refactor(flow): 重构流程候选用户名解析逻辑

- 提取候选用户名解析为独立方法 getCandidateUsernamesByExecution
- 添加对 EL 表达式的完整支持，包括 ${projectBean.getCommonReportManager(execution)} 形式
- 简化 AutoSkipTaskListener 中的用户名获取逻辑
- 统一多实例分配监听器中的候选用户处理方式
- 移除重复的字符串分割和变量获取代码
- 增强表达式求值的安全性，添加执行上下文验证

common/common-flow/src/main/java/apelet/common/flow/listener/AutoSkipTaskListener.java

@@ -135,16 +135,7 @@ public class AutoSkipTaskListener implements TaskListener {
         } else {
             FlowTaskExt flowTaskExt = flowTaskExtService
                     .getByProcessDefinitionIdAndTaskId(t.getProcessDefinitionId(), userTask.getId());
-            List<String> candidateUsernames;
-            if (StrUtil.isBlank(flowTaskExt.getCandidateUsernames())) {
-                candidateUsernames = Collections.emptyList();
-            } else if (!StrUtil.equals(flowTaskExt.getCandidateUsernames(), "${" + FlowConstant.TASK_APPOINTED_ASSIGNEE_VAR + "}")) {
-                candidateUsernames = StrUtil.split(flowTaskExt.getCandidateUsernames(), ",");
-            } else {
-                String value = flowApiService
-                        .getExecutionVariableStringWithSafe(t.getExecutionId(), FlowConstant.TASK_APPOINTED_ASSIGNEE_VAR);
-                candidateUsernames = value == null ? null : StrUtil.split(value, ",");
-            }
+            List<String> candidateUsernames = flowApiService.getCandidateUsernamesByExecution(flowTaskExt, t.getExecutionId());
             if (candidateUsernames != null && candidateUsernames.size() == 1) {
                 assignedUser = candidateUsernames.get(0);
             }

common/common-flow/src/main/java/apelet/common/flow/listener/MultiInstanceAssigneeListener.java

@@ -2,6 +2,7 @@ package apelet.common.flow.listener;
 
 import apelet.common.core.util.ApplicationContextHolder;
 import apelet.common.flow.model.FlowTaskExt;
+import apelet.common.flow.service.FlowApiService;
 import apelet.common.flow.service.FlowTaskExtService;
 import apelet.common.flow.util.BaseFlowIdentityExtHelper;
 import apelet.common.flow.util.FlowCustomExtFactory;
@@ -30,6 +31,8 @@ public class MultiInstanceAssigneeListener implements ExecutionListener {
 
     private final transient FlowCustomExtFactory flowCustomExtFactory = ApplicationContextHolder.getBean(FlowCustomExtFactory.class);
 
+    private final transient FlowApiService flowApiService = ApplicationContextHolder.getBean(FlowApiService.class);
+
 
     @Override
     public void notify(DelegateExecution execution) {
@@ -44,7 +47,10 @@ public class MultiInstanceAssigneeListener implements ExecutionListener {
         }
         List<String> candidateUsernames = new ArrayList<>();
         if (StrUtil.isNotBlank(flowTaskExt.getCandidateUsernames())) {
-            candidateUsernames.addAll(StrUtil.split(flowTaskExt.getCandidateUsernames(), ","));
+            List<String> configuredUsernames = flowApiService.getCandidateUsernamesByExecution(flowTaskExt, execution.getId());
+            if (CollUtil.isNotEmpty(configuredUsernames)) {
+                candidateUsernames.addAll(configuredUsernames);
+            }
         } else {
             BaseFlowIdentityExtHelper extHelper = flowCustomExtFactory.getFlowIdentityExtHelper();
             if (extHelper == null) {

common/common-flow/src/main/java/apelet/common/flow/service/FlowApiService.java

@@ -570,6 +570,16 @@ public interface FlowApiService {
     List<String> getCandidateUsernames(FlowTaskExt flowTaskExt, String taskId);
 
     /**
+     * 根据执行实例Id，获取当前任务在流程图中配置候选用户组数据。
+     * 配置值支持逗号分隔的登录名，以及${appointedAssignee}、${projectBean.getCommonReportManager(execution)}形式的EL表达式。
+     *
+     * @param flowTaskExt 流程任务扩展对象。
+     * @param executionId 执行实例Id。
+     * @return 候选用户组数据。
+     */
+    List<String> getCandidateUsernamesByExecution(FlowTaskExt flowTaskExt, String executionId);
+
+    /**
      * 获取当前任务在流程图中配置到的部门岗位Id集合和岗位Id集合。
      *
      * @param flowTaskExt       流程任务扩展对象。

common/common-flow/src/main/java/apelet/common/flow/service/impl/FlowApiServiceImpl.java

@@ -41,6 +41,7 @@ import lombok.extern.slf4j.Slf4j;
 import org.flowable.bpmn.converter.BpmnXMLConverter;
 import org.flowable.bpmn.model.*;
 import org.flowable.bpmn.model.Process;
+import org.flowable.common.engine.api.delegate.Expression;
 import org.flowable.common.engine.impl.de.odysseus.el.ExpressionFactoryImpl;
 import org.flowable.common.engine.impl.de.odysseus.el.util.SimpleContext;
 import org.flowable.common.engine.impl.identity.Authentication;
@@ -52,7 +53,10 @@ import org.flowable.engine.delegate.TaskListener;
 import org.flowable.engine.history.HistoricActivityInstance;
 import org.flowable.engine.history.HistoricProcessInstance;
 import org.flowable.engine.history.HistoricProcessInstanceQuery;
+import org.flowable.engine.impl.cfg.ProcessEngineConfigurationImpl;
+import org.flowable.engine.impl.persistence.entity.ExecutionEntity;
 import org.flowable.engine.impl.persistence.entity.ExecutionEntityImpl;
+import org.flowable.engine.impl.util.CommandContextUtil;
 import org.flowable.engine.repository.ProcessDefinition;
 import org.flowable.engine.runtime.ChangeActivityStateBuilder;
 import org.flowable.engine.runtime.Execution;
@@ -1526,14 +1530,78 @@ public class FlowApiServiceImpl implements FlowApiService {
 
     @Override
     public List<String> getCandidateUsernames(FlowTaskExt flowTaskExt, String taskId) {
-        if (StrUtil.isBlank(flowTaskExt.getCandidateUsernames())) {
+        String configured = flowTaskExt.getCandidateUsernames();
+        if (StrUtil.isBlank(configured)) {
             return Collections.emptyList();
         }
-        if (!StrUtil.equals(flowTaskExt.getCandidateUsernames(), "${" + FlowConstant.TASK_APPOINTED_ASSIGNEE_VAR + "}")) {
-            return StrUtil.split(flowTaskExt.getCandidateUsernames(), ",");
+        if (StrUtil.equals(configured, "${" + FlowConstant.TASK_APPOINTED_ASSIGNEE_VAR + "}")) {
+            String value = getTaskVariableStringWithSafe(taskId, FlowConstant.TASK_APPOINTED_ASSIGNEE_VAR);
+            return value == null ? null : StrUtil.splitTrim(value, ",");
         }
-        Object candidateUsernames = getTaskVariableStringWithSafe(taskId, FlowConstant.TASK_APPOINTED_ASSIGNEE_VAR);
-        return candidateUsernames == null ? null : StrUtil.split(candidateUsernames.toString(), ",");
+        if (!configured.startsWith("${")) {
+            return StrUtil.splitTrim(configured, ",");
+        }
+        Task task = this.getTaskById(taskId);
+        return task == null ? Collections.emptyList() : this.getCandidateUsernamesByExecution(flowTaskExt, task.getExecutionId());
+    }
+
+    @Override
+    public List<String> getCandidateUsernamesByExecution(FlowTaskExt flowTaskExt, String executionId) {
+        String configured = flowTaskExt.getCandidateUsernames();
+        if (StrUtil.isBlank(configured)) {
+            return Collections.emptyList();
+        }
+        if (StrUtil.equals(configured, "${" + FlowConstant.TASK_APPOINTED_ASSIGNEE_VAR + "}")) {
+            String value = getExecutionVariableStringWithSafe(executionId, FlowConstant.TASK_APPOINTED_ASSIGNEE_VAR);
+            return value == null ? null : StrUtil.splitTrim(value, ",");
+        }
+        if (!configured.startsWith("${")) {
+            return StrUtil.splitTrim(configured, ",");
+        }
+        // 形如${projectBean.getCommonReportManager(execution)}的EL表达式，交给引擎的表达式管理器求值。
+        return this.parseCandidateUsernames(this.getExpressionValue(configured, executionId));
+    }
+
+    private List<String> parseCandidateUsernames(Object value) {
+        if (value == null) {
+            return Collections.emptyList();
+        }
+        if (value instanceof Collection) {
+            List<String> candidateUsernames = new LinkedList<>();
+            for (Object element : (Collection<?>) value) {
+                if (element != null && StrUtil.isNotBlank(element.toString())) {
+                    candidateUsernames.add(element.toString());
+                }
+            }
+            return candidateUsernames;
+        }
+        if (StrUtil.isBlank(value.toString())) {
+            return Collections.emptyList();
+        }
+        return StrUtil.splitTrim(value.toString(), ",");
+    }
+
+    private Object getExpressionValue(String expressionStr, String executionId) {
+        ProcessEngineConfigurationImpl engineConfiguration = CommandContextUtil.getProcessEngineConfiguration();
+        if (engineConfiguration != null) {
+            return this.evaluateExpression(engineConfiguration, expressionStr, executionId);
+        }
+        // 待办详情等HTTP接口场景没有活动的命令上下文，交由引擎开启一次后再求值，保证execution关键字可正常绑定。
+        return managementService.executeCommand(commandContext -> this.evaluateExpression(
+                CommandContextUtil.getProcessEngineConfiguration(commandContext), expressionStr, executionId));
+    }
+
+    private Object evaluateExpression(
+            ProcessEngineConfigurationImpl engineConfiguration, String expressionStr, String executionId) {
+        ExecutionEntity execution = CommandContextUtil.getExecutionEntityManager().findById(executionId);
+        if (execution == null) {
+            log.error("Failed to getExpressionValue expression [{}], executionId [{}], execution not found.",
+                    expressionStr, executionId);
+            return null;
+        }
+        // 与引擎UserTaskActivityBehavior.handleAssignments的求值方式保持一致，execution关键字可正常绑定到当前执行流对象。
+        Expression expression = engineConfiguration.getExpressionManager().createExpression(expressionStr);
+        return expression.getValue(execution);
     }
 
     @Override

common/common-flow/src/main/java/apelet/common/flow/service/impl/FlowTaskExtServiceImpl.java

@@ -219,17 +219,7 @@ public class FlowTaskExtServiceImpl extends BaseService<FlowTaskExt, String> imp
             default:
                 break;
         }
-        List<String> candidateUsernames;
-        if (StrUtil.isBlank(flowTaskExt.getCandidateUsernames())) {
-            candidateUsernames = Collections.emptyList();
-        } else {
-            if (!StrUtil.equals(flowTaskExt.getCandidateUsernames(), " + FlowConstant.TASK_APPOINTED_ASSIGNEE_VAR + ")) {
-                candidateUsernames = StrUtil.split(flowTaskExt.getCandidateUsernames(), ",");
-            } else {
-                Object v = flowApiService.getExecutionVariableStringWithSafe(executionId, FlowConstant.TASK_APPOINTED_ASSIGNEE_VAR);
-                candidateUsernames = v == null ? null : StrUtil.split(v.toString(), ",");
-            }
-        }
+        List<String> candidateUsernames = flowApiService.getCandidateUsernamesByExecution(flowTaskExt, executionId);
         if (CollUtil.isNotEmpty(candidateUsernames)) {
             usernameSet.addAll(candidateUsernames);
         }