无法加载标记处理程序 class

Question

我在标签包中有这个 class 用于 tld 文件

package tag;

import java.io.IOException;
import java.time.LocalDate;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;


public class printDateTag extends TagSupport{

@Override
public int doStartTag() throws JspException {
    try {
        JspWriter writer = pageContext.getOut();
        writer.print(LocalDate.now());
    } catch (IOException ex) {System.out.println(ex);}
    return SKIP_BODY;
}

}

我使用那个 class 的 tld 文件是这个

<?xml version="1.0" encoding="UTF-8"?>
<taglib version="2.1" xmlns="http://java.sun.com/xml/ns/javaee" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee          
http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd">
<tlib-version>1.0</tlib-version>
<short-name>tags</short-name>
<uri>/WEB-INF/tlds/tags</uri>


<tag>
    <name>printDate</name>
    <tag-class>tag.printDateTag</tag-class>
</tag>

我出错的 jsp 是这个

 <%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@taglib prefix="ta" uri="/WEB-INF/tlds/tags.tld"%>
<!DOCTYPE html>
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>JSP Page</title>
</head>
<body>
    <ta:printDate/>
    <a href="index">go</a>
</body>
</html>

这里 <ta:printDate/> 我有错误 无法加载标签处理程序 class "tag.printDateTag" 标签“ta:printDate

Answer 1

根据您的代码，

looks like your tld file is not properly configure,

见下面我试过的代码，

printDateTag.java

package tag;

import java.io.IOException;

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

public class printDateTag extends TagSupport{
    @Override
    public int doStartTag() throws JspException {
        try {
            JspWriter writer = pageContext.getOut();
            writer.print("<u>Hello From Tag</u>"); //  <u>Hello From Tag</u>... it will display on JSP page
        } catch (IOException ex) {System.out.println(ex);}
        return SKIP_BODY;
    }
}

tags.tld

<?xml version="1.0" encoding="ISO-8859-1" ?>  
<!DOCTYPE taglib  
        PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"  
    "http://java.sun.com/j2ee/dtd/web-jsptaglibrary_1_2.dtd">  

<taglib>  

  <tlib-version>1.0</tlib-version>  
  <jsp-version>1.2</jsp-version>  
  <short-name>simple</short-name>  
 <!--  <uri>http://tomcat.apache.org/example-taglib</uri> -->  
  <uri>/WEB-INF/tlds/tags</uri>
<tag>
    <name>printDate</name>
    <tag-class>tag.printDateTag</tag-class>
</tag> 

</taglib>

test.jsp

 <%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@taglib prefix="ta" uri="/WEB-INF/tlds/tags.tld"%>
<!DOCTYPE html>
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>JSP Page</title>
</head>
<body>
    <ta:printDate/>
    <a href="index">go</a>
</body>
</html>

输出：

无法加载标记处理程序 class

Unable to load tag handler class

jsp

custom-tags

tag-handler