json对象中对Long类型和String类型相互转换

与前端联调接口时，后端一些字段设计为Long类型，这样就有可能导致前端缺失精度，这时候我们就需要将Long类型返回给前端时做数据类型转换，在使用springboot开发时，默认的json序列化和反序列化使用的是Jackson，所以可以有两种处理方式。
第一种是直接在字段上面添加注解，指定序列化字段类型：

@JsonSerialize(using = ToStringSerializer.class)
private Long id;

一般在项目中这样配置可以解决单个实体类中的字段序列化，如果项目中的实体类非常多，这种配置方式就会显得非常麻烦。所以我们可以调整Jackson的配置，在全局指定序列化配置：

import com.fasterxml.jackson.annotation.JsonInclude.Include;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
import com.fasterxml.jackson.datatype.jsr310.deser.LocalDateDeserializer;
import com.fasterxml.jackson.datatype.jsr310.deser.LocalDateTimeDeserializer;
import com.fasterxml.jackson.datatype.jsr310.deser.LocalTimeDeserializer;
import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateSerializer;
import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateTimeSerializer;
import com.fasterxml.jackson.datatype.jsr310.ser.LocalTimeSerializer;
import org.springframework.boot.autoconfigure.AutoConfigureBefore;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.jackson.Jackson2ObjectMapperBuilderCustomizer;
import org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.format.DateTimeFormatter;
import java.util.LinkedHashMap;
import java.util.Locale;
import java.util.Map;

@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(ObjectMapper.class)
@AutoConfigureBefore(JacksonAutoConfiguration.class)
public class JacksonConfiguration {

    private final Map<Class<?>, JsonSerializer<?>> serializers = new LinkedHashMap<>(5);

    private final Map<Class<?>, JsonDeserializer<?>> deserializers = new LinkedHashMap<>(3);

    @Bean
    @Order(Ordered.HIGHEST_PRECEDENCE)
    Jackson2ObjectMapperBuilderCustomizer jackson2ObjectMapperBuilderCustomizer() {

        // 序列化时对Long类型进行处理，避免前端js处理数据时精度缺失
        serializers.put(Long.class, ToStringSerializer.instance);
        serializers.put(Long.TYPE, ToStringSerializer.instance);

        // java8日期处理
        serializers.put(LocalDateTime.class,
                new LocalDateTimeSerializer(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")));
        serializers.put(LocalDate.class,
                new LocalDateSerializer(DateTimeFormatter.ofPattern("yyyy-MM-dd")));
        serializers.put(LocalTime.class,
                new LocalTimeSerializer(DateTimeFormatter.ofPattern("HH:mm:ss")));
        deserializers.put(LocalDateTime.class,
                new LocalDateTimeDeserializer(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")));
        deserializers.put(LocalDate.class,
                new LocalDateDeserializer(DateTimeFormatter.ofPattern("yyyy-MM-dd")));
        deserializers.put(LocalTime.class,
                new LocalTimeDeserializer(DateTimeFormatter.ofPattern("HH:mm:ss")));

        return customizer -> customizer
                .featuresToDisable(SerializationFeature.FAIL_ON_EMPTY_BEANS,
                        SerializationFeature.WRITE_DATES_AS_TIMESTAMPS,
                        SerializationFeature.WRITE_DURATIONS_AS_TIMESTAMPS,
                        DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
                //.propertyNamingStrategy(PropertyNamingStrategies.SNAKE_CASE)    // 驼峰字段转下划线字段
                .serializationInclusion(Include.NON_NULL).serializersByType(serializers)
                .deserializersByType(deserializers).simpleDateFormat("yyyy-MM-dd HH:mm:ss").timeZone("GMT+8")
                .locale(Locale.SIMPLIFIED_CHINESE);
    }

}

第二种方式可以避免每个实体类中都配置序列化方式，但是这种方式也限制了项目的灵活性，它会对全局数据都产生影响，对比第一种它显然不够灵活。