001/*
002 * Copyright 2002-2018 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.web.servlet.tags;
018
019import javax.servlet.jsp.JspException;
020import javax.servlet.jsp.tagext.BodyTagSupport;
021
022import org.springframework.lang.Nullable;
023
024/**
025 * The {@code <argument>} tag is based on the JSTL {@code fmt:param} tag.
026 * The purpose is to support arguments inside the message and theme tags.
027 *
028 * <p>This tag must be nested under an argument aware tag.
029 *
030 * <table>
031 * <caption>Attribute Summary</caption>
032 * <thead>
033 * <tr>
034 * <th>Attribute</th>
035 * <th>Required?</th>
036 * <th>Runtime Expression?</th>
037 * <th>Description</th>
038 * </tr>
039 * </thead>
040 * <tbody>
041 * <tr>
042 * <td>value</td>
043 * <td>false</td>
044 * <td>true</td>
045 * <td>The value of the argument.</td>
046 * </tr>
047 * </tbody>
048 * </table>
049 *
050 * @author Nicholas Williams
051 * @since 4.0
052 * @see MessageTag
053 * @see ThemeTag
054 */
055@SuppressWarnings("serial")
056public class ArgumentTag extends BodyTagSupport {
057
058        @Nullable
059        private Object value;
060
061        private boolean valueSet;
062
063
064        /**
065         * Set the value of the argument (optional).
066         * If not set, the tag's body content will get evaluated.
067         * @param value the parameter value
068         */
069        public void setValue(Object value) {
070                this.value = value;
071                this.valueSet = true;
072        }
073
074
075        @Override
076        public int doEndTag() throws JspException {
077                Object argument = null;
078                if (this.valueSet) {
079                        argument = this.value;
080                }
081                else if (getBodyContent() != null) {
082                        // Get the value from the tag body
083                        argument = getBodyContent().getString().trim();
084                }
085
086                // Find a param-aware ancestor
087                ArgumentAware argumentAwareTag = (ArgumentAware) findAncestorWithClass(this, ArgumentAware.class);
088                if (argumentAwareTag == null) {
089                        throw new JspException("The argument tag must be a descendant of a tag that supports arguments");
090                }
091                argumentAwareTag.addArgument(argument);
092
093                return EVAL_PAGE;
094        }
095
096        @Override
097        public void release() {
098                super.release();
099                this.value = null;
100                this.valueSet = false;
101        }
102
103}