Spring Framework example source code file (ClassPathScanningCandidateComponentProvider.java)

This example Spring Framework source code file (ClassPathScanningCandidateComponentProvider.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

classpathscanningcandidatecomponentprovider, classpathscanningcandidatecomponentprovider, default_resource_pattern, default_resource_pattern, io, ioexception, ioexception, linkedlist, list, resource, scannedgenericbeandefinition, set, string, string, typefilter, util

The Spring Framework ClassPathScanningCandidateComponentProvider.java source code

/*
 * Copyright 2002-2008 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.context.annotation;

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

import org.springframework.beans.factory.BeanDefinitionStoreException;
import org.springframework.beans.factory.annotation.AnnotatedBeanDefinition;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.context.ResourceLoaderAware;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
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.core.type.filter.AnnotationTypeFilter;
import org.springframework.core.type.filter.TypeFilter;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Controller;
import org.springframework.stereotype.Repository;
import org.springframework.stereotype.Service;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.SystemPropertyUtils;

/**
 * A component provider that scans the classpath from a base package. It then
 * applies exclude and include filters to the resulting classes to find candidates.
 *
 * <p>This implementation is based on Spring's
 * {@link org.springframework.core.type.classreading.MetadataReader MetadataReader}
 * facility, backed by an ASM {@link org.objectweb.asm.ClassReader ClassReader}.
 *
 * @author Mark Fisher
 * @author Juergen Hoeller
 * @author Ramnivas Laddad
 * @since 2.5
 * @see org.springframework.core.type.classreading.MetadataReaderFactory
 * @see org.springframework.core.type.AnnotationMetadata
 * @see ScannedGenericBeanDefinition
 */
public class ClassPathScanningCandidateComponentProvider implements ResourceLoaderAware {

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


	private ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver();

	private MetadataReaderFactory metadataReaderFactory = new CachingMetadataReaderFactory(this.resourcePatternResolver);

	private String resourcePattern = DEFAULT_RESOURCE_PATTERN;

	private final List<TypeFilter> includeFilters = new LinkedList();

	private final List<TypeFilter> excludeFilters = new LinkedList();


	/**
	 * Create a ClassPathScanningCandidateComponentProvider.
	 * @param useDefaultFilters whether to register the default filters for the
	 * {@link Component @Component}, {@link Repository @Repository},
	 * {@link Service @Service}, and {@link Controller @Controller}
	 * stereotype annotations
	 * @see #registerDefaultFilters()
	 */
	public ClassPathScanningCandidateComponentProvider(boolean useDefaultFilters) {
		if (useDefaultFilters) {
			registerDefaultFilters();
		}
	}


	/**
	 * Set the ResourceLoader to use for resource locations.
	 * This will typically be a ResourcePatternResolver implementation.
	 * <p>Default is PathMatchingResourcePatternResolver, also capable of
	 * resource pattern resolving through the ResourcePatternResolver interface.
	 * @see org.springframework.core.io.support.ResourcePatternResolver
	 * @see org.springframework.core.io.support.PathMatchingResourcePatternResolver
	 */
	public void setResourceLoader(ResourceLoader resourceLoader) {
		this.resourcePatternResolver = ResourcePatternUtils.getResourcePatternResolver(resourceLoader);
		this.metadataReaderFactory = new CachingMetadataReaderFactory(resourceLoader);
	}

	/**
	 * Return the ResourceLoader that this component provider uses.
	 */
	public final ResourceLoader getResourceLoader() {
		return this.resourcePatternResolver;
	}

	/**
	 * Set the resource pattern to use when scanning the classpath.
	 * This value will be appended to each base package name.
	 * @see #findCandidateComponents(String)
	 * @see #DEFAULT_RESOURCE_PATTERN
	 */
	public void setResourcePattern(String resourcePattern) {
		Assert.notNull(resourcePattern, "'resourcePattern' must not be null");
		this.resourcePattern = resourcePattern;
	}

	/**
	 * Add an include type filter to the <i>end of the inclusion list.
	 */
	public void addIncludeFilter(TypeFilter includeFilter) {
		this.includeFilters.add(includeFilter);
	}

	/**
	 * Add an exclude type filter to the <i>front of the exclusion list.
	 */
	public void addExcludeFilter(TypeFilter excludeFilter) {
		this.excludeFilters.add(0, excludeFilter);
	}

	/**
	 * Reset the configured type filters.
	 * @param useDefaultFilters whether to re-register the default filters for
	 * the {@link Component @Component}, {@link Repository @Repository},
	 * {@link Service @Service}, and {@link Controller @Controller}
	 * stereotype annotations
	 * @see #registerDefaultFilters()
	 */
	public void resetFilters(boolean useDefaultFilters) {
		this.includeFilters.clear();
		this.excludeFilters.clear();
		if (useDefaultFilters) {
			registerDefaultFilters();
		}
	}

	/**
	 * Register the default filter for {@link Component @Component}.
	 * This will implicitly register all annotations that have the
	 * {@link Component @Component} meta-annotation including the
	 * {@link Repository @Repository}, {@link Service @Service}, and
	 * {@link Controller @Controller} stereotype annotations.
	 */
	protected void registerDefaultFilters() {
		this.includeFilters.add(new AnnotationTypeFilter(Component.class));
	}


	/**
	 * Scan the class path for candidate components.
	 * @param basePackage the package to check for annotated classes
	 * @return a corresponding Set of autodetected bean definitions
	 */
	public Set<BeanDefinition> findCandidateComponents(String basePackage) {
		Set<BeanDefinition> candidates = new LinkedHashSet();
		try {
			String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
					resolveBasePackage(basePackage) + "/" + this.resourcePattern;
			Resource[] resources = this.resourcePatternResolver.getResources(packageSearchPath);
			for (int i = 0; i < resources.length; i++) {
				Resource resource = resources[i];
				if (resource.isReadable()) {
					MetadataReader metadataReader = this.metadataReaderFactory.getMetadataReader(resource);
					if (isCandidateComponent(metadataReader)) {
						ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
						sbd.setSource(resource);
						if (isCandidateComponent(sbd)) {
							candidates.add(sbd);
						}
					}
				}
			}
		}
		catch (IOException ex) {
			throw new BeanDefinitionStoreException("I/O failure during classpath scanning", ex);
		}
		return candidates;
	}

	/**
	 * Resolve the specified base package into a pattern specification for
	 * the package search path.
	 * <p>The default implementation resolves placeholders against system properties,
	 * and converts a "."-based package path to a "/"-based resource path.
	 * @param basePackage the base package as specified by the user
	 * @return the pattern specification to be used for package searching
	 */
	protected String resolveBasePackage(String basePackage) {
		return ClassUtils.convertClassNameToResourcePath(SystemPropertyUtils.resolvePlaceholders(basePackage));
	}

	/**
	 * Determine whether the given class does not match any exclude filter
	 * and does match at least one include filter.
	 * @param metadataReader the ASM ClassReader for the class
	 * @return whether the class qualifies as a candidate component
	 */
	protected boolean isCandidateComponent(MetadataReader metadataReader) throws IOException {
		for (TypeFilter tf : this.excludeFilters) {
			if (tf.match(metadataReader, this.metadataReaderFactory)) {
				return false;
			}
		}
		for (TypeFilter tf : this.includeFilters) {
			if (tf.match(metadataReader, this.metadataReaderFactory)) {
				return true;
			}
		}
		return false;
	}

	/**
	 * Determine whether the given bean definition qualifies as candidate.
	 * <p>The default implementation checks whether the class is concrete
	 * (i.e. not abstract and not an interface). Can be overridden in subclasses.
	 * @param beanDefinition the bean definition to check
	 * @return whether the bean definition qualifies as a candidate component
	 */
	protected boolean isCandidateComponent(AnnotatedBeanDefinition beanDefinition) {
		return (beanDefinition.getMetadata().isConcrete() && beanDefinition.getMetadata().isIndependent());
	}

}