java:基于spring的PathMatchingResourcePatternResolver实现基于包名(package)的类扫描

spring-core提供了资源扫描实现，可以获取到java程序运行时的所有类和其他资源，所以在spring环境下，也可以使用它来自己实现查找类的功能

导入依赖

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-core</artifactId>
      <version>5.3.12</version>
      <scope>compile</scope>
    </dependency>

实现代码：SpringResourceScanner.java

import java.io.IOException;
import java.net.URL;
import java.util.Set;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;

/**
 * 基于Spring {@link PathMatchingResourcePatternResolver}实现资源扫描
 * @author guyadong
 *
 */
public class SpringResourceScanner {
	private static final String CLASS_SUFFIX = ".class";
	private static final PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
	private Set<URL> getResources(String rootDirPath, String suffix) throws IOException {
		if(null==rootDirPath) {
			throw new NullPointerException("rootDirPath must not be null");
		}
		String path = rootDirPath;
		String locationPattern = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX + path;
		if(null != suffix) {
			locationPattern+="/**/*"+suffix;
		}
		Resource[] resources = resolver.getResources(locationPattern);
		return Stream.of(resources).map(input->{
			try {
				return input.getURL();
			} catch (IOException e) {
				throw new RuntimeException(e);
			}
		}).collect(Collectors.toSet());
	}
	/**
	 * 扫描指定包名下的所有类
	 * @param packagename
	 * @param filter
	 * @throws IOException
	 */
	public Set<Class<?>> getClasses(String packagename) throws IOException {
		if(null == packagename) {
			throw new NullPointerException("packagename must not be null");
		}
		final String path = packagename.replace('.', '/');
		Set<URL> rootDirs = getResources(path,null);
		Set<URL> urls = getResources(path, CLASS_SUFFIX);
		//final Set<String> rootPrefixes = rootDirs.stream().map(input->input.toString().substring(0,path.length)).collect(Collectors.toSet());
		// 根据网友 @sp42a 建议修改，
		// 字符替换操作改为只删除结尾内容，
		// 避免包名与groupId相同时将jar所在路径也错误替换的问题，
		// 如 jar:file:/path/com/ajaxjs/sqlman/1.0/sqlman-1.0.jar!/com/ajaxjs/sqlman
		final Set<String> rootPrefixes = rootDirs.stream().map(URL::toString)
				.map(input -> input.substring(0, input.length() - path.length())).collect(Collectors.toSet());
		return urls.stream().map(new CLassBuilder(rootPrefixes)).collect(Collectors.toSet());
	}

	protected static class CLassBuilder implements Function<URL, Class<?>>{
		private final Iterable<String> rootPrefixes;
		public CLassBuilder(Iterable<String> rootPrefixes) {
			this.rootPrefixes = rootPrefixes;
		}
		@Override
		public Class<?> apply(URL input) {
			String url = input.toString();
			for(String prefix:rootPrefixes) {
				if(url.startsWith(prefix)) {
					try {
						String p = url.substring(prefix.length(),url.length()-CLASS_SUFFIX.length());
						String className = p.replace('/', '.');
						return Class.forName( className,false,getDefaultClassLoader());
					} catch (Throwable e) {
						System.out.printf("%s:%s\n",e.getClass().getSimpleName(), e.getMessage());
						return null;
					}
				}
			};
			throw new IllegalArgumentException("INVALID URL "+input);
		}
		
	}
	public static ClassLoader getDefaultClassLoader() {
		ClassLoader cl = null;
		try {
			cl = Thread.currentThread().getContextClassLoader();
		}
		catch (Throwable ex) {
			// Cannot access thread context ClassLoader - falling back...
		}
		if (cl == null) {
			// No thread context class loader -> use class loader of this class.
			cl = SpringResourceScanner.class.getClassLoader();
			if (cl == null) {
				// getClassLoader() returning null indicates the bootstrap ClassLoader
				try {
					cl = ClassLoader.getSystemClassLoader();
				}
				catch (Throwable ex) {
					// Cannot access system ClassLoader - oh well, maybe the caller can live with null...
				}
			}
		}
		return cl;
	}
}

调用示例：SpringResourceScannerTest.java

import static org.junit.Assert.*;

import java.util.Set;

import static net.gdface.utils.SimpleLog.log;

import org.junit.Test;

public class SpringResourceScannerTest {
	public static final SpringResourceScanner SPRING_RESOURCE_SCANNER = new SpringResourceScanner();
	@Test
	public void test3SpringGetClasses() {
		try {
			Set<Class<?>> urls = SPRING_RESOURCE_SCANNER.getClasses("net.facelib.cell");
			for(Class<?> url:urls) {
				log("class:{}",url);
			}
			log("class count:{}",urls.size());
		} catch (Exception e) {
			e.printStackTrace();
			fail();
		}
	}
	@Test
	public void test4SpringGetClasses() {
		try {
			Set<Class<?>> urls = SPRING_RESOURCE_SCANNER.getClasses("org.springframework.core");
			for(Class<?> url:urls) {
				log("class:{}",url);
			}
			log("class count:{}",urls.size());
		} catch (Throwable e) {
			e.printStackTrace();
			fail();
		}
	}
}