Java对象为空时，不显示该对象属性，或者将null转换为""

第一种方法：

@JsonInclude(JsonInclude.Include.NON_NULL)

private String resourceName;

Include.ALWAYS 属性都序列化

Include.NON_DEFAULT 属性为默认值不序列化

Include.NON_EMPTY 属性为 空("") 或者为 NULL 都不序列化

Include.NON_NULL 属性为NULL 不序列化

第二种方法：自定义一个objectmapper

import java.io.IOException;

import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

import org.springframework.context.annotation.Primary;

import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;

import com.fasterxml.jackson.core.JsonGenerator;

import com.fasterxml.jackson.core.JsonProcessingException;

import com.fasterxml.jackson.databind.JsonSerializer;

import com.fasterxml.jackson.databind.ObjectMapper;

import com.fasterxml.jackson.databind.SerializerProvider;

/**

* null返回空字符串

*/

@Configuration

public class JacksonConfig {

@Bean

@Primary

@ConditionalOnMissingBean(ObjectMapper.class)

public ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder) {

ObjectMapper objectMapper = builder.createXmlMapper(false).build();

SerializerProvider serializerProvider = objectMapper.getSerializerProvider();

serializerProvider.setNullValueSerializer(new JsonSerializer() {

@Override

public void serialize(Object o, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException, JsonProcessingException {

jsonGenerator.writeString("");

}

});

return objectMapper;

}

}

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注意但是这个方法会把对象为空，list ,map ,枚举 为 null的情况下也转成 空字符串，这是个弊端，根据需求而用吧。

第三种方法：直接设置属性默认值

就是在初始化实体类的时候设置属性默认值

如：

private String name="";

———————————————— https://blog.csdn.net/qq_36802726/article/details/88895444

java 查询时实体不返回字段为空的数据

@JsonSerialize(include = JsonSerialize.Inclusion.NON_NULL)

public class VAuth extends Auth {

}

list转json时保存值为空的属性

String param=JSONObject.toJSONString(fhlist, SerializerFeature.WriteMapNullValue);

效果：[{"channel_id":1,"channel_name":"测试通道","channel_Url":null}]