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Spring Framework example source code file (ClassPathBeanDefinitionScanner.java)

This example Spring Framework source code file (ClassPathBeanDefinitionScanner.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

annotationbeannamegenerator, annotationscopemetadataresolver, beandefinition, beandefinition, beandefinitiondefaults, beandefinitionholder, beandefinitionholder, beandefinitionregistry, beandefinitionregistry, classpathbeandefinitionscanner, illegalstateexception, set, string, string, util

The Spring Framework ClassPathBeanDefinitionScanner.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.util.LinkedHashSet;
import java.util.Set;

import org.springframework.aop.scope.ScopedProxyUtils;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanDefinitionHolder;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionDefaults;
import org.springframework.beans.factory.support.BeanDefinitionReaderUtils;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.BeanNameGenerator;
import org.springframework.core.io.ResourceLoader;
import org.springframework.util.Assert;
import org.springframework.util.PatternMatchUtils;

/**
 * A bean definition scanner that detects bean candidates on the classpath,
 * registering corresponding bean definitions with a given registry (BeanFactory
 * or ApplicationContext).
 *
 * <p>Candidate classes are detected through configurable type filters. The
 * default filters include classes that are annotated with Spring's
 * {@link org.springframework.stereotype.Component @Component},
 * {@link org.springframework.stereotype.Repository @Repository},
 * {@link org.springframework.stereotype.Service @Service}, or
 * {@link org.springframework.stereotype.Controller @Controller} stereotype.
 *
 * @author Mark Fisher
 * @author Juergen Hoeller
 * @since 2.5
 * @see org.springframework.stereotype.Component
 * @see org.springframework.stereotype.Repository
 * @see org.springframework.stereotype.Service
 * @see org.springframework.stereotype.Controller
 */
public class ClassPathBeanDefinitionScanner extends ClassPathScanningCandidateComponentProvider {

	private final BeanDefinitionRegistry registry;

	private BeanDefinitionDefaults beanDefinitionDefaults = new BeanDefinitionDefaults();

	private BeanNameGenerator beanNameGenerator = new AnnotationBeanNameGenerator();

	private ScopeMetadataResolver scopeMetadataResolver = new AnnotationScopeMetadataResolver();

	private String[] autowireCandidatePatterns;

	private boolean includeAnnotationConfig = true;


	/**
	 * Create a new ClassPathBeanDefinitionScanner for the given bean factory.
	 * @param registry the BeanFactory to load bean definitions into,
	 * in the form of a BeanDefinitionRegistry
	 */
	public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry) {
		this(registry, true);
	}

	/**
	 * Create a new ClassPathBeanDefinitionScanner for the given bean factory.
	 * <p>If the passed-in bean factory does not only implement the BeanDefinitionRegistry
	 * interface but also the ResourceLoader interface, it will be used as default
	 * ResourceLoader as well. This will usually be the case for
	 * {@link org.springframework.context.ApplicationContext} implementations.
	 * <p>If given a plain BeanDefinitionRegistry, the default ResourceLoader will be a
	 * {@link org.springframework.core.io.support.PathMatchingResourcePatternResolver}.
	 * @param registry the BeanFactory to load bean definitions into,
	 * in the form of a BeanDefinitionRegistry
	 * @param useDefaultFilters whether to include the default filters for the
	 * {@link org.springframework.stereotype.Component @Component},
	 * {@link org.springframework.stereotype.Repository @Repository},
	 * {@link org.springframework.stereotype.Service @Service}, and
	 * {@link org.springframework.stereotype.Controller @Controller} stereotype
	 * annotations.
	 * @see #setResourceLoader
	 */
	public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, boolean useDefaultFilters) {
		super(useDefaultFilters);

		Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
		this.registry = registry;

		// Determine ResourceLoader to use.
		if (this.registry instanceof ResourceLoader) {
			setResourceLoader((ResourceLoader) this.registry);
		}
	}


	/**
	 * Return the BeanDefinitionRegistry that this scanner operates on.
	 */
	public final BeanDefinitionRegistry getRegistry() {
		return this.registry;
	}

	/**
	 * Set the defaults to use for detected beans.
	 * @see BeanDefinitionDefaults
	 */
	public void setBeanDefinitionDefaults(BeanDefinitionDefaults beanDefinitionDefaults) {
		this.beanDefinitionDefaults =
				(beanDefinitionDefaults != null ? beanDefinitionDefaults : new BeanDefinitionDefaults());
	}

	/**
	 * Set the name-matching patterns for determining autowire candidates.
	 * @param autowireCandidatePatterns the patterns to match against
	 */
	public void setAutowireCandidatePatterns(String[] autowireCandidatePatterns) {
		this.autowireCandidatePatterns = autowireCandidatePatterns;
	}

	/**
	 * Set the BeanNameGenerator to use for detected bean classes.
	 * <p>Default is a {@link AnnotationBeanNameGenerator}.
	 */
	public void setBeanNameGenerator(BeanNameGenerator beanNameGenerator) {
		this.beanNameGenerator = (beanNameGenerator != null ? beanNameGenerator : new AnnotationBeanNameGenerator());
	}

	/**
	 * Set the ScopeMetadataResolver to use for detected bean classes.
	 * Note that this will override any custom "scopedProxyMode" setting.
	 * <p>The default is an {@link AnnotationScopeMetadataResolver}.
	 * @see #setScopedProxyMode
	 */
	public void setScopeMetadataResolver(ScopeMetadataResolver scopeMetadataResolver) {
		this.scopeMetadataResolver = scopeMetadataResolver;
	}

	/**
	 * Specify the proxy behavior for non-singleton scoped beans.
	 * Note that this will override any custom "scopeMetadataResolver" setting.
	 * <p>The default is {@link ScopedProxyMode#NO}.
	 * @see #setScopeMetadataResolver
	 */
	public void setScopedProxyMode(ScopedProxyMode scopedProxyMode) {
		this.scopeMetadataResolver = new AnnotationScopeMetadataResolver(scopedProxyMode);
	}

	/**
	 * Specify whether to register annotation config post-processors.
	 * <p>The default is to register the post-processors. Turn this off
	 * to be able to ignore the annotations or to process them differently.
	 */
	public void setIncludeAnnotationConfig(boolean includeAnnotationConfig) {
		this.includeAnnotationConfig = includeAnnotationConfig;
	}


	/**
	 * Perform a scan within the specified base packages.
	 * @param basePackages the packages to check for annotated classes
	 * @return number of beans registered
	 */
	public int scan(String... basePackages) {
		int beanCountAtScanStart = this.registry.getBeanDefinitionCount();

		doScan(basePackages);

		// Register annotation config processors, if necessary.
		if (this.includeAnnotationConfig) {
			AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
		}

		return this.registry.getBeanDefinitionCount() - beanCountAtScanStart;
	}

	/**
	 * Perform a scan within the specified base packages,
	 * returning the registered bean definitions.
	 * <p>This method does not register an annotation config processor
	 * but rather leaves this up to the caller.
	 * @param basePackages the packages to check for annotated classes
	 * @return number of beans registered
	 */
	protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
		Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet();
		for (int i = 0; i < basePackages.length; i++) {
			Set<BeanDefinition> candidates = findCandidateComponents(basePackages[i]);
			for (BeanDefinition candidate : candidates) {
				String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
				if (candidate instanceof AbstractBeanDefinition) {
					postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
				}
				ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
				BeanDefinition beanDefinition = applyScope(candidate, beanName, scopeMetadata);
				if (checkCandidate(beanName, beanDefinition)) {
					BeanDefinitionHolder bdHolder = new BeanDefinitionHolder(beanDefinition, beanName);
					beanDefinitions.add(bdHolder);
					registerBeanDefinition(bdHolder, this.registry);
				}
			}
		}
		return beanDefinitions;
	}

	/**
	 * Apply further settings to the given bean definition,
	 * beyond the contents retrieved from scanning the component class.
	 * @param beanDefinition the scanned bean definition
	 * @param beanName the generated bean name for the given bean
	 */
	protected void postProcessBeanDefinition(AbstractBeanDefinition beanDefinition, String beanName) {
		beanDefinition.applyDefaults(this.beanDefinitionDefaults);
		if (this.autowireCandidatePatterns != null) {
			beanDefinition.setAutowireCandidate(PatternMatchUtils.simpleMatch(this.autowireCandidatePatterns, beanName));
		}
	}

	/**
	 * Register the specified bean with the given registry.
	 * <p>Can be overridden in subclasses, e.g. to adapt the registration
	 * process or to register further bean definitions for each scanned bean.
	 * @param definitionHolder the bean definition plus bean name for the bean
	 * @param registry the BeanDefinitionRegistry to register the bean with
	 */
	protected void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) {
		BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, registry);
	}


	/**
	 * Check the given candidate's bean name, determining whether the corresponding
	 * bean definition needs to be registered or conflicts with an existing definition.
	 * @param beanName the suggested name for the bean
	 * @param beanDefinition the corresponding bean definition
	 * @return <code>true if the bean can be registered as-is;
	 * <code>false if it should be skipped because there is an
	 * existing, compatible bean definition for the specified name
	 * @throws IllegalStateException if an existing, incompatible
	 * bean definition has been found for the specified name
	 */
	protected boolean checkCandidate(String beanName, BeanDefinition beanDefinition) throws IllegalStateException {
		if (!this.registry.containsBeanDefinition(beanName)) {
			return true;
		}
		BeanDefinition existingDef = this.registry.getBeanDefinition(beanName);
		if (isCompatible(beanDefinition, existingDef)) {
			return false;
		}
		throw new IllegalStateException("Annotation-specified bean name '" + beanName +
				"' for bean class [" + beanDefinition.getBeanClassName() + "] conflicts with existing, " +
				"non-compatible bean definition of same name and class [" + existingDef.getBeanClassName() + "]");
	}

	/**
	 * Determine whether the given new bean definition is compatible with
	 * the given existing bean definition.
	 * <p>The default implementation simply considers them as compatible
	 * when the bean class name matches.
	 * @param newDefinition the new bean definition, originated from scanning
	 * @param existingDefinition the existing bean definition, probably from
	 * an existing bean definition
	 * @return whether the definitions are considered as compatible, with the
	 * new definition to be skipped in favor of the existing definition
	 */
	protected boolean isCompatible(BeanDefinition newDefinition, BeanDefinition existingDefinition) {
		return newDefinition.getBeanClassName().equals(existingDefinition.getBeanClassName());
	}

	/**
	 * Apply the specified scope to the given bean definition.
	 * @param beanDefinition the bean definition to configure
	 * @param beanName the name of the bean
	 * @param scopeMetadata the corresponding scope metadata
	 * @return the final bean definition to use (potentially a proxy)
	 */
	private BeanDefinition applyScope(BeanDefinition beanDefinition, String beanName, ScopeMetadata scopeMetadata) {
		String scope = scopeMetadata.getScopeName();
		ScopedProxyMode scopedProxyMode = scopeMetadata.getScopedProxyMode();
		beanDefinition.setScope(scope);
		if (BeanDefinition.SCOPE_SINGLETON.equals(scope) || BeanDefinition.SCOPE_PROTOTYPE.equals(scope) ||
				scopedProxyMode.equals(ScopedProxyMode.NO)) {
			return beanDefinition;
		}
		boolean proxyTargetClass = scopedProxyMode.equals(ScopedProxyMode.TARGET_CLASS);
		BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(beanDefinition, beanName);
		return ScopedProxyCreator.createScopedProxy(definitionHolder, this.registry, proxyTargetClass);
	}


	/**
	 * Inner factory class used to just introduce an AOP framework dependency
	 * when actually creating a scoped proxy.
	 */
	private static class ScopedProxyCreator {

		public static BeanDefinition createScopedProxy(
				BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry, boolean proxyTargetClass) {

			BeanDefinitionHolder scopedProxyDefinition =
					ScopedProxyUtils.createScopedProxy(definitionHolder, registry, proxyTargetClass);
			return scopedProxyDefinition.getBeanDefinition();
		}
	}

}

Other Spring Framework examples (source code examples)

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