feat: add support for JSON+HTTP/REST

* Create JSON+HTTP/REST Client.
* Integrate PR from @ronantakizawa using regexp for server routing.
* Update server code to use proper JSON (de)serialization with Proto.
* Create Reference Implementation
* Removing the listTasks since it has been removed from the specs
* Removing io.grpc:* as direct dependencies for a2a-java-sdk-spec-grpc.

Signed-off-by: Emmanuel Hugonnet <[email protected]>

Author: fjuma

.gitignore

@@ -44,4 +44,3 @@ nb-configuration.xml
 # TLS Certificates
 .certs/
 nbproject/
-

README.md

@@ -81,7 +81,18 @@ To use the reference implementation with the gRPC protocol, add the following de
 Note that you can add more than one of the above dependencies to your project depending on the transports
 you'd like to support.
 
-Support for the HTTP+JSON/REST transport will be coming soon.
+To use the reference implementation with the HTTP+JSON/REST protocol, add the following dependency to your project:
+
+> *⚠️ The `io.github.a2asdk` `groupId` below is temporary and will likely change for future releases.*
+
+```xml
+<dependency>
+    <groupId>io.github.a2asdk</groupId>
+    <artifactId>a2a-java-sdk-reference-rest</artifactId>
+    <!-- Use a released version from https://github.com/a2aproject/a2a-java/releases --> 
+    <version>${io.a2a.sdk.version}</version>
+</dependency>
+```
 
 ### 2. Add a class that creates an A2A Agent Card
 
@@ -117,7 +128,7 @@ public class WeatherAgentCardProducer {
                         .tags(Collections.singletonList("weather"))
                         .examples(List.of("weather in LA, CA"))
                         .build()))
-                .protocolVersion("0.2.5")
+                .protocolVersion("0.3.0")
                 .build();
     }
 }
@@ -247,7 +258,7 @@ By default, the sdk-client is coming with the JSONRPC transport dependency. Desp
 dependency is included by default, you still need to add the transport to the Client as described in [JSON-RPC Transport section](#json-rpc-transport-configuration).
 
 
-If you want to use another transport (such as GRPC or HTTP+JSON), you'll need to add a relevant dependency:
+If you want to use GRPC transport, you'll need to add a relevant dependency:
 
 ----
 > *⚠️ The `io.github.a2asdk` `groupId` below is temporary and will likely change for future releases.*
@@ -262,7 +273,21 @@ If you want to use another transport (such as GRPC or HTTP+JSON), you'll need to
 </dependency>
 ```
 
-Support for the HTTP+JSON/REST transport will be coming soon.
+
+If you want to use HTTP+JSON/REST transport, you'll need to add a relevant dependency:
+
+----
+> *⚠️ The `io.github.a2asdk` `groupId` below is temporary and will likely change for future releases.*
+----
+
+```xml
+<dependency>
+    <groupId>io.github.a2asdk</groupId>
+    <artifactId>a2a-java-sdk-client-transport-rest</artifactId>
+    <!-- Use a released version from https://github.com/a2aproject/a2a-java/releases -->
+    <version>${io.a2a.sdk.version}</version>
+</dependency>
+```
 
 ### Sample Usage
 
@@ -360,6 +385,30 @@ Client client = Client
         .build();
 ```
 
+
+##### HTTP+JSON/REST Transport Configuration
+
+For
+For the HTTP+JSON/REST transport, if you'd like to use the default `JdkA2AHttpClient`, no additional
+configuration is needed. To use a custom HTTP client implementation, simply create a `RestTransportConfig`
+as follows:
+
+```java
+// Create a custom HTTP client
+A2AHttpClient customHttpClient = ...
+
+// Configure the client settings
+ClientConfig clientConfig = new ClientConfig.Builder()
+        .setAcceptedOutputModes(List.of("text"))
+        .build();
+
+Client client = Client
+        .builder(agentCard)
+        .clientConfig(clientConfig)
+        .withTransport(RestTransport.class, new RestTransportConfig(customHttpClient))
+        .build();
+```
+
 ##### Multiple Transport Configurations
 
 You can specify configuration for multiple transports, the appropriate configuration
@@ -371,6 +420,7 @@ Client client = Client
                 .builder(agentCard)
                 .withTransport(GrpcTransport.class, new GrpcTransportConfig(channelFactory))
                 .withTransport(JSONRPCTransport.class, new JSONRPCTransportConfig())
+                .withTransport(RestTransport.class, new RestTransportConfig())
                 .build();
 ```
 

client/base/pom.xml

@@ -54,6 +54,11 @@
             <artifactId>mockserver-netty</artifactId>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-jdk14</artifactId>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
 </project>

client/transport/grpc/pom.xml

@@ -33,6 +33,14 @@
             <groupId>${project.groupId}</groupId>
             <artifactId>a2a-java-sdk-client-transport-spi</artifactId>
         </dependency>
+        <dependency>
+            <groupId>io.grpc</groupId>
+            <artifactId>grpc-protobuf</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>io.grpc</groupId>
+            <artifactId>grpc-stub</artifactId>
+        </dependency>
         <dependency>
             <groupId>org.junit.jupiter</groupId>
             <artifactId>junit-jupiter-api</artifactId>

client/transport/jsonrpc/src/test/java/io/a2a/client/transport/jsonrpc/JSONRPCTransportTest.java

@@ -2,7 +2,6 @@
 
 import static io.a2a.client.transport.jsonrpc.JsonMessages.AGENT_CARD;
 import static io.a2a.client.transport.jsonrpc.JsonMessages.AGENT_CARD_SUPPORTS_EXTENDED;
-import static io.a2a.client.transport.jsonrpc.JsonMessages.AUTHENTICATION_EXTENDED_AGENT_CARD;
 import static io.a2a.client.transport.jsonrpc.JsonMessages.CANCEL_TASK_TEST_REQUEST;
 import static io.a2a.client.transport.jsonrpc.JsonMessages.CANCEL_TASK_TEST_RESPONSE;
 import static io.a2a.client.transport.jsonrpc.JsonMessages.GET_AUTHENTICATED_EXTENDED_AGENT_CARD_REQUEST;
@@ -50,7 +49,6 @@
 import io.a2a.spec.FilePart;
 import io.a2a.spec.FileWithBytes;
 import io.a2a.spec.FileWithUri;
-import io.a2a.spec.GetAuthenticatedExtendedCardResponse;
 import io.a2a.spec.GetTaskPushNotificationConfigParams;
 import io.a2a.spec.Message;
 import io.a2a.spec.MessageSendConfiguration;

client/transport/rest/pom.xml

@@ -0,0 +1,62 @@
+<?xml version="1.0"?>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"
+         xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>io.github.a2asdk</groupId>
+        <artifactId>a2a-java-sdk-parent</artifactId>
+        <version>0.3.0.Beta1-SNAPSHOT</version>
+        <relativePath>../../../pom.xml</relativePath>
+    </parent>
+    <artifactId>a2a-java-sdk-client-transport-rest</artifactId>
+    <packaging>jar</packaging>
+
+    <name>Java SDK A2A Client Transport: JSON+HTTP/REST</name>
+    <description>Java SDK for the Agent2Agent Protocol (A2A) - JSON+HTTP/REST Client Transport</description>
+
+    <dependencies>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>a2a-java-sdk-common</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>a2a-java-sdk-spec</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>a2a-java-sdk-spec-grpc</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>a2a-java-sdk-client-transport-spi</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>io.github.a2asdk</groupId>
+            <artifactId>a2a-java-sdk-http-client</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.google.protobuf</groupId>
+            <artifactId>protobuf-java-util</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.mock-server</groupId>
+            <artifactId>mockserver-netty</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-jdk14</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+</project>

client/transport/rest/src/main/java/io/a2a/client/transport/rest/RestErrorMapper.java

@@ -0,0 +1,80 @@
+package io.a2a.client.transport.rest;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+import io.a2a.client.http.A2AHttpResponse;
+import io.a2a.spec.A2AClientException;
+import io.a2a.spec.AuthenticatedExtendedCardNotConfiguredError;
+import io.a2a.spec.ContentTypeNotSupportedError;
+import io.a2a.spec.InternalError;
+import io.a2a.spec.InvalidAgentResponseError;
+import io.a2a.spec.InvalidParamsError;
+import io.a2a.spec.InvalidRequestError;
+import io.a2a.spec.JSONParseError;
+import io.a2a.spec.MethodNotFoundError;
+import io.a2a.spec.PushNotificationNotSupportedError;
+import io.a2a.spec.TaskNotCancelableError;
+import io.a2a.spec.TaskNotFoundError;
+import io.a2a.spec.UnsupportedOperationError;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+/**
+ * Utility class to A2AHttpResponse to appropriate A2A error types
+ */
+public class RestErrorMapper {
+
+    private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper().registerModule(new JavaTimeModule());
+
+    public static A2AClientException mapRestError(A2AHttpResponse response) {
+        return RestErrorMapper.mapRestError(response.body(), response.status());
+    }
+
+    public static A2AClientException mapRestError(String body, int code) {
+        try {
+            if (body != null && !body.isBlank()) {
+                JsonNode node = OBJECT_MAPPER.readTree(body);
+                String className = node.findValue("error").asText();
+                String errorMessage = node.findValue("message").asText();
+                return mapRestError(className, errorMessage, code);
+            }
+            return mapRestError("", "", code);
+        } catch (JsonProcessingException ex) {
+            Logger.getLogger(RestErrorMapper.class.getName()).log(Level.SEVERE, null, ex);
+            return new A2AClientException("Failed to parse error response: " + ex.getMessage());
+        }
+    }
+
+    public static A2AClientException mapRestError(String className, String errorMessage, int code) {
+        switch (className) {
+            case "io.a2a.spec.TaskNotFoundError":
+                return new A2AClientException(errorMessage, new TaskNotFoundError());
+            case "io.a2a.spec.AuthenticatedExtendedCardNotConfiguredError":
+                return new A2AClientException(errorMessage, new AuthenticatedExtendedCardNotConfiguredError());
+            case "io.a2a.spec.ContentTypeNotSupportedError":
+                return new A2AClientException(errorMessage, new ContentTypeNotSupportedError(null, null, errorMessage));
+            case "io.a2a.spec.InternalError":
+                return new A2AClientException(errorMessage, new InternalError(errorMessage));
+            case "io.a2a.spec.InvalidAgentResponseError":
+                return new A2AClientException(errorMessage, new InvalidAgentResponseError(null, null, errorMessage));
+            case "io.a2a.spec.InvalidParamsError":
+                return new A2AClientException(errorMessage, new InvalidParamsError());
+            case "io.a2a.spec.InvalidRequestError":
+                return new A2AClientException(errorMessage, new InvalidRequestError());
+            case "io.a2a.spec.JSONParseError":
+                return new A2AClientException(errorMessage, new JSONParseError());
+            case "io.a2a.spec.MethodNotFoundError":
+                return new A2AClientException(errorMessage, new MethodNotFoundError());
+            case "io.a2a.spec.PushNotificationNotSupportedError":
+                return new A2AClientException(errorMessage, new PushNotificationNotSupportedError());
+            case "io.a2a.spec.TaskNotCancelableError":
+                return new A2AClientException(errorMessage, new TaskNotCancelableError());
+            case "io.a2a.spec.UnsupportedOperationError":
+                return new A2AClientException(errorMessage, new UnsupportedOperationError());
+            default:
+                return new A2AClientException(errorMessage);
+        }
+    }
+}