最修正です

team1/src/main/java/com/example/demo/entity/Book_collectionEntity.java

@@ -51,8 +51,8 @@ public class Book_collectionEntity {
     private String noteText;
 	
 	//貸出フラグ   -> charに変更する
-	@Column(name = "flg_lending", length = 1, nullable = false)
-    private String flgLending;
+	@Column(name = "flg_lending", nullable = false, columnDefinition = "default 0")
+    private Character flgLending;
 	
 	//更新者
 	@Column(name = "id_update", nullable = false)

team1/src/main/java/com/example/demo/entity/Borrow_booksEntity.java

@@ -54,7 +54,7 @@ public class Borrow_booksEntity {
 	 * ステータス
 	 * */
 	@Column(name = "status", nullable = false, columnDefinition = "default 1")
-	private char status;
+	private Character status;
 
 	/*
 	 * 承認者