后端整合模块

src/main/java/com/example/demo/mapper/UserMapper.java

@@ -11,7 +11,12 @@ import java.util.List;
 @Mapper
 public interface UserMapper {
     @Select({
-            "select jwcode from user where jwcode=#{jwcode}"
+            "<script>",
+            "select jwcode from user",
+            "<where>",
+            "<if test='jwcode!=null and jwcode.length>0'>and jwcode=#{jwcode}</if>",
+            "</where>",
+            "</script>"
     })
     List<String> selectJwcode();
     @Select({