通过bean parser实现spring scan groovy文件装载bean

Spring使用groovy作为bean，官方用了lang标签，但都是一个个文件。Groovy本身编译成class文件后当然可以和Java完全一样可以被component-scan。

但是我想实现能够扫描groovy文件，并且groovy文件发生修改时候能够重新load（方便开发环境中提高效率），网上查查了，然后自己摸索了下，简单实现了。

思路：

1. 通过NamespaceHandlerSupport自己写一个parser，parser和已有的component-scan的区别就是修改了ClassPathBeanDefinitionScanner的reourceLoader，classloader用GroovyClassLoader，metadataReaderFactory重写了一个支持groovy class的，spring的是用asm去解析class文件（所以他也只支持编译后的）。

2. 写个timer监听groovy文件的最后修改时间，发生变化的，就让application context reload。

代码献上

import org.springframework.beans.factory.xml.ParserContext;
import org.springframework.context.annotation.ClassPathBeanDefinitionScanner;
import org.springframework.context.annotation.ComponentScanBeanDefinitionParser;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.type.filter.AnnotationTypeFilter;
import org.springframework.stereotype.Component;
import org.w3c.dom.Element;

public class ComponentGroovyScanParser extends ComponentScanBeanDefinitionParser {
	
	@Override
	protected ClassPathBeanDefinitionScanner configureScanner(ParserContext parserContext, Element element) {
		ClassPathBeanDefinitionScanner scanner = createScanner(parserContext.getReaderContext(), true);
		scanner.setEnvironment(parserContext.getReaderContext().getEnvironment());
		scanner.setBeanDefinitionDefaults(parserContext.getDelegate().getBeanDefinitionDefaults());
		scanner.setAutowireCandidatePatterns(parserContext.getDelegate().getAutowireCandidatePatterns());

		scanner.addIncludeFilter(new AnnotationTypeFilter(Component.class));

		scanner.setResourceLoader(new PathMatchingResourcePatternResolver(ClassLoaderHolder.gcl));
		scanner.setResourcePattern("**/*.groovy");
		PathMatchingResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver(
				ClassLoaderHolder.gcl);
		scanner.setMetadataReaderFactory(new CachingMetadataReaderFactory2(resourcePatternResolver));

		return scanner;
	}
}

?

import java.io.IOException;
import java.lang.annotation.Annotation;
import java.util.LinkedHashMap;
import java.util.Map;

import org.springframework.asm.Opcodes;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.core.type.ClassMetadata;
import org.springframework.core.type.classreading.AnnotationMetadataReadingVisitor;
import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.core.type.classreading.SimpleMetadataReaderFactory;

public class CachingMetadataReaderFactory2 extends SimpleMetadataReaderFactory {

	/** Default maximum number of entries for the MetadataReader cache: 256 */
	public static final int DEFAULT_CACHE_LIMIT = 256;

	private volatile int cacheLimit = DEFAULT_CACHE_LIMIT;

	@SuppressWarnings("serial")
	private final Map<Resource, MetadataReader> metadataReaderCache = new LinkedHashMap<Resource, MetadataReader>(
			DEFAULT_CACHE_LIMIT, 0.75f, true) {
		@Override
		protected boolean removeEldestEntry(Map.Entry<Resource, MetadataReader> eldest) {
			return size() > getCacheLimit();
		}
	};

	/**
	 * Create a new CachingMetadataReaderFactory for the default class loader.
	 */
	public CachingMetadataReaderFactory2() {
		super();
	}

	/**
	 * Create a new CachingMetadataReaderFactory for the given resource loader.
	 * 
	 * @param resourceLoader
	 *            the Spring ResourceLoader to use (also determines the
	 *            ClassLoader to use)
	 */
	public CachingMetadataReaderFactory2(ResourceLoader resourceLoader) {
		super(resourceLoader);
	}

	/**
	 * Create a new CachingMetadataReaderFactory for the given class loader.
	 * 
	 * @param classLoader
	 *            the ClassLoader to use
	 */
	public CachingMetadataReaderFactory2(ClassLoader classLoader) {
		super(classLoader);
	}

	/**
	 * Specify the maximum number of entries for the MetadataReader cache.
	 * Default is 256.
	 */
	public void setCacheLimit(int cacheLimit) {
		this.cacheLimit = cacheLimit;
	}

	/**
	 * Return the maximum number of entries for the MetadataReader cache.
	 */
	public int getCacheLimit() {
		return this.cacheLimit;
	}

	@Override
	public MetadataReader getMetadataReader(Resource resource) throws IOException {
		if (getCacheLimit() <= 0) {
			return super.getMetadataReader(resource);
		}
		synchronized (this.metadataReaderCache) {
			MetadataReader metadataReader = this.metadataReaderCache.get(resource);
			if (metadataReader == null) {
				metadataReader = genReader(resource);
				this.metadataReaderCache.put(resource, metadataReader);
			}
			return metadataReader;
		}
	}

	@SuppressWarnings("rawtypes")
	private MetadataReader genReader(final Resource resource) throws IOException {
		Class clz = ClassLoaderHolder.gcl.parseClass(resource.getFile());

		final AnnotationMetadataReadingVisitor visitor = new AnnotationMetadataReadingVisitor(
				super.getResourceLoader().getClassLoader());

		Class[] ll = clz.getInterfaces();
		// must has GroovyObject
		String[] interfaces = new String[ll.length];
		for (int i = 0; i < interfaces.length; i++) {
			interfaces[i] = ll[i].getName();
		}
		visitor.visit(0, Opcodes.ACC_PUBLIC, clz.getName(), null, clz.getSuperclass().getName(), interfaces);

		Annotation[] ll2 = clz.getAnnotations();
		if (ll2.length > 0) {
			for (Annotation ano : ll2) {
				visitor.getAnnotationTypes().add(ano.annotationType().getName());
			}
		}

		MetadataReader reader = new MetadataReader() {
			@Override
			public Resource getResource() {
				return resource;
			}

			@Override
			public ClassMetadata getClassMetadata() {
				return visitor;
			}

			@Override
			public AnnotationMetadata getAnnotationMetadata() {
				return visitor;
			}

		};
		return reader;
	}

	/**
	 * Clear the entire MetadataReader cache, removing all cached class
	 * metadata.
	 */
	public void clearCache() {
		synchronized (this.metadataReaderCache) {
			this.metadataReaderCache.clear();
		}
	}

}

?

import groovy.lang.GroovyClassLoader;

public class ClassLoaderHolder {
	public static GroovyClassLoader gcl = new GroovyClassLoader();

	static {
		gcl.addClasspath("src");
	}
}

?

原文：http://key232323.iteye.com/blog/2294518