json

目录

• 下划线驼峰转化问题
  • 代码方式
  • 配置类
  • 注解方式
• map转T泛型对象
• json转对象（java）
  • 代码方式
  • 注解方式
• 对象转Map(一层，无法递归)

下划线驼峰转化问题

代码方式

ObjectMapper mapper = new ObjectMapper();
       mapper.setPropertyNamingStrategy(PropertyNamingStrategies.SNAKE_CASE);
// params是任意Object
String json = mapper.writeValueAsString(params);

配置类

package cn.yottacloud.pc.core.json;

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.PropertyNamingStrategies;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
import com.fasterxml.jackson.datatype.jdk8.Jdk8Module;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import com.fasterxml.jackson.module.paramnames.ParameterNamesModule;
import io.swagger.v3.core.jackson.ModelResolver;
import org.springframework.boot.autoconfigure.jackson.Jackson2ObjectMapperBuilderCustomizer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;

/**
 * jackson配置
 */
@Configuration
public class JacksonConfiguration implements Jackson2ObjectMapperBuilderCustomizer {

    @Override
    public void customize(Jackson2ObjectMapperBuilder jacksonObjectMapperBuilder) {
        //空字符转为null
        jacksonObjectMapperBuilder.featuresToEnable(
            DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);
        jacksonObjectMapperBuilder.deserializerByType(String.class,
            new JacksonEmptyStringDeserializer());
        //未知属性报错关闭
        jacksonObjectMapperBuilder.featuresToDisable(
            DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
        //属性为null不序列化
        jacksonObjectMapperBuilder.serializationInclusion(JsonInclude.Include.ALWAYS);
        //属性命名自动转换为下划线方式
        jacksonObjectMapperBuilder.propertyNamingStrategy(PropertyNamingStrategies.SNAKE_CASE);
        //long转字符串
        jacksonObjectMapperBuilder.serializerByType(Long.class, ToStringSerializer.instance);
        //date转long
        jacksonObjectMapperBuilder.featuresToEnable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
        //第三方模块
        jacksonObjectMapperBuilder.modules(new JavaTimeModule(), new Jdk8Module(),
            new ParameterNamesModule());
    }

    @Bean
    public ModelResolver modelResolver(ObjectMapper objectMapper) {
        return new ModelResolver(objectMapper);
    }
}

注解方式

对象按指定名称接受（不受转化影响）
加在属性上

@JsonProperty("paymentAmt")

map转T泛型对象

阿里的 jackson com.fasterxml.jackson.databind.ObjectMapper可以
任意对象都可以转

convertValue(Object fromValue, Class toValueType)

json转对象（java）

代码方式

hutool的工具类

JSONUtil.toBean(respStr, DingfuResult.class);

注解方式

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

@JsonIgnoreProperties(ignoreUnknown = true)
类上加此注解，类的属性找不到json对象的属性时，可防止报错

对象转Map(一层，无法递归)

  /**
     * 将对象转换为 Map(只支持一层，无法递归对子孙属性转换)
     * @param obj
     * @return
     */
    public static Map<String, String> object2Map(Object obj) {
        Map<String, String> map = new HashMap<>();
        Class<?> objClass = obj.getClass();

        // 获取对象的所有字段
        Field[] fields = objClass.getDeclaredFields();

        for (Field field : fields) {
            field.setAccessible(true); // 允许访问私有字段

            try {
                // 获取字段名
                String fieldName = field.getName();
                // 获取字段值，并转换为字符串
                String fieldValue = field.get(obj).toString();

                // 将字段名和字段值添加到Map中
                map.put(fieldName, fieldValue);
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        }
        return map;
    }