spring ArgumentTag 源码
spring ArgumentTag 代码
文件路径：/spring-webmvc/src/main/java/org/springframework/web/servlet/tags/ArgumentTag.java
/*
* Copyright 2002-2018 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
*
* https://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.springframework.web.servlet.tags;
import jakarta.servlet.jsp.JspException;
import jakarta.servlet.jsp.tagext.BodyTagSupport;
import org.springframework.lang.Nullable;
/**
* The {@code <argument>} tag is based on the JSTL {@code fmt:param} tag.
* The purpose is to support arguments inside the message and theme tags.
*
* <p>This tag must be nested under an argument aware tag.
*
* <table>
* <caption>Attribute Summary</caption>
* <thead>
* <tr>
* <th>Attribute</th>
* <th>Required?</th>
* <th>Runtime Expression?</th>
* <th>Description</th>
* </tr>
* </thead>
* <tbody>
* <tr>
* <td>value</td>
* <td>false</td>
* <td>true</td>
* <td>The value of the argument.</td>
* </tr>
* </tbody>
* </table>
*
* @author Nicholas Williams
* @since 4.0
* @see MessageTag
* @see ThemeTag
*/
@SuppressWarnings("serial")
public class ArgumentTag extends BodyTagSupport {
@Nullable
private Object value;
private boolean valueSet;
/**
* Set the value of the argument (optional).
* If not set, the tag's body content will get evaluated.
* @param value the parameter value
*/
public void setValue(Object value) {
this.value = value;
this.valueSet = true;
}
@Override
public int doEndTag() throws JspException {
Object argument = null;
if (this.valueSet) {
argument = this.value;
}
else if (getBodyContent() != null) {
// Get the value from the tag body
argument = getBodyContent().getString().trim();
}
// Find a param-aware ancestor
ArgumentAware argumentAwareTag = (ArgumentAware) findAncestorWithClass(this, ArgumentAware.class);
if (argumentAwareTag == null) {
throw new JspException("The argument tag must be a descendant of a tag that supports arguments");
}
argumentAwareTag.addArgument(argument);
return EVAL_PAGE;
}
@Override
public void release() {
super.release();
this.value = null;
this.valueSet = false;
}
}
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