feat: add exchange rates currency sample

samples/java/agents/README.md

@@ -22,6 +22,9 @@ Each agent can be run as its own A2A server with the instructions in its README.
 * [**Magic 8 Ball Agent (Security)**](magic_8_ball_security/README.md)  
   Sample agent that can respond to yes/no questions by consulting a Magic 8 Ball. This sample demonstrates how to secure an A2A server with Keycloak using bearer token authentication and it shows how to configure an A2A client to specify the token when sending requests.
 
+* [**Currency Exchange Rates (Multi-turn Conversations)**](currency_exchange_rates/README.md)  
+  Sample agent to provide currency conversion. This agent demonstrates multi-turn dialogue and streaming responses.
+
 ## Disclaimer
 
 Important: The sample code provided is for demonstration purposes and illustrates the

samples/java/agents/currency_exchange_rates/README.md

@@ -0,0 +1,144 @@
+# Currency Exchange Rates
+
+This sample demonstrates a currency conversion agent exposed through the A2A protocol.
+It showcases conversational interactions with support for multi-turn dialogue and streaming responses.
+The agent is written using Quarkus LangChain4j and makes use of the [A2A Java](https://github.com/a2aproject/a2a-java) SDK.
+
+## How It Works
+
+This agent uses an Ollama LLM (for example, qwen2.5:7b) to provide currency exchange information.
+The A2A protocol enables standardized interaction with the agent, allowing clients to send requests and receive real-time updates.
+
+```mermaid
+sequenceDiagram
+    participant Client as A2A Client
+    participant Server as A2A Server
+    participant API as Frankfurter API
+
+    Client->>Server: Send task with currency query
+
+    alt Complete Information
+        Server->>API: Call get_exchange_rate tool
+        API->>Server: Return exchange rate data
+        Server->>Server: Process data & return result
+        Server->>Client: Respond with currency information
+    else Incomplete Information
+        Server->>Server: Request additional input
+        Server->>Client: Set state to "input-required"
+        Client->>Server: Send additional information
+        Server->>API: Call get_exchange_rate tool
+        API->>Server: Return exchange rate data
+        Server->>Server: Process data & return result
+        Server->>Client: Respond with currency information
+    end
+
+    alt With Streaming
+        Note over Client,Server: Real-time status updates
+        Server->>Client: "Looking up exchange rates..."
+        Server->>Client: "Processing exchange rates..."
+        Server->>Client: Final result
+    end
+```
+
+## Key Features
+
+- **Multi-turn Conversations**: Agent can request additional information when needed
+- **Real-time Streaming**: Provides status updates during processing
+- **Conversational Memory**: Maintains context across interactions
+- **Currency Exchange Tool**: Integrates with Frankfurter API for real-time rates
+
+## Prerequisites
+
+- Java 17 or higher
+- Access to an LLM (Ollama)
+- Ollama installed (see [Download Ollama](https://ollama.com/download))
+
+## Running the Sample
+
+This sample consists of an A2A server agent, which is in the `server` directory, and an A2A client,
+which is in the `client` directory.
+
+### Running Ollama
+
+1. Launch the Ollama server by default on port 11434 ([Local Ollama server](http://localhost:11434))
+
+    ```bash
+   ollama serve
+    ```
+
+2. In this example, we use the model qwen2.5:7b. Download this model and run it
+
+    ```bash
+   ollama pull qwen2.5:7b
+   ollama run qwen2.5:7b
+    ```
+
+### Running the A2A Server Agent
+
+1. Navigate to the `currency_exchange_rates` sample directory:
+
+    ```bash
+    cd samples/java/agents/currency_exchange_rates/server
+    ```
+
+2. Start the A2A server agent
+
+   **NOTE:**
+   By default, the agent will start on port 10000. To override this, add the `-Dquarkus.http.port=YOUR_PORT`
+   option at the end of the command below.
+
+   ```bash
+   mvn quarkus:dev
+   ```
+
+### Running the A2A Java Client
+
+The Java `TestClient` communicates with the Currency Agent using the A2A Java SDK.
+
+Since the A2A server agent's [transport](samples/java/agents/currency_exchange_rates/server/pom.xml) is JsonRpc and since our client
+also [supports](client/src/main/java/com/samples/a2a/TestClient.java) gRPC and JsonRpc, the JsonRpc transport will be used.
+
+1. Make sure you have [JBang installed](https://www.jbang.dev/documentation/guide/latest/installation.html)
+
+2. Run the client using the JBang script:
+
+   ```bash
+   cd samples/java/agents/currency_exchange_rates/client/src/main/java/com/samples/a2a/client
+   jbang TestClientRunner.java
+   ```
+## Expected Client Output
+
+The Java A2A client will:
+1. Connect to the currency agent
+2. Fetch the agent card
+3. Automatically select JsonRpc as the transport to be used
+4. Send the message "how much is 10 USD in INR?"
+5. Display the exchange rate result from the agent
+6. Send the message "How much is the exchange rate for 1 USD?"
+7. Receive the request for additional input "Please specify the currency you want to convert USD to"
+8. Send additional information "CAD"
+9. Display the exchange rate result from the agent
+
+## Learn More
+
+- [A2A Protocol Documentation](https://a2a-protocol.org/)
+- [Frankfurter API](https://www.frankfurter.app/docs/)
+- [Ollama](https://docs.ollama.com/)
+
+## Disclaimer
+Important: The sample code provided is for demonstration purposes and illustrates the
+mechanics of the Agent-to-Agent (A2A) protocol. When building production applications,
+it is critical to treat any agent operating outside of your direct control as a
+potentially untrusted entity.
+
+All data received from an external agent—including but not limited to its AgentCard,
+messages, artifacts, and task statuses—should be handled as untrusted input. For
+example, a malicious agent could provide an AgentCard containing crafted data in its
+fields (e.g., description, name, skills.description). If this data is used without
+sanitization to construct prompts for a Large Language Model (LLM), it could expose
+your application to prompt injection attacks.  Failure to properly validate and
+sanitize this data before use can introduce security vulnerabilities into your
+application.
+
+Developers are responsible for implementing appropriate security measures, such as
+input validation and secure handling of credentials to protect their systems and users.

samples/java/agents/currency_exchange_rates/client/pom.xml

@@ -0,0 +1,54 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>com.samples.a2a</groupId>
+        <artifactId>currency_exchange_rates</artifactId>
+        <version>0.1.0</version>
+    </parent>
+
+    <artifactId>currency-agent-client</artifactId>
+    <name>Currency Agent Client</name>
+    <description>A2A Currency Agent Test Client</description>
+
+    <dependencies>
+        <dependency>
+            <groupId>io.github.a2asdk</groupId>
+            <artifactId>a2a-java-sdk-client</artifactId>
+            <version>${io.a2a.sdk.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>io.github.a2asdk</groupId>
+            <artifactId>a2a-java-sdk-client-transport-grpc</artifactId>
+            <version>${io.a2a.sdk.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>io.grpc</groupId>
+            <artifactId>grpc-netty-shaded</artifactId>
+            <scope>runtime</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+            </plugin>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <configuration>
+                    <mainClass>com.samples.a2a.TestClient</mainClass>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</project>