JavassistProxyFactory.java

/*
 *    Copyright 2009-2024 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
 *
 *       https://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.apache.ibatis.executor.loader.javassist;

import java.lang.reflect.Method;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.locks.ReentrantLock;

import javassist.util.proxy.MethodHandler;
import javassist.util.proxy.Proxy;
import javassist.util.proxy.ProxyFactory;

import org.apache.ibatis.executor.ExecutorException;
import org.apache.ibatis.executor.loader.AbstractEnhancedDeserializationProxy;
import org.apache.ibatis.executor.loader.AbstractSerialStateHolder;
import org.apache.ibatis.executor.loader.ResultLoaderMap;
import org.apache.ibatis.executor.loader.WriteReplaceInterface;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;
import org.apache.ibatis.reflection.ExceptionUtil;
import org.apache.ibatis.reflection.factory.ObjectFactory;
import org.apache.ibatis.reflection.property.PropertyCopier;
import org.apache.ibatis.reflection.property.PropertyNamer;
import org.apache.ibatis.session.Configuration;

/**
 * @author Eduardo Macarron
 */
public class JavassistProxyFactory implements org.apache.ibatis.executor.loader.ProxyFactory {

  private static final String FINALIZE_METHOD = "finalize";
  private static final String WRITE_REPLACE_METHOD = "writeReplace";

  public JavassistProxyFactory() {
    try {
      Resources.classForName("javassist.util.proxy.ProxyFactory");
    } catch (Throwable e) {
      throw new IllegalStateException(
          "Cannot enable lazy loading because Javassist is not available. Add Javassist to your classpath.", e);
    }
  }

  @Override
  public Object createProxy(Object target, ResultLoaderMap lazyLoader, Configuration configuration,
      ObjectFactory objectFactory, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
    return EnhancedResultObjectProxyImpl.createProxy(target, lazyLoader, configuration, objectFactory,
        constructorArgTypes, constructorArgs);
  }

  public Object createDeserializationProxy(Object target, Map<String, ResultLoaderMap.LoadPair> unloadedProperties,
      ObjectFactory objectFactory, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
    return EnhancedDeserializationProxyImpl.createProxy(target, unloadedProperties, objectFactory, constructorArgTypes,
        constructorArgs);
  }

  static Object createStaticProxy(Class<?> type, MethodHandler callback, List<Class<?>> constructorArgTypes,
      List<Object> constructorArgs) {

    ProxyFactory enhancer = new ProxyFactory();
    enhancer.setSuperclass(type);

    try {
      type.getDeclaredMethod(WRITE_REPLACE_METHOD);
      // ObjectOutputStream will call writeReplace of objects returned by writeReplace
      if (LogHolder.log.isDebugEnabled()) {
        LogHolder.log.debug(WRITE_REPLACE_METHOD + " method was found on bean " + type + ", make sure it returns this");
      }
    } catch (NoSuchMethodException e) {
      enhancer.setInterfaces(new Class[] { WriteReplaceInterface.class });
    } catch (SecurityException e) {
      // nothing to do here
    }

    Object enhanced;
    Class<?>[] typesArray = constructorArgTypes.toArray(new Class[constructorArgTypes.size()]);
    Object[] valuesArray = constructorArgs.toArray(new Object[constructorArgs.size()]);
    try {
      enhanced = enhancer.create(typesArray, valuesArray);
    } catch (Exception e) {
      throw new ExecutorException("Error creating lazy proxy.  Cause: " + e, e);
    }
    ((Proxy) enhanced).setHandler(callback);
    return enhanced;
  }

  private static class EnhancedResultObjectProxyImpl implements MethodHandler {
    private final Class<?> type;
    private final ResultLoaderMap lazyLoader;
    private final boolean aggressive;
    private final Set<String> lazyLoadTriggerMethods;
    private final ObjectFactory objectFactory;
    private final List<Class<?>> constructorArgTypes;
    private final List<Object> constructorArgs;
    private final ReentrantLock lock = new ReentrantLock();

    private EnhancedResultObjectProxyImpl(Class<?> type, ResultLoaderMap lazyLoader, Configuration configuration,
        ObjectFactory objectFactory, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
      this.type = type;
      this.lazyLoader = lazyLoader;
      this.aggressive = configuration.isAggressiveLazyLoading();
      this.lazyLoadTriggerMethods = configuration.getLazyLoadTriggerMethods();
      this.objectFactory = objectFactory;
      this.constructorArgTypes = constructorArgTypes;
      this.constructorArgs = constructorArgs;
    }

    public static Object createProxy(Object target, ResultLoaderMap lazyLoader, Configuration configuration,
        ObjectFactory objectFactory, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
      final Class<?> type = target.getClass();
      EnhancedResultObjectProxyImpl callback = new EnhancedResultObjectProxyImpl(type, lazyLoader, configuration,
          objectFactory, constructorArgTypes, constructorArgs);
      Object enhanced = createStaticProxy(type, callback, constructorArgTypes, constructorArgs);
      PropertyCopier.copyBeanProperties(type, target, enhanced);
      return enhanced;
    }

    @Override
    public Object invoke(Object enhanced, Method method, Method methodProxy, Object[] args) throws Throwable {
      final String methodName = method.getName();
      lock.lock();
      try {
        if (WRITE_REPLACE_METHOD.equals(methodName)) {
          Object original;
          if (constructorArgTypes.isEmpty()) {
            original = objectFactory.create(type);
          } else {
            original = objectFactory.create(type, constructorArgTypes, constructorArgs);
          }
          PropertyCopier.copyBeanProperties(type, enhanced, original);
          if (!lazyLoader.isEmpty()) {
            return new JavassistSerialStateHolder(original, lazyLoader.getProperties(), objectFactory,
                constructorArgTypes, constructorArgs);
          } else {
            return original;
          }
        }
        if (!lazyLoader.isEmpty() && !FINALIZE_METHOD.equals(methodName)) {
          if (aggressive || lazyLoadTriggerMethods.contains(methodName)) {
            lazyLoader.loadAll();
          } else if (PropertyNamer.isSetter(methodName)) {
            final String property = PropertyNamer.methodToProperty(methodName);
            lazyLoader.remove(property);
          } else if (PropertyNamer.isGetter(methodName)) {
            final String property = PropertyNamer.methodToProperty(methodName);
            if (lazyLoader.hasLoader(property)) {
              lazyLoader.load(property);
            }
          }
        }
        return methodProxy.invoke(enhanced, args);
      } catch (Throwable t) {
        throw ExceptionUtil.unwrapThrowable(t);
      } finally {
        lock.unlock();
      }
    }
  }

  private static class EnhancedDeserializationProxyImpl extends AbstractEnhancedDeserializationProxy
      implements MethodHandler {

    private EnhancedDeserializationProxyImpl(Class<?> type, Map<String, ResultLoaderMap.LoadPair> unloadedProperties,
        ObjectFactory objectFactory, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
      super(type, unloadedProperties, objectFactory, constructorArgTypes, constructorArgs);
    }

    public static Object createProxy(Object target, Map<String, ResultLoaderMap.LoadPair> unloadedProperties,
        ObjectFactory objectFactory, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
      final Class<?> type = target.getClass();
      EnhancedDeserializationProxyImpl callback = new EnhancedDeserializationProxyImpl(type, unloadedProperties,
          objectFactory, constructorArgTypes, constructorArgs);
      Object enhanced = createStaticProxy(type, callback, constructorArgTypes, constructorArgs);
      PropertyCopier.copyBeanProperties(type, target, enhanced);
      return enhanced;
    }

    @Override
    public Object invoke(Object enhanced, Method method, Method methodProxy, Object[] args) throws Throwable {
      final Object o = super.invoke(enhanced, method, args);
      return o instanceof AbstractSerialStateHolder ? o : methodProxy.invoke(o, args);
    }

    @Override
    protected AbstractSerialStateHolder newSerialStateHolder(Object userBean,
        Map<String, ResultLoaderMap.LoadPair> unloadedProperties, ObjectFactory objectFactory,
        List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
      return new JavassistSerialStateHolder(userBean, unloadedProperties, objectFactory, constructorArgTypes,
          constructorArgs);
    }
  }

  private static class LogHolder {
    private static final Log log = LogFactory.getLog(JavassistProxyFactory.class);
  }

}