"上一篇我们讲了spring boot 整合 JdbcTemplate来进行数据的持久化，这篇我们来说下怎么通过 spring boot 整合 JPA 来实现数据的持久化。一、代码实现　修改 pom，引入依赖 org.springframework.boot spring-boot-start ...."

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spring boot 系列之四：spring boot 整合JPA

上一篇我们讲了spring boot 整合 JdbcTemplate来进行数据的持久化，

这篇我们来说下怎么通过 spring boot 整合 JPA 来实现数据的持久化。

一、代码实现　

修改 pom，引入依赖

  <!-- 引入 jpa 依赖 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>

修改 application.properties，配置相关信息

#修改 tomcat 默认端口号
server.port=8090
#修改 context path
server.context-path=/test
#配置数据源信息
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/test
spring.datasource.username=root
spring.datasource.password=root
#配置 jpa
spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true
spring.jackson.serialization.indent_output=true

创建实体类

package com.study.entity;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name="t_user")
public class User {
@Id @GeneratedValue(strategy</span>=<span style="color: rgba(0, 0, 0, 1)">GenerationType.AUTO)
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Integer id;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> String userName;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> String password;

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Integer getId() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setId(Integer id) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.id =<span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String getUserName() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> userName;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setUserName(String userName) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.userName =<span style="color: rgba(0, 0, 0, 1)"> userName;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String getPassword() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> password;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setPassword(String password) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.password =<span style="color: rgba(0, 0, 0, 1)"> password;
}

}

创建 repository 接口并继承 CrudRepository

package com.study.repository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.CrudRepository;
import org.springframework.data.repository.query.Param;
import com.study.entity.User;
/**


注意：


1. 这里这里是 interface，不是 class



2.CrudRepository 里面的泛型，第一个是实体类，第二个是主键的类型



3. 由于 crudRepository 里面已经有一些接口了，如 deleteAll，findOne 等， 我们直接调用即可



4. 当然，我们也可以根据自己的情况来实现自己的接口, 如下面的 getUser() 方法，jpql 语句和 hql 语句差不多



*/
public interface UserRepository extends CrudRepository<User, Integer> {
/**

我们这里只需要写接口，不需要写实现，spring boot 会帮忙自动实现

*/

@Query("from User where id =:id")
public User getUser(@Param("id")Integer id);
}

创建 service

接口

package com.study.service;
import com.study.entity.User;
public interface UserService {
public User getUser(Integer id);
}

实现

package com.study.service.impl;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.study.entity.User;
import com.study.repository.UserRepository;
import com.study.service.UserService;
@Service
public class UserServiceImpl implements UserService {
@Autowired
UserRepository repository;

@Override
</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> User getUser(Integer id) {
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">有两种方式：
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">1.调用crudRepository的接口

//        return repository.findOne(id);
//2. 调用我们自己写的接口
return repository.getUser(id);
}
}

创建 controller

package com.study.controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.study.entity.User;
import com.study.service.UserService;
@RestController
public class UserController {
@Autowired
UserService service;
@RequestMapping(</span>"/getUser/{id}"<span style="color: rgba(0, 0, 0, 1)">)
</span><span style="color: rgba(0, 0, 255, 1)">public</span> User getUser(@PathVariable("id"<span style="color: rgba(0, 0, 0, 1)">) Integer id){
    
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> service.getUser(id);
}

}

测试，页面以 json 格式显示数据库值

二、知识点引申

关于 Repository 知识点，可以去看下下面这篇文章

https://segmentfault.com/a/1190000012346333

spring boot 系列之四：spring boot 整合JPA

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spring boot 系列之四：spring boot 整合JPA