Java對象為空時，不顯示該對象屬性，或者將null轉換為""
第一種方法：
@JsonInclude(JsonInclude.Include.NON_NULL)
private String resourceName;
Include.ALWAYS 屬性都序列化
Include.NON_DEFAULT 屬性為默認值不序列化
Include.NON_EMPTY 屬性為 空（""） 或者為 NULL 都不序列化
Include.NON_NULL 屬性為NULL 不序列化
第二種方法：自定義一個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<Object>() {
@Override
public void serialize(Object o, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException, JsonProcessingException {
jsonGenerator.writeString("");
}
});
return objectMapper;
}
}
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注意但是這個方法會把對象為空，list ,map ,枚舉 為 null的情況下也轉成 空字符串，這是個弊端，根據需求而用吧。
第三種方法：直接設置屬性默認值
就是在初始化實體類的時候設置屬性默認值
如：
private String name="";
———————————————— https://blog.csdn.net/qq_36802726/article/details/88895444
java 查詢時實體不返回字段為空的數據
@JsonSerialize(include = JsonSerialize.Inclusion.NON_NULL)
public class VAuth extends Auth {
}
list轉json時保存值為空的屬性
String param=JSONObject.toJSONString(fhlist, SerializerFeature.WriteMapNullValue);
效果：[{"channel_id":1,"channel_name":"測試通道","channel_Url":null}]