Java 自定义标签不起作用/使用有问题

Question

我在 JSP 中的自定义标记方面遇到了巨大的问题。我在 WEB-INF/tlds 中创建了一个名为“decorate”的标签库描述 rune 件。我将前缀设置为“d”。然后我创建了名为“decorateHandler”的标记处理程序类。

我想以简单的方式装饰 JSP 标题页中的文本，但出现错误...

我的decorate.tld 文件:

<tlib-version>1.0</tlib-version>
  <short-name>l</short-name>
  <uri>/WEB-INF/tlds/decorate</uri>
  <tag>
    <name>decorate</name>
    <tag-class>decorateHandler</tag-class>
    <body-content>JSP</body-content> 
    <attribute>
        <name>value</name>
    </attribute>
  </tag>
</taglib>

在decorateHandler.java中我尝试这样做:

private String value;

    private void writeTagBodyContent(JspWriter out, BodyContent bodyContent) throws IOException {

        out.println("<font color='"+value+"'>");
        bodyContent.writeOut(out);
        out.println("</font>");

        bodyContent.clearBody();
    }

当然，我已经为字符串值变量创建了 getter 和 setter。

在index.jsp中我已经包含了taglib，如下所示:

<%@taglib uri="/WEB-INF/tlds/decorate.tld" prefix="d" %>

我尝试了这样的事情:

 <d:decorate value="red">Lorem ipsum</d:decorate>

但我有一个异常(exception):

org.apache.jasper.JasperException: Unable to compile class for JSP: 

An error occurred at line: [112] in the jsp file: [/index.jsp]
decorateHandler cannot be resolved to a type
109:                         <li class="nav-item">
110:                             <a class="nav-link" href="index.jsp">
111:                                 <img src="logo.png" height="20px" width="20px">
112:                                 <d:decorate value="red">Lorem ipsum</d:decorate>
113:                             </a>
114:                         </li>
115:                     </ul>      


An error occurred at line: [112] in the jsp file: [/index.jsp]
decorateHandler cannot be resolved to a type
109:                         <li class="nav-item">
110:                             <a class="nav-link" href="index.jsp">
111:                                 <img src="logo.png" height="20px" width="20px">
112:                                 <d:decorate value="red">Lorem ipsum</d:decorate>
113:                             </a>
114:                         </li>
115:                     </ul>      


An error occurred at line: [112] in the jsp file: [/index.jsp]
The method get(Class<? extends Tag>) in the type TagHandlerPool is not applicable for the arguments (Class<decorateHandler>)
109:                         <li class="nav-item">
110:                             <a class="nav-link" href="index.jsp">
111:                                 <img src="logo.png" height="20px" width="20px">
112:                                 <d:decorate value="red">Lorem ipsum</d:decorate>
113:                             </a>
114:                         </li>
115:                     </ul>      


An error occurred at line: [112] in the jsp file: [/index.jsp]
decorateHandler cannot be resolved to a type
109:                         <li class="nav-item">
110:                             <a class="nav-link" href="index.jsp">
111:                                 <img src="logo.png" height="20px" width="20px">
112:                                 <d:decorate value="red">Lorem ipsum</d:decorate>
113:                             </a>
114:                         </li>
115:                     </ul>      


Stacktrace:
    org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:102)
    org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:212)
    org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:549)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:378)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:350)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:334)
    org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:595)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:399)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:386)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:330)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    Filtr2.doFilter(Filtr2.java:67)

我不知道问题出在哪里...:/

Answer 1

首先，我认为您应该检查 Web 容器的日志(例如 Tomcat、Glassfish？)。该错误的堆栈跟踪将在那里可用，并提示您实际原因是什么。不管怎样，乍一看，很明显错误是由自定义装饰器 taglib 引起的，它似乎在最后做了一个 bodyContent.clearBody() 。我认为这里不允许这样做，也许您打算改为执行 bodyContent.flush() ？

Here有关如何创建自定义 jsp 标记的教程。