Over a million developers have joined DZone.

Java RegEx: How to Replace All With Pre-processing on a Captured Group

· Java Zone

Microservices! They are everywhere, or at least, the term is. When should you use a microservice architecture? What factors should be considered when making that decision? Do the benefits outweigh the costs? Why is everyone so excited about them, anyway?  Brought to you in partnership with IBM.

Need to replace all occurances of a pattern text and replace it with a captured group? Something like this in Java works nicely:

 String html = "<a href='myurl?id=1123'>myurl</a>\n" +
                "<a href='myurl2?id=2123'>myurl2</a>\n" +
                "<a href='myurl3?id=3123'>myurl3</a>";
        html = html.replaceAll("id=(\\w+)'?", "productId=$1'");

Here I swapped the query name from "id" to "productId" on all the links that matched my criteria. But what happen if I needed to pre-process the captured ID value before replacing it? Let's say now I want to do a lookup and transform the ID value to something else?

This extra requirement would lead us to dig deeper into Java RegEx package. Here is what I come up with:

import java.util.regex.*;
...
    public String replaceAndLookupIds(String html) {
        StringBuffer newHtml = new StringBuffer();
        Pattern p = Pattern.compile("id=(\\w+)'?");
        Matcher m = p.matcher(html);
        while (m.find()) {
            String id= m.group(1);
            String newId = lookup(id);
            String rep = "productId=" + newId + "'";
            m.appendReplacement(newHtml, rep);
        }
        m.appendTail(newHtml);
        return newHtml.toString();
    }




Discover how the Watson team is further developing SDKs in Java, Node.js, Python, iOS, and Android to access these services and make programming easy. Brought to you in partnership with IBM.

Topics:
java ,regex

Published at DZone with permission of Zemian Deng, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

The best of DZone straight to your inbox.

SEE AN EXAMPLE
Please provide a valid email address.

Thanks for subscribing!

Awesome! Check your inbox to verify your email so you can start receiving the latest in tech news and resources.
Subscribe

{{ parent.title || parent.header.title}}

{{ parent.tldr }}

{{ parent.urlSource.name }}