getAttribute()和getParameter()的区别

HttpServletRequest类中的getAttribute()和getParameter()方法有什么区别?

当前回答

通常，参数是一个字符串值，最常见的是从客户端发送到服务器(例如表单post)并从servlet请求检索的值。令人沮丧的例外是ServletContext初始参数，它们是在web.xml中配置的字符串参数，存在于服务器上。

属性是存在于指定范围内的服务器变量，即:

应用程序，在整个应用程序的生命周期内可用会话，在会话的生命周期内可用请求，仅在请求的生命期内可用页面(仅限JSP)，仅对当前JSP页面可用

2011-03-09 09:39:37

其他回答

另一种应该使用.getParameter()的情况是在jsp中转发参数:

<jsp:forward page="destination.jsp">
    <jsp:param name="userName" value="hamid"/>
</jsp:forward>

在destination.jsp中，你可以像这样访问userName:

request.getParameter("userName")

2017-08-08 08:03:46

重要的是要知道属性不是参数。

属性的返回类型是Object，而参数的返回类型是String。在调用getAttribute(字符串名称)方法时，请记住必须强制转换属性。

此外，没有servlet特定的属性，也没有会话参数。

这篇文章的目的是联系@Bozho的回复，作为对其他人有用的额外信息。

2012-11-28 19:26:27

The difference between getAttribute and getParameter is that getParameter will return the value of a parameter that was submitted by an HTML form or that was included in a query string. getAttribute returns an object that you have set in the request, the only way you can use this is in conjunction with a RequestDispatcher. You use a RequestDispatcher to forward a request to another resource (JSP / Servlet). So before you forward the request you can set an attribute which will be available to the next resource.

2013-02-27 18:27:33

getparameter ():

<html>
<body>
<form name="testForm" method="post" action="testJSP.jsp">
<input type="text" name="testParam" value="ClientParam">
<input type="submit">
</form>
</body>
</html>

    <html>
    <body>
    <%
    String sValue = request.getParameter("testParam");
    %>
    <%= sValue %>
    </body>
    </html>

request.getParameter("testParam")将从名为"testParam"的输入框的发布形式中获取值，即"Client param"。然后它会把它打印出来，所以你应该在屏幕上看到“Client Param”。因此request.getParameter()将检索客户端已提交的值。您将在服务器端获得该值。

getattribute (): request.getAttribute()，这都是服务器端完成的。你将属性添加到请求中，并将请求提交给另一个资源，客户端不知道这一点。所以所有处理这个问题的代码通常都在servlet中。getAttribute总是返回对象。

2014-08-01 06:51:20

从http://www.coderanch.com/t/361868/Servlets/java/request-getParameter-request-getAttribute

A "parameter" is a name/value pair sent from the client to the server - typically, from an HTML form. Parameters can only have String values. Sometimes (e.g. using a GET request) you will see these encoded directly into the URL (after the ?, each in the form name=value, and each pair separated by an &). Other times, they are included in the body of the request, when using methods such as POST. An "attribute" is a server-local storage mechanism - nothing stored in scoped attribues is ever transmitted outside the server unless you explicitly make that happen. Attributes have String names, but store Object values. Note that attributes are specific to Java (they store Java Objects), while parameters are platform-independent (they are only formatted strings composed of generic bytes). There are four scopes of attributes in total: "page" (for JSPs and tag files only), "request" (limited to the current client's request, destroyed after request is completed), "session" (stored in the client's session, invalidated after the session is terminated), "application" (exist for all components to access during the entire deployed lifetime of your application). The bottom line is: use parameters when obtaining data from the client, use scoped attributes when storing objects on the server for use internally by your application only.

2016-03-01 05:49:45

getAttribute()和getParameter()的区别

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