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'rapiddweller Common' is an open source Java library forked from Databene Commons by Volker Bergmann. It provides extensions to the Java core library by utility classes, abstract concepts and concrete implementations.

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/*
 * Copyright (C) 2004-2015 Volker Bergmann ([email protected]).
 * All rights reserved.
 *
 * 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 com.rapiddweller.common.bean;

import com.rapiddweller.common.ArrayUtil;
import com.rapiddweller.common.ConfigurationError;
import com.rapiddweller.common.StringUtil;

import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.HashMap;
import java.util.Map;

/**
 * Creates {@link ObservableBean} implementations from interfaces.
 * Created at 17.07.2008 14:57:53
 *
 * @author Volker Bergmann
 * @since 0.4.5
 */
public class ObservableFactory {

  /**
   * Create e.
   *
   * @param   the type parameter
   * @param type the type
   * @return the e
   */
  @SuppressWarnings("unchecked")
  public static  E create(Class type) {
    if (!type.isInterface()) {
      throw new ConfigurationError("Not an interface: " + type);
    }
    ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
    ObservableBeanInvocationHandler handler = new ObservableBeanInvocationHandler(type);
    return (E) Proxy.newProxyInstance(classLoader, new Class[] {type}, handler);
  }

  private static class ObservableBeanInvocationHandler implements InvocationHandler {

    private final Map propertyValues = new HashMap<>();
    private PropertyChangeSupport support;
    private final Class type;

    /**
     * Instantiates a new Observable bean invocation handler.
     *
     * @param type the type
     */
    public ObservableBeanInvocationHandler(Class type) {
      this.type = type;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) {
      if (support == null) {
        this.support = new PropertyChangeSupport(proxy);
      }
      String methodName = method.getName();
      if (methodName.startsWith("get") && ArrayUtil.isEmpty(args)) {
        String propertyName = methodName.substring(3);
        propertyName = StringUtil.uncapitalize(propertyName);
        return propertyValues.get(propertyName);
      } else if (methodName.startsWith("set")) {
        String propertyName = methodName.substring(3);
        propertyName = StringUtil.uncapitalize(propertyName);
        Object oldValue = propertyValues.get(propertyName);
        propertyValues.put(propertyName, args[0]);
        support.firePropertyChange(propertyName, oldValue, args[0]);
      } else if ("addPropertyChangeListener".equals(methodName)) {
        if (args.length == 2) {
          support.addPropertyChangeListener((String) args[0], (PropertyChangeListener) args[1]);
        } else {
          support.addPropertyChangeListener((PropertyChangeListener) args[0]);
        }
      } else if ("removePropertyChangeListener".equals(methodName)) {
        if (args.length == 2) {
          support.removePropertyChangeListener((String) args[0], (PropertyChangeListener) args[1]);
        } else {
          support.removePropertyChangeListener((PropertyChangeListener) args[0]);
        }
      } else if ("equals".equals(methodName)) {
        Object other = args[0];
        if (proxy == other) {
          return true;
        }
        if (other == null) {
          return false;
        }
        if (!proxy.getClass().equals(other.getClass())) {
          return false;
        }
        ObservableBeanInvocationHandler otherHandler = (ObservableBeanInvocationHandler) Proxy.getInvocationHandler(proxy);
        return (this.propertyValues.equals(otherHandler.propertyValues));
      } else if ("hashCode".equals(methodName)) {
        return propertyValues.hashCode();
      } else if ("toString".equals(methodName)) {
        return type.getName() + propertyValues;
      } else {
        throw new UnsupportedOperationException("Operation not supported: " + method);
      }
      return null;
    }

  }
}