接上节继续，在某些循环迭代流程中，希望人工干预来影响流程走向，也就是所谓的human_in_the_loop
代码示例
public class HumanInLoopGraphApplication {private static final String LOOP_COUNT_KEY = "loopCount";/*** 共享 Scanner，不关闭以免关闭 System.in导致后续无法读取*/private static final Scanner CONSOLE_SCANNER = new Scanner(System.in);public static void main(String[] args) throws GraphStateException {StateGraph<AgentState> graph = getLoopGraph();System.out.println(graph.getGraph(GraphRepresentation.Type.MERMAID, "human-in-loop Graph", true).content());AsyncGenerator<NodeOutput<AgentState>> stream = graph.compile().stream(Map.of());for (NodeOutput<AgentState> output : stream) {System.out.println(output.node() + "->" + output.state().value(LOOP_COUNT_KEY).orElse(0));}}public static StateGraph<AgentState> getLoopGraph() throws GraphStateException {return new StateGraph<>(AgentState::new).addNode("node-1", node_async(state -> Map.of(LOOP_COUNT_KEY, (int) state.value(LOOP_COUNT_KEY).orElse(0) + 1))).addNode("node-2", node_async(state -> Map.of())).addEdge(GraphDefinition.START, "node-1").addEdge("node-2", "node-1").addConditionalEdges("node-1", state -> CompletableFuture.supplyAsync(HumanInLoopGraphApplication::waitForHumanDecision),Map.of("exit", GraphDefinition.END,"next", "node-2","back", "node-1"));}/*** 控制台等待用户输入：C(Continue) 进入 node-2，Q(Quit) 结束到 END。* 使用共享 CONSOLE_SCANNER，不能关闭否则会关闭 System.in 导致下次 No line found。*/private static String waitForHumanDecision() {while (true) {System.out.print("请输入 N(next) 继续到 node-2，B(back) 退回到 node-1，或 Q(Quit) 结束 [N/B/Q]: ");if (!CONSOLE_SCANNER.hasNextLine()) {return "exit";}String input = CONSOLE_SCANNER.nextLine();if (input == null) {continue;}String trimmed = input.trim().toUpperCase();if ("N".equals(trimmed)) {return "next";}if ("B".equals(trimmed)) {return "back";}if ("Q".equals(trimmed)) {return "exit";}System.out.println("无效输入，请只输入 N 或 B 或 Q");}}
}
运行效果
请输入 N(next) 继续到 node-2，B(back) 退回到 node-1，或 Q(Quit) 结束 [N/B/Q]: N __START__->0 node-1->1 请输入 N(next) 继续到 node-2，B(back) 退回到 node-1，或 Q(Quit) 结束 [N/B/Q]: N node-2->1 node-1->2 请输入 N(next) 继续到 node-2，B(back) 退回到 node-1，或 Q(Quit) 结束 [N/B/Q]: B node-2->2 请输入 N(next) 继续到 node-2，B(back) 退回到 node-1，或 Q(Quit) 结束 [N/B/Q]: B node-1->3 请输入 N(next) 继续到 node-2，B(back) 退回到 node-1，或 Q(Quit) 结束 [N/B/Q]: Q node-1->4 node-1->5 __END__->5
复杂示例
上面的示例比较简单，可以引入CheckPoint，在进入node-2、node-reset 这两个节点前interrupt，同时也触发checkpoint保存。
- 按N后，从保存的checkpoint中恢复，继续执行
- 按R后，将loopCount恢复初始值，同时清空checkpoint历史记录
/*** 人机协同（Human-in-the-Loop）示例：在图执行到指定节点前中断，等待控制台输入后再恢复。* <p>* 图结构：START → node-1 → [条件边] → node-2 / node-reset / node-1 / END* <ul>* <li>node-1：递增 loopCount，然后根据用户输入决定下一跳</li>* <li>node-2、node-reset：空节点，执行后回到 node-1</li>* <li>条件边由 {@link #waitForHumanDecision()} 驱动：N(next)→node-2，B(back)→node-1，R(Reset)→node-reset，Q(Quit)→END</li>* </ul>* 通过 {@code interruptBefore("node-2")} 与 {@code interruptBefore("node-reset")} 在进入下一节点前暂停，* 使用 checkpoint 保存状态，再通过 {@link GraphInput#resume()} 恢复执行，实现“按 N 一直循环”等人机交互。** @see org.bsc.langgraph4j.CompiledGraph#stream* @see org.bsc.langgraph4j.CompileConfig.Builder#interruptBefore*/
public class HumanInLoopGraph2Application {/*** 状态中的循环计数字段名*/private static final String LOOP_COUNT_KEY = "loopCount";/*** 控制台输入扫描器，供 waitForHumanDecision 使用*/private static final Scanner CONSOLE_SCANNER = new Scanner(System.in);public static void main(String[] args) throws Exception {// ---------- 1. 构建图并打印 Mermaid ----------StateGraph<AgentState> graph = getLoopGraph();System.out.println(graph.getGraph(GraphRepresentation.Type.MERMAID, "human-in-loop Graph", true).content());// ---------- 2. 配置：在 node-2、node-reset 前中断，并使用 MemorySaver 做 checkpoint ----------BaseCheckpointSaver saver = new MemorySaver();CompileConfig compileConfig = CompileConfig.builder().interruptBefore("node-2").interruptBefore("node-reset").checkpointSaver(saver).interruptBeforeEdge(false).build();RunnableConfig runnableConfig = RunnableConfig.builder().threadId("thread-1").build();// ---------- 3. 首次执行：跑到第一次中断（interruptBefore）后 stream 结束 ----------CompiledGraph<AgentState> workflow = graph.compile(compileConfig);AsyncGenerator.Cancellable<NodeOutput<AgentState>> stream = workflow.stream(Map.of(), runnableConfig);for (NodeOutput<AgentState> output : stream) {System.out.println(output.node() + "->" + output.state().value(LOOP_COUNT_KEY).orElse(0));}// ---------- 4. 循环：取 checkpoint → 按需更新状态（含 reset 时清零 loopCount）→ resume 直至用户选 Q 或无快照 ----------boolean isQuit = false;while (true) {StateSnapshot<AgentState> snapshot = workflow.getState(runnableConfig);if (snapshot == null || isQuit) {break;}System.out.println("snapshot=>" + snapshot.state().data());AsyncGenerator.Cancellable<NodeOutput<AgentState>> streamResume;if (snapshot.next().contains("reset")) {System.out.println("reset");streamResume = workflow.stream(GraphInput.resume(), workflow.updateState(runnableConfig, Map.of(LOOP_COUNT_KEY, 0)));//reset后，清空历史checkpointsaver.release(runnableConfig);} else {streamResume = workflow.stream(GraphInput.resume(), workflow.updateState(runnableConfig, snapshot.state().data()));}for (NodeOutput<AgentState> output : streamResume) {System.out.println(output.node() + "->" + output.state().value(LOOP_COUNT_KEY).orElse(0));if (output.node().contains("END")) {isQuit = true;}}Thread.sleep(20);}System.out.println("done");}/*** 构建人机协同的循环图：node-1 自增 loopCount，根据控制台输入路由到 node-2 / node-reset / node-1 / END。** @return 已配置节点与条件边的 StateGraph* @throws GraphStateException 图状态异常*/public static StateGraph<AgentState> getLoopGraph() throws GraphStateException {return new StateGraph<>(AgentState::new).addNode("node-1", node_async(state -> Map.of(LOOP_COUNT_KEY, (int) state.value(LOOP_COUNT_KEY).orElse(0) + 1))).addNode("node-2", node_async(state -> Map.of())).addNode("node-reset", node_async(state -> Map.of())).addEdge(GraphDefinition.START, "node-1").addEdge("node-2", "node-1").addEdge("node-reset", "node-1").addConditionalEdges("node-1", state -> CompletableFuture.supplyAsync(HumanInLoopGraph2Application::waitForHumanDecision),Map.of("exit", GraphDefinition.END,"reset", "node-reset","next", "node-2","back", "node-1"));}/*** 在控制台阻塞等待用户输入，映射为图的条件边取值。* <ul>* <li>N → "next"（到 node-2）</li>* <li>B → "back"（回到 node-1）</li>* <li>R → "reset"（到 node-reset，外部可配合将 loopCount 置 0）</li>* <li>Q → "exit"（到 END）</li>* </ul>** @return 条件边键："next" | "back" | "reset" | "exit"*/private static String waitForHumanDecision() {while (true) {System.out.print("请输入 N(next) 继续到 node-2，B(back) 退回到 node-1，R(Reset) 重置，或 Q(Quit) 结束 [N/B/R/Q]: ");if (!CONSOLE_SCANNER.hasNextLine()) {return "exit";}String input = CONSOLE_SCANNER.nextLine();if (input == null) {continue;}String trimmed = input.trim().toUpperCase();if ("N".equals(trimmed)) {return "next";}if ("R".equals(trimmed)) {return "reset";}if ("B".equals(trimmed)) {return "back";}if ("Q".equals(trimmed)) {return "exit";}System.out.println("无效输入，请只输入[N/B/R/Q]");}}
}
文中源码：langgraph4j-study/src/main/java/org/bsc/langgraph4j/agent/_09_human_in_loop at main · yjmyzz/langgraph4j-study · GitHub