Class DefaultA2AClientBuilder<T>

java.lang.Object

dev.langchain4j.agentic.a2a.DefaultA2AClientBuilder<T>

All Implemented Interfaces:

A2AClientBuilder<T>, InternalAgent, AgentInstance, InvocationHandler

public class DefaultA2AClientBuilder<T>
extends Object
implements A2AClientBuilder<T>, InternalAgent, InvocationHandler

Method Summary

Modifier and Type	Method	Description
AgentCondition	activationCondition()	The condition under which this agent runs when it is invoked as a subagent, or null when it always runs.
DefaultA2AClientBuilder<T>	activationCondition(String description, Predicate<AgenticScope> activationCondition)	Sets the condition under which the agent runs when it is invoked as a subagent of an agentic system.
String	agentId()
void	appendId(String idSuffix)
List<AgentArgument>	arguments()
boolean	async()
DefaultA2AClientBuilder<T>	async(boolean async)	Sets whether the agent should be invoked asynchronously, allowing the workflow to continue without waiting for the agent's result.
T	build()	Builds the A2A client proxy implementing the agent service interface.
DefaultA2AClientBuilder<T>	clientCustomizer(Consumer<?> clientCustomizer)	Sets a customizer that will be applied to the underlying a2a-java SDK ClientBuilder before the Client is constructed.
String	description()
DefaultA2AClientBuilder<T>	inputKeys(String... inputKeys)	Sets the state keys whose values will be sent as message parts to the remote agent.
Object	invoke(Object proxy, Method method, Object[] args)
AgentListener	listener()
DefaultA2AClientBuilder<T>	listener(AgentListener agentListener)	Sets an AgentListener for observing agent invocations.
String	name()
String	outputKey()
DefaultA2AClientBuilder<T>	outputKey(String outputKey)	Sets the state key under which the agent's response will be stored.
Type	outputType()
AgentInstance	parent()
Class<? extends Planner>	plannerType()
void	registerInheritedParentListener(AgentListener parentListener)
void	setParent(InternalAgent parent)
A2AClientBuilder<T>	streamingClientListener(A2AStreamingClientListener<?> clientListener)	Sets an A2AStreamingClientListener for observing updates received from the remote agent during streaming invocation.
List<AgentInstance>	subagents()
DefaultA2AClientBuilder<T>	tenant(String tenant)	Sets the tenant identifier that will be sent with every A2A message.
AgenticSystemTopology	topology()
Class<?>	type()

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface A2AClientBuilder

activationCondition

Methods inherited from interface AgentInstance

as, leaf, optional

Methods inherited from interface InternalAgent

allowChatMemory, allowStreamingOutput, compensateOnError, enableCrossAgentCompensation, setAgentId

Method Details

build

public T build()

Description copied from interface: A2AClientBuilder

Builds the A2A client proxy implementing the agent service interface.

Specified by:

build in interface A2AClientBuilder<T>

Returns:

the proxy instance

invoke

public Object invoke(Object proxy,
 Method method,
 Object[] args)
              throws Exception

Specified by:

invoke in interface InvocationHandler

Throws:

Exception

inputKeys

public DefaultA2AClientBuilder<T> inputKeys(String... inputKeys)

Description copied from interface: A2AClientBuilder

Sets the state keys whose values will be sent as message parts to the remote agent.

Specified by:

inputKeys in interface A2AClientBuilder<T>

Parameters:

inputKeys - the names of the input keys

Returns:

this builder for method chaining

outputKey

public DefaultA2AClientBuilder<T> outputKey(String outputKey)

Description copied from interface: A2AClientBuilder

Sets the state key under which the agent's response will be stored.

Specified by:

outputKey in interface A2AClientBuilder<T>

Parameters:

outputKey - the name of the output key

Returns:

this builder for method chaining

async

public DefaultA2AClientBuilder<T> async(boolean async)

Description copied from interface: A2AClientBuilder

Sets whether the agent should be invoked asynchronously, allowing the workflow to continue without waiting for the agent's result.

Specified by:

async in interface A2AClientBuilder<T>

Parameters:

async - true for asynchronous invocation

Returns:

this builder for method chaining

listener

public DefaultA2AClientBuilder<T> listener(AgentListener agentListener)

Description copied from interface: A2AClientBuilder

Sets an AgentListener for observing agent invocations.

Specified by:

listener in interface A2AClientBuilder<T>

Parameters:

agentListener - the listener to attach

Returns:

this builder for method chaining

activationCondition

public DefaultA2AClientBuilder<T> activationCondition(String description,
 Predicate<AgenticScope> activationCondition)

Description copied from interface: A2AClientBuilder

Sets the condition under which the agent runs when it is invoked as a subagent of an agentic system. When the condition is false the remote agent is not called and the agent is skipped. It can be evaluated more than once, so it must be free of side effects.

Specified by:

activationCondition in interface A2AClientBuilder<T>

Parameters:

description - a human-readable description of the condition, used in logs, listeners and reports

activationCondition - the predicate deciding whether the agent runs

Returns:

this builder for method chaining

clientCustomizer

public DefaultA2AClientBuilder<T> clientCustomizer(Consumer<?> clientCustomizer)

Description copied from interface: A2AClientBuilder

Sets a customizer that will be applied to the underlying a2a-java SDK ClientBuilder before the Client is constructed.

The wildcard type avoids a compile-time dependency on the a2a-java SDK in this module. At runtime the value must be a Consumer<org.a2aproject.sdk.client.ClientBuilder>.

Specified by:

clientCustomizer in interface A2AClientBuilder<T>

Parameters:

clientCustomizer - a Consumer<ClientBuilder> from the a2a-java SDK

Returns:

this builder for method chaining

streamingClientListener

public A2AClientBuilder<T> streamingClientListener(A2AStreamingClientListener<?> clientListener)

Description copied from interface: A2AClientBuilder

Sets an A2AStreamingClientListener for observing updates received from the remote agent during streaming invocation.

Like DefaultA2AClientBuilder, which uses a2a-java, can be used with the following example:

streamingClientListener((TaskUpdateEvent event) -> {
    // handle the streaming event
});

The listener is invoked with task update events received from the remote agent.

Specified by:

streamingClientListener in interface A2AClientBuilder<T>

Parameters:

clientListener - the listener to attach

Returns:

this builder for method chaining

setParent

public void setParent(InternalAgent parent)

Specified by:

setParent in interface InternalAgent

registerInheritedParentListener

public void registerInheritedParentListener(AgentListener parentListener)

Specified by:

registerInheritedParentListener in interface InternalAgent

appendId

public void appendId(String idSuffix)

Specified by:

appendId in interface InternalAgent

listener

public AgentListener listener()

Specified by:

listener in interface InternalAgent

type

public Class<?> type()

Specified by:

type in interface AgentInstance

plannerType

public Class<? extends Planner> plannerType()

Specified by:

plannerType in interface AgentInstance

name

public String name()

Specified by:

name in interface AgentInstance

agentId

public String agentId()

Specified by:

agentId in interface AgentInstance

description

public String description()

Specified by:

description in interface AgentInstance

outputType

public Type outputType()

Specified by:

outputType in interface AgentInstance

outputKey

public String outputKey()

Specified by:

outputKey in interface AgentInstance

async

public boolean async()

Specified by:

async in interface AgentInstance

activationCondition

public AgentCondition activationCondition()

Description copied from interface: AgentInstance

The condition under which this agent runs when it is invoked as a subagent, or null when it always runs. When the condition is false, the agent is skipped: it is not invoked, it writes nothing to the AgenticScope and its parent's planner is notified of the skip. The condition is ignored when the agent is invoked directly, as the root of an agentic system.

The condition can be evaluated more than once for a single invocation, by the planner of the parent while selecting its next agents and again when the agent is invoked, so it must be cheap and free of side effects.

Specified by:

activationCondition in interface AgentInstance

arguments

public List<AgentArgument> arguments()

Specified by:

arguments in interface AgentInstance

parent

public AgentInstance parent()

Specified by:

parent in interface AgentInstance

subagents

public List<AgentInstance> subagents()

Specified by:

subagents in interface AgentInstance

topology

public AgenticSystemTopology topology()

Specified by:

topology in interface AgentInstance

tenant

public DefaultA2AClientBuilder<T> tenant(String tenant)

Description copied from interface: A2AClientBuilder

Sets the tenant identifier that will be sent with every A2A message.

Specified by:

tenant in interface A2AClientBuilder<T>

Parameters:

tenant - the tenant identifier

Returns:

this builder for method chaining