fix default_difficulty_degree

examcloud-core-questions-base/src/main/java/cn/com/qmth/examcloud/core/questions/base/Constants.java

@@ -25,4 +25,9 @@ public interface Constants {
      */
     String SYS_CODE_400 = "000400";
 
+    /**
+     * 默认难度系数
+     */
+    double DEFAULT_DIFFICULTY_DEGREE = 0.5;
+
 }

examcloud-core-questions-dao/src/main/java/cn/com/qmth/examcloud/core/questions/dao/entity/Question.java

@@ -4,6 +4,7 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 
+import cn.com.qmth.examcloud.core.questions.base.Constants;
 import org.springframework.data.annotation.Transient;
 
 import cn.com.qmth.examcloud.core.questions.base.question.enums.QuesStructType;
@@ -386,6 +387,9 @@ public class Question extends MongoBaseEntity {
 	}
 
 	public Double getDifficultyDegree() {
+		if(difficultyDegree == null){
+			difficultyDegree = Constants.DEFAULT_DIFFICULTY_DEGREE;
+		}
 		return difficultyDegree;
 	}