FunctionExecutionComponentProvider.java

/*
 * Copyright 2002-2013 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.data.gemfire.function.config;

import java.io.IOException;
import java.lang.annotation.Annotation;
import java.lang.annotation.Inherited;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;

import org.springframework.beans.factory.annotation.AnnotatedBeanDefinition;
import org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.core.type.classreading.MetadataReaderFactory;
import org.springframework.core.type.filter.AbstractTypeHierarchyTraversingFilter;
import org.springframework.core.type.filter.TypeFilter;
import org.springframework.util.Assert;

/**
 * Custom {@link ClassPathScanningCandidateComponentProvider} scanning for interfaces annotated for 
 * function execution
 * 
 * @author David Turanski
 */
class FunctionExecutionComponentProvider extends ClassPathScanningCandidateComponentProvider {

	 
	private final Set<Class<? extends Annotation>> functionExecutionAnnotationTypes;

	/**
	 * Creates a new {@link FunctionExecutionComponentProvider} using the given {@link TypeFilter} to include components to be
	 * picked up.
	 * 
	 * @param includeFilters the {@link TypeFilter}s to select function execution interfaces to consider, must not be
	 *          {@literal null}.
	 */
	public FunctionExecutionComponentProvider(Iterable<? extends TypeFilter> includeFilters , Set<Class<? extends Annotation>> functionExecutionAnnotationTypes) {

		super(false);

		this.functionExecutionAnnotationTypes = functionExecutionAnnotationTypes;
		Assert.notNull(includeFilters);

		if (includeFilters.iterator().hasNext()) {
			for (TypeFilter filter : includeFilters) {
				addIncludeFilter(filter);
			}			
		} else {
			for (Class<? extends Annotation> annotation: this.functionExecutionAnnotationTypes) {
				super.addIncludeFilter(new AnnotationTypeFilter(annotation, true, true));
			}
		} 
	}
	
	/**
	 * Custom extension of {@link #addIncludeFilter(TypeFilter)} to extend the added {@link TypeFilter}. For the
	 * {@link TypeFilter} handed we'll have two filters registered: one additionally enforcing the
	 * {@link FunctionExecutionDefinition} annotation, the other one forcing the extension of {@link AbstractFunctionExecution}.
	 * 
	 * @see ClassPathScanningCandidateComponentProvider#addIncludeFilter(TypeFilter)
	 */
	@Override
	public void addIncludeFilter(TypeFilter includeFilter) {

		List<TypeFilter> filterPlusInterface = new ArrayList<TypeFilter>();
		filterPlusInterface.add(includeFilter);
 
		super.addIncludeFilter(new AllTypeFilter(filterPlusInterface));

		List<TypeFilter> filterPlusAnnotation = new ArrayList<TypeFilter>();
		filterPlusAnnotation.add(includeFilter);
		for (Class<? extends Annotation> annotation: this.functionExecutionAnnotationTypes) {
			filterPlusAnnotation.add(new AnnotationTypeFilter(annotation, true, true));
		}

		super.addIncludeFilter(new AllTypeFilter(filterPlusAnnotation)); 
	}

	/*
	 * (non-Javadoc)
	 * @see org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider#isCandidateComponent(org.springframework.beans.factory.annotation.AnnotatedBeanDefinition)
	 */
	@Override
	protected boolean isCandidateComponent(AnnotatedBeanDefinition beanDefinition) {

 		boolean isTopLevelType = !beanDefinition.getMetadata().hasEnclosingClass();

		return isTopLevelType;
	}


	// Copy of Spring's AnnotationTypeFilter until SPR-8336 gets resolved.

	/**
	 * A simple filter which matches classes with a given annotation, checking inherited annotations as well.
	 * <p>
	 * The matching logic mirrors that of <code>Class.isAnnotationPresent()</code>.
	 * 
	 * @author Mark Fisher
	 * @author Ramnivas Laddad
	 * @author Juergen Hoeller
	 * @since 2.5
	 */
	private static class AnnotationTypeFilter extends AbstractTypeHierarchyTraversingFilter {

		private final Class<? extends Annotation> annotationType;

		private final boolean considerMetaAnnotations;

		/**
		 * Create a new AnnotationTypeFilter for the given annotation type. This filter will also match meta-annotations. To
		 * disable the meta-annotation matching, use the constructor that accepts a ' <code>considerMetaAnnotations</code>'
		 * argument. The filter will not match interfaces.
		 * 
		 * @param annotationType the annotation type to match
		 */
		@SuppressWarnings("unused")
		public AnnotationTypeFilter(Class<? extends Annotation> annotationType) {
			this(annotationType, true);
		}

		/**
		 * Create a new AnnotationTypeFilter for the given annotation type. The filter will not match interfaces.
		 * 
		 * @param annotationType the annotation type to match
		 * @param considerMetaAnnotations whether to also match on meta-annotations
		 */
		public AnnotationTypeFilter(Class<? extends Annotation> annotationType, boolean considerMetaAnnotations) {
			this(annotationType, considerMetaAnnotations, false);
		}

		/**
		 * Create a new {@link AnnotationTypeFilter} for the given annotation type.
		 * 
		 * @param annotationType the annotation type to match
		 * @param considerMetaAnnotations whether to also match on meta-annotations
		 * @param considerInterfaces whether to also match interfaces
		 */
		public AnnotationTypeFilter(Class<? extends Annotation> annotationType, boolean considerMetaAnnotations,
				boolean considerInterfaces) {
			super(annotationType.isAnnotationPresent(Inherited.class), considerInterfaces);
			this.annotationType = annotationType;
			this.considerMetaAnnotations = considerMetaAnnotations;
		}

		@Override
		protected boolean matchSelf(MetadataReader metadataReader) {
			AnnotationMetadata metadata = metadataReader.getAnnotationMetadata();
			return metadata.hasAnnotation(this.annotationType.getName())
					|| (this.considerMetaAnnotations && metadata.hasMetaAnnotation(this.annotationType.getName()));
		}

		@Override
		protected Boolean matchSuperClass(String superClassName) {
			if (Object.class.getName().equals(superClassName)) {
				return Boolean.FALSE;
			} else if (superClassName.startsWith("java.")) {
				try {
					Class<?> clazz = getClass().getClassLoader().loadClass(superClassName);
					return (clazz.getAnnotation(this.annotationType) != null);
				} catch (ClassNotFoundException ex) {
					// Class not found - can't determine a match that way.
				}
			}
			return null;
		}
	}

	/**
	 * Helper class to create a {@link TypeFilter} that matches if all the delegates match.
	 * 
	 * @author Oliver Gierke
	 */
	private static class AllTypeFilter implements TypeFilter {

		private final List<TypeFilter> delegates;

		/**
		 * Creates a new {@link AllTypeFilter} to match if all the given delegates match.
		 * 
		 * @param delegates must not be {@literal null}.
		 */
		public AllTypeFilter(List<TypeFilter> delegates) {

			Assert.notNull(delegates);
			this.delegates = delegates;
		}

		/* 
		 * (non-Javadoc)
		 * @see org.springframework.core.type.filter.TypeFilter#match(org.springframework.core.type.classreading.MetadataReader, org.springframework.core.type.classreading.MetadataReaderFactory)
		 */
		public boolean match(MetadataReader metadataReader, MetadataReaderFactory metadataReaderFactory) throws IOException {

			for (TypeFilter filter : delegates) {
				if (!filter.match(metadataReader, metadataReaderFactory)) {
					return false;
				}
			}

			return true;
		}
	}
}