自定义JSP标记和Tomcat 8

Question

自定义JSP标记和Tomcat 8出现了奇怪的错误。使用Tomcat 7可以正常工作。

TLD文件：

<?xml version="1.0" encoding="UTF-8" ?>
<taglib version="2.0"
        xmlns="http://java.sun.com/xml/ns/j2ee"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd">
   <tlib-version>1.0</tlib-version>
   <short-name>Example TLD</short-name>
   <uri>http://www.hello.com/tags/hello</uri>
   <tag>
      <name>Hello</name>
      <tag-class>myapp.tag.HelloTag</tag-class>
      <body-content>empty</body-content>
   </tag>
</taglib>

处理程序类：

import javax.servlet.jsp.tagext.*;
import javax.servlet.jsp.*;
import java.io.*;

public class HelloTag extends SimpleTagSupport {

    public void doTag() throws JspException, IOException {
        JspWriter out = getJspContext().getOut();
        out.println("Hello Custom Tag!");
    }
}

JSP（仅第6行）：

...
<%@ taglib prefix="ex" uri="/WEB-INF/lib/custom.tld"%>
...

错误：

Caused by: org.apache.jasper.JasperException: /WEB-INF/jsp/myapp.jsp (line: 6, column: 1) null
at org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:41)
at org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:275)
at org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:91)
at org.apache.jasper.compiler.Parser.processIncludeDirective(Parser.java:325)
at org.apache.jasper.compiler.Parser.parseIncludeDirective(Parser.java:358)
at org.apache.jasper.compiler.Parser.parseXMLDirective(Parser.java:527)
at org.apache.jasper.compiler.Parser.parseElements(Parser.java:1432)
at org.apache.jasper.compiler.Parser.parse(Parser.java:139)
at org.apache.jasper.compiler.ParserController.doParse(ParserController.java:227)
at org.apache.jasper.compiler.ParserController.parse(ParserController.java:100)
at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:199)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:356)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:336)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:323)
at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:570)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:356)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:721)
at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:584)
at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:523)
at org.apache.tiles.request.servlet.ServletRequest.doInclude(ServletRequest.java:243)

Answer 1

我注意到了几件事：

1. 尝试像这样在uri中包含一个开始/符号： <%@ taglib prefix="ex" uri="/WEB-INF/lib/custom.tld" %>
2. 您在问题中提供的TLD文件（希望命名为custom.tld）看起来不完整。 它缺少结束标签。 它缺少初始定义。

我的TLD文件如下所示：

<?xml version="1.0"?>
<taglib version="2.0"
        xmlns="http://java.sun.com/xml/ns/j2ee"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd">
  <tlib-version>1.0</tlib-version>
  <short-name>custom</short-name>
  <uri>http://example.com/tags/custom</uri>
  <tag>
    ...
  </tag>
</taglib>

在JSP中，我像这样通过URI导入它们，并且在Tomcat 8上运行良好：

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

Answer 2

Tomcat 8希望将tld文件放在WEB-INF文件夹中。 将custom.tld文件移动到此处，并将jsp文件中的第6行更正为：

<%@ taglib prefix="ex" uri="/WEB-INF/custom.tld"%>

现在应该可以了