AnnotationCollector.java

/**
 * Copyright (C) 2010 Daniel Manzke <daniel.manzke@googlemail.com>
 *
 * 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 de.devsurf.injection.guice.scanner.asm;

import java.lang.annotation.Annotation;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;

import org.objectweb.asm.AnnotationVisitor;
import org.objectweb.asm.Attribute;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.FieldVisitor;
import org.objectweb.asm.MethodVisitor;

import de.devsurf.injection.guice.scanner.features.ScannerFeature;

/**
 * Visitor implementation to collect field annotation information from class.
 * 
 * @author Daniel Manzke
 */
public class AnnotationCollector implements ClassVisitor {
	public static final int ASM_FLAGS = ClassReader.SKIP_CODE | ClassReader.SKIP_DEBUG
	| ClassReader.SKIP_FRAMES;
	protected Logger _logger = Logger.getLogger(AnnotationCollector.class.getName());
	protected String _name;
	protected Class<?> _class;
	protected boolean _ignore;
	protected Map<String, Annotation> _annotations;

	protected List<ScannerFeature> _features;

	public static final AnnotationVisitor EMPTY_ANNOTATION_VISITOR = new AnnotationVisitor() {
		@Override
		public void visitEnum(String name, String desc, String value) {
		}

		@Override
		public void visitEnd() {
		}

		@Override
		public AnnotationVisitor visitArray(String name) {
			return this;
		}

		@Override
		public AnnotationVisitor visitAnnotation(String name, String desc) {
			return this;
		}

		@Override
		public void visit(String name, Object value) {
		}
	};

	public AnnotationCollector() {
		_features = new LinkedList<ScannerFeature>();
		_annotations = new HashMap<String, Annotation>();
	}

	public void addScannerFeature(ScannerFeature listener) {
		_features.add(listener);
	}

	public void removerScannerFeature(ScannerFeature listener) {
		_features.remove(listener);
	}

	public List<ScannerFeature> getScannerFeatures() {
		return new ArrayList<ScannerFeature>(_features);
	}
	
	public void destroy(){
		_annotations.clear();
		_annotations = null;
		_class = null;
		_features.clear();
		_features = null;
	}

	@Override
	public void visit(int version, int access, String name, String signature, String superName,
			String[] interfaces) {
		_name = name.replace('/', '.');
		for (String interf : interfaces) {
			if (interf.equals("java/lang/annotation/Annotation")) {
				_ignore = true;
				return;
			}
		}
	}

	@SuppressWarnings("unchecked")
	public AnnotationVisitor visitAnnotation(String sig, boolean visible) {
		if (_ignore) {
			return EMPTY_ANNOTATION_VISITOR;
		}
		String annotationClassStr = sig.replace('/', '.').substring(1, sig.length() - 1);
		if (_class == null) {
			try {
				_class = Thread.currentThread().getContextClassLoader().loadClass(_name);
			} catch (ClassNotFoundException e) {
				_logger.log(Level.WARNING,
					"Failure while visitAnnotation. Class could not be loaded.", e);
				return EMPTY_ANNOTATION_VISITOR;
			}
		}
		try {
			Class<Annotation> annotationClass = (Class<Annotation>) getClass().getClassLoader()
				.loadClass(annotationClassStr);
			Annotation annotation = _class.getAnnotation(annotationClass);
			_annotations.put(annotationClassStr, annotation);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
			_logger.log(Level.WARNING, "Failure while visitAnnotation. Class could not be loaded.",
				e);
		}

		return EMPTY_ANNOTATION_VISITOR;
	}

	@SuppressWarnings("unchecked")
	@Override
	public void visitEnd() {
		if (!_ignore && _annotations.size() > 0 && !_annotations.containsKey("javax.enterprise.inject.Alternative")) {
			for (ScannerFeature listener : _features) {
				listener.found((Class<Object>) _class, _annotations);
			}
		}
		_name = null;
		_class = null;
		_ignore = false;
		_annotations.clear();
	}

	@Override
	public void visitAttribute(Attribute attr) {
	}

	@Override
	public FieldVisitor visitField(int access, String name, String desc, String signature,
			Object value) {
		return null;
	}

	@Override
	public void visitInnerClass(String name, String outerName, String innerName, int access) {
	}

	@Override
	public MethodVisitor visitMethod(int access, String name, String desc, String signature,
			String[] exceptions) {
		return null;
	}

	@Override
	public void visitOuterClass(String owner, String name, String desc) {
	}

	@Override
	public void visitSource(String source, String debug) {
	}
}