SpringData核心数据访问接口--CrudRepository示例

水深无声 2023-10-17 22:37 12阅读 0赞

1.Spring Data JPA可以极大地简化JPA的写法，在几乎不用写接口实现的情况下完成对数据的访问和操作。

2.Spring Data通过提供Repository接口来约定数据访问的统一标准。

3.Repository接口下包含一些常用的子接口：

CrudRepository、PagingAndSortingRepository、JpaRepository

4.在进行spring boot 项目的开发中，开发者只需要定义自己项目的数据访问接口，然后实现Spring Data提供的这些接口，就可以实现对数据的CRUD操作。

CrudRepository提供了最基本的对实体类的增删改查操作

新建新的Maven项目，命名SpringBoot\_crudrepositorytest,按照Maven项目的规范，在src/main下新建一个名为resource的文件夹

①修改pom.xml

<groupId>com.ysh</groupId>  
<artifactId>crudrepositorytest</artifactId>  
<version>0.0.1-SNAPSHOT</version>  
<packaging>jar</packaging>

<name>crudrepositorytest</name>  
<url>http://maven.apache.org</url>

<parent>  
<groupId>org.springframework.boot</groupId>  
<artifactId>spring-boot-starter-parent</artifactId>  
<version>2.0.0.RELEASE</version>  
<relativePath/>  
</parent>  
  
<properties>  
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>  
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>  
<java.version>1.8</java.version>  
</properties>

<dependencies>  
  
  
<dependency>  
<groupId>org.springframework.boot</groupId>  
<artifactId>spring-boot-starter-web</artifactId>  
</dependency>  
  
  
<dependency>  
<groupId>org.springframework.boot</groupId>  
<artifactId>spring-boot-starter-thymeleaf</artifactId>  
</dependency>  
  
  
<dependency>  
<groupId>mysql</groupId>  
<artifactId>mysql-connector-java</artifactId>  
</dependency>  
  
  
<dependency>  
<groupId>org.springframework.boot</groupId>  
<artifactId>spring-boot-starter-data-jpa</artifactId>  
</dependency>  
  
  
<dependency>  
<groupId>junit</groupId>  
<artifactId>junit</artifactId>  
<scope>test</scope>  
</dependency>  
</dependencies>  
</project>

②配置基本属性

在src/main/resource下新建一个全局配置文件，命名为application.properties,在该配置文件中配置数据源和JPA相关的属性

\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#  
\#\#\#  
\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#  
spring.datasource.url=jdbc:mysql://localhost:3306/springdatajpa  
  
spring.datasource.username=root  
  
spring.datasource.password=  
  
spring.datasource.driverClassName=com.mysql.jdbc.Driver  
  
spring.datasource.max-active=20

spring.datasource.max-idle=8  
  
spring.datasource.min-idle=8  
  
spring.datasource.initial-size=10  
  
spring.jpa.database=MySQL  
  
spring.jpa.show-sql=true  
  
  
spring.jpa.hibernate.ddl-auto=update  
  
spring.jpa.hibernate.naming-strategy=org.hibernate.cfg.ImprovedNamingStrategy  
  
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5Dialect

附：

\#数据库地址，其中springdatajpa是数据库名称

spring.datasource.url=jdbc:mysql://localhost:3306/springdatajpa

\#数据库用户名

spring.datasource.username=root

\#数据库密码，要改成自己的密码

spring.datasource.password=yourpassword

\#数据库驱动，固定格式

spring.datasource.driverClassName=com.mysql.jdbc.Driver

\#指定连接池中最大的活跃连接数

spring.datasource.max-active=20

\#指定连接池最大的空闲连接

spring.datasource.max-idle=8

\#指定必须保持连接的最小值

spring.datasource.min-idle=8

spring.datasource.initial-size=10

\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#  
\#\#\# JPA持久化配置  
\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#  
\# 指定数据库类型  
spring.jpa.database=MySQL  
\# 指定是否需要在日志中显示sql语句  
spring.jpa.show-sql=true  
\# 指定自动创建|更新|验证数据库表结构等配置  
\# 表示如果数据库中存在持久化类对应的表就不创建，不存在就创建对应的表  
spring.jpa.hibernate.ddl-auto=update  
\# 指定命名策略  
spring.jpa.hibernate.naming-strategy=org.hibernate.cfg.ImprovedNamingStrategy  
\#指定数据库方言  
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5Dialect

③创建持久化类

在com.ysh下新建4个包，bean(放置持久化类)、controller(控制器)、repository(定义数据访问接口的类)、service(业务逻辑处理类)

在bean下创建持久化类User.java

packagecom.ysh.crudrepositorytest.bean;

importjava.io.Serializable;

import javax.persistence.Entity;  
import javax.persistence.GeneratedValue;  
import javax.persistence.GenerationType;  
import javax.persistence.Id;  
importjavax.persistence.Table;

@Entity  
// 用于标记持久化类,Spring Boot项目加载后会自动根据持久化类建表  
@Table(name="tb\_user")  
public class User implementsSerializable\{

private static final long serialVersionUID =1L;

/\*\*  
\* 使用@Id指定主键. 使用代码@GeneratedValue(strategy=GenerationType.AUTO)  
\* 指定主键的生成策略,mysql默认的是自增长。  
\*  
\*/  
@Id  
@GeneratedValue(strategy = GenerationType.IDENTITY)  
private int id;//主键.

private String username;// 姓名username

private StringloginName;

private char sex;//性别

private int age; //年龄

public int getId() \{  
return id;  
\}

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

public String getUsername() \{  
return username;  
\}

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

public String getLoginName() \{  
return loginName;  
\}

public void setLoginName(String loginName) \{  
this.loginName = loginName;  
\}

public char getSex() \{  
return sex;  
\}

public void setSex(char sex) \{  
this.sex = sex;  
\}

public int getAge() \{  
return age;  
\}

public void setAge(int age) \{  
this.age = age;  
\}  
\}

④定义数据访问层接口

在com.ysh.crudrepository.repository包下新建一个接口，命名为UserRepository,让该接口继承CrudRepository接口，以持久化对象User作为CrudRepository的第一个参数，表示当前操作的持久化对象类型，Integer作为CrudRepository的第二个参数，用于指定ID类型

packagecom.ysh.crudrepositorytest.repository;

importorg.springframework.data.repository.CrudRepository;

importcom.ysh.crudrepositorytest.bean.User;

public interface UserRepository extends CrudRepository<User,Integer>\{

⑤定义业务层类

UserService.java

packagecom.ysh.crudrepositorytest.service;

importjava.util.Optional;

import javax.annotation.Resource;  
importjavax.transaction.Transactional;

importorg.springframework.stereotype.Service;

import com.ysh.crudrepositorytest.bean.User;  
importcom.ysh.crudrepositorytest.repository.UserRepository;

@Service  
public class UserService\{

// 注入UserRepository  
@Resource  
private UserRepositoryuserRepository;

/\*\*  
\* save,update ,delete 方法需要绑定事务. 使用@Transactional进行事务的绑定.  
\*  
\* 保存对象  
\* @param User  
\* @return 包含自动生成的id的User对象  
\*/  
@Transactional  
public User save(User User) \{  
return userRepository.save(User);  
\}

/\*\*  
\* 根据id删除对象  
\*  
\* @param id  
\*/  
@Transactional  
public void delete(int id) \{  
userRepository.deleteById(id);  
  
\}

/\*\*  
\* 查询所有数据  
\*  
\* @return 返回所有User对象  
\*/  
public Iterable<User> getAll() \{  
return userRepository.findAll();  
\}  
  
/\*\*  
\* 根据id查询数据  
\*  
\* @return 返回id对应的User对象  
\*/  
public User getById(Integer id) \{  
// 根据id查询出对应的持久化对象  
Optional<User> op = userRepository.findById(id);  
return op.get();  
\}  
/\*\*  
\* 修改用户对象数据，持久化对象修改会自动更新到数据库  
\*  
\* @param user  
\*/  
@Transactional  
public void update(User user) \{  
// 直接调用持久化对象的set方法修改对象的数据  
user.setUsername("张三");  
user.setLoginName("zhangsan");  
\}

在业务层需要注入数据访问对象，使用@Resources注解将UserRepository接口对应的实现类注入进来的。

只要数据访问层接口实现了CrudRepository，SpringBoot项目会自动扫描该类并为该类创建实习类对象。

⑥定义控制器类

UserController.java:

packagecom.ysh.crudrepositorytest.controller;

importjavax.annotation.Resource;

import org.springframework.web.bind.annotation.RequestMapping;  
importorg.springframework.web.bind.annotation.RestController;

import com.ysh.crudrepositorytest.bean.User;  
importcom.ysh.crudrepositorytest.service.UserService;

@RestController  
@RequestMapping("/user")  
public class UserController \{  
  
// 注入UserService  
@Resource  
private UserServiceuserService;

@RequestMapping("/save")  
public String save() \{  
User user = new User();  
user.setLoginName("badao");  
user.setUsername("霸道");  
user.setSex('男');  
user.setAge(3);  
user = userService.save(user);  
System.out.println("保存数据成功，返回的结果：" + user);  
return "保存数据成功！";  
\}

@RequestMapping("/update")  
public String update() \{  
// 修改的对象必须是持久化对象，所以先从数据库查询出id为1的对象进行修改  
User user = userService.getById(1);  
userService.update(user);  
return "修改数据成功!";  
\}

@RequestMapping("/delete")  
public String delete() \{  
userService.delete(1);  
return "删除数据成功！";  
\}

@RequestMapping("/getAll")  
public Iterable<User> getAll() \{  
return userService.getAll();  
\}  
\}

⑦测试应用

打开Mysql服务，启动Mysql数据库，新建数据库springdatajpa:

![70][]

![70 1][]

在crudrepository包下新建App.java启动类

packagecom.ysh.crudrepositorytest;

import org.springframework.boot.SpringApplication;  
importorg.springframework.boot.autoconfigure.SpringBootApplication;

/\*\*  
\* @SpringBootApplication指定这是一个 spring boot的应用程序.  
\*/  
@SpringBootApplication  
public class App  
\{  
public static void main( String\[\] args )  
\{  
// SpringApplication 用于从main方法启动Spring应用的类。  
SpringApplication.run(App.class, args);  
\}  
\}

运行项目

JPA会在数据库中自动创建持久化类对应的tb\_user表，按照JPA规范，实体类User的属性loginName映射到数据库的时候，自动生成的数据库列名为login\_name

在浏览器中输入：[http://localhost:8080/user/save][http_localhost_8080_user_save]

![70 2][]

查看数据库中的表，刷新一下

![70 3][]

测试修改，在浏览器中输入：[http://localhost:8080/user/update][http_localhost_8080_user_update]

![70 4][]

查看修改后的数据库

![70 5][]

测试查询所有用户数据，在浏览器中输入：[http://localhost:8080/user/getAll][http_localhost_8080_user_getAll]

请求会提交到UserController类的getAll方法进行处理，如果该方法执行查询所有用户成功，即可返回查询到的所有用户信息的JSON格式的字符串

![70 6][]

测试删除：[http://localhost:8080/user/delete][http_localhost_8080_user_delete]

![70 7][]

![70 8][]

附：项目目录结构

![70 9][]

示例代码下载：

[https://download.csdn.net/download/badao\_liumang\_qizhi/10548351][https_download.csdn.net_download_badao_liumang_qizhi_10548351]

[http_maven.apache.org_POM_4.0.0]: http://maven.apache.org/POM/4.0.0
[http_www.w3.org_2001_XMLSchema-instance]: http://www.w3.org/2001/XMLSchema-instance
[http_maven.apache.org_xsd_maven-4.0.0.xsd]: http://maven.apache.org/xsd/maven-4.0.0.xsd
[70]: https://img-blog.csdn.net/20180718112508846?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[70 1]: https://img-blog.csdn.net/20180718112524530?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[http_localhost_8080_user_save]: http://localhost:8080/user/save
[70 2]: https://img-blog.csdn.net/20180718112546974?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[70 3]: https://img-blog.csdn.net/20180718112608904?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[http_localhost_8080_user_update]: http://localhost:8080/user/update
[70 4]: https://img-blog.csdn.net/20180718112629174?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[70 5]: https://img-blog.csdn.net/20180718112644618?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[http_localhost_8080_user_getAll]: http://localhost:8080/user/getAll
[70 6]: https://img-blog.csdn.net/20180718112714575?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[http_localhost_8080_user_delete]: http://localhost:8080/user/delete
[70 7]: https://img-blog.csdn.net/20180718112731804?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[70 8]: https://img-blog.csdn.net/20180718112755813?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[70 9]: https://img-blog.csdn.net/20180718112823417?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JBREFPX0xJVU1BTkdfUUlaSEk=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[https_download.csdn.net_download_badao_liumang_qizhi_10548351]: https://download.csdn.net/download/badao_liumang_qizhi/10548351