CollectionFieldHandler

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package org.exolab.castor.xml.handlers;

import java.lang.reflect.Array;
import java.util.StringTokenizer;

import org.exolab.castor.mapping.FieldHandler;
import org.exolab.castor.mapping.ValidityException;
import org.exolab.castor.xml.TypeValidator;
import org.exolab.castor.xml.ValidationException;
import org.exolab.castor.xml.XMLFieldHandler;

/**
 * A FieldHandler for the XML Schema Collection type.
 * <p>
 * TODO : support all kind of XSList.
 *
 * @author <a href="blandin@intalio.com">Arnaud Blandin</a>
 * @version $Revision$ $Date: 2003-03-03 00:05:44 -0700 (Mon, 03 Mar 2003) $
 */
public class CollectionFieldHandler extends XMLFieldHandler {

  /** The field handler to which we delegate. */
  private final FieldHandler _handler;
  /** Type validator to use to validate an instance of this type. */
  private final TypeValidator _validator;

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

  /**
   * Creates a new CollectionFieldHandler using the given FieldHandler for delegation.
   *
   * @param fieldHandler the fieldHandler for delegation.
   */
  public CollectionFieldHandler(final FieldHandler fieldHandler) {
    this(fieldHandler, null);
  } // -- CollectionFieldHandler

  /**
   * Creates a new CollectionFieldHandler using the given FieldHandler for delegation and the given
   * type validator for validation.
   *
   * @param fieldHandler the fieldHandler for delegation.
   * @param validator Type validator to use to validate an instance of this type.
   */
  public CollectionFieldHandler(final FieldHandler fieldHandler, final TypeValidator validator) {
    super();
    if (fieldHandler == null) {
      String err = "The FieldHandler argument passed to "
          + "the constructor of CollectionFieldHandler must not be null.";
      throw new IllegalArgumentException(err);
    }
    this._handler = fieldHandler;
    this._validator = validator;
  } // -- CollectionFieldHandler

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

  /**
   * Sets the value of the field associated with this descriptor. If paased a String, then String is
   * tokenized and each token is added as an individual instance to the collection.
   *
   * @param target the object in which to set the value
   * @param value the value of the field
   * @throws IllegalStateException if any value provided fails validation.
   */
  public void setValue(final Object target, final Object value)
      throws java.lang.IllegalStateException {
    if (value == null) {
      return;
    }

    // If not a String, assume we are passed something the field handler understands
    if (!(value instanceof String)) {
      _handler.setValue(target, value);
      return;
    }

    StringTokenizer temp = new StringTokenizer((java.lang.String) value, " ");
    final int size = temp.countTokens();
    for (int i = 0; i < size; i++) {
      String tempValue = temp.nextToken();
      try {
        if (_validator != null) {
          _validator.validate(tempValue, null);
        }
      } catch (ValidationException e) {
        throw new IllegalStateException(e.getMessage());
      }
      _handler.setValue(target, tempValue);
    }
  } // -- setValue

  /**
   * Gets the value of the field associated with this descriptor. If the value is an array, it
   * returns a string 'representing' this array
   *
   * @param target the object from which to get the value
   * @return the value of the field associated with this descriptor.
   * @throws IllegalStateException if any value provided fails validation.
   */
  public Object getValue(final Object target) throws java.lang.IllegalStateException {
    // Needs to return the proper object
    Object temp = _handler.getValue(target);

    if (temp == null) {
      return temp;
    }

    if (!temp.getClass().isArray()) {
      return temp.toString();
    }

    int size = Array.getLength(temp);
    if (size == 0) {
      return null;
    }

    StringBuilder result = new StringBuilder();
    for (int i = 0; i < size; i++) {
      if (i > 0) {
        result.append(' ');
      }
      Object obj = Array.get(temp, i);
      result.append(obj);
    }
    return result.toString();
  }

  /**
   * Sets the value of the field to a default value.
   *
   * @param target The object to reset
   * @throws IllegalStateException if 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 resetValue(final Object target) throws java.lang.IllegalStateException {
    _handler.resetValue(target);
  }

  /**
   * 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 null;
  } // -- 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.
   *
   * @param obj The object to compare to <code>this</code>.
   *
   * @return true if the given object is an XMLFieldHandler that is equivalent to this one.
   */
  public boolean equals(final Object obj) {
    if (obj == null || !(obj instanceof XMLFieldHandler)) {
      return false;
    }
    return _handler.getClass().isInstance(obj);
  } // -- equals

} // -- CollectionFieldHandler