Class BlackboardPlanner

java.lang.Object

dev.langchain4j.agentic.patterns.blackboard.BlackboardPlanner

All Implemented Interfaces:

Planner

public class BlackboardPlanner
extends Object
implements Planner

A blackboard planner that activates agents based on data availability in the shared scope.

Agents are knowledge sources that post partial results to the AgenticScope (the blackboard). After each agent completes, the planner inspects the blackboard and activates whichever single agent can contribute next. When multiple agents are ready, a ConflictResolutionStrategy determines which one fires; if no strategy is provided, declaration order is used.

The planner terminates successfully when:

• The goal predicate is satisfied (by default, when the planner's outputKey is present in scope)
• No agent can fire (quiescence)

If the maximum number of invocations is reached before the goal is satisfied, the planner throws an IllegalStateException.

Constructor Summary

Constructors

Constructor	Description
BlackboardPlanner()
BlackboardPlanner(ConflictResolutionStrategy conflictResolutionStrategy)
BlackboardPlanner(Predicate<AgenticScope> goalPredicate)
BlackboardPlanner(Predicate<AgenticScope> goalPredicate, int maxInvocations)
BlackboardPlanner(Predicate<AgenticScope> goalPredicate, int maxInvocations, ConflictResolutionStrategy conflictResolutionStrategy)
BlackboardPlanner(Predicate<AgenticScope> goalPredicate, ConflictResolutionStrategy conflictResolutionStrategy)

Method Summary

Modifier and Type	Method	Description
Map<String,Object>	executionState()	Returns the planner's current execution state as a map of serializable values.
Action	firstAction(PlanningContext planningContext)	Returns the first action to execute when the planner starts (or resumes).
void	init(InitPlanningContext initPlanningContext)
Action	nextAction(PlanningContext planningContext)	Determines the next action to execute based on the result of the previous agent invocation.
void	restoreExecutionState(Map<String,Object> state)	Restores the planner's execution state from a previously saved map.
AgenticSystemTopology	topology()	Returns the topology of the agentic system managed by this planner.

Methods inherited from class Object

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

Methods inherited from interface Planner

as, call, call, done, done, noOp, suspend, terminated

Constructor Details

BlackboardPlanner

public BlackboardPlanner()

BlackboardPlanner

public BlackboardPlanner(Predicate<AgenticScope> goalPredicate)

BlackboardPlanner

public BlackboardPlanner(ConflictResolutionStrategy conflictResolutionStrategy)

BlackboardPlanner

public BlackboardPlanner(Predicate<AgenticScope> goalPredicate,
 int maxInvocations)

BlackboardPlanner

public BlackboardPlanner(Predicate<AgenticScope> goalPredicate,
 ConflictResolutionStrategy conflictResolutionStrategy)

BlackboardPlanner

public BlackboardPlanner(Predicate<AgenticScope> goalPredicate,
 int maxInvocations,
 ConflictResolutionStrategy conflictResolutionStrategy)

Method Details

init

public void init(InitPlanningContext initPlanningContext)

Specified by:

init in interface Planner

firstAction

public Action firstAction(PlanningContext planningContext)

Description copied from interface: Planner

Returns the first action to execute when the planner starts (or resumes). Defaults to delegating to Planner.nextAction(PlanningContext).

Specified by:

firstAction in interface Planner

Parameters:

planningContext - the current planning context

Returns:

the first action to execute

nextAction

public Action nextAction(PlanningContext planningContext)

Description copied from interface: Planner

Determines the next action to execute based on the result of the previous agent invocation.

Specified by:

nextAction in interface Planner

Parameters:

planningContext - the current planning context, including the previous agent's result

Returns:

the next action to execute

executionState

public Map<String,Object> executionState()

Description copied from interface: Planner

Returns the planner's current execution state as a map of serializable values. This state is persisted to the AgenticScope after each agent invocation, enabling the planner to resume from the correct position after a crash.

The returned state must be such that, when passed to Planner.restoreExecutionState(Map) and Planner.firstAction(PlanningContext) is called, the planner produces the correct resume action.

Stateless planners (e.g., parallel, conditional) can use the default empty implementation.

Specified by:

executionState in interface Planner

Returns:

a map of state entries to persist, or an empty map if no state needs saving

restoreExecutionState

public void restoreExecutionState(Map<String,Object> state)

Description copied from interface: Planner

Restores the planner's execution state from a previously saved map. Called by the execution loop before Planner.firstAction(PlanningContext) when recovering from a persisted scope.

Specified by:

restoreExecutionState in interface Planner

Parameters:

state - the previously saved execution state

topology

public AgenticSystemTopology topology()

Description copied from interface: Planner

Returns the topology of the agentic system managed by this planner.

Specified by:

topology in interface Planner

Returns:

the topology (defaults to AgenticSystemTopology.SEQUENCE)