feat(printer): 实现任务状态的原子性更新与同步锁机制

- 添加 compareAndSetTaskStatus 方法以支持基于期望状态的任务更新
- 引入 ReentrantLock 实现任务同步处理，防止并发冲突
- 在 XML 映射文件中定义 compareAndSetTaskStatus 的 SQL 更新语句
- 定义任务状态常量：TASK_STATUS_PENDING 和 TASK_STATUS_PROCESSING
- 优化任务获取逻辑，确保任务状态在处理前正确更新为 PROCESSING

src/main/java/com/ycwl/basic/mapper/PrinterMapper.java

@@ -28,6 +28,10 @@ public interface PrinterMapper {
 
     int updateTaskStatus(@Param("id") Integer id, @Param("status") Integer status);
 
+    int compareAndSetTaskStatus(@Param("id") Integer id,
+                                @Param("expectStatus") Integer expectStatus,
+                                @Param("newStatus") Integer newStatus);
+
     PrintTaskEntity getTaskById(Integer id);
 
     List<PrinterResp> listByScenicId(@Param("scenicId") Long scenicId);
@@ -51,4 +55,4 @@ public interface PrinterMapper {
     void updateUserPhotoListToPrinter(Long memberId, Long scenicId, Integer printerId);
 
     List<MemberPrintResp> listRelationByOrderId(Long orderId);
-}
+}

src/main/java/com/ycwl/basic/service/printer/impl/PrinterServiceImpl.java

@@ -69,6 +69,8 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.UUID;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
 import java.util.stream.Collectors;
 
 @Slf4j
@@ -151,11 +153,26 @@ public class PrinterServiceImpl implements PrinterService {
             printer.setPrinters(printersStr);
             printerMapper.update(printer);
         }
-        PrintTaskResp task = printerMapper.findTaskByPrinterId(printer.getId());
+        syncTaskLock.lock();
-        if (task == null) {
+        try {
-            return Collections.emptyList();
+            while (true) {
+                PrintTaskResp task = printerMapper.findTaskByPrinterId(printer.getId());
+                if (task == null) {
+                    return Collections.emptyList();
+                }
+                int updatedRows = printerMapper.compareAndSetTaskStatus(
+                        task.getId(),
+                        TASK_STATUS_PENDING,
+                        TASK_STATUS_PROCESSING
+                );
+                if (updatedRows == 1) {
+                    task.setStatus(TASK_STATUS_PROCESSING);
+                    return Collections.singletonList(task);
+                }
+            }
+        } finally {
+            syncTaskLock.unlock();
         }
-        return Collections.singletonList(task);
     }
 
     @Override
@@ -427,6 +444,9 @@ public class PrinterServiceImpl implements PrinterService {
     @Autowired
     private RedisTemplate<String, String> redisTemplate;
     private static final String USER_PHOTO_LIST_TO_PRINTER = "USER_PHOTO_LIST_TO_PRINTER:";
+    private static final int TASK_STATUS_PENDING = 0;
+    private static final int TASK_STATUS_PROCESSING = 3;
+    private final Lock syncTaskLock = new ReentrantLock();
 
     @Override
     public void setUserIsBuyItem(Long memberId, Long id, Long orderId) {
@@ -550,4 +570,4 @@ public class PrinterServiceImpl implements PrinterService {
             printTaskMapper.insertTask(task);
         });
     }
-}
+}

src/main/resources/mapper/PrinterMapper.xml

@@ -152,6 +152,11 @@
     <update id="updateTaskStatus">
         UPDATE print_task SET status = #{status}, update_time = NOW() WHERE id = #{id}
     </update>
+    <update id="compareAndSetTaskStatus">
+        UPDATE print_task
+        SET status = #{newStatus}, update_time = NOW()
+        WHERE id = #{id} AND status = #{expectStatus}
+    </update>
     <update id="setPhotoCropped">
         UPDATE member_print SET crop_url = #{url}, update_time = NOW(), print_url = null WHERE id = #{id}
     </update>
@@ -172,4 +177,4 @@
     <delete id="deleteUserPhoto">
         DELETE FROM member_print WHERE member_id = #{memberId} AND scenic_id = #{scenicId} AND id = #{relationId} LIMIT 1;
     </delete>
-</mapper>
+</mapper>