Java. Regular Expression. How Parse?

Question

As input parameters I can have two types of String:

codeName=SomeCodeName&codeValue=SomeCodeValue

or

codeName=SomeCodeName

without codeValue.

codeName and codeValue are the keys.

How can I use regular expression to return the key's values? In this example it would return only SomeCodeName and SomeCodeValue.

would your SomeCodeName and SomeCodeValue may contain & or = ? — Prashant Bhate
– Prashant Bhate, Commented Nov 18, 2011 at 1:53

ewan.chalmers · Accepted Answer · 2011-11-17 13:50:04Z

5

I wouldn't bother with a regex for that. String.split with simple tokens ('&', '=') will do the job.

String[] args = inputParams.split("&");
for (String arg: args) {
    String[] split = arg.split("=");
    String name = split[0];
    String value = split[1];
}

edited Nov 17, 2011 at 13:50

answered Nov 17, 2011 at 13:43

ewan.chalmers

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4 Comments

John B Over a year ago

Check out Guava's Splitter.MapSplitter

ruakh Over a year ago

+1, but I think you should change arg.split("=") to arg.split("=", 2), since equals-signs are allowed in the values of query-string parameters.

Prashant Bhate Over a year ago

Note that Argument to String.split is a regex

Prashant Bhate Over a year ago

You might need to consider using Pattern as new pattern gets created in every iteration when arg.split("=") is used

John B · Accepted Answer · 2011-11-17 13:44:13Z

3

Consider using Guava's Splitter

String myinput = "...";
Map<String, String> mappedValues = 
           Splitter.on("&")
                   .withKeyValueSeparator("=")
                   .split(myinput);

answered Nov 17, 2011 at 13:44

John B

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Comments

AlexR · Accepted Answer · 2011-11-17 13:49:59Z

1

The simple way is to split the source string first and then to run 2 separate regular expressions against 2 parts.

Pattern pCodeName = Pattern.compile("codeName=(.*)");
Pattern pCodeValue = Pattern.compile("codeValue=(.*)");

String[] parts = str.split("\\&");
Matcher m = pCodeName.matcher(parts[0]);
String codeName = m.find() ? m.group(1) : null;

String codeValue = null;
if (parts.length > 1) {
    m = pCodeValue.matcher(parts[1]);
    codeValue = m.find() ? m.group(1) : null;
}

}

But if you want you can also say:

Pattern p = Pattern.compile("codeName=(\\w+)(\\&codeValue=(\\w+))?");
Matcher m = p.matcher(str);

String codeName = null;
String codeValue = null;

if (m.find()) {
    codeName = m.group(1);
    codeValue = m.groupCount() > 1 ? m.group(2) : null;
}

answered Nov 17, 2011 at 13:49

AlexR

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1 Comment

Prashant Bhate Over a year ago

IMO Second option is better as it would be a stricter match

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