rdap-java

A lightweight, high-performance RDAP client library for Java. A modern, structured alternative to legacy WHOIS socket queries to check domain registration status and availability.

Supports all TLDs via IANA bootstrap data, automatic RDAP server discovery, and built-in fallbacks.

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Features

• Domain Availability Check: Instantly determine if a domain is registered or available.
• Universal TLD Support: Covers ~1200+ TLDs via dynamic IANA bootstrap + curated fallbacks for unlisted registries.
• Automatic Server Discovery: Resolves official RDAP base URLs per TLD automatically with thread-safe caching.
• Server Failover: Built-in fallback mechanism across multiple RDAP servers per TLD.
• IDN & Punycode Ready: Native handling for internationalized domain names (e.g., umlauts, non-Latin scripts).
• Nameserver Extraction: Easily extract authoritative nameservers from RDAP responses.
• Custom Endpoints: Register custom RDAP server endpoints at runtime.
• Zero Heavyweight Frameworks: Uses pure Java 11+ HttpClient and org.json (~5 KB library overhead).

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Requirements

• Java 11 or higher

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Installation

Gradle (Kotlin DSL)

repositories {
    mavenCentral()
}

dependencies {
    implementation("com.slxca:rdap-java:1.0.0")
}

Gradle (Groovy DSL)

repositories {
    mavenCentral()
}

dependencies {
    implementation 'com.slxca:rdap-java:1.0.0'
}

Maven

<dependency>
    <groupId>com.slxca</groupId>
    <artifactId>rdap-java</artifactId>
    <version>1.0.0</version>
</dependency>

Manual Download

Grab the latest pre-built .jar from the Releases page.

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Usage

Check Domain Availability

import com.slxca.rdap.RDAPClient;
import com.slxca.rdap.RDAPResult;
import com.slxca.rdap.RDAPException;

public class Main {
    public static void main(String[] args) {
        RDAPClient client = new RDAPClient();

        try {
            RDAPResult result = client.checkDomain("example.com");

            if (result.isRegistered()) {
                System.out.println(result.getDomain() + " is already taken.");
                System.out.println("RDAP Server: " + result.getServerUrl());
            } else {
                System.out.println(result.getDomain() + " is available for registration!");
            }
        } catch (RDAPException e) {
            System.err.println("RDAP lookup failed: " + e.getMessage());
        }
    }
}

Extract Nameservers

RDAPResult result = client.checkDomain("google.com");

if (result.isRegistered()) {
    System.out.println("Nameservers:");
    for (String ns : result.getNameservers()) {
        System.out.println(" - " + ns);
    }
}

Custom RDAP Server Registration

If a registry is not part of the IANA bootstrap registry or uses a dedicated endpoint, register it manually:

client.registerServer("io", "[https://rdap.afilias.net/rdap/](https://rdap.afilias.net/rdap/)");
RDAPResult result = client.checkDomain("example.io");

Custom HttpClient Configuration

Pass your own configured HttpClient (e.g., custom timeouts, proxy settings):

import java.net.http.HttpClient;
import java.time.Duration;

HttpClient customHttp = HttpClient.newBuilder()
    .connectTimeout(Duration.ofSeconds(5))
    .build();

RDAPClient client = new RDAPClient(customHttp);

Command Line Interface (CLI)

Run the packaged JAR directly from your terminal:

java -jar rdap-java.jar google.com

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API Reference

RDAPClient

Method	Returns	Description
RDAPClient()		Creates an instance using the default HttpClient.
RDAPClient(HttpClient client)		Creates an instance using a custom HttpClient.
checkDomain(String domain)	RDAPResult	Performs an RDAP lookup for the given domain.
registerServer(String tld, String serverUrl)	void	Registers or overrides an RDAP server URL for a specific TLD.

RDAPResult

Method	Returns	Description
getDomain()	String	Returns the queried domain.
isRegistered()	boolean	Returns true if HTTP 200 (registered), false if HTTP 404 (available).
getServerUrl()	String	Returns the RDAP endpoint URL used for the query.
getNameservers()	List<String>	Returns authoritative nameservers parsed from the RDAP response.

Exceptions

• RDAPException – Thrown on network issues, HTTP errors other than 404, or if no RDAP endpoint was discoverable.
• IllegalArgumentException – Thrown when passing null, empty, or malformed domain strings.

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How It Works

1. TLD Extraction: Normalizes the input and isolates the top-level domain (e.g., sub.example.co.uk or münchen.de via IDN Punycode).
2. Endpoint Resolution: Checks custom registered servers first, then queries cached IANA bootstrap data, and falls back to curated registry lists.
3. HTTP Query: Sends an authenticated HTTP GET request with header Accept: application/rdap+json.
4. Status Evaluation: Treats HTTP 200 as registered and parses details; treats HTTP 404 as available.

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Supported TLDs

Registry Source	Count	Examples
IANA Bootstrap	~1200+	.com, .org, .net, .uk, .fr
Built-in Fallbacks	Curated	.de, .ch, .us, .no, .nl

Missing a TLD? Feel free to open an issue or submit a Pull Request.

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License

This project is licensed under the MIT License