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Difference between getAttribute() and getParameter()

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情话喂你
情话喂你 2020-11-22 08:44

What is the difference between getAttribute() and getParameter() methods within HttpServletRequest class?

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  • Happy的楠姐
    2020-11-22 09:03

    • getParameter() returns http request parameters. Those passed from the client to the server. For example http://example.com/servlet?parameter=1. Can only return String

    • getAttribute() is for server-side usage only - you fill the request with attributes that you can use within the same request. For example - you set an attribute in a servlet, and read it from a JSP. Can be used for any object, not just string.

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  • 一生所求
    2020-11-22 09:06

    -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") will get the value from the posted form of the input box named "testParam" which is "Client param". It will then print it out, so you should see "Client Param" on the screen. So request.getParameter() will retrieve a value that the client has submitted. You will get the value on the server side.

    -getAttribute() : request.getAttribute(), this is all done server side. YOU add the attribute to the request and YOU submit the request to another resource, the client does not know about this. So all the code handling this would typically be in servlets.getAttribute always return object.

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  • 不要未来只要你来
    2020-11-22 09:14

    It is crucial to know that attributes are not parameters.

    The return type for attributes is an Object, whereas the return type for a parameter is a String. When calling the getAttribute(String name) method, bear in mind that the attributes must be cast.

    Additionally, there is no servlet specific attributes, and there are no session parameters.

    This post is written with the purpose to connect on @Bozho's response, as additional information that can be useful for other people.

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  • 慢半拍i
    2020-11-22 09:15

    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.

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