Decoding URI query string in Java

Question

I need to decode a URI that contains a query string; expected input/output behavior is something like the following:

abstract class URIParser {            /** example input:        * something?alias=pos&FirstName=Foo+A%26B%3DC&LastName=Bar */     URIParser(String input) { ... }     /** should return "something" for the example input */     public String getPath();      /** should return a map        * {alias: "pos", FirstName: "Foo+A&B=C", LastName: "Bar"} */     public Map<String,String> getQuery(); } 

I've tried using java.net.URI, but it seems to decode the query string so in the above example I'm left with "alias=pos&FirstName=Foo+A&B=C&LastName=Bar" so there is ambiguity whether a "&" is a query separator or is a character in a query component.

Edit: I just tried URI.getRawQuery() and it doesn't do the encoding, so I can split the query string with a &, but then what do I do? Javascript has decodeURIComponent, I can't seem to find the corresponding method in Java.

Any suggestions? I would prefer not to use any new libraries.

Answer 1

Use

URLDecoder.decode(proxyRequestParam.replace("+", "%2B"), "UTF-8")           .replace("%2B", "+") 

to simulate decodeURIComponent. Java's URLDecoder decodes the plus sign to a space, which is not what you want, therefore you need the replace statements.

Warning: the .replace("%2B", "+") at the end will corrupt your data if the original (pre-x-www-form-urlencoded) contained that string, as @xehpuk pointed out.