JPA(Java Persistence API)學習五（實體和表CRUD功能）
阿新 • • 發佈：2020-09-08
1.示例(查詢)--要找到一個實體，EntityManger介面提供了find()方法，該方法根據主鍵搜尋一個元素。
EntityManagerFactory emf = Persistence.createEntityManagerFactory("Student_details");
EntityManager em = emf.createEntityManager(); //預設是主鍵查詢 StudentEntity s = em.find(StudentEntity.class, 1001); System.out.println("Student id = " + s.getS_id());System.out.println("Student Name = " + s.getS_name());
System.out.println("Student Age = " + s.getS_age());
2.示例(更新)
EntityManagerFactory emf = Persistence.createEntityManagerFactory("Student_details");
System.out.println("Student id = " + s.getS_id());
System.out.println("Student Name = " + s.getS_name());
System.out.println("Student Age = " + s.getS_age()); s.setS_age(30);//重點，這裡執行完之後資料庫相應的也做了跟新 System.out.println("After Updation");
System.out.println("Student id = " + s.getS_id());
System.out.println("Student Age = " + s.getS_age());