exceptionmapperfactory.java

来自「resetful样式的ws样例,一种面向资源的webservices服务」· Java 代码 · 共 150 行

/*
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
 * 
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://jersey.dev.java.net/CDDL+GPL.html
 * or jersey/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 * 
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at jersey/legal/LICENSE.txt.
 * Sun designates this particular file as subject to the "Classpath" exception
 * as provided by Sun in the GPL Version 2 section of the License file that
 * accompanied this code.  If applicable, add the following below the License
 * Header, with the fields enclosed by brackets [] replaced by your own
 * identifying information: "Portions Copyrighted [year]
 * [name of copyright owner]"
 * 
 * Contributor(s):
 * 
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */
package com.sun.jersey.impl.application;

import com.sun.jersey.impl.model.ReflectionHelper;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.util.HashSet;
import java.util.Set;
import javax.ws.rs.ext.ExceptionMapper;

/**
 *
 * @author [e-mail]
 */
public class ExceptionMapperFactory {
    
    private static class ExceptionMapperType {
        ExceptionMapper em;
        Class<? extends Throwable> c;
        
        public ExceptionMapperType(ExceptionMapper em, Class<? extends Throwable> c) {
            this.em = em;
            this.c = c;
        }
    } 

    private Set<ExceptionMapperType> emts = new HashSet<ExceptionMapperType>();
    
    public ExceptionMapperFactory(ComponentProviderCache componentProviderCache) {
        for (ExceptionMapper em : componentProviderCache.getProviders(ExceptionMapper.class)) {
            Class<? extends Throwable> c = getExceptionType(em.getClass());
            if (c != null) {
                emts.add(new ExceptionMapperType(em, c));
            }
        }
    }
    
    public ExceptionMapper find(Class<? extends Throwable> c) {
        int distance = Integer.MAX_VALUE;
        ExceptionMapper selectedEm = null;
        for (ExceptionMapperType emt : emts) {
            int d = distance(c, emt.c);
            if (d < distance) { 
                distance = d;
                selectedEm = emt.em;
                if (distance == 0) break;
            }
        }
        
        return selectedEm;
    }
    
    private int distance(Class<?> c, Class<?> emtc) {
        int distance = 0;
        if (!emtc.isAssignableFrom(c))
            return Integer.MAX_VALUE;
        
        while (c != emtc) {
            c = c.getSuperclass();
            distance++;
        }
        
        return distance;
    }
    
    @SuppressWarnings("unchecked")
    private Class<? extends Throwable> getExceptionType(Class<? extends ExceptionMapper> c) {
        Class<?> t = getType(c);
        if (Throwable.class.isAssignableFrom(t))
            return (Class<? extends Throwable>)t;
        
        // TODO log warning
        return null;
    }
    
    private Class getType(Class<? extends ExceptionMapper> c) {
        Class _c = c;
        while (_c != Object.class) {
            Type[] ts = _c.getGenericInterfaces();
            for (Type t : ts) {
                if (t instanceof ParameterizedType) {
                    ParameterizedType pt = (ParameterizedType)t;
                    if (pt.getRawType() == ExceptionMapper.class) {
                        return getResolvedType(pt.getActualTypeArguments()[0], c, _c);
                    }
                }
            }
            
            _c = _c.getSuperclass();
        }
        
        // This statement will never be reached
        return null;        
    }
    
    private Class getResolvedType(Type t, Class c, Class dc) {
        if (t instanceof Class)
            return (Class)t;
        else if (t instanceof TypeVariable) {
            ReflectionHelper.ClassTypePair ct = ReflectionHelper.
                    resolveTypeVariable(c, dc, (TypeVariable)t);
            if (ct != null)
                return ct.c;
            else 
                return null;
        } else if (t instanceof ParameterizedType) {
            ParameterizedType pt = (ParameterizedType)t;
            return (Class)pt.getRawType();
        } else {
            // TODO log 
            return null;
        }
    }
}