Java regular expression to extract key value pairs

Question

How can I extract the value of the bookid from this string using Java?

href="http://www.books.com/?bookname=cooking&bookid=12345678&bookprice=123.45">cooking book

Tried Pshemo's solution.

Amir Ghahrai
– Amir Ghahrai

2012-07-29 12:23:24 +00:00
Commented Jul 29, 2012 at 12:23 — Amir Ghahrai
– Amir Ghahrai, Commented Jul 29, 2012 at 12:23

Pshemo · Accepted Answer · 2012-07-28 19:24:50Z

4

Normally you should use some parser but if your String is really this short then maybe regular expression can be option like

String s="href=\"http://www.books.com/?bookname=cooking&bookid=12345678&bookprice=123.45\">cooking book";
Pattern p= Pattern.compile("(?<=bookid=)\\d+");
Matcher m=p.matcher(s);
if (m.find())
    System.out.println(m.group());

output:

12345678

answered Jul 28, 2012 at 19:24

Pshemo

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2 Comments

Amir Ghahrai Over a year ago

Thanks Pshemo, Actually the String is the full HTML source of a page where this is just a part where the bookid is present, so I guess I can use your solution for that as well?

Pshemo Over a year ago

Actually regular expressions are considered as bad practice for parsing HTML. For example my solution will find number that is preceded by "bookid=" so if your HTML will contain that combination before your href (for example in some comment or other content generated by user) you can have bad results. For parsing entire HTML code use special tools designed for that. Maybe this will help you a little.

afrin216 · Accepted Answer · 2012-07-28 19:32:47Z

1

A very simple answer would be

String[] queryParams =  url.split("\\?")[1].split("&");

This would give you all the parameters in a=b form in each of the element. You can then just split the needed param.

But ideally you should extract the value by param name

answered Jul 28, 2012 at 19:32

afrin216

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Comments

ricardoespsanto · Accepted Answer · 2012-07-28 19:26:50Z

0

Pshemo you beat me to it but you can also use this: "(id\=[0-9]*)"

and try RegexPlanet to try out your regex and retrieve the escapped string in java format

answered Jul 28, 2012 at 19:26

ricardoespsanto

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A Null Pointer · Accepted Answer · 2012-07-28 19:29:28Z

0

You can use the following code snippet:

            String str = "href=\"http://www.books.com/?bookname=cooking&bookid=12345678&bookprice=123.45\">cooking book";
            String[] strArray = str.split("&");
            String bookId = "";
            for(int i=0;i<strArray.length;i++)
            {
               if(strArray[i].startsWith("bookid"))
               {
                  bookId = strArray[i].split("=")[1];
               }
            }
            System.out.println("Book ID = "+bookId);

answered Jul 28, 2012 at 19:29

A Null Pointer

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1 Comment

nkr Over a year ago

Wouldn't it be better to use strArray[i].split("=", 1)[1] instead of strArray[i].split("=")[1]?

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