java - .forward(req, resp) 之后的 HttpServletRequest 有什么问题？

Question

我有一个简单的 Servlet 测试，它获取 jsp 文件。在此 servlet 操作中 request.setAttribute("key", "value") 但在调用 .forward() 之后，当我执行 request.getAttribute("key"时) 我得到null。为什么会发生这种情况？此行为决定模拟对象中的forward或原因？

这是Servlet的doPost:

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {

    final boolean success = addUserInDatabase(req);

    if (success) req.setAttribute("serverAnswer", EDIT_SUCCESS.get());//this write value
    else req.setAttribute("serverAnswer", ERR_UNIQUE_L_P.get());

    req.getRequestDispatcher(ANSWER.get())
            .forward(req, resp);
}

这是测试:

//mock http.
HttpServletRequest request = mock(HttpServletRequest.class);
HttpServletResponse response = mock(HttpServletResponse.class);


RequestDispatcher dispatcher = mock(RequestDispatcher.class);
when(request.getRequestDispatcher(ANSWER.get()))
                  .thenReturn(dispatcher);
servlet.doPost(request, response);
String result = (String) request.getAttribute("serverAnswer");//get value
Assert.assertThat(result, is(EDIT_SUCCESS.get()));// result == null

为什么我得到 Null？调用forward后是否可以获取setAttribute的值？如何测试这种行为？谢谢。

Answer 1

如果您在调用 req.getRequestDispatcher(ANSWER.get()) 之前添加 String result = (String)req.getAttribute("serverAnswer"); servlet 并检查 result 的值，它仍然为 null。

原因是您的请求对象不是真实的而是模拟的。你必须做这样的事情。

when(request.getAttribute(eq("serverAnswer"))).thenReturn(EDIT_SUCCESS.get());