spring boot jpa

红太狼 2022-05-22 09:43 190阅读 0赞

SpringBoot 提供的JPARepository基本满足我们的业务需求，不要写sql语句，自己也可以写方法，名字按jpa的命名格式即可

此测试采用 MySQL 数据库+idea工具  
首先新建一个springboot数据库

## maven配置 ##

<dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-jpa</artifactId>
            </dependency>
    
            
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
            </dependency>

## application.yml ##

spring:
      datasource:
        url: jdbc:mysql://localhost:3306/springboot
        username: ***
        password: ***
        driver-class-name: com.mysql.jdbc.Driver
      jpa:
        hibernate:
          ddl-auto: update
        show-sql: true

说明（此处百度去看）  
show-sql: true 打印出sql语句  
jpa.hibernate.ddl-auto是hibernate的配置属性，其主要作用是：自动创建、更新、验证数据库表结构。该参数的几种配置如下：  
·create：每次加载hibernate时都会删除上一次的生成的表，然后根据你的model类再重新来生成新表 哪怕两次没有任何改变也要这样执行，这就是导致数据库表数据丢失的一个重要原因。  
·create-drop：每次加载hibernate时根据model类生成表，但是sessionFactory一关闭,表就自动删除。  
·update：最常用的属性，第一次加载hibernate时根据model类会自动建立起表的结构（前提是先建立好数据库），  
以后加载hibernate时根据model类自动更新表结构，即使表结构改变了但表中的行仍然存在不会删除以前的行。  
要注意的是当部署到服务器后，表结构是不会被马上建立起来的，是要等应用第一次运行起来后才会。

## 具体代码 ##

**1.User实体对象**  
这个会自动生成user表，和hibernate框架一样

@Entity
    @Data //自带get,set
    @Component
    public class User { 
        @Id              //主键
        @GeneratedValue  // 自增
        private Integer id;
        private String name;
        private Integer age;
    }

**2.新建一个JPARepository**  
UserRepository 继承 JpaRepository 即可

public interface UserRepository extends JpaRepository<User,Integer>{ 
         // Integer 是id的类型
         // User 是返回的对象
         // 根据年龄查询
         List<User> findByAge(Integer age);
    }

**3.controller类**

@RestController
    public class JpaController { 
    
        @Autowired
        private UserRepository userRepository;
    
        @GetMapping("/hello")
        public String hello(){
            System.out.println("JpaController.hello 11111");
            return "public String hello()";
        }
    
        /** * <p>获取所有用户</p> * @return */
        @GetMapping("/users")
        public List<User> getUsers(){
            return userRepository.findAll();
        }
    
        /** * <p>添加一个用户</p> * @return */
        @PostMapping("/add")
        public Message<User> addUser(@Valid User user){
            userRepository.save(user);
            return "";
        }
    
        /** * <p>查询某个用户</p> * @param id * @return */
        @GetMapping("/user/{id}")
        public User getUser(@PathVariable("id") Integer id){
            User one = userRepository.findOne(id);
            return one;
        }
    
        /** * <p>删除某个用户</p> * @param id */
        @DeleteMapping("/user/{id}")
        public void delUser(@PathVariable("id") Integer id){
            userRepository.delete(id);
        }
    
        /** * <p>修改某个用户信息</p> * @param id * @param name * @param age * @return */
        @PutMapping("/user/{id}")
        public User updateUser(@PathVariable("id") Integer id,
                               @RequestParam("name") String name,
                               @RequestParam("age") Integer age){
            User user = new User();
            user.setId(id);
            user.setAge(age);
            user.setName(name);
            return userRepository.save(user);
        }
    
        /** * <p>根据年龄查询</p> * @param age * @return */
        @GetMapping("/user/age/{age}")
        public List<User> findByAge(@PathVariable("age") Integer age){
            List<User> byAge = userRepository.findByAge(age);
            return byAge;
        }
    
    }

说明  
根据年龄查询是自己写的方法，在UserRepository 按它的格式来就可以  
到这里user表的增删改查就都有了，有些方法的注解可以不合理，LZ只是想测试一下更多的注解而已

<table> 
 <thead> 
  <tr> 
   <th>Keyword(关键字)</th> 
   <th align="center">Sample(命名)</th> 
   <th align="right">JPQL snippet(sql示例)</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>And</td> 
   <td align="center">findByLastnameAndFirstname</td> 
   <td align="right">… where x.lastname = ?1 and x.firstname = ?2</td> 
  </tr> 
  <tr> 
   <td>Or</td> 
   <td align="center">findByLastnameOrFirstname</td> 
   <td align="right">… where x.lastname = ?1 or x.firstname = ?2</td> 
  </tr> 
  <tr> 
   <td>Is,Equals</td> 
   <td align="center">findByFirstname,findByFirstnameIs,findByFirstnameEquals</td> 
   <td align="right">… where x.firstname = 1?</td> 
  </tr> 
  <tr> 
   <td>Between</td> 
   <td align="center">findByStartDateBetween</td> 
   <td align="right">… where x.startDate between 1? and ?2</td> 
  </tr> 
  <tr> 
   <td>LessThan</td> 
   <td align="center">findByAgeLessThan</td> 
   <td align="right">… where x.age &lt; ?1</td> 
  </tr> 
  <tr> 
   <td>LessThanEqual</td> 
   <td align="center">findByAgeLessThanEqual</td> 
   <td align="right">… where x.age &lt;= ?1</td> 
  </tr> 
  <tr> 
   <td>GreaterThan</td> 
   <td align="center">findByAgeGreaterThan</td> 
   <td align="right">… where x.age &gt; ?1</td> 
  </tr> 
  <tr> 
   <td>GreaterThanEqual</td> 
   <td align="center">findByAgeGreaterThanEqual</td> 
   <td align="right">… where x.age &gt;= ?1</td> 
  </tr> 
  <tr> 
   <td>After</td> 
   <td align="center">findByStartDateAfter</td> 
   <td align="right">… where x.startDate &gt; ?1</td> 
  </tr> 
  <tr> 
   <td>Before</td> 
   <td align="center">findByStartDateBefore</td> 
   <td align="right">… where x.startDate &lt; ?1</td> 
  </tr> 
  <tr> 
   <td>IsNull</td> 
   <td align="center">findByAgeIsNull</td> 
   <td align="right">… where x.age is null</td> 
  </tr> 
  <tr> 
   <td>IsNotNull,NotNull</td> 
   <td align="center">findByAge(Is)NotNull</td> 
   <td align="right">… where x.age not null</td> 
  </tr> 
  <tr> 
   <td>Like</td> 
   <td align="center">findByFirstnameLike</td> 
   <td align="right">… where x.firstname like ?1</td> 
  </tr> 
  <tr> 
   <td>NotLike</td> 
   <td align="center">findByFirstnameNotLike</td> 
   <td align="right">… where x.firstname not like ?1</td> 
  </tr> 
  <tr> 
   <td>StartingWith</td> 
   <td align="center">findByFirstnameStartingWith</td> 
   <td align="right">… where x.firstname like ?1 (parameter bound with appended %)</td> 
  </tr> 
  <tr> 
   <td>EndingWith</td> 
   <td align="center">findByFirstnameEndingWith</td> 
   <td align="right">… where x.firstname like ?1 (parameter bound with prepended %)</td> 
  </tr> 
  <tr> 
   <td>Containing</td> 
   <td align="center">findByFirstnameContaining</td> 
   <td align="right">… where x.firstname like ?1 (parameter bound wrapped in %)</td> 
  </tr> 
  <tr> 
   <td>OrderBy</td> 
   <td align="center">findByAgeOrderByLastnameDesc</td> 
   <td align="right">… where x.age = ?1 order by x.lastname desc</td> 
  </tr> 
  <tr> 
   <td>Not</td> 
   <td align="center">findByLastnameNot</td> 
   <td align="right">… where x.lastname &lt;&gt; ?1</td> 
  </tr> 
  <tr> 
   <td>In</td> 
   <td align="center">findByAgeIn(Collection ages)</td> 
   <td align="right">… where x.age in ?1</td> 
  </tr> 
  <tr> 
   <td>NotIn</td> 
   <td align="center">findByAgeNotIn(Collection age)</td> 
   <td align="right">… where x.age not in ?1</td> 
  </tr> 
  <tr> 
   <td>True</td> 
   <td align="center">findByActiveTrue()</td> 
   <td align="right">… where x.active = true</td> 
  </tr> 
  <tr> 
   <td>False</td> 
   <td align="center">findByActiveFalse()</td> 
   <td align="right">… where x.active = false</td> 
  </tr> 
  <tr> 
   <td>IgnoreCase</td> 
   <td align="center">findByFirstnameIgnoreCase</td> 
   <td align="right">… where UPPER(x.firstame) = UPPER(?1)</td> 
  </tr> 
 </tbody> 
</table>

推荐 博客 [https://www.ibm.com/developerworks/cn/opensource/os-cn-spring-jpa/index.html][https_www.ibm.com_developerworks_cn_opensource_os-cn-spring-jpa_index.html]

[https_www.ibm.com_developerworks_cn_opensource_os-cn-spring-jpa_index.html]: https://www.ibm.com/developerworks/cn/opensource/os-cn-spring-jpa/index.html