添加查询书籍；BookDO映射文件更新；DOMapper添加@Repository注解；添加自定义业务异常处理；添加Validation验证

bookshelfplus/src/main/java/plus/bookshelf/Common/Enum/Language.java

@@ -1,15 +0,0 @@
-package plus.bookshelf.Common.Enum;
-
-public enum Language {
-    SIMPLIFIED_CHINESE(1000, "简体中文"),
-    ENGLISH(1001, "English"),
-    TRADITIONAL_CHINESE(1001, "繁体中文");
-
-    private Language(Integer langId, String langName) {
-        this.langId = langId;
-        this.langName = langName;
-    }
-
-    private Integer langId;
-    private String langName;
-}