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/*
 * Based on JUEL 2.2.1 code, 2006-2009 Odysseus Software GmbH
 *
 * 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.activiti.engine.impl.juel;

import org.activiti.engine.impl.javax.el.ELContext;
import org.activiti.engine.impl.javax.el.ELException;

/**
 * Object wrapper expression.
 * 
 * @author Christoph Beck
 */
public final class ObjectValueExpression extends org.activiti.engine.impl.javax.el.ValueExpression {
  private static final long serialVersionUID = 1L;

  private final TypeConverter converter;
  private final Object object;
  private final Class type;

  /**
   * Wrap an object into a value expression.
   * 
   * @param converter
   *          type converter
   * @param object
   *          the object to wrap
   * @param type
   *          the expected type this object will be coerced in {@link #getValue(ELContext)}.
   */
  public ObjectValueExpression(TypeConverter converter, Object object, Class type) {
    super();

    this.converter = converter;
    this.object = object;
    this.type = type;

    if (type == null) {
      throw new NullPointerException(LocalMessages.get("error.value.notype"));
    }
  }

  /**
   * Two object value expressions are equal if and only if their wrapped objects are equal.
   */
  @Override
  public boolean equals(Object obj) {
    if (obj != null && obj.getClass() == getClass()) {
      ObjectValueExpression other = (ObjectValueExpression) obj;
      if (type != other.type) {
        return false;
      }
      return object == other.object || object != null && object.equals(other.object);
    }
    return false;
  }

  @Override
  public int hashCode() {
    return object == null ? 0 : object.hashCode();
  }

  /**
   * Answer the wrapped object, coerced to the expected type.
   */
  @Override
  public Object getValue(ELContext context) {
    return converter.convert(object, type);
  }

  /**
   * Answer null.
   */
  @Override
  public String getExpressionString() {
    return null;
  }

  /**
   * Answer false.
   */
  @Override
  public boolean isLiteralText() {
    return false;
  }

  /**
   * Answer null.
   */
  @Override
  public Class getType(ELContext context) {
    return null;
  }

  /**
   * Answer true.
   */
  @Override
  public boolean isReadOnly(ELContext context) {
    return true;
  }

  /**
   * Throw an exception.
   */
  @Override
  public void setValue(ELContext context, Object value) {
    throw new ELException(LocalMessages.get("error.value.set.rvalue", "