Doh4j: DNS over HTTPS (DoH) for Java

The Doh4j library is a powerful yet simple DNS Over HTTPS (DoH) client implementation for Java 11+, packaged neatly into a streamlined and powerful API. The Doh4j client uses Google, Cloudflare, and Quad9 DoH resolvers by default, but it also supports custom RFC 8484-compliant resolvers.

Features

• Perform DNS lookup over HTTPS: The Doh4jClient class provides a client for performing DNS over HTTPS (DoH) lookups using a list of resolvers.
• Configurable Resolvers: By default, Google, Cloudflare, and Quad9 are used as resolvers. However, custom resolvers can be supplied.
• Fallback Mechanism: If a DNS lookup fails with the first resolver, the client tries the next one until a resolver responds or no resolvers are left.
• Synchronous and Asynchronous Operations: Supports both blocking synchronous and non-blocking asynchronous operations.
• Utilizes Native Java HttpClient: Leverages the native HttpClient available from Java 11 and onwards. This makes the library efficient and reliable, as it uses the well-maintained and high-performing HTTP API provided by Java itself

Installation

The Doh4j library can be easily installed using JitPack, see Gradle and Maven examples below.

Gradle

Add the following to your build.gradle file:

repositories {
    mavenCentral()
    maven { url "https://jitpack.io" }
}

dependencies {
    implementation 'com.github.thewaterfall:doh4j:1.0.0'
}

Maven

Add the following to your pom.xml file:

<repositories>
    <repository>
        <id>jitpack.io</id>
        <url>https://jitpack.io</url>
    </repository>
</repositories>

<dependencies>
    <dependency>
        <groupId>com.github.thewaterfall</groupId>
        <artifactId>doh4j</artifactId>
        <version>1.0.0</version>
    </dependency>
</dependencies>

Usage

The Doh4j client provides a simple and straightforward interface, making the process of DNS lookups easy. Below are examples of how you can carry out DNS lookups using predefined and custom resolvers.

Synchronous lookup with predefined resolvers

Doh4j.newClient()
    .lookup("example.com", Type.A);

Synchronous lookup with custom resolvers

Doh4j.builder()
    .resolver("https://resolve.com/resolve")
    .build()
    .lookup("example.com", Type.A);

Synchronous lookup with custom HTTP client

You can also use a custom java.net HTTP client while performing DNS lookups. This feature can be useful in situations where there is a need for custom configuration for HTTP requests like timeouts, handlers, proxies, and more. Here's how you can perform a DNS lookup with a custom resolver and a custom HTTP client:

HttpClient client = HttpClient.newHttpClient();

Doh4j.builder()
    .client(client)
    .resolver("https://resolve.com/resolve")
    .build()
    .lookup("example.com", Type.A);

Asynchronous lookup

Do4J.newClient()
    .lookupAsync("example.com", Type.A)
    .thenAccept(result -> System.out.println(result.getStatus())); // Callback, called if no exception is thrown
    
Do4J.builder()
    .resolver("https://resolver1.com/resolve")
    .resolver("https://resolver2.com/resolve")
    .build()
    .lookupAsync("example.com", Type.A)
    .thenAccept(result -> System.out.println(result.getStatus())); // Callback, called if no exception is thrown
    
// Exception handling    
Do4J.newClient()
    .lookupAsync("example.com", Type.A)
    .whenComplete((result, e) -> {
        if (e != null) {
         // Handle exception
        }
    });