org.springframework.data.neo4j.support.AbstractConstructorEntityInstantiator.java Source code

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Here is the source code for org.springframework.data.neo4j.support.AbstractConstructorEntityInstantiator.java

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/**
 * Copyright 2011 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.neo4j.support;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.data.persistence.StateBackedCreator;
import org.springframework.data.persistence.StateProvider;
import org.springframework.util.ClassUtils;
import sun.reflect.ReflectionFactory;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.HashMap;
import java.util.Map;

/**
 * Try for a constructor taking state: failing that, try a no-arg constructor and then setUnderlyingNode().
 * 
 * @author Rod Johnson
 */
public abstract class AbstractConstructorEntityInstantiator<STATE> implements EntityInstantiator<STATE> {

    private final Log log = LogFactory.getLog(getClass());
    private final Map<Class<?>, StateBackedCreator<?, STATE>> cache = new HashMap<Class<?>, StateBackedCreator<?, STATE>>();

    @SuppressWarnings("unchecked")
    public <T> T createEntityFromState(STATE n, Class<T> c) {
        try {
            StateBackedCreator<T, STATE> creator = (StateBackedCreator<T, STATE>) cache.get(c);
            if (creator != null)
                return creator.create(n, c);
            synchronized (cache) {
                creator = (StateBackedCreator<T, STATE>) cache.get(c);
                if (creator != null)
                    return creator.create(n, c);
                Class<STATE> stateClass = (Class<STATE>) n.getClass();
                creator = createInstantiator(c, stateClass);
                cache.put(c, creator);
                return creator.create(n, c);
            }
        } catch (IllegalArgumentException e) {
            throw e;
        } catch (InvocationTargetException e) {
            throw new IllegalArgumentException(e.getTargetException());
        } catch (Exception e) {
            throw new IllegalArgumentException(e);
        }
    }

    public void setInstantiators(Map<Class<?>, StateBackedCreator<?, STATE>> instantiators) {
        this.cache.putAll(instantiators);
    }

    protected <T> StateBackedCreator<T, STATE> createInstantiator(Class<T> type, final Class<STATE> stateType) {
        StateBackedCreator<T, STATE> creator = stateTakingConstructorInstantiator(type, stateType);
        if (creator != null)
            return creator;
        creator = emptyConstructorStateSettingInstantiator(type, stateType);
        if (creator != null)
            return creator;
        return createFailingInstantiator(stateType);
    }

    protected <T> StateBackedCreator<T, STATE> createFailingInstantiator(final Class<STATE> stateType) {
        return new StateBackedCreator<T, STATE>() {
            public T create(STATE n, Class<T> c) throws Exception {
                throw new IllegalArgumentException(getFailingMessageForClass(c, stateType));
            }
        };
    }

    protected String getFailingMessageForClass(Class<?> entityClass, Class<STATE> stateClass) {
        return getClass().getSimpleName() + ": entity " + entityClass + " must have either a constructor taking ["
                + stateClass + "] or a no-arg constructor and state setter.";
    }

    private <T> StateBackedCreator<T, STATE> emptyConstructorStateSettingInstantiator(Class<T> type,
            Class<STATE> stateType) {
        final Constructor<T> constructor = getNoArgConstructor(type);
        if (constructor == null)
            return null;

        log.info("Using " + type + " no-arg constructor");

        return new StateBackedCreator<T, STATE>() {
            public T create(STATE state, Class<T> c) throws Exception {
                try {
                    StateProvider.setUnderlyingState(state);
                    T newInstance = constructor.newInstance();
                    setState(newInstance, state);
                    return newInstance;
                } finally {
                    StateProvider.retrieveState();
                }
            }
        };
    }

    protected <T> StateBackedCreator<T, STATE> createWithoutConstructorInvocation(final Class<T> type,
            Class<STATE> stateType) {
        ReflectionFactory rf = ReflectionFactory.getReflectionFactory();
        Constructor<?> objectConstructor = getDeclaredConstructor(Object.class);
        final Constructor<?> serializationConstructor = rf.newConstructorForSerialization(type, objectConstructor);
        return new StateBackedCreator<T, STATE>() {
            public T create(STATE state, Class<T> c) throws Exception {
                final T result = type.cast(serializationConstructor.newInstance());
                setState(result, state);
                return result;
            }
        };
    }

    protected <T> Constructor<T> getNoArgConstructor(Class<T> type) {
        Constructor<T> constructor = ClassUtils.getConstructorIfAvailable(type);
        if (constructor != null)
            return constructor;
        return getDeclaredConstructor(type);
    }

    protected <T> StateBackedCreator<T, STATE> stateTakingConstructorInstantiator(Class<T> type,
            Class<STATE> stateType) {
        @SuppressWarnings("unchecked")
        Class<? extends STATE> stateInterface = (Class<? extends STATE>) stateType.getInterfaces()[0];
        final Constructor<T> constructor = ClassUtils.getConstructorIfAvailable(type, stateInterface);
        if (constructor == null)
            return null;

        log.info("Using " + type + " constructor taking " + stateInterface);
        return new StateBackedCreator<T, STATE>() {
            public T create(STATE n, Class<T> c) throws Exception {
                return constructor.newInstance(n);
            }
        };
    }

    protected <T> Constructor<T> getDeclaredConstructor(Class<T> c) {
        try {
            final Constructor<T> declaredConstructor = c.getDeclaredConstructor();
            declaredConstructor.setAccessible(true);
            return declaredConstructor;
        } catch (NoSuchMethodException e) {
            return null;
        }
    }

    /**
     * Subclasses must implement to set state
     * 
     * @param entity
     * @param s
     */
    protected abstract void setState(Object entity, STATE s);

}