingMetadataReaderFactory(resourceLoader);
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }

    private Environment getEnvironment() {
        return applicationContext.getEnvironment();
    }
}