这篇文章主要介绍“SpringBoot如何解决BigDecimal传到前端后精度丢失问题”,在日常操作中,相信很多人在SpringBoot如何解决BigDecimal传到前端后精度丢失问题问题上存在疑惑,小编查阅了各式资料,整理出简单好用的操作方法,希望对大家解答”SpringBoot如何解决BigDecimal传到前端后精度丢失问题”的疑惑有所帮助!接下来,请跟着小编一起来学习吧!
问题描述
实例
Controller
package com.knife.controller; import com.knife.entity.UserVO;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController; import java.math.BigDecimal; @RestController@RequestMapping("user")public class UserController { @GetMapping("save") public UserVO save(BigDecimal amount) { UserVO userVO = new UserVO(); userVO.setId(1L); userVO.setUsername("Tony"); userVO.setAmount(amount); return userVO; }}
Entity
package com.knife.entity; import lombok.Data; import java.math.BigDecimal; @Datapublic class UserVO { private Long id; private String username; private BigDecimal amount;}
测试
访问:http://localhost:8080/user/save?amount=12345671234567.1234
结果
问题复现
场景描述
实际项目中前端会这样处理:调用后端接口获得JSON格式的响应字符串,然后将JSON字符串解析为JavaScript对象(用于展示到对应的位置、方便计算等)。
前端调后端的写接口(增删改)时,会将JavaScript对象序列化为JSON格式的字符串,然后将其作为参数请求后端接口。
实例1:精度丢失
const json = '{"id": 1, "name": "Tony", "amount": 12345671234567.12345}';const obj = JSON.parse(json);console.log(obj.amount); // 12345671234567.123console.log(JSON.stringify(obj)); // {"id":1,"name":"Tony","amount":12345671234567.123}
可以看到,在将json字符串转为JavaScript对象后,“amount” 丢失了精度。
实例2:丢失小数位
const json = '{"id": 1, "name": "Tony", "amount": 12345671234567.00000}';const obj = JSON.parse(json);console.log(obj.amount); // 12345671234567console.log(JSON.stringify(obj)); // {"id":1,"name":"Tony","amount":12345671234567}
可以看到,在将json字符串转为JavaScript对象后,“amount” 丢失了小数。
其他示例
const json = '{"id": 1, "name": "Tony", "amount": 12345671234567.12345}';const obj = JSON.parse(json);console.log(obj.amount); // 12345671234567.123 const json = '{"id": 1, "name": "Tony", "amount": 123456712345678.12345}';const obj = JSON.parse(json);console.log(obj.amount); // 123456712345678.12 const json = '{"id": 1, "name": "Tony", "amount": 98765432198765.12345}';const obj = JSON.parse(json);console.log(obj.amount); // 98765432198765.12 const json = '{"id": 1, "name": "Tony", "amount": 987654321987654321.12345}';const obj = JSON.parse(json);console.log(obj.amount); // 987654321987654300
Java后端BigDecimal的范围
范围没有限制,可以认为无限大、无限小
可以通过如下代码验证:
package com.example.a; import java.math.BigDecimal; public class Demo { public static void main(String[] args) { BigDecimal bigDecimal = new BigDecimal( "1234567890123456789012345678901234567890" + "1234567890123456789012345678901234567890" + ".123456789" ); System.out.println(bigDecimal); }}
执行结果:
12345678901234567890123456789012345678901234567890123456789012345678901234567890.123456789
解决方案
把BigDecimal的序列化值改成字符串类型即可。
方案1:全局处理
法1:ToStringSerializer
配置类
package com.knife.config; import com.fasterxml.jackson.databind.ObjectMapper;import com.fasterxml.jackson.databind.module.SimpleModule;import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder; import java.math.BigDecimal; @Configurationpublic class JacksonConfig { @Bean public ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder) { ObjectMapper objectMapper = builder.createXmlMapper(false).build(); // 全局配置序列化返回 JSON 处理 SimpleModule simpleModule = new SimpleModule(); // 将使用String来序列化BigDecimal类型 simpleModule.addSerializer(BigDecimal.class, ToStringSerializer.instance); objectMapper.registerModule(simpleModule); return objectMapper; }}
测试
访问:http://localhost:8080/user/save?amount=12345671234567.1234
结果:
法2:自定义序列化
自定义序列化器
package com.knife.config; import com.fasterxml.jackson.core.JsonGenerator;import com.fasterxml.jackson.databind.SerializerProvider;import com.fasterxml.jackson.databind.annotation.JacksonStdImpl;import com.fasterxml.jackson.databind.jsontype.TypeSerializer;import com.fasterxml.jackson.databind.ser.std.ToStringSerializer; import java.io.IOException;import java.math.BigDecimal;import java.math.RoundingMode; @JacksonStdImplclass BigDecimalToStringSerializer extends ToStringSerializer { public final static BigDecimalToStringSerializer instance = new BigDecimalToStringSerializer(); public BigDecimalToStringSerializer() { super(Object.class); } public BigDecimalToStringSerializer(Class<?> handledType) { super(handledType); } @Override public boolean isEmpty(SerializerProvider prov, Object value) { if (value == null) { return true; } String str = ((BigDecimal) value).stripTrailingZeros().toPlainString(); return str.isEmpty(); } @Override public void serialize(Object value, JsonGenerator gen, SerializerProvider provider) throws IOException { gen.writeString(((BigDecimal) value).stripTrailingZeros().toPlainString()); // 如果要求所有BigDecimal保留两位小数,可以这么写: // gen.writeString(((BigDecimal) value).setScale(2, RoundingMode.HALF_UP) // .stripTrailingZeros().toPlainString()); } @Override public void serializeWithType(Object value, JsonGenerator gen, SerializerProvider provider, TypeSerializer typeSer) throws IOException { // no type info, just regular serialization serialize(value, gen, provider); }}
配置类
package com.knife.config; import com.fasterxml.jackson.databind.ObjectMapper;import com.fasterxml.jackson.databind.module.SimpleModule;import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder; import java.math.BigDecimal; @Configurationpublic class JacksonConfig { @Bean public ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder) { ObjectMapper objectMapper = builder.createXmlMapper(false).build(); // 全局配置序列化返回 JSON 处理 SimpleModule simpleModule = new SimpleModule(); // 将使用String来序列化BigDecimal类型 simpleModule.addSerializer(BigDecimal.class, BigDecimalToStringSerializer.instance); objectMapper.registerModule(simpleModule); return objectMapper; }}
测试
访问:http://localhost:8080/user/save?amount=12345671234567.1234
结果:
方案2:局部处理
法1:@JsonSerialize
在相应字段上加此注解:
@JsonSerialize(using= ToStringSerializer.class)
示例
package com.knife.entity; import com.fasterxml.jackson.databind.annotation.JsonSerialize;import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;import lombok.Data; import java.math.BigDecimal; @Datapublic class UserVO { private Long id; private String username; @JsonSerialize(using= ToStringSerializer.class) private BigDecimal amount;}
测试
访问:http://localhost:8080/user/save?amount=12345671234567.1234
结果:
法2:@JsonFormat
在相应字段上加此注解:
@JsonFormat(shape = JsonFormat.Shape.STRING)
示例
package com.knife.entity; import com.fasterxml.jackson.annotation.JsonFormat;import lombok.Data; import java.math.BigDecimal; @Datapublic class UserVO { private Long id; private String username; @JsonFormat(shape = JsonFormat.Shape.STRING) private BigDecimal amount;}
测试
访问:http://localhost:8080/user/save?amount=12345671234567.1234
结果:
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