HIbernate逐渐入门01-jpa

逃离我推掉我的手 2023-01-01 15:58 12阅读 0赞

接手了一个数据表比较多的项目，打算从原来的Mybatis转到hibernate，今日从jpa开始一步步探索  
1.首先是包引入

<dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-data-jpa</artifactId>
         <version>2.1.0.RELEASE</version>
    </dependency>

2.配置文件，主要是两部分，一部分是数据库的链接还有一部分是hibernate的配置，数据库就不贴了，到处都有

#----------------------JPA------------------------------
    spring.jpa.database = MYSQL
    spring.jpa.show-sql = true
    # (create, create-drop, update)
    spring.jpa.hibernate.ddl-auto = create
    spring.jpa.hibernate.naming-strategy = org.hibernate.cfg.DefaultNamingStrategy
    spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5Dialect

3.创建一个实体

package com.Entity;
    import lombok.Data;
    import javax.persistence.*;
    @Data
    @Entity
    @Table(name = "user")
    public class User { 
        @Id
        @GeneratedValue
        private Long id;
        private String name;
    }

4.此时数据库中是没有任何表的，当我们启动springboot后表会自动创建，如下图，执行了sql  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDcxNDgwOA_size_16_color_FFFFFF_t_70]  
5.其次，我们需要创建一个UserRepository来继承Jpa原有的方法

import org.springframework.data.jpa.repository.JpaRepository;
    import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
    import org.springframework.stereotype.Repository;
    @Repository
    public interface UserRepository extends
            JpaRepository<User,Integer>, JpaSpecificationExecutor<User> { 
    }

6.之后便可运用UserRepository中的方法对User表进行各种操作了，这里插入一个记录

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDcxNDgwOA_size_16_color_FFFFFF_t_70 1]

import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    @Service
    public class UserService { 
        @Autowired
        private UserRepository UserRepository;
        public void Insert() { 
            User aa=new User();
            aa.setName("aaa");
            UserRepository.save(aa);
        }
    }

我们用URL测试下

import com.Entity.UserService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    @RestController
    public class text { 
        @Autowired
        UserService userService;
        @RequestMapping("/aa")
        public void text(){ 
            userService.Insert();
        }
    }

7.请求了一次/aa，结果如下  
![在这里插入图片描述][2021010321424881.png]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDcxNDgwOA_size_16_color_FFFFFF_t_70 2]  
后续会慢慢一步步从jpa到hibernate的学习记录的，如果有什么不正确的，请各位大佬指正下。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDcxNDgwOA_size_16_color_FFFFFF_t_70_pic_center]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDcxNDgwOA_size_16_color_FFFFFF_t_70]: /images/20221120/16e048ebf7264a0ba84e150638cf9506.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDcxNDgwOA_size_16_color_FFFFFF_t_70 1]: /images/20221120/d6c47b1cdb974666b4030d91eb53f02b.png
[2021010321424881.png]: /images/20221120/2275353b9dc446ae8c141dbe29c63545.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDcxNDgwOA_size_16_color_FFFFFF_t_70 2]: /images/20221120/3d77fac6ec1e472ca90b0defdd7d238a.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDcxNDgwOA_size_16_color_FFFFFF_t_70_pic_center]: /images/20221120/44ba2cf715d54f689d6bc66501409f5b.png