SpringBoot-解决空字符串转枚举异常

简介

本文介绍如何解决Java的SpringBoot中空字符串转枚举时报错的问题。

问题复现

org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot deserialize value of type *.**.**.PayType from String “”: value not one of declared Enum instance names: [ALIPAY, WECHAT_PAY, BANK_UNION]; nested exception is com.fasterxml.jackson.databind.exc.InvalidFormatException: Cannot deserialize value of type *.**.**.PayType from String “”: value not one of declared Enum instance names: [ALIPAY, WECHAT_PAY, BANK_UNION]

原因分析

字符串与枚举类的对应关系是：字符串对应枚举类的字面量（或者说name()方法）；null对应null，如果是空字符串，会找不到对应的枚举类，就会报错。

解决方案

方案1：空字符串转null

@Configuration
public class JackSonConfig {
    @Bean
    public ObjectMapper objectMapper(Jackson2ObjectMapperBuilder builder,
                                     JacksonProperties jacksonProperties) {
       ObjectMapper objectMapper = builder.build();
 
       // 将不匹配的enum转为null，防止报错
       objectMapper.configure(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_AS_NULL, true);
       return objectMapper;
    }
}

修改后，这些数据都会对应null枚举类：null、空字符串、不匹配的任意字符串。

方案2：空字符串转特定枚举成员

枚举对应默认值上添加注解 @JsonEnumDefaultValue

@Configuration
public class JackSonConfig {
    @Bean
    public ObjectMapper objectMapper(Jackson2ObjectMapperBuilder builder,
									JacksonProperties jacksonProperties) {
		ObjectMapper objectMapper = builder.build();
        // 将不匹配的enum转为默认值，防止报错
        objectMapper.configure(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE, true); 
        return objectMapper;
    }
}

修改后，这些数据都会对应则使用添加@JsonEnumDefaultValue注解的枚举值：空字符串、不匹配的任意字符串。 ​