SpringBoot Entity中枚举类型详细使用介绍
作者:IT利刃出鞘
简介方案对比
本处列举表示类型或状态的常用方法的对比。
法1:使用数字表示(不推荐)
//1:支付宝支付;2:微信支付;3:银行卡支付 private Integer payType;
这种方法的缺点:可读性极差,排查问题也麻烦。比如:前端页面上看到了2这个类型,还要看接口文档或者问后端这是什么意思,浪费时间!
法2:使用字符串表示(不推荐)
//ALIPAY:支付宝;WECHAT_PAY:微信;BANK_CARD_PAY:银行卡支付 private String payType;
这种方式比法1好一些了,提高了数据库的可读性和排查问题速度。
缺点:难以控制不允许数据库的pay_type为空字符串这种情况;支持的类型没有限制死,前端传个其他的字符串也能存入数据库。
法3:使用枚举表示(推荐)
枚举是这种场景最好的方案(枚举本身就是为了表示可穷举类型而发明出来的!)。
定义一个枚举类
package com.example.demo.order.enums; import lombok.Getter; @Getter public enum PayTypeEnum { ALIPAY("支付宝"), WECHAT_PAY("微信支付"), BANK_CARD_PAY("银行卡支付"), ; private final String description; PayTypeEnum(String description) { this.description = description; } }
Entity中定义枚举类型字段
private PayTypeEnum payType;
优点
- 可读性极高,排查问题很快(比如:前端页面上看到ALIPAY这个类型,一眼就能知道是支付宝)
- 可以控制不允许数据库的pay_type为空字符串这种情况(因为枚举字段不可能有空字符串)
- 支持的类型限制死,前端传个其他的字符串无法存入数据库。
枚举用法示例
建表
CREATE TABLE `t_order` ( `id` bigint NOT NULL COMMENT 'ID', `order_no` varchar(64) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL COMMENT '订单号', `pay_type` varchar(64) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '支付类型。ALIPAY:支付宝;WECHAT_PAY:微信;BANK_CARD_PAY:银行卡支付。', PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='订单';
pay_type字段加了NOT NULL限制。
Entity
package com.example.demo.order.entity; import com.baomidou.mybatisplus.annotation.TableName; import com.example.demo.order.enums.PayTypeEnum; import lombok.Data; @Data @TableName("t_order") public class Order { private Long id; private String orderNo; private PayTypeEnum payType; }
Enum
package com.example.demo.order.enums; import lombok.Getter; @Getter public enum PayTypeEnum { ALIPAY("支付宝"), WECHAT_PAY("微信支付"), BANK_CARD_PAY("银行卡支付"), ; private final String description; PayTypeEnum(String description) { this.description = description; } }
Controller
package com.example.demo.order.controller; import com.example.demo.order.entity.Order; import com.example.demo.order.service.OrderService; import com.example.demo.user.entity.User; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.PostMapping; import org.springframework.web.bind.annotation.RequestBody; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; @RestController @RequestMapping("/order") public class OrderController { @Autowired private OrderService orderService; @PostMapping("pay") public void pay(@RequestBody Order order) { orderService.save(order); } }
Service
接口
package com.example.demo.order.service; import com.baomidou.mybatisplus.extension.service.IService; import com.example.demo.order.entity.Order; public interface OrderService extends IService<Order> { }
实现
package com.example.demo.order.service.impl; import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl; import com.example.demo.order.entity.Order; import com.example.demo.order.mapper.OrderMapper; import com.example.demo.order.service.OrderService; import org.springframework.stereotype.Service; @Service public class OrderServiceImpl extends ServiceImpl<OrderMapper, Order> implements OrderService { }
Mapper
package com.example.demo.order.mapper; import com.baomidou.mybatisplus.core.mapper.BaseMapper; import com.example.demo.order.entity.Order; import org.springframework.stereotype.Repository; @Repository public interface OrderMapper extends BaseMapper<Order> { }
测试
1.正常操作
写入成功,枚举的name()方法的值会写到数据库。
后端结果
数据库结果
2.前端传空字符串
此时会报错,因为枚举中没有对应空字符串的。
后端结果(无法将空字符串反序列化为枚举对象)
2022-09-10 10:14:30.406 WARN 128760 --- [nio-8080-exec-8] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot deserialize value of type `com.example.demo.order.enums.PayTypeEnum` from String "": not one of the values accepted for Enum class: [ALIPAY, BANK_CARD_PAY, WECHAT_PAY]; nested exception is com.fasterxml.jackson.databind.exc.InvalidFormatException: Cannot deserialize value of type `com.example.demo.order.enums.PayTypeEnum` from String "": not one of the values accepted for Enum class: [ALIPAY, BANK_CARD_PAY, WECHAT_PAY]
at [Source: (PushbackInputStream); line: 4, column: 16] (through reference chain: com.example.demo.order.entity.Order["payType"])]
数据库结果(没写入数据)
3.前端传null
后端结果(pay_type为null,写入数据库时报错)
2022-09-10 10:24:20.514 ERROR 128760 --- [io-8080-exec-10] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.dao.DataIntegrityViolationException:
### Error updating database. Cause: java.sql.SQLException: Field 'pay_type' doesn't have a default value
### The error may exist in com/example/demo/order/mapper/OrderMapper.java (best guess)
### The error may involve com.example.demo.order.mapper.OrderMapper.insert-Inline
### The error occurred while setting parameters
### SQL: INSERT INTO t_order ( id, order_no ) VALUES ( ?, ? )
### Cause: java.sql.SQLException: Field 'pay_type' doesn't have a default value
; Field 'pay_type' doesn't have a default value; nested exception is java.sql.SQLException: Field 'pay_type' doesn't have a default value] with root cause
java.sql.SQLException: Field 'pay_type' doesn't have a default value
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129) ~[mysql-connector-java-8.0.25.jar:8.0.25]
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) ~[mysql-connector-java-8.0.25.jar:8.0.25]
at com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:953) ~[mysql-connector-java-8.0.25.jar:8.0.25]
at com.mysql.cj.jdbc.ClientPreparedStatement.execute(ClientPreparedStatement.java:370) ~[mysql-connector-java-8.0.25.jar:8.0.25]
at com.zaxxer.hikari.pool.ProxyPreparedStatement.execute(ProxyPreparedStatement.java:44) ~[HikariCP-3.4.5.jar:na]
......
数据库结果(没写入数据)
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