最修正です

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

@@ -15,6 +15,7 @@ import lombok.AllArgsConstructor;
 import lombok.Data;
 import lombok.NoArgsConstructor;
  
+//テーブル名
 @Table(name = "book_collection")
 @Entity
 @Data
@@ -49,9 +50,9 @@ public class Book_collectionEntity {
 	@Column(name = "note text", nullable = true)
     private String noteText;
 	
-	//貸出フラグ
+	//貸出フラグ   -> charに変更する
-	@Column(name = "flg_lending", length = 1, nullable = false)
+	@Column(name = "flg_lending", nullable = false, columnDefinition = "default 0")
-    private String flgLending;
+    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