原創部落格地址：https://blog.csdn.net/cheidou123/article/details/84428092

JPA 基礎(一)

JPA全稱Java Persistence API，是一組用於將資料存入資料庫的類和方法的集合。

一、JPA的基本配置

1 jpa配置

<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
 

</dependency>
<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

  


   
2 建立dto物件

   
package com.example.demo.dto;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
 

import javax.persistence.GenerationType;
import javax.persistence.Id;
@Entity
public class Customer {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Long id;
    private String firstName;
    private String lastName;
    protected Customer() {}
    public Customer(String firstName,
 
 String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }
    @Override
    public String toString() {
        return String.format(
                "Customer[id=%d, firstName='%s', lastName='%s']",
                id, firstName, lastName);
    }
}

    


     
3 建立操作資料的Repository物件

     
package com.example.demo.repositories;
import com.example.demo.dto.Customer;
import org.springframework.data.jpa.repository.JpaRepository;
public interface CustomerRepository extends JpaRepository<Customer, Long>; {
}

      


       
二、JpaRepository

       
JpaRepository

       
PagingAndSortingRepository

       
CrudRepository

       
QueryByExampleExecutor

       
三、自定義的方法

       
1.一些基本的自定義方法樣例

       






       
2.舉個例子

       
在CustomerRepository介面中，有如下定義

       
/**
 * 根據lastName查詢結果
 * @param lastName
 * @return
 */
List<Customer> findByLastName(String lastName);