在JSP中使用自定义标记设置变量并将其传递给servlet

<taglib xmlns="http://java.sun.com/xml/ns/j2ee" version="2.0">
  <tlib-version>1.0</tlib-version>
  <short-name>custom</short-name>
  <uri>http://example.com/custom</uri>
  
  <tag>
    <name>setVariable</name>
    <tag-class>com.example.SetVariableTag</tag-class>
    <body-content>empty</body-content>
    <attribute>
      <name>name</name>
      <required>true</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
    <attribute>
      <name>value</name>
      <required>true</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>
</taglib>

package com.example;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;

public class SetVariableTag extends TagSupport {
  private String name;
  private Object value;

  public void setName(String name) {
    this.name = name;
  }

  public void setValue(Object value) {
    this.value = value;
  }

  @Override
  public int doEndTag() throws JspException {
    pageContext.setAttribute(name, value);
    return EVAL_PAGE;
  }
}

<%@ taglib prefix="custom" uri="http://example.com/custom" %>

<custom:setVariable name="message" value="Hello, World!" />

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  String message = (String) request.getAttribute("message");
  // 使用变量进行后续处理
}