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


当前回答

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。

其他回答

getParameter -用于从客户端的HTML页面获取所需的信息

getAttribute——用于获取先前在另一个或相同的JSP或Servlet页面中设置的参数。

基本上,如果您正在从一个jsp/servlet转发或只是从一个jsp/servlet转到另一个jsp/servlet,那么除非您选择将它们放在一个对象中并使用set-属性存储在一个会话变量中,否则就无法获得所需的信息。

使用getAttribute,您可以检索Session变量。

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.

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。

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.

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")