ServletRequest中 getParameter 与 getAttribute的区别

getParameter 与 getAttribute的区别

request.getAttribute():是request时设置的变量的值,用request.setAttribute("name","您自己的值");来设置值,   request.getParameter():提取发送过来的参数如:本网页http://community.csdn.net/Expert/topic/4633/4633804.xml?temp=.3488123  request.getParameter("temp")==".3488123"

request.getParameter
是用来接受来自get方法或post方法的参数


ok
只能接受java.lang.String
也就是说String hotel_id = request.getParameter(“hotel_id”);
request.getAttribute
是用来接受来自servlet的变量或Action(其实Action就是特殊的Servlet)
在Action中，request.setAttribute(“ret”,ret);
只能接受java.lang.Object
也就是说List ret = (List)request.getAttribute(“ret”);
如果你只用JSP，根本用不到request.getAttribute()

request.getAttribute()和request.getParameter()的区别是request.getAttribute()获得的是对象类型，

而request.getParameter()获得的是字符串类型
一般的网页应用，如同 chenshaizi(陈绍彬) 所说，基本上是基于Post方式的传递，用getParameter

取值。对于自己控制的，可以通过request.setAttribute和getAttribute 实现值得传递。
对于应用Structs框架的，getAttribute用的多一点，其他的基本上用getParameter

我的理解：
session.getAttribute();获得session
request.getParameter();获得parameter

1.getParameter可以获得客户端传送给服务器端的参数值。
getAttribute可以得到由setAttribute设置的参数值，就相当于是使用getAttribute得到一个自己定义

的参数，而不是从客户端得到的参数。
2.getParameter只能传递string类型的变量，getAttribute能传递vector。

getParameter(),获取表单的值 getAttribute()获得session的值

getParameterNames() 获得表单或则url中的参数的数组
getattributeNames()：返回request对象所有属性的名字，结果集是一个Enumeration（枚举）类的实例

根据楼上，是不是 getParameter()得到的值如果下次不提交或保存起来的话，下次重定向后就没啦？
：理解对了
getAttribute()所要得到的属性值因为存在session中，所以重定向后仍可以取出？
getAttribute()在request和session中都有，只是作用域不同，在取之前肯定是要在某个地方存一下，这种

东东可以存取对象

http://community.csdn.net/Expert/topic/4763/4763471.xml?temp=.1793177
看见后面的?temp=.1793177没有，？号后面的这个东西用request.getAttribute(“temp”)就能得到字符

串”.1793177”，
而getAttribute()之前，你必须在页面或者逻辑中用serAttribute()设置了才能用，已经很清楚了，我不再

说了哈

Parameter是html裡傳來的像 checkbox textfield password radio …的value
getAttribute是取得jsp中用setAttribute設定的attribute

還有….
parameter得到的是string
attribute得到的是object

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• 个人经验：当用forward标签及request.getRequestDispatcher.forward()时，可以用setAttribute和getAttribute,表单提交和超链接提交都只能读取name属性相关的value，用getParameter();reponse.sendRediretion(“MyJsp.jsp?username=luocong”)，这样也可以用getParameter(“username”)来提取.

• Get 方法通过 URL 请求来传递用户的数据，将表单内各字段名称与其内容，以成对的字符串连接，置于 action 属性所指程序的 url 后，如[url]http://www.mdm.com/test.asp?name=asd&password=sad[/url]，数据都会直接显示在 url 上，就像用户点击一个链接一样；Post 方法通过 HTTP post 机制，将表单内各字段名称与其内容放置在 HTML 表头(header)内一起传送给服务器端交由 action 属性能所指的程序处理，该程序会通过标准输入(stdin)方式，将表单的数据读出并加以处理

• request.setAttribute无法用表单提交的原因，设定值的request，与表单请求的request不是一个request，不是同一时间生成的。

来自 : http://blog.sina.com.cn/s/blog_600046120100tnaj.html

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参考:

package javax.servlet;/** * Defines an object to provide client request information to a servlet.  The * servlet container creates a <code>ServletRequest</code> object and passes * it as an argument to the servlet's <code>service</code> method. * * <p>A <code>ServletRequest</code> object provides data including * parameter name and values, attributes, and an input stream. * Interfaces that extend <code>ServletRequest</code> can provide * additional protocol-specific data (for example, HTTP data is * provided by {@link javax.servlet.http.HttpServletRequest}. *  * @author Various * * @see javax.servlet.http.HttpServletRequest * */public interface ServletRequest {    /**     * Returns the value of the named attribute as an <code>Object</code>,     * or <code>null</code> if no attribute of the given name exists.      *     * <p> Attributes can be set two ways.  The servlet container may set     * attributes to make available custom information about a request.     * For example, for requests made using HTTPS, the attribute     * <code>javax.servlet.request.X509Certificate</code> can be used to     * retrieve information on the certificate of the client.  Attributes     * can also be set programatically using      * {@link ServletRequest#setAttribute}.  This allows information to be     * embedded into a request before a {@link RequestDispatcher} call.     *     * <p>Attribute names should follow the same conventions as package     * names. This specification reserves names matching <code>java.*</code>,     * <code>javax.*</code>, and <code>sun.*</code>.      *     * @param name a <code>String</code> specifying the name of the attribute     *     * @return an <code>Object</code> containing the value of the attribute,     * or <code>null</code> if the attribute does not exist     */    public Object getAttribute(String name);    /**     * Stores an attribute in this request.     * Attributes are reset between requests.  This method is most     * often used in conjunction with {@link RequestDispatcher}.     *     * <p>Attribute names should follow the same conventions as     * package names. Names beginning with <code>java.*</code>,     * <code>javax.*</code>, and <code>com.sun.*</code>, are     * reserved for use by Sun Microsystems.     *<br> If the object passed in is null, the effect is the same as     * calling {@link #removeAttribute}.     * <br> It is warned that when the request is dispatched from the     * servlet resides in a different web application by     * <code>RequestDispatcher</code>, the object set by this method     * may not be correctly retrieved in the caller servlet.     *     * @param name a <code>String</code> specifying      * the name of the attribute     *     * @param o the <code>Object</code> to be stored     *     */    public void setAttribute(String name, Object o);    /**     * Returns the value of a request parameter as a <code>String</code>,     * or <code>null</code> if the parameter does not exist. Request parameters     * are extra information sent with the request.  For HTTP servlets,     * parameters are contained in the query string or posted form data.     *     * <p>You should only use this method when you are sure the     * parameter has only one value. If the parameter might have     * more than one value, use {@link #getParameterValues}.     *     * <p>If you use this method with a multivalued     * parameter, the value returned is equal to the first value     * in the array returned by <code>getParameterValues</code>.     *     * <p>If the parameter data was sent in the request body, such as occurs     * with an HTTP POST request, then reading the body directly via {@link     * #getInputStream} or {@link #getReader} can interfere     * with the execution of this method.     *     * @param name a <code>String</code> specifying the name of the parameter     *     * @return a <code>String</code> representing the single value of     * the parameter     *     * @see #getParameterValues     */    public String getParameter(String name);}