org.exolab.castor.xml.handlers.ValueOfFieldHandler Maven / Gradle / Ivy

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package org.exolab.castor.xml.handlers;

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

import org.exolab.castor.mapping.FieldDescriptor;
import org.exolab.castor.mapping.FieldHandler;
import org.exolab.castor.mapping.GeneralizedFieldHandler;
import org.exolab.castor.mapping.MappingException;

/**
 * An implementation of GeneralizedFieldHandler for classes that have a built-in valueOf(String)
 * factory method, such as type-safe enumeration classes, java.sql.Timestamp, etc.
 *
 * @author Keith Visco
 * @version $Revision$ $Date: 2006-04-14 04:14:43 -0600 (Fri, 14 Apr 2006) $
 * @see FieldDescriptor
 * @see FieldHandler
 */
public class ValueOfFieldHandler extends GeneralizedFieldHandler {

  /** The Class[] holding the argument types of the factory method. */
  private static final Class[] ARGS = new Class[] {String.class};
  /** The Factory Method name. */
  private static final String METHOD_NAME = "valueOf";

  /** The class type for this FieldHandler. */
  private final Class _type;
  /** The valueOf method reference. */
  private final Method _valueOf;

  /**
   * Creates a new ValueOfFieldHandler.
   *
   * @param type the class type to create the FieldHandler for
   * @throws MappingException if the valueOf method cannot be found
   */
  public ValueOfFieldHandler(final Class type) throws MappingException {
    super();
    if (type == null) {
      throw new IllegalArgumentException("The argument 'type' must not be null.");
    }

    _type = type;

    Method method = null;
    try {
      method = type.getMethod(METHOD_NAME, ARGS);
    } catch (java.lang.NoSuchMethodException nsme) {
      throw new MappingException(nsme);
    }
    if (!Modifier.isStatic(method.getModifiers())) {
      String err = "No static method '" + METHOD_NAME + "' found in class: " + type.getName();
      throw new MappingException(err);
    }

    _valueOf = method;
  } // -- ValueOfFieldHandler

  /**
   * This method is used to convert the value when the getValue method is called. The getValue
   * method will obtain the actual field value from given 'parent' object. This convert method is
   * then invoked with the field's value. The value returned from this method will be the actual
   * value returned by getValue method.
   *
   * @param value the object value to convert after performing a get operation
   * @return the converted value.
   */
  public Object convertUponGet(final Object value) {
    // -- no conversion necessary for marshaling
    return value;
  } // -- convertUponGet

  /**
   * This method is used to convert the value when the setValue method is called. The setValue
   * method will call this method to obtain the converted value. The converted value will then be
   * used as the value to set for the field.
   *
   * @param value the object value to convert before performing a set operation
   * @return the converted value.
   */
  public Object convertUponSet(final Object value) {
    Object[] args = new Object[1];

    if (value != null) {
      args[0] = value.toString();
    }

    Object result = null;

    try {
      result = _valueOf.invoke(null, args);
    } catch (java.lang.IllegalAccessException iae) {
      throw new IllegalStateException(iae.getMessage());
    } catch (java.lang.reflect.InvocationTargetException ite) {
      throw new IllegalStateException(ite.getMessage());
    }

    return result;
  } // -- convertUponSet;

  /**
   * Returns the class type for the field that this GeneralizedFieldHandler converts to and from.
   * This should be the type that is used in the object model.
   *
   * @return the class type of of the field
   */
  public Class getFieldType() {
    return _type;
  } // -- getFieldType

  /**
   * 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 null;
  }

} // -- ValueOfFieldHandler