Camunda：如何让DMN输出两个变量至BPMN流程上下文？

Let's break down what's happening first: that ENGINE-22002 error is expected behavior. The CollectEntriesDecisionResultMapper you're using is designed exclusively for DMN tables with a single output column—it tries to collect all values for one specific output, so when it sees two outputs (ROUT_TO_DEPT and OUT_CATEGORY), it throws an error.

Here are three practical ways to get those two outputs as independent variables in your BPMN context:

1. Use Multi-Result Mappings in the Business Rule Task (Recommended) #

This is the simplest, no-code approach if you're using Camunda 7.x or later:

• Open your Business Rule Task's properties panel
• Navigate to the Result Mappings section (may be labeled "Output Mappings" in older versions)
• Add two separate mappings:
  • First Mapping:
    • Source: ${decisionResult.singleResult().get('ROUT_TO_DEPT')}
    • Target: routToDept (or whatever variable name you want)
  • Second Mapping:
    • Source: ${decisionResult.singleResult().get('OUT_CATEGORY')}
    • Target: outCategory
• Make sure the Decision Result Mapper dropdown is set to Default (not Collect or Single Result—we're handling the mapping ourselves via expressions)
• Save your changes. After the DMN runs, routToDept and outCategory will be available as standalone variables for all subsequent BPMN steps.

2. Fetch a Single Result Map, Then Split with a Script Task #

If your Camunda version doesn't support multi-result mappings, use a script to split the map into individual variables:

1. Configure the Business Rule Task:
   • Set Result Variable to something like dmnOutputMap
   • Set Decision Result Mapper to Single Result (this converts the winning DMN row into a Java Map)
2. Add a Script Task right after the Business Rule Task:
   • Choose your preferred script language (Groovy or JavaScript work well):
     Groovy Example:

     // Pull values from the map and set them as independent process variables
     execution.setVariable('routToDept', dmnOutputMap.get('ROUT_TO_DEPT'))
     execution.setVariable('outCategory', dmnOutputMap.get('OUT_CATEGORY'))
     

     JavaScript Example:

     execution.setVariable('routToDept', dmnOutputMap.get('ROUT_TO_DEPT'));
     execution.setVariable('outCategory', dmnOutputMap.get('OUT_CATEGORY'));
     

3. Run the process—your two variables will be ready to use after the script task.

3. Custom Decision Result Mapper (For Complex Use Cases) #

If you need reusable logic for multiple processes, build a custom mapper:

• Implement Camunda's DecisionResultMapper interface:

  import org.camunda.bpm.engine.impl.dmn.result.DecisionResultMapper;
  import org.camunda.bpm.dmn.engine.DmnDecisionTableResult;
  import java.util.Map;
  
  public class MultiOutputMapper implements DecisionResultMapper {
      @Override
      public Object mapDecisionResult(DmnDecisionTableResult result) {
          // Return the first matching row as a Map (adjust if you need multiple rows)
          return result.isEmpty() ? null : result.singleResult();
      }
  }
  

• Register the mapper in your Camunda engine configuration (via XML or Java config)
• Select your custom mapper in the Business Rule Task's Decision Result Mapper dropdown
• Then use the multi-result mappings from Option 1 to split the map into variables.

Quick Note: Double-Check Spelling! #

I noticed in your error stack you wrote OUT_CATETORY (extra 'T')—make sure your DMN output column name matches exactly what you use in your expressions. A typo here will cause variables to be null.

内容的提问来源于stack exchange，提问作者Espresso