request.getParameter ()

我们使用request. getparameter()来提取请求参数(即通过发布html表单发送的数据)。request.getParameter()总是返回String值，数据来自客户端。

request.getAttribute ()

We use request.getAttribute() to get an object added to the request scope on the server side i.e. using request.setAttribute(). You can add any type of object you like here, Strings, Custom objects, in fact any object. You add the attribute to the request and forward the request to another resource, the client does not know about this. So all the code handling this would typically be in JSP/servlets. You can use request.setAttribute() to add extra-information and forward/redirect the current request to another resource.

例如，考虑first.jsp，

//First Page : first.jsp
<%@ page import="java.util.*" import="java.io.*"%>
<% request.setAttribute("PAGE", "first.jsp");%>
<jsp:forward page="/second.jsp"/>

和second.jsp:

<%@ page import="java.util.*" import="java.io.*"%>
From Which Page : <%=request.getAttribute("PAGE")%><br>
Data From Client : <%=request.getParameter("CLIENT")%>

在浏览器中运行first.jsp?CLIENT=您，浏览器上的输出为

From Which Page : *first.jsp*
Data From Client : you

getAttribute()和getParameter()之间的基本区别是，第一个方法提取一个(序列化的)Java对象，而另一个方法提供一个String值。对于这两种情况，都会给出一个名称，以便可以查找和提取它的值(无论是字符串还是java bean)。

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")

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

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.

getAttribute()和getParameter()之间的基本区别是返回类型。

java.lang.Object getAttribute(java.lang.String name)
java.lang.String getParameter(java.lang.String name)

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。