javax.servlet.ServletException: File amp;quot;/demo/header.jsp" not found

wrong reason

<jsp:include page="${ctx}/header.jsp"></jsp:include>
${ctx}Is the project name, set on the login page<c:set var="ctx" scope="application" value="${pageContext.request.contextPath}"/>
Note: If you use the idea to deploy without specifying the project name, you can access it successfully.${ctx}="/"

solve

use<%@include file="/header.jsp"%>replace<jsp:include page="${ctx}/header.jsp"/>

why

When the jsp foreground is displayed, it will be translated into a Servlet first, and then used.javax.servlet.http.HttpServletResponse responseShow at the front desk

<jsp:include page="${ctx}/header.jsp"/>

<jsp:include/>manual

1. When there is jsp use<jsp:include page="${ctx}/header.jsp"></jsp:include>Turn the user intoServlet，
2. Putheader.jspFirst translated intoServlet，
3. userServletMedium configurationheader.jspofServlet

verification
under Tomcat\work\Catalina\localhostCan be found underheader_jsp.javaFile, the user also has a corresponding file, open to see

 org.apache.jasper.runtime.JspRuntimeLibrary.include(request, response, (java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${ctx}/header.jsp", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null, false), out, false);

Reference header.jsp in the servlet
<%@include%>The code is introduced, the code is included, and when new JSP is added, it will be generated by default.

<%@include file="/header.jsp"%>

<%@include%>manual

1. Introducing header.jsp in jsp file
2. User translation servlet

View jsp translated files and found noheader_jsp.java, can be seen in the user

	  out.write("\r\n");
	  ···
	  ···
	  ···
     /**
     *Content in the header.jsp file
     */
      out.write("</head>");

to sum up

the difference	include	jsp:include
execution time	Translation stage	Executed during the request processing phase
Introduced content	Introduce static text,First include, post-compilation	Introduce the response text generated by the execution page or servlet. The included fileCompile first, then includeCome in, then show

Translation stage:

The jsp page cannot be transferred to the browser as it is, and all jsp elements must be processed by the server first. This is done by translating the jsp page into a servlet and then executing the servlet. The server needs a jsp container to handle the jsp page. The jsp container is usually implemented in the form of a servlet that is configured to handle all requests to the jsp page.
The Jsp container also converts the jsp page into a servlet (called the JSP Page implementation class) and compiles the servlet. These two steps form the translation phase.

Request processing phase:

In addition to the above mentioned Jsp container to convert the jsp page into a servlet, it also calls the jsp page implementation class to process each request and generate a response. This stage is called the request processing stage. The request processing stage only executes the class documentation.