Tomcat 7.0.23 不适用于标签库答案

【问题标题】：Tomcat 7.0.23 does not work with tag librariesTomcat 7.0.23 不适用于标签库
【发布时间】：2012-01-16 16:22:50
【问题描述】：

截至 2011 年 1 月 16 日，我已经下载了最新版本的 tomcat 7，即 7.0.23。我发现我的 jakarta 标记库组件都没有在 jsps 中工作。每个jsp中的故障点都是相同且一致的。这是

org.apache.taglibs.input.Select _jspx_th_input_005fselect_005f0 = (org.apache.taglibs.input.Select)_jsp_instancemanager.newInstance("org.apache.taglibs.input.Select", this.getClass().getClassLoader());

我还写了一个自定义标签来看看它是否工作，我也遇到了同样的问题。

com.ah.util.customtags.SelectTag _jspx_th_hirezon_005fform_005fselect_005f0 = (com.ah.util.customtags.SelectTag)_jsp_instancemanager.newInstance("com.ah.util.customtags.SelectTag", this.getClass().getClassLoader());

jsp代码是

<%@ page extends="com.ah.servlets.BaseJSPServlet"%>
<%@ taglib uri="/WEB-INF/hirezon_form.tld" prefix="hirezon_form" %>
<html>
<body>Test tags
<%
System.setProperty("org.apache.jasper.Constants.USE_INSTANCE_MANAGER_FOR_TAGS", "true");
%>
<hirezon_form:select count="100"/>
</body>
</html>

CustomTagSupport 类的代码是

package com.ah.util.customtags;

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

public class SelectTag extends TagSupport {

    String count;
    public String getCount() {
        return count;
    }
    public void setCount(String count) {
        this.count = count;
    }
    public int doStartTag() throws JspException {
        // This means the JSP must evaluate the contents of any CHild tags
        // in this tag;
        return EVAL_BODY_INCLUDE;
    }
    // This method is called when the JSP encounters the end of te tag
    // implemented by this class
    public int doEndTag() throws JspException {

        String sum = "200000";
        try {
            pageContext.getOut().write("The Sum of first " + count + " numbers is " + sum);
        } catch (IOException e) {
            throw new JspException("Fatal Error: HelloTag could'nt write to the JSP out");
        }
        // This return type tells the JSP page to continue processing
        // the rest of the page
        return EVAL_PAGE;
    }
}

Tomcat 7.0.23 中是否存在已知错误？我做了很多研究，还尝试将 USE_INSTANCE_MANAGER_FOR_TAGS 属性设置为 true，但我仍然遇到同样的错误。任何建议将不胜感激，谢谢

【问题讨论】：

标签： jsp jsp-tags tomcat7

【解决方案1】：

我发现了问题，是我的jsp。该 jsp 扩展了一个名为 BaseJSPServlet 的 servlet。默认情况下，当为 jsp 创建 java 类时，它扩展 org.apache.jasper.runtime.HttpJspBase，但是当您添加页面扩展指令时，您的 java 类将扩展您提到的类而不是 org.apache.jasper。运行时.HttpJspBase。因此，您需要确保您的父类与 HttpJspBase 类所做的几乎一样。

这是一个可以在jsp中使用page extends指令扩展的父类的示例代码。

import java.io.IOException;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.HttpJspPage;
import org.apache.jasper.compiler.Localizer;

public abstract class BaseJSPServlet2 implements javax.servlet.jsp.HttpJspPage

{
  private static final long serialVersionUID = 1L;

  public final void init(ServletConfig config)
    throws ServletException
  {
    super.init(config);
    jspInit();
    _jspInit();
  }

  public String getServletInfo()
  {
    return Localizer.getMessage("jsp.engine.info");
  }

  public final void destroy()
  {
    jspDestroy();
    _jspDestroy();
  }

  public final void service(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException
  {
    _jspService(request, response);
  }

  public void jspInit()
  {
  }

  public void _jspInit()
  {
  }

  public void jspDestroy()
  {
  }

  protected void _jspDestroy()
  {
  }

  public abstract void _jspService(HttpServletRequest paramHttpServletRequest, HttpServletResponse paramHttpServletResponse)
    throws ServletException, IOException;

}

【讨论】：