SpringBoot之使用jpa/hibernate

水深无声 2022-01-13 23:03 239阅读 0赞

[2019独角兽企业重金招聘Python工程师标准>>> ][2019_Python_] ![hot3.png][]

Springboot版本是2.1.3.RELEASE

## １、依赖 ##

*List-1.1*

<dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-jdbc</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.47</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>1.18.2</version>
    </dependency>

## ２、项目整体结构 ##

![39db6ed24ec0ae6afe83f5bd413f3f72370.jpg][]

图2.1

bootstrap.yml内容如下，我们不需要手动创建数据库表，jpa/hiberate会自动会为我们创建的

server:
      port: 9092
      servlet:
        context-path: /serviceB
    
    spring:
      application:
        name: cat-service-b
      datasource:
        type: com.zaxxer.hikari.HikariDataSource
        driver-class-name: com.mysql.jdbc.Driver
        username: root
        password: ******
        url: jdbc:mysql://pig-mysql:3306/cat?characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=false&allowMultiQueries=true
        database: mysql
        hibernate:
          ddl-auto: update
          naming:
            physical-strategy: org.springframework.boot.orm.jpa.hibernate.SpringPhysicalNamingStrategy
        show-sql: true
        properties:
          hibernate:
            format_sql: true

physical-strategy的值为org.springframework.boot.orm.jpa.hibernate.SpringPhysicalNamingStrategy，那么当实体的属性为驼峰结构时，对应到数据库表的字段上，会用"\_"隔开。

## ３、代码详解 ##

*    List-3.1 *BaseEntity的内容，所有的实体都要继承这个类

import lombok.Data;
    import org.springframework.data.annotation.CreatedBy;
    import org.springframework.data.annotation.CreatedDate;
    import org.springframework.data.annotation.LastModifiedDate;
    
    import javax.persistence.GeneratedValue;
    import javax.persistence.GenerationType;
    import javax.persistence.Id;
    import javax.persistence.MappedSuperclass;
    import java.util.Date;
    
    @Data
    @MappedSuperclass
    public class BaseEntity {
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        protected Integer id;
        /** 创建人 */
        @CreatedBy
        protected String creator;
        /** 创建时间 */
        @CreatedDate
        protected Date createDate;
        /** 更新时间，默认是当前时间 */
        @LastModifiedDate
        protected Date updateDate = new Date();
        /** 状态 0 表示删除, 1表示可操作 */
        protected Integer status = 1;
    
        public BaseEntity() {
            if (null == this.id && null == this.createDate) {
                this.createDate = new Date();
            }
        }
    }

*List-3.2* User的内容

import lombok.Data;
    import lombok.ToString;
    import org.hibernate.annotations.SQLDelete;
    import org.hibernate.annotations.Where;
    
    import javax.persistence.Entity;
    import javax.persistence.Table;
    
    @Data
    @ToString
    
    @Entity
    @Table(name = "cat_user")
    @SQLDelete(sql = "update cat_user set status = 0 where id = ?")
    @Where(clause = "status <> 0")
    public class User extends BaseEntity{
        private String name;
        private Integer age;
    }

*List-3.3 *UserRepository的内容

import com.mjduan.project.catserviceb.entity.User;
    import org.springframework.data.repository.CrudRepository;
    
    public interface UserRepository extends CrudRepository<User, Integer> {
    
    }

*List-3.4* UserController的内容

import com.mjduan.project.catserviceb.entity.User;
    import com.mjduan.project.catserviceb.repository.UserRepository;
    import lombok.extern.slf4j.Slf4j;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RestController;
    
    import java.util.Optional;
    
    @Slf4j
    @RestController
    public class UserController {
        @Autowired
        private UserRepository userRepository;
    
        @GetMapping(value = "/queryUser/{id}")
        public User queryUser(@PathVariable(value = "id") Integer id) {
            log.info("查询用户,id={}", id);
            Optional<User> optionalUser = userRepository.findById(id);
            User user = optionalUser.isPresent() ? optionalUser.get() : null;
            log.info("返回，{}", user);
            return user;
        }
    
        @GetMapping(value = "/saveUser/{name}")
        public User saveUser(@PathVariable(value = "name") String name) {
            log.info("新增用户,name={}", name);
            User user = new User();
            user.setAge(20);
            user.setName(name);
            User save = userRepository.save(user);
            log.info("返回,{}", save);
            return save;
        }
    }

## ４、验证 ##

在浏览器地址栏中输入

*List-4.1*

#保存name为Tom的用户
    http://localhost:9092/serviceB/saveUser/Tom
    #查询Id为1的用户
    
    http://localhost:9092/serviceB/queryUser/1

一些思考：

1.  自动创建表结构，我们不需要手动去创建，我们修改实体的时候，系统会自动更新数据库中的表结构。
2.  所有实体都继承BaseEntity，那么每个实体对应的数据库表，在创建日期、更新日期等共有属性都同一了，这样在一定程度上便于代码理解和系统维护。

## ５、Reference ##

1.  Springboot配置mysql连接的部分配置参考：https://github.com/pristinecore/springbootsample/blob/master/springbootsample/src/main/resources/database.properties
2.  格式化SQL输出的参考：https://stackoverflow.com/questions/25720396/how-to-set-hibernate-format-sql-in-spring-boot

转载于:https://my.oschina.net/u/2518341/blog/3010931

[2019_Python_]: https://my.oschina.net/u/2663968/blog/3061697
[hot3.png]: /images/20220113/0a80145cdcf04133bca427698dc66dce.png
[39db6ed24ec0ae6afe83f5bd413f3f72370.jpg]: /images/20220113/99123ecfd53847c6a4a9dde3af3b50b8.png