java - 在java web应用程序中找不到对象的实例化(响应、请求、应用程序)

Question

我必须开发一个别人做过的java web应用程序。由于我是 java web 开发的新手，我扫描了一些代码并偶然发现了一些实例化对象，在这些对象中我找不到对其实例化位置的引用，即在 .jsp 页面中

    ...some includes
    UserFactory uf=null;

    if (application.getAttribute("userFactory") == null){
    ...
    strUser=request.getParameter("user");
    pw=request.getParameter("pw");
    ...

(通知应用程序、请求、响应)

现在我意识到它可能已在某些包含中声明，并且我确实浏览了所有内容但找不到声明(尽管我确实监督了它)。现在的问题是:这些对象是否以某种方式由 tomcat 全局实例化(如果是，我在哪里可以找到)，如果不是这种情况，如何在一个相当大的项目中找到它们(顺便说一句，我正在使用 Eclipse JUNO)(即像Eclipse 的功能来查找实例化)，最好不要手动查看每个单独的包含。

Answer 1

在 JSP 中，这些变量称为“隐式对象”。在此处查找 JSP 中可用的所有隐式对象:http://docs.oracle.com/javaee/5/tutorial/doc/bnahq.html#bnaij :

Implicit Objects

The JSP expression language defines a set of implicit objects:

• pageContext: The context for the JSP page. Provides access to various objects including:
  • servletContext: The context for the JSP page’s servlet and any web components contained in the same application. See Accessing the Web Context.
  • session: The session object for the client. See Maintaining Client State.
  • request: The request triggering the execution of the JSP page. See Getting Information from Requests.
  • response: The response returned by the JSP page. See Constructing Responses.

In addition, several implicit objects are available that allow easy access to the following objects:

• param: Maps a request parameter name to a single value
• paramValues: Maps a request parameter name to an array of values
• header: Maps a request header name to a single value
• headerValues: Maps a request header name to an array of values
• cookie: Maps a cookie name to a single cookie
• initParam: Maps a context initialization parameter name to a single value

Finally, there are objects that allow access to the various scoped variables described in Using Scope Objects.

• pageScope: Maps page-scoped variable names to their values
• requestScope: Maps request-scoped variable names to their values
• sessionScope: Maps session-scoped variable names to their values
• applicationScope: Maps application-scoped variable names to their values