org.apache.wicket.markup.html.form.ChoiceRenderer.java Source code

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Here is the source code for org.apache.wicket.markup.html.form.ChoiceRenderer.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.wicket.markup.html.form;

import java.util.List;

import org.apache.wicket.core.util.lang.PropertyResolver;
import org.apache.wicket.model.IModel;
import org.apache.wicket.util.io.IClusterable;

/**
 * Renders one choice. Separates the 'id' values used for internal representation from 'display
 * values' which are the values shown to the user of components that use this renderer.
 *
 * Usage:
 * <p>
 * 
 * <pre>
 * new DropDownChoice&lt;User&gt;(&quot;users&quot;, new Model&lt;User&gt;(selectedUser), listOfUsers)
 * </pre>
 * 
 * creates a DropDownChoice of users and the display value will be toString() and the id the index
 * of the object in the ListOfUsers.
 * </p>
 * <p>
 * 
 * <pre>
 * new DropDownChoice&lt;User&gt;(&quot;users&quot;, new Model&lt;User&gt;(selectedUser), listOfUsers,
 *    new ChoiceRenderer&lt;User&gt;(&quot;name&quot;))
 * </pre>
 * 
 * creates a DropDownChoice of users and the display value will be looked up by property expression
 * ("name") and the id the index of the object in the ListOfUsers
 * </p>
 * <p>
 * 
 * <pre>
 * new DropDownChoice&lt;User&gt;(&quot;users&quot;, new Model&lt;User&gt;(selectedUser), listOfUsers,
 *    new ChoiceRenderer&lt;User&gt;(&quot;name&quot;, &quot;id&quot;))
 * </pre>
 * 
 * creates a DropDownChoice of users and the display value will be looked up by property expression
 * ("name") and the id will be looked up by the property expression "id"
 * </p>
 * 
 * @author jcompagner
 * 
 * @param <T>
 *            The model object type
 */
public class ChoiceRenderer<T> implements IChoiceRenderer<T>, IClusterable {
    private static final long serialVersionUID = 1L;

    /** expression for getting the display value. */
    private final String displayExpression;

    /** expression for getting the id. */
    private final String idExpression;

    /**
     * Constructor. 
     * 
     * When you use this constructor, the display value will be determined by calling
     * toString() on the list object, and the id will be based on the list index. the id value will
     * be the index
     */
    public ChoiceRenderer() {
        this(null);
    }

    /**
     * Constructor. 
     * 
     * When you use this constructor, the display value will be determined by executing
     * the given property expression on the list object, and the id will be based on the list index.
     * The display value will be calculated by the given property expression
     * 
     * @param displayExpression
     *            A property expression to get the display value
     */
    public ChoiceRenderer(String displayExpression) {
        this(displayExpression, null);
    }

    /**
     * Constructor. 
     * 
     * When you use this constructor, both the id and the display value will be
     * determined by executing the given property expressions on the list object.
     * 
     * @param displayExpression
     *            A property expression to get the display value
     * @param idExpression
     *            A property expression to get the id value
     */
    public ChoiceRenderer(String displayExpression, String idExpression) {
        this.displayExpression = displayExpression;
        this.idExpression = idExpression;
    }

    @Override
    public Object getDisplayValue(T object) {
        Object returnValue = object;
        if ((displayExpression != null) && (object != null)) {
            returnValue = PropertyResolver.getValue(displayExpression, object);
        }

        if (returnValue == null) {
            return "";
        }

        return returnValue;
    }

    @Override
    public String getIdValue(T object, int index) {
        if (idExpression == null) {
            return Integer.toString(index);
        }

        if (object == null) {
            return "";
        }

        Object returnValue = PropertyResolver.getValue(idExpression, object);
        if (returnValue == null) {
            return "";
        }

        return returnValue.toString();
    }

    @Override
    public T getObject(String id, IModel<? extends List<? extends T>> choices) {
        List<? extends T> _choices = choices.getObject();
        for (int index = 0; index < _choices.size(); index++) {
            // Get next choice
            final T choice = _choices.get(index);
            if (getIdValue(choice, index).equals(id)) {
                return choice;
            }
        }
        return null;
    }
}