修改docker配置文件

backend/src/main/resources/application.yml

@@ -7,9 +7,9 @@ spring:
 #数据库账号密码
   datasource:
     driver-class-name: org.postgresql.Driver
-    url: jdbc:postgresql://localhost:5432/StudyingSystem
-    username: postgres
-    password: 123456
+    url: ${SPRING_DATASOURCE_URL:jdbc:postgresql://localhost:5432/StudyingSystem}
+    username: ${SPRING_DATASOURCE_USERNAME:postgres}
+    password: ${SPRING_DATASOURCE_PASSWORD:123456}
 
   jpa:
     hibernate: