springboot整合jpa（书籍）

pom文件（启动时报错无效的源发型版本：11，将 <java.version>11</java.version>改为 <java.version>8</java.version>）

 <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.0.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>springboot-jpa</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>springboot-jpa</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>8</java.version>
    </properties>

    <dependencies>
        <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>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

application.yml

spring:
  datasource:
    url:  jdbc:mysql://localhost:3306/binzi?useUnicode=true&characterEncoding=utf8&characterSetResults=utf8&serverTimezone=GMT%2B8
    driver-class-name: com.mysql.cj.jdbc.Driver
    hikari:  # springboot 2.0 整合了hikari ,据说这是目前性能最好的java数据库连接池
      username: root
      password: root
  jpa:
    hibernate:
      ddl-auto: create # 第一次建表create  后面用update，要不然每次重启都会新建表
    show-sql: true

User类

@Entity(name = "tb_user") //表名
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)//主键由数据库自动生成（主要是自动增长型）
    private Long id;
    @Column(nullable =false,unique = true,length = 20)
    private String username;
    @Column(length = 100)
    private String password;

    public Long getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

UserDao类

public interface UserDao extends JpaRepository<User,Long> {
   User findByUsername(String username);
}

UserServiceImpl类（接口就不粘贴了）

@Service
public class UserServiceImpl implements UserService {
    @Autowired
    private UserDao userDao;

    @Override
    public User findUserByUsername(String username) {
        return userDao.findByUsername(username);
    }
}

UserController类

@RestController
@RequestMapping("/user")
public class UserController {
    @Autowired
    private UserService userService;
    @GetMapping("/username/{username}")
    public User findUserByUsername(@PathVariable String username){
        return userService.findUserByUsername(username);

    }
}

启动程序，会自动创建tb_user的表，给表添加数据，

访问http://localhost:8080/user/username/123