Springboot使用JPA框架对数据库实现增删改查（附详细代码）

前言

1、本文将详细阐述如何使用JPA框架对数据库实现增删改查操作，业务中比较常见的应用场景几乎在这里都能看到，并且有详尽的代码可供直观演示，其中遇到的坑也进行了实时标注。
2、JPA的环境配置在前面的章节已有总结，不再赘述，直接上干货。

环境准备
步骤1：创建实体类对象

@Entity //该注解必须加，表明这是一个与数据库映射的实体类
@Data
@NoArgsConstructor
@AllArgsConstructor
@Table(name = "merchant_info") //项目启动后数据库会自动创建merchant_info表
@ApiModel(value = "商户信息表") //该注解以及后续controller中所有以@Api开头的注解表明引入swagger框架，可不加，丝毫不影响，我是为了便于用wagger调用接口演示。
public class MerchantInfo {@Id@GeneratedValue(strategy = GenerationType.IDENTITY) //必须加该注解，表明id自增，且唯一@ApiModelProperty(value = "主键id")private Long id;@ApiModelProperty(value = "商户名称")private String merchantName;@ApiModelProperty(value = "城市名称")private String cityName;@ApiModelProperty(value = "父对象id")private Long parentId;@ApiModelProperty(value = "商户状态: 1 生效 2 失效")private Long status;@ApiModelProperty(value = "随机生成码")private String invitationCode;@ApiModelProperty(value = "创建时间")private Date createTime;@ApiModelProperty(value = "更新时间")private Date updateTime;@ApiModelProperty(value = "备注")private String remark;@ApiModelProperty(value = "负责人")private String principal;@ApiModelProperty(value = "负责人联系方式")private String principalPhone;}

步骤2：创建与实体类MerchantInfo相关的JPA接口，并使其继承JpaRepository接口，泛型传递<MerchantInfo, Long>

//此注解必加，表明它是一个bean类，项目启动后spring容器扫描到该注解，会将该类初始化成bean对象，便于其他程序调用
@Component
public interface MerchantInfoJpaRepository extends JpaRepository<MerchantInfo,Long> {}

步骤3：SpringBoot主程序入口，如果只用JPA框架，相关的配置只需加@EnableJpaRepositories注解即可

@SpringBootApplication
@EnableJpaRepositories
public class WebapitestApplication {public static void main(String[] args) {SpringApplication.run(WebapitestApplication.class, args);}
}

步骤4：创建Controller类
下面是controller类整体格式，后面对数据库表merchant_info进行增删改查的所有代码都会在这个controller类里书写。

@RestController //此注解等同于@Controller(用在类上) + @ResponseBody(用在方法上)注解组合
@Slf4j //该注解可以在程序中直接使用log.info()打印日志
@Api(tags = "数据库表merchant_info进行增删改查") //此项是swagger的注解，可以不加，丝毫不影响
public class MerchantInfoController {@Autowiredprivate MerchantInfoJpaRepository merchantInfoJpaRepository;方法1: ...{}方法2: ...{}方法3: ...{}}}

JPA查询功能

1、findAll()方法：无条件查询merchant_info表中所有数据

步骤1：Controller中代码如下：

public class MerchantInfoController {@Autowiredprivate MerchantInfoJpaRepository merchantInfoJpaRepository;/***  JPA findAll() 无条件查询表中所有数据* @return*/@GetMapping("/getAllMerchantInfo")@ApiOperation(value = "获取所有商户信息")public List<MerchantInfo> getAllMerchantInfo(){List<MerchantInfo> merchantInfoList = merchantInfoJpaRepository.findAll();log.info("打印所有商户列表:{}",merchantInfoList);return merchantInfoList;}}}

步骤2：接口调用：http://localhost:8080/getAllMerchantInfo
步骤3：接口返回结果：

[{"id": 1,"merchantName": "广州泽天君成科技有限公司","cityName": "广州","parentId": null,"status": 2,"invitationCode": "207717","createTime": "2021-03-23T03:37:00.000+00:00","updateTime": "2021-04-27T09:02:11.000+00:00","remark": null,"principal": null,"principalPhone": null},{"id": 2,"merchantName": "广州市青豪企业管理有限责任公司","cityName": "温州","parentId": null,"status": 2,"invitationCode": "126155","createTime": "2021-03-23T03:43:43.000+00:00","updateTime": "2021-04-27T06:47:00.000+00:00","remark": null,"principal": null,"principalPhone": null},...省略若干...
]

2、findById(Long id)方法：根据id查询merchant_info表中对应的数据

步骤1：Controller中代码如下：

/*** JPA findById(Long id) 根据主键id查询表中相应数据* @param id* @return*/@GetMapping("/getMerchantById")@ApiOperation(value = "获取指定id的商户信息")@ApiImplicitParam(name = "id",value = "商户id",required = true,defaultValue = "15")public MerchantInfo getMerchantById(@RequestParam(name = "id") Long id){Optional<MerchantInfo> merchantInfoOptional = merchantInfoJpaRepository.findById(id);MerchantInfo merchantInfo = merchantInfoOptional.get();log.info("打印id={}的商户信息为:{}",id,merchantInfo);return merchantInfo;}

步骤2：调用接口：http://localhost:8080/getMerchantById?id=15
步骤3：接口返回结果如下：

{"id": 15,"merchantName": "浙江橙米企业管理有限公司","cityName": "绍兴","parentId": null,"status": 2,"invitationCode": "342149","createTime": "2021-03-23T03:43:43.000+00:00","updateTime": "2021-04-26T09:11:50.000+00:00","remark": null,"principal": null,"principalPhone": null
}

3、findAllById(Iterable<ID> var1)方法：根据传入的多个id集合查询merchant_info表中对应的数据

步骤1：Controller中代码

/*** JPA  findAllById(Iterable<ID> var1) 查询多个id表中相应数据* @param ids* @return*/@GetMapping("/getMerchantByIds")@ApiOperation(value = "获取多个id对应的商户信息")public List<MerchantInfo> getMerchantByIds(@RequestParam(name = "ids")  String ids ){log.info("打印后端接收post请求体数据 String[] ids：{}",ids);//将传入的数组字符串解析成JsonArray对象JSONArray jsonArray = JSON.parseArray(ids);log.info("打印转换后的JsonArray对象：{}",jsonArray); List<Long> longList = new ArrayList<Long>();//遍历jsonArray对象取出id元素并添加到List集合中for (int i  = 0; i < jsonArray.size(); i++){longList.add(jsonArray.getLong(i));}log.info("打印转换后的Long集合：{}",longList);//查询longList集合中所有id对应的数据List<MerchantInfo> merchantInfoList = merchantInfoJpaRepository.findAllById(longList);log.info("打印商户集合：{}",merchantInfoList);return merchantInfoList;}

步骤2：接口调用：http://localhost:8080/getMerchantByIds?ids=%5B2%2C3%2C6%5D
Note：%5B %2C %5D分别代表[ , ]，它们都是URL编码，实际上ids参数传递的是[2, 3, 6]只是不能明文传输，必须转成符合URL编码规则的格式。

步骤3：接口返回结果如下：

[{"id": 2,"merchantName": "广州市青豪企业管理有限责任公司","cityName": "温州","parentId": null,"status": 2,"invitationCode": "126155","createTime": "2021-03-23T03:43:43.000+00:00","updateTime": "2021-04-27T06:47:00.000+00:00","remark": null,"principal": null,"principalPhone": null},{"id": 3,"merchantName": "苏州合和众科技有限公司","cityName": "苏州","parentId": null,"status": 2,"invitationCode": "807624","createTime": "2021-03-24T09:23:05.000+00:00","updateTime": "2021-04-27T06:46:58.000+00:00","remark": null,"principal": null,"principalPhone": null},{"id": 6,"merchantName": "义乌市铃芝电动车行","cityName": "杭州","parentId": null,"status": 2,"invitationCode": "798048","createTime": "2021-03-23T03:43:43.000+00:00","updateTime": "2021-04-27T06:46:57.000+00:00","remark": null,"principal": null,"principalPhone": null}
]

4、findAll(Example<S> example)方法：构建example查询条件进行查询

步骤1：Controller中代码

/*** JPA  List<S> findAll(Example<S> example) 构建example查询条件进行查询* @param merchantInfo* @return*/@PostMapping("/getMerchantByExample")@ApiOperation(value = "根据example查询符合条件的商户信息")public List<MerchantInfo> getMerchantByExample(@RequestBody MerchantInfo merchantInfo){log.info("打印传入的请求体merchantInfo:{}",merchantInfo);//构建查询exampleExample<MerchantInfo> merchantInfoExample = Example.of(merchantInfo);//返回数据库中所有符合example查询条件对应的数据List<MerchantInfo> merchantInfoList = merchantInfoJpaRepository.findAll(merchantInfoExample);log.info("打印符合条件的商户列表：{}",merchantInfoList);return merchantInfoList;}

步骤2：接口调用
post：
http://localhost:8080/getMerchantByExample
parameters:

{"cityName": "广州","remark": null,"status": 2
}

步骤3：接口返回结果

[{"id": 1,"merchantName": "广州泽天君成科技有限公司","cityName": "广州","parentId": null,"status": 2,"invitationCode": "207717","createTime": "2021-03-23T03:37:00.000+00:00","updateTime": "2021-04-27T09:02:11.000+00:00","remark": null,"principal": null,"principalPhone": null},{"id": 4,"merchantName": "成都欧韵聚网络科技有限公司","cityName": "广州","parentId": null,"status": 2,"invitationCode": "859655","createTime": "2021-03-23T03:37:00.000+00:00","updateTime": "2021-05-10T03:22:48.000+00:00","remark": null,"principal": null,"principalPhone": null}
]

5、findAll(Example<S> example, Pageable pageable)方法：构建example查询条件并进行分页查询

步骤1：Controller中代码

/*** JPA  <S extends T> Page<S> findAll(Example<S> example, Pageable pageable) 构建example查询条件，并进行分页查询* note: page起始页 0* @param page* @param size* @param merchantInfo* @return*/@PostMapping("/findAllByPageAble/{page}/{size}")@ApiOperation(value = "查询结果翻页处理")public List<MerchantInfo> findAllByPageAble(@PathVariable("page") Integer page, @PathVariable("size") Integer size, @RequestBody MerchantInfo merchantInfo){//根据前端传入的page和size，构建Pageable对象，用于后续的分页查询Pageable pageable = PageRequest.of(page-1,size);//根据前端传入的请求体构建Example查询条件Example<MerchantInfo> merchantInfoExample = Example.of(merchantInfo);Page<MerchantInfo> merchantInfoPage = merchantInfoJpaRepository.findAll(merchantInfoExample, pageable);//获取对应页的数据内容List<MerchantInfo> merchantInfoList = merchantInfoPage.getContent();log.info("打印第{}页,每页数量{}条,\n该页查询结果为:{}",page,size,merchantInfoList);return merchantInfoList;}

步骤2：接口调用
post：http://localhost:8080/findAllByPageAble/2/3
parameters：

{"cityName": "广州","remark": null,"status": 2
}

步骤3：接口返回结果

[{"id": 12,"merchantName": "中山市古镇超途餐饮服务部","cityName": "广州","parentId": null,"status": 2,"invitationCode": "689589","createTime": "2021-03-23T03:43:43.000+00:00","updateTime": "2021-05-10T03:22:34.000+00:00","remark": null,"principal": null,"principalPhone": null},{"id": 13,"merchantName": "广州骑士之家数字科技有限公司","cityName": "广州","parentId": null,"status": 2,"invitationCode": "513000","createTime": "2021-03-23T03:43:43.000+00:00","updateTime": "2021-04-27T06:46:52.000+00:00","remark": null,"principal": null,"principalPhone": null},{"id": 16,"merchantName": "六安市煜祥人力资源开发有限公司(深圳)","cityName": "广州","parentId": null,"status": 2,"invitationCode": "422057","createTime": "2021-03-23T03:43:43.000+00:00","updateTime": "2021-05-10T03:22:35.000+00:00","remark": null,"principal": null,"principalPhone": null}
]

JPA新增、修改功能

1、save(S s)方法：可对传入的单个Entity对象映射到数据库表中实现新增数据或修改表数据功能

步骤1：Controller中代码

/*** JPA  <S extends T> S save(S s) save方法可是实现新增或修改功能* @apiNote 传入一个Entity对象，若该对象中存在主键id，则是修改；若主键不存在，则是新增* @param merchantInfo* @return*/@PostMapping("/saveMerchantByEntity")@ApiOperation(value = "新增或修改商户信息")public MerchantInfo saveMerchantByEntity(@RequestBody MerchantInfo merchantInfo){//判断主键是否存在，若存在，则修改该主键对应的表记录if(merchantInfo.getId()!= null && merchantInfo.getId() > 0){MerchantInfo merchantInfo1 = merchantInfoJpaRepository.findById(merchantInfo.getId()).get();/*** copyProperties(source,target,ignoreProperties) 将源对象属性值反射到目标对象对应的属性上，如果不加ignoreProperties参数* 则源对象中属性值为null的值会覆盖掉目标对象中对应属性不为null的值，ignoreProperties参数可以指定源对象中不覆盖目标对象的属性。* 如果源对象不存在某个属性，而目标对象存在某个属性，这种情况反射后，目标对象的该属性不会被覆盖*/BeanUtils.copyProperties(merchantInfo,merchantInfo1,new String[]{"createTime","invitationCode"});merchantInfo1.setUpdateTime(new Date());return merchantInfoJpaRepository.save(merchantInfo1);}else{//若主键id不存在，则新增一条记录到数据库表中merchantInfo.setCreateTime(new Date());merchantInfo.setUpdateTime(new Date());MerchantInfo merchantInfo1 = merchantInfoJpaRepository.save(merchantInfo);return merchantInfo1;}}

步骤2：接口调用
post：http://localhost:8080/saveMerchantByEntity
parameters 1：

//请求体中不存在id主键，因此是新增
{"cityName": "大理01","invitationCode": "333333","merchantName": "大理测试商户05","principal": "马二麻子","principalPhone": "18900001111"
}

parameters 2：

//请求体中存在id主键54，因此是修改
{"id":54,"cityName": "大理01","invitationCode": "333333","merchantName": "大理测试商户099","principal": "马二麻子","principalPhone": "18900000000"
}

步骤3：接口返回结果
response 1:

{"id": 54,"merchantName": "大理测试商户05","cityName": "大理01","parentId": null,"status": null,"invitationCode": "333333","createTime": "2021-05-12T08:56:25.763+00:00","updateTime": "2021-05-12T08:56:25.763+00:00","remark": null,"principal": "马二麻子","principalPhone": "18900001111"
}

response 2:

{"id": 54,"merchantName": "大理测试商户099","cityName": "大理01","parentId": null,"status": null,"invitationCode": "333333","createTime": "2021-05-12T08:56:26.000+00:00","updateTime": "2021-05-12T09:01:40.810+00:00","remark": null,"principal": "马二麻子","principalPhone": "18900000000"
}

Note：
a）接口传parameters 1，无id，则新增一条表记录，自增生成的主键ID值54，见response 1；
b）接口传parameters 2，有id，则修改该id对应的表记录，见response 1。

2、saveAll(Iterable<S> iterable)方法：可对传入的多个Entity对象集合映射到数据库表中实现批量新增数据或修改表数据功能

步骤1：Controller中代码

/*** JPA  <S extends T> List<S> saveAll(Iterable<S> iterable) saveAll方法可实现批量新增或修改功能* @param merchantInfoList* @return*/@PostMapping("/saveMerchantByEntityList")@ApiOperation(value = "批量新增或修改商户信息")public List<MerchantInfo> saveMerchantByEntityList(@RequestBody List<MerchantInfo> merchantInfoList){//创建一个新List集合，装载处理后的Entity对象List<MerchantInfo> updateMerchantList = new ArrayList<MerchantInfo>();for (MerchantInfo merchantInfo : merchantInfoList){if (merchantInfo.getId() != null && merchantInfo.getId() > 0){//获取数据库中对应id的原始数据映射到entityMerchantInfo merchantInfo1 = merchantInfoJpaRepository.findById(merchantInfo.getId()).get();BeanUtils.copyProperties(merchantInfo,merchantInfo1,new String[]{"createTime","invitationCode"});merchantInfo1.setUpdateTime(new Date());updateMerchantList.add(merchantInfo1);}else{merchantInfo.setCreateTime(new Date());merchantInfo.setUpdateTime(new Date());updateMerchantList.add(merchantInfo);}}log.info("打印处理后的MerchantInfo对象集合：\n{}",updateMerchantList);//批量进行新增或修改List<MerchantInfo> merchantInfoList1 = merchantInfoJpaRepository.saveAll(updateMerchantList);return merchantInfoList1;}

步骤2：接口调用
post：http://localhost:8090/saveMerchantByEntityList
parameters：

//参数数据中既有存在id的条目，又有不存在id的条目，有id的条目执行修改，无id的条目执行插入新增
[{"id":50,"merchantName": "大理测试商户01","cityName": "大理01","status": 1,"invitationCode": "888888","principal":"臧三","principalPhone":"13811112222"},{"id":51,"merchantName": "大理测试商户02","cityName": "大理01","status": 1,"invitationCode": "888888","principal":"女四","principalPhone":"1381111333333"},{"id":52,"merchantName": "大理测试商户03","cityName": "大理01","status": 1,"invitationCode": "999999","principal":"万五","principalPhone":"13811114444"},
{"merchantName": "大理测试商户04","cityName": "大理01","status": 1,"invitationCode": "713713","principal":"万五赵六","principalPhone":"13811115555"}
]

步骤3：接口返回结果

//前三条数据进行了修改，最后一条数据新增插入数据库中。
[{"id": 50,"merchantName": "大理测试商户01","cityName": "大理01","parentId": null,"status": 1,"invitationCode": "111222","createTime": "2021-05-12T03:29:23.000+00:00","updateTime": "2021-05-12T03:43:45.732+00:00","remark": null,"principal": "臧三","principalPhone": "13811112222"},{"id": 51,"merchantName": "大理测试商户02","cityName": "大理01","parentId": null,"status": 1,"invitationCode": "2222333","createTime": "2021-05-12T03:29:23.000+00:00","updateTime": "2021-05-12T03:43:45.845+00:00","remark": null,"principal": "女四","principalPhone": "1381111333333"},{"id": 52,"merchantName": "大理测试商户03","cityName": "大理01","parentId": null,"status": 1,"invitationCode": "333444","createTime": "2021-05-12T03:29:23.000+00:00","updateTime": "2021-05-12T03:43:45.923+00:00","remark": null,"principal": "万五","principalPhone": "13811114444"},{"id": 53,"merchantName": "大理测试商户04","cityName": "大理01","parentId": null,"status": 1,"invitationCode": "713713","createTime": "2021-05-12T03:43:45.923+00:00","updateTime": "2021-05-12T03:43:45.923+00:00","remark": null,"principal": "万五赵六","principalPhone": "13811115555"}
]

JPA删除功能
1、deleteAll()方法：删除merchant_info表中所有数据

 /*** JPA deleteAll() 删除表中所有数据* 删除对应数据库表中所有数据，谨慎操作*/@GetMapping("/deleteAllMerchantInfo")@ApiOperation(value = "删除merchant_info表中所有数据")public void deleteAllMerchantInfo(){merchantInfoJpaRepository.deleteAll();}

2、deleteById(Long)方法：删除merchant_info表中对应id的数据

 /*** JPA deleteById(Long) 删除对应id的表数据* 删除数据库表中对应id的条目* @param id*/@GetMapping("/deleteMerchantInfoById")@ApiOperation(value = "删除merchant_info表中对应id的数据")public void deleteMerchantInfoById(@RequestParam("id") Long id){merchantInfoJpaRepository.deleteById(id);}

3、delete(T t)方法：删除Entity对应的表数据

 /*** JPA delete(T t) 删除Entity对应的表数据* @param merchantInfo*/@PostMapping("/deleteMerchantInfoByEntity")@ApiOperation(value = "删除Entity对象映射对应的表数据")public void deleteMerchantInfoByEntity(@RequestBody MerchantInfo merchantInfo){log.info("打印请求体merchantInfo对象:{}",merchantInfo);Example<MerchantInfo> merchantInfoExample = Example.of(merchantInfo);MerchantInfo merchantInfo1 = merchantInfoJpaRepository.findOne(merchantInfoExample).get();merchantInfoJpaRepository.delete(merchantInfo1);}

4、deleteAll(Iterable<? extends T> iterable)方法：删除merchant_info表中多条记录

 /*** JPA deleteAll(Iterable<? extends T> iterable)* @param merchantInfo*/@PostMapping("/deleteMerchantInfoByEntitysList")@ApiOperation(value = "删除merchant_info表中多条记录")public void deleteMerchantInfoByEntitysList(@RequestBody MerchantInfo merchantInfo){Example<MerchantInfo> merchantInfoExample = Example.of(merchantInfo);List<MerchantInfo> merchantInfoList = merchantInfoJpaRepository.findAll(merchantInfoExample);merchantInfoJpaRepository.deleteAll(merchantInfoList);}

附merchant_info表结构

CREATE TABLE `merchant_info` (`id` bigint NOT NULL AUTO_INCREMENT COMMENT '主键id',`merchant_name` varchar(150) DEFAULT NULL COMMENT '商户名称',`city_name` varchar(255) DEFAULT NULL COMMENT '城市名称',`parent_id` bigint DEFAULT NULL COMMENT '父商户Id',`status` int DEFAULT '1' COMMENT '状态：1：有效 2：无效',`invitation_code` varchar(64) DEFAULT NULL COMMENT '邀请码',`create_time` datetime NOT NULL COMMENT '创建时间',`update_time` datetime NOT NULL COMMENT '修改时间',`remark` varchar(255) DEFAULT NULL COMMENT '备注',`principal` varchar(64) DEFAULT NULL COMMENT '负责人',`principal_phone` varchar(64) DEFAULT NULL COMMENT '负责人电话',PRIMARY KEY (`id`)
)

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