SpringBoot-快速搭建一套JPA

Bertha 。 2023-10-03 22:23 6阅读 0赞

#### 文章目录 ####

*   *  结构
     *  Maven
     *  application.yml
     *  实体类
     *  dao
     *  service
     *  controller
     *  测试

### 结构 ###

![在这里插入图片描述][1e09c34d95944681972ea2d217b660de.png]

### Maven ###

<parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>2.7.6</version>
      <relativePath/> 
     </parent>
    
     <groupId>com.example</groupId>
     <artifactId>springboot-jpa</artifactId>
     <version>0.0.1-SNAPSHOT</version>
     <name>springboot-jpa</name>
     <description>springboot-jpa</description>
    
     <properties>
      <java.version>1.8</java.version>
      
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
      
      <maven.compiler.encoding>UTF-8</maven.compiler.encoding>
     </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>com.mysql</groupId>
       <artifactId>mysql-connector-j</artifactId>
       <scope>runtime</scope>
      </dependency>
      <dependency>
       <groupId>com.alibaba</groupId>
       <artifactId>druid</artifactId>
       <version>1.2.15</version>
      </dependency>
    
      <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-configuration-processor</artifactId>
       <optional>true</optional>
      </dependency>
      <dependency>
       <groupId>org.projectlombok</groupId>
       <artifactId>lombok</artifactId>
       <optional>true</optional>
      </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>
        <configuration>
         <excludes>
          <exclude>
           <groupId>org.projectlombok</groupId>
           <artifactId>lombok</artifactId>
          </exclude>
         </excludes>
        </configuration>
       </plugin>
      </plugins>
     </build>

使用IDEA的可以安装下面的插件这样在使用JPA进行编码的时候非常舒服,各种提示  
![在这里插入图片描述][05e9125b94f74a548a984f51003dadd4.png]

### application.yml ###

server:
      port: 9878
    
    spring:
      datasource:
        driver-class-name: com.mysql.cj.jdbc.Driver #驱动
        url: jdbc:mysql://localhost:3306/demo?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8&useSSL=true
        type: com.alibaba.druid.pool.DruidDataSource
        username: root
        password: root
      jpa:
        hibernate:
          ddl-auto: update #自动更新  ,每次运行程序，没有表格会新建表格，表内有数据不会清空，只会更新
        show-sql: true  #日志中显示sql语句   ,生产环境不要开启
        properties:
          hibernate:
            enable_lazy_load_no_trans: true #懒加载

### 实体类 ###

注意: 实体类中的字段类型 必须是包装类型,否则会导致查询出现默认值的现象

package com.example.springbootjpa.entity;
    
    
    import lombok.*;
    import org.hibernate.Hibernate;
    
    import javax.persistence.*;
    import java.util.Date;
    import java.util.Objects;
    
    @Getter
    @Setter
    @ToString
    @RequiredArgsConstructor
    @Entity // 标识这是一个实体类，并且使用默认的orm规则，即class名即数据库表中表名，class字段名即表中的字段名
    @Table(name = "t_user") //来改变class名与数据库中表名的映射规则
    public class UserEntity {
        
        @Id
        // GenerationType.IDENTITY使用数据库的自增
        // 如果是oracle则需要使用GenerationType.SEQUENCE配合@SequenceGenerator
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        @Column(name = "id", nullable = false)
        private Long id;
        @Column
        private String name;
        @Column
        private String email;
        @Column
        private  String phone;
        @Column
        private String password;
        @Column
        private  Integer age;
        @Column
        private  Integer sex;
        @Column
        private Integer status;
    
        @Temporal(TemporalType.TIMESTAMP)
        @Column
        private Date creationTime;
        @Column
        private  String site;
    
        @Override
        public boolean equals(Object o) {
        
            if (this == o) return true;
            if (o == null || Hibernate.getClass(this) != Hibernate.getClass(o)) return false;
            UserEntity that = (UserEntity) o;
            return id != null && Objects.equals(id, that.id);
        }
    
        @Override
        public int hashCode() {
        
            return getClass().hashCode();
        }
    }

一般来说,我们都是先设计数据库然后在设计实体类, 如果你是使用的是jpa就可以先设计实体类,而对应的表在启动项目的时候就会自动创建了

### dao ###

public interface UserDao extends JpaRepository<UserEntity, Long> {
        
    }

一般来说继承JpaRepository即可 ,内部包括常规的增删改查

### service ###

package com.example.springbootjpa.service;
    
    import com.example.springbootjpa.entity.UserEntity;
    
    import java.util.List;
    
    public interface UserService {
        
    
        //查询全部用户
        List<UserEntity> findAll();
    
    
    }
    
    
    
    package com.example.springbootjpa.service.impl;
    
    import com.example.springbootjpa.dao.UserDao;
    import com.example.springbootjpa.entity.UserEntity;
    import com.example.springbootjpa.service.UserService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    
    import java.util.List;
    
    @Service
    public class UserServiceImpl  implements UserService {
        
        @Autowired
        private UserDao userDao;
    
    
        @Override
        public List<UserEntity> findAll() {
        
            return userDao.findAll();
        }
    }

### controller ###

package com.example.springbootjpa.controller;
    
    import com.example.springbootjpa.entity.UserEntity;
    import com.example.springbootjpa.service.UserService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.http.ResponseEntity;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    import java.util.List;
    
    @RestController
    @RequestMapping("/user")
    public class UserController {
        
        @Autowired
        private UserService userService;
    
        @RequestMapping("/findAll")
        public ResponseEntity<List<UserEntity>> findAll(){
        
            return  ResponseEntity.ok(userService.findAll());
        }
    }

### 测试 ###

package com.example.springbootjpa;
    
    import com.example.springbootjpa.controller.UserController;
    import com.example.springbootjpa.dao.UserDao;
    import com.example.springbootjpa.entity.UserEntity;
    import org.junit.jupiter.api.Test;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.test.context.SpringBootTest;
    import org.springframework.http.ResponseEntity;
    
    import java.util.List;
    
    @SpringBootTest
    class SpringbootJpaApplicationTests {
        
     @Autowired
     private UserController userController;
     @Test
     void contextLoads() {
        
      ResponseEntity<List<UserEntity>> all = userController.findAll();
      List<UserEntity> body = all.getBody();
      System.out.println(body);
     }
    
    }

![在这里插入图片描述][241d60d901ab468c8532f2a2d4413093.gif]

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[1e09c34d95944681972ea2d217b660de.png]: https://img-blog.csdnimg.cn/1e09c34d95944681972ea2d217b660de.png
[05e9125b94f74a548a984f51003dadd4.png]: https://img-blog.csdnimg.cn/05e9125b94f74a548a984f51003dadd4.png
[241d60d901ab468c8532f2a2d4413093.gif]: https://img-blog.csdnimg.cn/241d60d901ab468c8532f2a2d4413093.gif