CollectionFieldSetter.java

/*
 * Copyright (c) 2009-present the original author or authors.
 *
 * 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.planet57.gshell.util.setter;

import java.lang.reflect.Field;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

/**
 * Setter for fields of collection types.  Currently supports lists and sets.
 *
 * @author <a href="mailto:jason@planet57.com">Jason Dillon</a>
 * @since 2.0
 */
public class CollectionFieldSetter
    extends FieldSetter
{
  public CollectionFieldSetter(final Object bean, final Field field) {
    super(field, bean);

    if (!Collection.class.isAssignableFrom(field.getType())) {
      throw new IllegalArgumentException(messages.ILLEGAL_FIELD_SIGNATURE(field.getType()));
    }
  }

  public boolean isMultiValued() {
    return true;
  }

  public Class getType() {
    Type type = field.getGenericType();

    if (type instanceof ParameterizedType) {
      ParameterizedType ptype = (ParameterizedType) type;
      type = ptype.getActualTypeArguments()[0];

      if (type instanceof Class) {
        return (Class) type;
      }
    }

    // If collection types don't have a parameter type, then the ObjectHandler will be used
    // which basically is the same as the StringHandler
    return Object.class;
  }

  protected void doSet(final Object value) throws IllegalAccessException {
    Object obj = field.get(getBean());

    // If the field is not set, then create a new instance of the collection and set it
    if (obj == null) {
      Class type = field.getType();

      if (List.class.isAssignableFrom(type)) {
        obj = new ArrayList();
      }
      else if (Set.class.isAssignableFrom(type)) {
        obj = new LinkedHashSet();
      }
      else if (Collection.class.isAssignableFrom(type)) {
        obj = new ArrayList();
      }
      else {
        try {
          obj = type.newInstance();
        }
        catch (Exception e) {
          throw new IllegalStateException("Unsupported collection type: " + field.getType(), e);
        }
      }

      field.set(getBean(), obj);
    }

    // This should never happen
    if (!(obj instanceof Collection)) {
      throw new IllegalStateException("Field is not a collection type: " + field);
    }

    // noinspection unchecked
    ((Collection) obj).add(value);
  }
}