【JavaWeb】jsp内置对象、EL表达式以及跳转重定向等

1、dictionary.jsp跳转至DictionaryServlet

@WebServlet("/dictionary")
public class DictionaryServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Map map = new HashMap<>(10);
        map.put("苹果","apple");
        map.put("香蕉","banana");
        map.put("桃子","peach");
        String word= request.getParameter("word");

        if(map.containsKey(word)){
            request.setAttribute("answer",map.get(word));
            request.getRequestDispatcher("/success.jsp").forward(request,response);
        }else{
            HttpSession session = request.getSession();
            session.setAttribute("answer","没有找到对应的单词解释");
            //重定向的路径设置与转发不同 不是/fail.jsp
            response.sendRedirect("fail.jsp");
        }

    }
}

2、success.jsp
//或者使用EL表达式
${requestScope.get(“answer”)}或
${requestScope.answer}

  
    
  
  
  		//或者使用EL表达式
  		${requestScope.get("answer")}
      <%
      //内置request、out对象
        String answer = request.getAttribute("answer").toString();
        out.println(answer);
      %>
  

3、 fail.jsp( //重定向的路径设置与转发不同 不是/fail.jsp)

  
    
  
  
    <%
    //内置request、out
        out.println(request.getSession().getAttribute("answer").toString());
    %>
  

附注：
EL：1、${} 不需要<%%>
2、使用toString方法
3、作用域page、request、session、context
4、内置param.参数名（即getParamater）