joni

Introduction to the Joni Project

Joni is a remarkable Java port of the Oniguruma regular expression (regexp) library. It offers Java developers a powerful tool for handling complex string pattern-matching tasks. Joni is particularly useful for those needing advanced regex capabilities within Java projects, drawing upon the robust foundation provided by the Oniguruma library.

Key Features of Joni

1. Java Integration: As a Java port, Joni seamlessly integrates with Java applications, providing native support for regex operations using Java syntax.

2. Advanced Pattern Matching: Joni allows developers to utilize sophisticated pattern-matching techniques, suitable for a wide range of applications, from simple string checks to intricate parsing tasks.

3. Oniguruma Foundation: Oniguruma is renowned for its regex capabilities, and Joni brings this power into the Java ecosystem, ensuring that developers can leverage these advanced features.

How to Use Joni

Importing Joni

To get started with Joni, developers need to import the necessary classes from the library. This typically includes classes like Regex, Matcher, and specific encoding classes such as UTF8Encoding.

import org.jcodings.specific.UTF8Encoding;
import org.joni.Matcher;
import org.joni.Option;
import org.joni.Regex;

Basic Matching

A simple example of using Joni involves creating a regex pattern and matching it against a string. In this case, the pattern "a*" is matched against the string "aaa".

byte[] pattern = "a*".getBytes();
byte[] str = "aaa".getBytes();

Regex regex = new Regex(pattern, 0, pattern.length, Option.NONE, UTF8Encoding.INSTANCE);
Matcher matcher = regex.matcher(str);
int result = matcher.search(0, str.length, Option.DEFAULT);

Capturing Groups

Joni also supports capturing groups, which allow parts of the matching strings to be extracted for further processing.

byte[] pattern = "(a*)".getBytes();
byte[] str = "aaa".getBytes();

Regex regex = new Regex(pattern, 0, pattern.length, Option.NONE, UTF8Encoding.INSTANCE);
Matcher matcher = regex.matcher(str);
int result = matcher.search(0, str.length, Option.DEFAULT);
if (result != -1) {
    Region region = matcher.getEagerRegion();
}

Named Captures

For more clarity in code, Joni supports named captures, making it easier to reference specific parts of the matching string using descriptive names.

byte[] pattern = "(?<name>a*)".getBytes();
byte[] str = "aaa".getBytes();

Regex regex = new Regex(pattern, 0, pattern.length, Option.NONE, UTF8Encoding.INSTANCE);
Matcher matcher = regex.matcher(str);
int result = matcher.search(0, str.length, Option.DEFAULT);
if (result != -1) {
    Region region = matcher.getEagerRegion();
    for (Iterator<NameEntry> entry = regex.namedBackrefIterator(); entry.hasNext();) {
        NameEntry e = entry.next();
        int number = e.getBackRefs()[0];
    }
}

Licensing

Joni is freely available under the MIT License, which allows for broad usage, modifications, and distribution, making it accessible to a wide range of developers and projects.

In summary, Joni is a versatile and powerful tool for Java developers needing advanced regex capabilities. Its integration with Java makes it a crucial component for complex string processing tasks. Whether you are dealing with simple matches or sophisticated parsing, Joni has the features and reliability required to help you manage your regex needs effectively.