更新统计模块

seecoder-bok-server/src/main/java/cn/seecoder/seecoderbokserver/domain/Statistic.java

@@ -29,6 +29,15 @@ public class Statistic {
     @Column(name = "correct_frequency", nullable = false, columnDefinition = "int default 0")
     private Integer correctFrequency;
 
+    public Statistic() {
+    }
+
+    public Statistic(String questionId, Integer frequency, Integer correctFrequency) {
+        this.questionId = questionId;
+        this.frequency = frequency;
+        this.correctFrequency = correctFrequency;
+    }
+
     public String getQuestionId() {
         return questionId;
     }

seecoder-bok-server/src/main/java/cn/seecoder/seecoderbokserver/service/StatisticService.java

@@ -7,6 +7,8 @@ import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
 import java.util.Optional;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
 
 @Service
 public class StatisticService {
@@ -17,6 +19,9 @@ public class StatisticService {
         this.statisticRepository = statisticRepository;
     }
 
+    // 可重入锁，用于保证并发更新作答统计时的正确性
+    private final Lock lock = new ReentrantLock();
+
     /**
      * 获取题目作答统计
      */
@@ -39,7 +44,8 @@ public class StatisticService {
         if (frequency < correctFrequency) {
             throw new MyServiceException("400", "frequency should be no less than to correctFrequency");
         }
-        // todo: 这里要加行锁
+        // 这里要加锁，因为先查询再更新的操作不是原子的
+        lock.lock();
         Optional<Statistic> optional = statisticRepository.findById(questionId);
         Statistic s;
         if (optional.isPresent()) {
@@ -47,12 +53,10 @@ public class StatisticService {
             s.setFrequency(s.getFrequency() + frequency);
             s.setCorrectFrequency(s.getCorrectFrequency() + correctFrequency);
         } else {
-            s = new Statistic();
-            s.setQuestionId(questionId);
-            s.setFrequency(frequency);
-            s.setCorrectFrequency(correctFrequency);
+            s = new Statistic(questionId, frequency, correctFrequency);
         }
         statisticRepository.save(s);
+        lock.unlock();
     }
 
 }