java - 在用户描述符中不起作用 pageContext.getOut ("")

Question

我有一个下一个问题。在 jsp 页面中，我根据角色使用 2 个用户(导师和学生)的菜单，我从菜单文件中选择应包含的内容。像这样

<c:if test="${role eq 'Tutor'}">
                <c:import url="/page/menuForTutor.html" charEncoding="UTF-8"/>
</c:if>
<c:if test="${role eq 'Student'}">
             <c:import url="/page/menuForStudent.html" charEncoding="UTF-8"/>
</c:if>

我应该使用用户描述符

public class MenuTag extends TagSupport{

    private static final String PARAM_ROLE_TUTOR = "Tutor";
    private static final String PARAM_ROLE_STUDENT = "Student";

    @Override
    public int doStartTag(){
        HttpServletRequest request = (HttpServletRequest)pageContext.
                                                   getRequest();
        HttpSession session = request.getSession();
        String role = (String) session.getAttribute("role");
        if (PARAM_ROLE_TUTOR.equals(role)){
            try {
                pageContext.getOut().print("<c:import url=\"/page/menuForTutor.html\" charEncoding=\"UTF-8\"/>");
            } catch (IOException ex) {
                Logger.getLogger(MenuTag.class.getName()).log(Level.SEVERE, null, ex);
            }
        } else if(PARAM_ROLE_STUDENT.equals(role)){
        }
        return SKIP_BODY;
    }       
}

当我使用 debag 时，我看到我执行了所有步骤，但 jsp 上未显示导师菜单。有什么想法吗？

Answer 1

我假设 session("role") 是在另一个代码部分中设置的!

设置 JspWriter out = pageContext.getOut();

类似于代码中的内容

JspFactory  factory     = JspFactory.getDefaultFactory();
PageContext pageContext = factory.getPageContext(
this,
request,
response,
null,  // errorPageURL
false, // needsSession
JspWriter.DEFAULT_BUFFER,
true   // autoFlush
);

    ....
            JspWriter   out     = pageContext.getOut();
            HttpSession session = request.getSession();
            String role = (String) session.getAttribute("role");
            if (PARAM_ROLE_TUTOR.equals(role)){
                try {
                    out.println("<c:import url=\"/page/menuForTutor.html\" charEncoding=\"UTF-8\"/>");
                    out.flush();
                    // Evaluate the body if there is one
                    return EVAL_BODY_BUFFERED;
.......

else return SKIP_BODY;

编辑查看代码:您必须“return EVAL_BODY_BUFFERED;”