Question

我希望通过扩展类BodyTagSupport，但是获取运行时异常，从标记处理程序中显示自定义标记名称中的JSP的正文值; o）

JSP代码是：

<html><body>
<%@ taglib prefix="mine" uri="simpleTags" %>

Advisor page
<mine:simple>
Balle Balle
</mine:simple>
</html></body>

和Tag处理程序类是：

package foo;

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

public class SelectTagHandler extends BodyTagSupport
{
public int doStartTag() throws JspException{

return EVAL_BODY_BUFFERED;
}

public int EndTag()
{
try{
pageContext.getOut().print(bodyContent);
}
catch(Exception e)
{
}
return EVAL_PAGE;
}

和异常，我得到的是：

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: foo.SelectTagHandler.setJspContext(Ljavax/servlet/jsp/JspContext;)V
    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:460)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:355)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)

root cause

javax.servlet.ServletException: foo.SelectTagHandler.setJspContext(Ljavax/servlet/jsp/JspContext;)V
    org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:841)
    org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:774)
    org.apache.jsp.new_jsp._jspService(new_jsp.java:60)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)

root cause

java.lang.NoSuchMethodError: foo.SelectTagHandler.setJspContext(Ljavax/servlet/jsp/JspContext;)V
    org.apache.jsp.new_jsp._jspx_meth_mine_005fsimple_005f0(new_jsp.java:73)
    org.apache.jsp.new_jsp._jspService(new_jsp.java:51)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)

note The full stack trace of the root cause is available in the Apache Tomcat/5.5.27 logs.

编辑：我的TLD文件的代码是：

<taglib 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/web-jsptaglibrary_2_0.xsd" version="2.0">

<tlib-version>1.2</tlib-version>
<uri>simpleTags</uri>
<tag>
<name>simple</name>
<tag-class>foo.SelectTagHandler</tag-class>
<body-content>scriptless</body-content>
</tag>
</taglib>

我在这里做错了什么？

Answer 1

setJspContext仅适用于SimpleTag和SimpleTagSupport，而不适用BodyTag（不要问我原因）。由于某种原因，Tomcat将您的标记视为SimpleTag。问题可能出在您的TLD文件中，您可以修改问题以添加该文件吗？

Answer 2

您在代码中直接打印bodyContent：

pageContext.getOut().print(bodyContent);

bodyContent不是String，它是javax.servlet.jsp.tagext.BodyContent类的对象，它没有定义合适的toString（）方法（也不应该）以这种方式使用。您应该通过getString()方法获取实际的身体内容：

if (bodyContent!=null) {
    String bodyText = bodyContent.getString();
    pageContext.getOut().print(bodyText); // or whatever you want to do with it
}

Answer 3

如果您使用Taglib版本2.1而不是2.0，则会发生这种情况。更改tld文件中taglib-Tag的版本和架构属性。看起来应该是这样的：

<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">

运行Classic标记处理程序时出现问题

3 个答案: