Package org.a2aproject.sdk.client.http

@NullMarked package org.a2aproject.sdk.client.http

HTTP client utilities for A2A protocol communication.

This package provides a pluggable HTTP client abstraction for making HTTP requests to A2A agents, including support for fetching agent cards, synchronous requests, and Server-Sent Events (SSE) streaming.

Core Components

• A2AHttpClient - Main HTTP client interface with builder pattern
• A2AHttpClientFactory - Factory for creating client instances via ServiceLoader
• A2ACardResolver - Utility for fetching agent cards from standard endpoints
• A2AHttpResponse - Response wrapper with status and body

Provider System

The module uses a ServiceLoader-based provider system allowing different HTTP client implementations to be plugged in:

• JdkA2AHttpClient - Default implementation using JDK 11+ HttpClient (priority 0)
• VertxA2AHttpClient - Vertx-based implementation when available (priority 100)

Usage Example

 // Fetch an agent card
 A2ACardResolver resolver = A2ACardResolver.builder().baseUrl("http://localhost:9999").build();
 AgentCard card = resolver.getAgentCard();

 // Make HTTP requests
 A2AHttpClient client = A2AHttpClientFactory.create();
 A2AHttpResponse response = client.createGet()
     .url("http://localhost:9999/api/endpoint")
     .addHeader("Authorization", "Bearer token")
     .get();

 // Server-Sent Events (SSE) streaming
 client.createPost()
     .url("http://localhost:9999/message:stream")
     .body(jsonBody)
     .postAsyncSSE(
         message -> System.out.println("Received: " + message),
         error -> System.err.println("Error: " + error),
         () -> System.out.println("Stream complete")
     );
 

Agent Card Resolution

Agent cards are fetched from the standard /.well-known/agent-card.json endpoint by default, with support for tenant-specific paths and custom authentication headers.

See Also:

• A2AHttpClient
• A2ACardResolver
• AgentCard

Related Packages

Package	Description
org.a2aproject.sdk.client
org.a2aproject.sdk.client.config

Class	Description
A2ACardResolver	Utility for fetching agent cards from A2A agents.
A2ACardResolver.Builder	Builder for creating A2ACardResolver instances with a fluent API.
A2AHttpClient	HTTP client interface for making HTTP requests to A2A agents.
A2AHttpClient.Builder<T extends A2AHttpClient.Builder<T>>	Base builder interface for HTTP requests.
A2AHttpClient.DeleteBuilder	Builder for HTTP DELETE requests.
A2AHttpClient.GetBuilder	Builder for HTTP GET requests.
A2AHttpClient.PostBuilder	Builder for HTTP POST requests.
A2AHttpClientFactory	Factory for creating A2AHttpClient instances using the ServiceLoader mechanism.
A2AHttpClientProvider	Service provider interface for creating A2AHttpClient instances.
A2AHttpHeaders	Read-only abstraction over HTTP response headers.
A2AHttpResponse	HTTP response wrapper containing status code and response body.
AndroidA2AHttpClient	Android-specific implementation of A2AHttpClient using HttpURLConnection.
AndroidA2AHttpClientProvider	Service provider for AndroidA2AHttpClient.
JdkA2AHttpClient	Default HTTP client implementation using JDK 11+ HttpClient.
JdkA2AHttpClientProvider	Service provider for JdkA2AHttpClient.
ServerSentEvent	Represents a parsed Server-Sent Event (SSE).
ServerSentEventParser	Streaming parser for Server-Sent Events (SSE).
VertxA2AHttpClient	Vert.x WebClient-based implementation of A2AHttpClient.
VertxA2AHttpClientProvider	Service provider for VertxA2AHttpClient.