This one is regarding request parameters in HTTP.
Being implemented as a HashMap, while retrieving the request parameters order wasn't guaranteed. Should have been obvious...But stupid me...was atleast able to go to a good discussion on the issue.
Here it is..
http://www.velocityreviews.com/forums/t297612-get-request-parameters-are-not-in-order.html
Transcript:
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 | Java - get request parameters are not in order |
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 06-07-2006, 12:53 AM | #1 |
| |  get request parameters are not in order Here's the code fragment to enumerate the request parameters list, but the order is not the same as in the query string. http://localhost:9999/projWeb/EStore...=1&b=2&c=3&d=4 ========================== Code ========================== for (Enumeration e = req.getParameterNames(); e.hasMoreElements()  { Object obj = e.nextElement(); String key = obj.toString(); String value = req.getParameter(key); out.println(key + "," + value + " "); } ========================== output =========================== b,2 a,1 sub,Logon d,4 c,3 any ideas? please advise. thanks!! John. John |
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| 06-07-2006, 01:28 PM | #2 |
| Posts: n/a | Re: get request parameters are not in order "John" <> wrote in message news: oups.com... > Here's the code fragment to enumerate the request parameters list, but > the order > is not the same as in the query string. > > http://localhost:9999/projWeb/EStore...=1&b=2&c=3&d=4 > The parameters are name-value pairs without any presumption of order. They are probably stored in a HashMap and the enumeration order depends on the hashing. I tried your code and the parameters came back in mixed order for JBoss 4.0.2. I searched through various javadocs and could not find anything that says the parameters should be retrievable in their original order. If your design relies on parameter order, something is going to have to change. Also, I don't think there's any guarantee that forms or other external sources will put the parameters in the textual order given, or that URL transforms (URL rewriting) will preserve the order. If you can't change the design, you can retrieve the original query string (getQueryString) and pick off the parameters yourself. There are some libraries to do this, although I don't know their names. Especially for POST requests, reading the body as a stream may interfere with the ability to read the names in order. Cheers, Matt Humphrey http://www.iviz.com/ |
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| 06-07-2006, 07:10 PM | #3 |
| Posts: n/a | Re: get request parameters are not in order John wrote: > Here's the code fragment to enumerate the request parameters list, but > the order > is not the same as in the query string. > > > > > any ideas? > > please advise. thanks!! > John. > The order is not guaranteed and can be affected by the the sending client and the receiving server. Why do you need to read the parameters in a specific order ? If you need to do that then you will have to do the ordering yourself, possibly by appending a number to the parameter name to give the order, i.e. http://localhost:9999/projWeb/EStore...am3=3¶m4=4 and then parsing this using the know prefix 'param'. |
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| 06-08-2006, 03:34 AM | #4 |
| Posts: n/a | Re: get request parameters are not in order On Wed, 07 Jun 2006 18:10:31 +0000, Andy Flowers wrote: > John wrote: >> Here's the code fragment to enumerate the request parameters list, but >> the order >> is not the same as in the query string. >> >> >> > >> >> any ideas? >> >> please advise. thanks!! >> John. >> > > The order is not guaranteed and can be affected by the the sending client and > the receiving server. No, only by the receiving server. According to the HTTP and URL/URI specifications the URLs http://www.example.com/someapp/servlet?a=foo&b=bar and http://www.example.com/someapp/servlet?b=bar&a=foo are distinct resources. The Java servlet specification allows the servlet container to reorder request parameters because in practice those are more often the same resource with two names than two distinct resources, and storing the parsed parameters in a hashmap is far faster than seeking through them in order. IMO parameters should probably be provided in a LinkedMap or LinkedHashMap stored in URL order, because there are some useful idioms based on multiple occurrences of the same parameter, but I haven't written a servlet container or plugin, so my opinion's worth the electrons to print it and not a bit more. Owen |
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| 06-08-2006, 05:47 PM | #5 |
| Posts: n/a | Re: get request parameters are not in order Owen Jacobson wrote: > IMO parameters should probably be provided in a LinkedMap or LinkedHashMap > stored in URL order, because there are some useful idioms based on > multiple occurrences of the same parameter, but I haven't written a > servlet container or plugin, so my opinion's worth the electrons to print > it and not a bit more. At least in Tomcat my experience has been that repeated parameters are always returned in order. I.e. using getParametervalues() with: http://www.example.com/someapp/servlet?a=X&a=Y&x=Z returns an array in the "natural" order. I agree this is a useful idiom and could be a solution for the OP, but I don't see it guaranteed anywhere in the spec. HT |
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