Struts example source code file (ComboBox.java)

This example Struts source code file (ComboBox.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Struts tags/keywords

collection, collection, combobox, http, if, map, object, request, response, servlet, set, set, string, string, strutstagattribute, strutstagattribute, template, util, you

The Struts ComboBox.java source code

/*
 * $Id: ComboBox.java 651946 2008-04-27 13:41:38Z apetrelli $
 *
 * 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.struts2.components;

import java.util.Collection;
import java.util.Iterator;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.struts2.views.annotations.StrutsTag;
import org.apache.struts2.views.annotations.StrutsTagAttribute;
import org.apache.struts2.util.MakeIterator;

import com.opensymphony.xwork2.util.ValueStack;

/**
 * <!-- START SNIPPET: javadoc -->
 * The combo box is basically an HTML INPUT of type text and HTML SELECT grouped together to give you a combo box
 * functionality. You can place text in the INPUT control by using the SELECT control or type it in directly in
 * the text field.<p/>
 *
 * In this example, the SELECT will be populated from id=year attribute. Counter is itself an Iterator. It will
 * span from first to last. The population is done via javascript, and requires that this tag be surrounded by a
 * <form>.<p/>
 *
 * Note that unlike the <s:select/> tag, there is no ability to define the individual <option> tags' id attribute
 * or content separately. Each of these is simply populated from the toString() method of the list item. Presumably
 * this is because the select box isn't intended to actually submit useful data, but to assist the user in filling
 * out the text field.<p/>
 * <!-- END SNIPPET: javadoc -->
 *
 * <p/> Examples
 *
 * <pre>
 * <!-- START SNIPPET: example -->
 * JSP:
 * <-- Example One -->
 * <s:bean name="struts.util.Counter" var="year">
 *   <s:param name="first" value="text('firstBirthYear')"/>
 *   <s:param name="last" value="2000"/>
 *
 *   <s:combobox label="Birth year" size="6" maxlength="4" name="birthYear" list="#year"/>
 * </s:bean>
 *
 * <-- Example Two -->
 * <s:combobox
 *     label="My Favourite Fruit"
 *     name="myFavouriteFruit"
 *     list="{'apple','banana','grape','pear'}"
 *     headerKey="-1"
 *     headerValue="--- Please Select ---"
 *     emptyOption="true"
 *     value="banana" />
 *
 * <-- Example Two -->
 * <s:combobox
 *    label="My Favourite Color"
 *    name="myFavouriteColor"
 *    list="#{'red':'red','green':'green','blue':'blue'}"
 *    headerKey="-1"
 *    headerValue="--- Please Select ---"
 *    emptyOption="true"
 *    value="green" />
 *
 * Velocity:
 * #tag( ComboBox "label=Birth year" "size=6" "maxlength=4" "name=birthYear" "list=#year" )
 * <!-- END SNIPPET: example -->
 * </pre>
 *
 */
@StrutsTag(name="combobox", tldTagClass="org.apache.struts2.views.jsp.ui.ComboBoxTag", description="Widget that fills a text box from a select")
public class ComboBox extends TextField {
    final public static String TEMPLATE = "combobox";

    protected String list;
    protected String listKey;
    protected String listValue;
    protected String headerKey;
    protected String headerValue;
    protected String emptyOption;


    public ComboBox(ValueStack stack, HttpServletRequest request, HttpServletResponse response) {
        super(stack, request, response);
    }

    protected String getDefaultTemplate() {
        return TEMPLATE;
    }

    public void evaluateExtraParams() {
        super.evaluateExtraParams();

        Object value = findListValue();

        if (headerKey != null) {
            addParameter("headerKey", findString(headerKey));
        }
        if (headerValue != null) {
            addParameter("headerValue", findString(headerValue));
        }
        if (emptyOption != null) {
            addParameter("emptyOption", findValue(emptyOption, Boolean.class));
        }

        if (value != null) {
            if (value instanceof Collection) {
                Collection tmp = (Collection) value;
                addParameter("list", tmp);
                if (listKey != null) {
                    addParameter("listKey", listKey);
                }
                if (listValue != null) {
                    addParameter("listValue", listValue);
                }
            } else if (value instanceof Map) {
                Map tmp = (Map) value;
                addParameter("list", MakeIterator.convert(tmp));
                addParameter("listKey", "key");
                addParameter("listValue", "value");                
            } else { // also covers "if (value.getClass().isArray())"
                Iterator i = MakeIterator.convert(value);
                addParameter("list", i);
                if (listKey != null) {
                    addParameter("listKey", listKey);
                }
                if (listValue != null) {
                    addParameter("listValue", listValue);
                }
            }
        }
    }

    protected Object findListValue() {
        return findValue(list, "list",
                "You must specify a collection/array/map/enumeration/iterator. " +
                "Example: people or people.{name}");
    }

    @StrutsTagAttribute(description="Iteratable source to populate from. " +
                "If this is missing, the select widget is simply not displayed.", required=true)
    public void setList(String list) {
        this.list = list;
    }

    @StrutsTagAttribute(description="Decide if an empty option is to be inserted. Default false.")
    public void setEmptyOption(String emptyOption) {
        this.emptyOption = emptyOption;
    }

    @StrutsTagAttribute(description="Set the header key for the header option.")
    public void setHeaderKey(String headerKey) {
        this.headerKey = headerKey;
    }

    @StrutsTagAttribute(description="Set the header value for the header option.")
    public void setHeaderValue(String headerValue) {
        this.headerValue = headerValue;
    }

    @StrutsTagAttribute(description="Set the key used to retrive the option key.")
    public void setListKey(String listKey) {
        this.listKey = listKey;
    }

    @StrutsTagAttribute(description="Set the value used to retrive the option value.")
    public void setListValue(String listValue) {
        this.listValue = listValue;
    }


}