JPA是什麼? JPA(Java Persistence API)是Sun官方提出的Java持久化規範. 為Java開發人員提供了一種物件/關聯對映工具來管理Java應用中的關係資料. 它的出現是為了簡化現有的持久化開發工作和整合ORM技術. 結束各個ORM框架各自為營的局面.
JPA 其實是一種規範，它的實現中比較出名的是 Hibernate 框架；

1、pom 引入依賴：

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

    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <scope>runtime</scope>
      <version>5.1.18</version>
    </dependency>
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>druid-spring-boot-starter</artifactId>
      <version>1.1.10</version>
    </dependency>

2、新增配置檔案

#資料庫連線資訊
spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.username=root
spring.datasource.password=521hui
spring.datasource.url=jdbc:mysql://localhost:3306/test
#JPA設定
spring.jpa.show-sql=true
spring.jpa.database=mysql
spring.jpa.database-platform=mysql
spring.jpa.hibernate.ddl-auto=update

spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL57Dialect

3、編寫 bean

@Entity(name = "t_book")
public class Book {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Integer id;
  private String name;
  private String author;

  public Integer getId() {
    return id;
  }

  public void setId(Integer id) {
    this.id = id;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public String getAuthor() {
    return author;
  }

  public void setAuthor(String author) {
    this.author = author;
  }

  @Override
  public String toString() {
    return "Book{" +
        "id=" + id +
        ",name='" + name + '\'' +
        ",author='" + author + '\'' +
        '}';
  }
}

4、編寫 介面

public interface BookDao extends JpaRepository<Book,Integer> {
}

5、啟動程式，資料庫建立表

6、進行 CRUD 測試

@Autowired
  BookDao bookDao;
  @Test
  void testInsert() {
    Book book = new Book();
    book.setName("孔雀翎");
    book.setAuthor("古龍");

    bookDao.save(book);
  }
  @Test
  void testupdate() {
    Book book = new Book();
    book.setName("笑傲江湖");
    book.setAuthor("金庸");
    book.setId(1);
    bookDao.saveAndFlush(book);
  }
  @Test
  void testdelete() {
    bookDao.deleteById(1);
  }

  @Test
  void testFind() {
    System.out.println(bookDao.findById(4).toString());
  }

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