javax.servlet.ServletException: bean [name] not found within scope

问题

I'm getting this error:

javax.servlet.ServletException: bean not found within scope

on a page with this at the top.

<jsp:useBean id="bean" type="com.example.Bean" scope="request" />

The class exists in the classpath, it worked this morning, and I don't get what not found within scope means.

How is this caused and how can I solve it?

回答1:

You need the class attribute instead of the type attribute.

The following:

<jsp:useBean id="bean" type="com.example.Bean" scope="request" />

does basically the following behind the scenes:

Bean bean = (Bean) pageContext.getAttribute("bean", PageContext.REQUEST_SCOPE);

if (bean == null) {
    throw new ServletException("bean not found within scope");
}

// Use bean ...

While the following:

<jsp:useBean id="bean" class="com.example.Bean" scope="request" />

does basically the following behind the scenes:

Bean bean = (Bean) pageContext.getAttribute("bean", PageContext.REQUEST_SCOPE);

if (bean == null) {
    bean = new Bean();
    pageContext.setAttribute("bean", bean, PageContext.REQUEST_SCOPE);
}

// Use bean ...

If it has worked before and it didn't work "in a sudden", then it means that something which is responsible for putting the bean in the scope has stopped working. For example a servlet which does the following in the doGet():

request.setAttribute("bean", new Bean());
request.getRequestDispatcher("page.jsp").forward(request, response);

Maybe you've invoked the JSP page directly by URL instead of invoking the Servlet by URL. If you'd like to disable direct access to JSP pages, then put them in /WEB-INF and forward to it instead.

回答2:

You must add

<jsp:useBean id="givingFormBean" type="some.packg.GivingForm" scope="request" />

Because by default the bean is looked on the page scope

来源：https://stackoverflow.com/questions/270444/javax-servlet-servletexception-bean-name-not-found-within-scope

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java

jsp

usebean