EnumFieldHandler

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 * without prior written permission of Intalio, Inc. For written permission, please contact
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 * 4. Products derived from this Software may not be called "Exolab" nor may "Exolab" appear in
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 *
 * 5. Due credit should be given to the Exolab Project (http://www.exolab.org/).
 *
 * THIS SOFTWARE IS PROVIDED BY INTALIO, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESSED OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL INTALIO, INC. OR ITS
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
 * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Copyright 1999 (C) Intalio, Inc. All Rights Reserved.
 *
 * Portions of this file developed by Keith Visco after Jan 19 2005 are Copyright (C) 2005 Keith
 * Visco. All Rights Reserverd.
 *
 * $Id$
 */
package org.exolab.castor.xml.handlers;

import java.lang.reflect.Array;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

import org.exolab.castor.mapping.FieldHandler;
import org.exolab.castor.mapping.ValidityException;

/**
 * A specialized FieldHandler for the XML Schema enumeration types.
 *
 * @author <a href="keith AT kvisco  DOT com">Keith Visco</a>
 * @version $Revision$ $Date: 2006-04-13 06:47:36 -0600 (Thu, 13 Apr 2006) $
 */
public class EnumFieldHandler implements FieldHandler {

  /** Used to find the method "valueOf" taking an argument of type String. */
  private static final Class[] STRING_ARGS = new Class[] {String.class};
  /** The Factory Method name. */
  private static final String METHOD_VALUEOF = "valueOf";
  private static final String METHOD_FROMVALUE = "fromValue";
  private static final String METHOD_VALUE = "value";
  private static final String METHOD_TOSTRING = "toString";

  /** The <code>valueOf(String)</code> method for the provided enumtype. */
  private final Method _valueOf;
  /** The field handler to which we delegate. */
  private final FieldHandler _handler;

  // ----------------/
  // - Constructors -/
  // ----------------/

  /**
   * Creates a new EnumFieldHandler with the given type and FieldHandler.
   *
   * @param enumType the Class type of the described field
   * @param handler the FieldHandler to delegate to
   */
  public EnumFieldHandler(final Class enumType, final FieldHandler handler) {
    this._handler = handler;
    this._valueOf = getUnmarshallMethod(enumType);
  } // -- EnumFieldHandler

  /**
   * Reflectively finds the <code>valueOf(String)</code> method for the provided class type.
   *
   * @param type the Class for which to locate the valueOf method.
   * @return the Method <code>valueOf(String)</code>
   */
  private Method getUnmarshallMethod(final Class type) {
    if (type == null) {
      String err = "The Class argument passed to the "
          + "constructor of EnumMarshalDescriptor cannot be null.";
      throw new IllegalArgumentException(err);
    }

    Method method = null;

    // try the fromValue method to support enums with value object
    try {
      method = type.getMethod(METHOD_FROMVALUE, STRING_ARGS);
      return method;
    } catch (NoSuchMethodException exception) {
      // do nothing, check valueOf
    }

    //
    try {
      method = type.getMethod(METHOD_VALUEOF, STRING_ARGS);
    } catch (NoSuchMethodException nsme) {
      String err = type.getName() + " does not contain one of the required methods public static "
          + type.getName() + " valueOf(String); " + "or public static " + type.getName()
          + ".fromvalue(String value)";
      throw new IllegalArgumentException(err);
    }

    if (!Modifier.isStatic(method.getModifiers())) {
      String err = type.getName() + " public " + type.getName()
          + " valueOf(String); exists but is not static";
      throw new IllegalArgumentException(err);
    }
    return method;
  }

  private Method getMarshallMethod(final Class type) {
    if (type == null) {
      String err = "The Class argument passed to the "
          + "constructor of EnumMarshalDescriptor cannot be null.";
      throw new IllegalArgumentException(err);
    }

    Method method = null;

    // try the value() method to support enums with value object
    try {
      method = type.getMethod(METHOD_VALUE, null);
      return method;
    } catch (NoSuchMethodException exception) {
      // do nothing, use toString
    }

    //
    try {
      method = type.getMethod(METHOD_TOSTRING, null);
    } catch (NoSuchMethodException nsme) {
      String err =
          type.getName() + " does not contain one of the required methods value() or toString() ";
      throw new IllegalArgumentException(err);
    }

    return method;
  }

  // ------------------/
  // - Public Methods -/
  // ------------------/

  /**
   * Returns the value of the field associated with this descriptor from the given target object.
   *
   * @param target the object to get the value from
   * @return the value of the field associated with this descriptor from the given target object.
   * @throws IllegalStateException The Java object has changed and is no longer supported by this
   *         handler, or the handler is not compatible with the Java object
   */
  public Object getValue(final Object target) throws java.lang.IllegalStateException {
    Object val = _handler.getValue(target);
    if (val == null) {
      return val;
    }

    Object result = null;
    if (val.getClass().isArray()) {
      int size = Array.getLength(val);
      String[] values = new String[size];

      for (int i = 0; i < size; i++) {
        Object obj = Array.get(val, i);
        try {
          values[i] = (String) getMarshallMethod(obj.getClass()).invoke(obj, null);
        } catch (Exception e) {
          throw new IllegalStateException(e.toString());
        }
      }
      result = values;
    } else {
      try {
        result = getMarshallMethod(val.getClass()).invoke(val, null);
      } catch (Exception e) {
        throw new IllegalStateException(e.toString());
      }
    }
    return result;
  } // -- getValue

  /**
   * Sets the value of the field associated with this descriptor.
   *
   * @param target the object in which to set the value
   * @param value the value of the field
   * @throws IllegalStateException The Java object has changed and is no longer supported by this
   *         handler, or the handler is not compatible with the Java object.
   */
  public void setValue(final Object target, final Object value)
      throws java.lang.IllegalStateException {
    Object obj = null;
    if (value != null) {
      Object[] args = new String[1];
      args[0] = value.toString();
      try {
        obj = _valueOf.invoke(null, args);
      } catch (java.lang.reflect.InvocationTargetException ite) {
        Throwable toss = ite.getTargetException();
        throw new IllegalStateException(toss.toString());
      } catch (java.lang.IllegalAccessException iae) {
        throw new IllegalStateException(iae.toString());
      }
    }
    _handler.setValue(target, obj);
  } // -- setValue

  /**
   * Sets the value of the field to a default value -- for enum, no action needed.
   *
   * @param target The object.
   */
  public void resetValue(final Object target) {
    // No action needed
  }

  /**
   * Checks the field validity. Returns successfully if the field can be stored, is valid, etc,
   * throws an exception otherwise.
   *
   * @param object The object
   * @throws ValidityException The field is invalid, is required and null, or any other validity
   *         violation
   * @throws IllegalStateException The Java object has changed and is no longer supported by this
   *         handler, or the handler is not compatiable with the Java object
   */
  public void checkValidity(final Object object) throws ValidityException, IllegalStateException {
    // -- do nothing for now
  } // -- checkValidity

  /**
   * Creates a new instance of the object described by this field.
   *
   * @param parent The object for which the field is created
   * @return A new instance of the field's value
   * @throws IllegalStateException This field is a simple type and cannot be instantiated
   */
  public Object newInstance(final Object parent) throws IllegalStateException {
    return "";
  } // -- newInstance

  /**
   * Returns true if the given object is an XMLFieldHandler that is equivalent to the delegated
   * handler. An equivalent XMLFieldHandler is an XMLFieldHandler that is an instances of the same
   * class.
   *
   * @return true if the given object is an XMLFieldHandler that is equivalent to this one.
   */
  public boolean equals(final Object obj) {
    if (obj == null) {
      return false;
    }
    if (obj == this) {
      return true;
    }
    if (!(obj instanceof FieldHandler)) {
      return false;
    }
    return (_handler.getClass().isInstance(obj) || getClass().isInstance(obj));
  } // -- equals

} // -- EnumFieldHandler