Some abnormal error reports and precautions of flowable (1)

Question 1 ：

java.util.LinkedHashMap cannot be cast to org.flowable.form.api.FormModel

When getting the form information of the input parameter , Code ：

FormInfo formInfo = (FormInfo)taskPo.getFormInfo();
Report errors ：
java.util.LinkedHashMap cannot be cast to org.flowable.form.api.FormModel
resolvent ： 
String postr=JSONObject.toJSONString(taskPo.getFormInfo());
FormInfo formInfo= JSONObject.parseObject(postr,FormInfo.class);

Question two ：

org.flowable.form.engine.FlowableFormValidationException: Form field description is required, but no value was found

flowable The form data submitted by the task node is verified , For mandatory fields, there will be mandatory verification . In source GetVariablesFromFormSubmissionCmd  There will be required verification in the required fields , Reflected in the following places ：

public Map<String, Object> execute(CommandContext commandContext) {
        if (this.values == null) {
            this.values = Collections.emptyMap();
        }

        SimpleFormModel formModel = (SimpleFormModel)this.formInfo.getFormModel();
        Map<String, FormField> fieldMap = formModel.allFieldsAsMap();
        Map<String, Object> variables = new HashMap();
        Iterator targetVariable = fieldMap.keySet().iterator();

        while(targetVariable.hasNext()) {
            String fieldId = (String)targetVariable.next();
            Object variableValue = null;
            FormField formField = (FormField)fieldMap.get(fieldId);
            if (!"expression".equals(formField.getType()) && !"container".equals(formField.getType())) {
                if (this.values.containsKey(fieldId)) {
                    variableValue = this.transformFormFieldValueToVariableValue(formField, this.values.get(fieldId));
                    variables.put(formField.getId(), variableValue);
                }

                if (formField.isRequired() && variableValue == null && !"upload".equals(formField.getType())) {
                    throw new FlowableFormValidationException("Form field " + formField.getId() + " is required, but no value was found");
                }
            }
        }

        if (this.outcome != null) {
            targetVariable = null;
            String targetVariable;
            if (formModel.getOutcomeVariableName() != null) {
                targetVariable = formModel.getOutcomeVariableName();
            } else {
                targetVariable = "form_" + formModel.getKey() + "_outcome";
            }

            variables.put(targetVariable, this.outcome);
        }

        return variables;
    }

So when submitting nodes with external forms , The required fields in the form and their corresponding values , Required

Question 3 ：

org.flowable.common.engine.api.FlowableIllegalArgumentException: Delegate expression taskCompleteListener did not resolve to an implementation of interface org.flowable.task.service.delegate.TaskListener

In process design , The proxy expression method is used when setting the task listener ,,delegateExpression It has been written. "taskCompleteListener" , Process save 、 The deployment did not report an error , There is no error when starting the process instance , An error is reported when submitting the first task node . The correct way is as follows ：

delegateExpression="${ taskCompleteListener}" 

<userTask id="test" name=" test " flowable:assignee="${applyUserId}" flowable:formKey="testForm">
     <extensionElements>
         <flowable:taskListener event="complete" delegateExpression="${taskCompleteListener }"></flowable:taskListener> 
     </extensionElements>
</userTask>