spring ParamTag 源码
spring ParamTag 代码
文件路径：/spring-webmvc/src/main/java/org/springframework/web/servlet/tags/ParamTag.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 <param>} tag collects name-value parameters and passes them to a
* {@link ParamAware} ancestor in the tag hierarchy.
*
* <p>This tag must be nested under a param 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>name</td>
* <td>true</td>
* <td>true</td>
* <td>The name of the parameter.</td>
* </tr>
* <tr>
* <td>value</td>
* <td>false</td>
* <td>true</td>
* <td>The value of the parameter.</td>
* </tr>
* </tbody>
* </table>
*
* @author Scott Andrews
* @author Nicholas Williams
* @since 3.0
* @see Param
* @see UrlTag
*/
@SuppressWarnings("serial")
public class ParamTag extends BodyTagSupport {
private String name = "";
@Nullable
private String value;
private boolean valueSet;
/**
* Set the name of the parameter (required).
*/
public void setName(String name) {
this.name = name;
}
/**
* Set the value of the parameter (optional).
*/
public void setValue(String value) {
this.value = value;
this.valueSet = true;
}
@Override
public int doEndTag() throws JspException {
Param param = new Param();
param.setName(this.name);
if (this.valueSet) {
param.setValue(this.value);
}
else if (getBodyContent() != null) {
// Get the value from the tag body
param.setValue(getBodyContent().getString().trim());
}
// Find a param aware ancestor
ParamAware paramAwareTag = (ParamAware) findAncestorWithClass(this, ParamAware.class);
if (paramAwareTag == null) {
throw new JspException("The param tag must be a descendant of a tag that supports parameters");
}
paramAwareTag.addParam(param);
return EVAL_PAGE;
}
@Override
public void release() {
super.release();
this.name = "";
this.value = null;
this.valueSet = false;
}
}
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