Regex Class — spring-boot Architecture

Source Code

buildpack/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/type/Regex.java lines 37–121

final class Regex implements CharSequence {

	static final Pattern DOMAIN;
	static {
		Regex component = Regex.oneOf("[a-zA-Z0-9]", "[a-zA-Z0-9][a-zA-Z0-9-]*[a-zA-Z0-9]");
		Regex dotComponent = Regex.group("[.]", component);
		Regex colonPort = Regex.of("[:][0-9]+");
		Regex dottedDomain = Regex.group(component, dotComponent.oneOrMoreTimes());
		Regex dottedDomainAndPort = Regex.group(component, dotComponent.oneOrMoreTimes(), colonPort);
		Regex nameAndPort = Regex.group(component, colonPort);
		DOMAIN = Regex.oneOf(dottedDomain, nameAndPort, dottedDomainAndPort, "localhost").compile();
	}

	private static final Regex PATH_COMPONENT;
	static {
		Regex segment = Regex.of("[a-z0-9]+");
		Regex separator = Regex.group("[._-]{1,2}");
		Regex separatedSegment = Regex.group(separator, segment).oneOrMoreTimes();
		PATH_COMPONENT = Regex.of(segment, Regex.group(separatedSegment).zeroOrOnce());
	}

	static final Pattern PATH;
	static {
		Regex component = PATH_COMPONENT;
		Regex slashComponent = Regex.group("[/]", component);
		Regex slashComponents = Regex.group(slashComponent.oneOrMoreTimes());
		PATH = Regex.of(component, slashComponents.zeroOrOnce()).compile();
	}

	static final Pattern TAG = Regex.of("^[\\w][\\w.-]{0,127}").compile();

	static final Pattern DIGEST = Regex.of("^[A-Za-z][A-Za-z0-9]*(?:[-_+.][A-Za-z][A-Za-z0-9]*)*[:][[A-Fa-f0-9]]{32,}")
		.compile();

	private final String value;

	private Regex(CharSequence value) {
		this.value = value.toString();
	}

	private Regex oneOrMoreTimes() {
		return new Regex(this.value + "+");
	}

	private Regex zeroOrOnce() {
		return new Regex(this.value + "?");
	}

	Pattern compile() {
		return Pattern.compile("^" + this.value + "$");
	}

	@Override
	public int length() {
		return this.value.length();
	}

	@Override
	public char charAt(int index) {
		return this.value.charAt(index);
	}

	@Override
	public CharSequence subSequence(int start, int end) {
		return this.value.subSequence(start, end);
	}

	@Override
	public String toString() {
		return this.value;
	}

	private static Regex of(CharSequence... expressions) {
		return new Regex(String.join("", expressions));
	}

	private static Regex oneOf(CharSequence... expressions) {
		return new Regex("(?:" + String.join("|", expressions) + ")");
	}

	private static Regex group(CharSequence... expressions) {
		return new Regex("(?:" + String.join("", expressions) + ")");
	}

}