在Kogito的Serverless Workflow foreach状态调用REST接口遇问题求助

问题描述 #

1. 核心业务异常 #

• ${ .item }变量始终为null，导致REST调用参数错误
• 将${ .item }替换为固定值后，outputCollection: .greetings未收集两次迭代调用的结果，返回空数组

2. 工作流调用命令 #

curl -X POST -H 'Content-Type:application/json' -H 'Accept:application/json' -d '{"workflowdata" : {"name": "Helber", "language": ["Spanish","English"]}}' http://localhost:8080/greeting

3. 当前工作流定义 #

{
  "id": "greeting",
  "version": "1.0",
  "specVersion": "0.8",
  "name": "Greeting workflow",
  "description": "JSON based greeting workflow",
  "start": "Loop",
  "functions": [
    {
      "name": "getGreetingFunction",
      "operation": "openapi.yml#getGreeting"
    }
  ],
  "states": [    
    {
      "name": "Loop",
      "type": "foreach",
      "inputCollection": ".languages",
      "iterationParam": "item",
      "outputCollection": ".greetings",
      "actions": [
        {
          "name": "getGreeting",
          "functionRef": {
            "refName": "getGreetingFunction",
            "arguments": {
                  "name": "${ .name }",
                  "language": "${ .item }"
              }
          }
        }
      ],      
      "end": true
    }
  ]
}

4. 错误日志输出 #

2022-09-02 17:15:55,227 WARN  [org.kog.wor.res.RestWorkItemHandler] (executor-thread-0) Cannot find definition for variable Loop_5
2022-09-02 17:15:55,296 ERROR [org.jbp.wor.ins.imp.NodeInstanceImpl] (executor-thread-0) Could not find variable Loop_5
2022-09-02 17:15:55,296 ERROR [org.jbp.wor.ins.imp.NodeInstanceImpl] (executor-thread-0) Using process-level scope
2022-09-02 17:15:55,298 INFO  [org.kie.kog.exp.jq.JqExpressionHandler] (executor-thread-0) Using default scope

问题修复方案 #

1. 修正inputCollection的字段路径错误 #

调用请求中传入的数组字段是language，但工作流定义里写的是.languages（多了一个s），这是导致item变量为null的直接原因：

• 原定义：inputCollection: ".languages"
• 修正为：inputCollection: ".language"

确保遍历的目标数组存在，item变量才会被正确赋值为数组的每个元素。

2. 配置动作输出映射，填充outputCollection #

Kogito的foreach状态不会自动收集函数返回值，需要通过actionDataFilter明确指定迭代动作的输出内容，才能将结果写入outputCollection：

"actions": [
  {
    "name": "getGreeting",
    "functionRef": {
      "refName": "getGreetingFunction",
      "arguments": {
            "name": "${ .name }",
            "language": "${ .item }"
        }
    },
    "actionDataFilter": {
      "results": "${ .greeting }" // 对应getGreetingFunction返回的greeting字段
    }
  }
]

3. 日志中Loop_5变量的处理 #

该错误是Kogito生成foreach内部变量时的作用域问题，修复前两个核心问题后，该日志错误通常会自动消失。如果仍存在，建议：

• 升级Kogito到与specVersion 0.8兼容的稳定版本（推荐1.20.x及以上）
• 确保项目依赖的Quarkus版本与Kogito版本匹配

修复后的完整工作流 #

{
  "id": "greeting",
  "version": "1.0",
  "specVersion": "0.8",
  "name": "Greeting workflow",
  "description": "JSON based greeting workflow",
  "start": "Loop",
  "functions": [
    {
      "name": "getGreetingFunction",
      "operation": "openapi.yml#getGreeting"
    }
  ],
  "states": [    
    {
      "name": "Loop",
      "type": "foreach",
      "inputCollection": ".language",
      "iterationParam": "item",
      "outputCollection": ".greetings",
      "actions": [
        {
          "name": "getGreeting",
          "functionRef": {
            "refName": "getGreetingFunction",
            "arguments": {
                  "name": "${ .name }",
                  "language": "${ .item }"
              }
          },
          "actionDataFilter": {
            "results": "${ .greeting }"
          }
        }
      ],      
      "end": true
    }
  ]
}

验证结果 #

重新部署后执行原curl命令，会得到包含正确greetings数组的输出，示例：

{
  "id": "xxx-xxx-xxx",
  "workflowdata": {
    "name": "Helber",
    "language": ["Spanish","English"],
    "greetings": [
      "Greetings from Serverless Workflow, Helber! (Spanish)",
      "Greetings from Serverless Workflow, Helber! (English)"
    ]
  }
}

内容的提问来源于stack exchange，提问作者Cyril C.