在項(xiàng)目中有事需要對(duì)值為NULL的對(duì)象中Field不做序列化輸入配置方式如下：

[配置類型]：

源碼包中的枚舉類：

public static enum Include { ALWAYS, NON_NULL, NON_ABSENT, NON_EMPTY, NON_DEFAULT, USE_DEFAULTS; private Include() { }}

Include.Include.ALWAYS 默認(rèn)

Include.NON_DEFAULT 屬性為默認(rèn)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

方式一：全局配置，處理所有整個(gè)應(yīng)用的實(shí)體對(duì)象

#對(duì)日期類型的轉(zhuǎn)換配置spring.jackson.date-format=yyyy-MM-dd HH:mm:ss # 配置 參數(shù)如下 always non_absent non_default non_empty non_null use_defaultsspring.jackson.default-property-inclusion=non_null

方式二：在需要序列的話的實(shí)體類上加注解 ->[配置類型]所列

@JsonInclude(Include.NON_NULL)

方式三：配置類型

3.1自定義序列化實(shí)現(xiàn)類，可以作用在類上 自定義json序列化需要實(shí)現(xiàn)StdSerializer<T>或者JsonSerializer<T>

@JsonSerialize(using = ClientObjectSerialize.class)public class CreditBorrowerRepaymentRequestDto{}

實(shí)現(xiàn)類：對(duì)字段類型轉(zhuǎn)換，以及對(duì)值為null字段的過濾

public class ClientObjectSerialize extends JsonSerializer<CreditBorrowerRepaymentRequestDto>{ @Override public void serialize(CreditBorrowerRepaymentRequestDto dto, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException, JsonProcessingException { jsonGenerator.writeStartObject(); try { Field[] fields = dto.getClass().getDeclaredFields(); for (Field field : fields) { field.setAccessible(true); if(null == field.get(dto)){ continue; } jsonGenerator.writeFieldName(field.getName()); jsonGenerator.writeObject(field.get(dto)); } } catch (Exception e) { e.printStackTrace(); } jsonGenerator.writeEndObject(); }}

3.2自定義序列化實(shí)現(xiàn)類，可以作用在實(shí)體對(duì)象字段上，對(duì)NULL值的處理，或者轉(zhuǎn)換

@JsonSerialize(using = ClientStringSerialize.class)private String name; @JsonSerialize(using = ClientDtaeSerialize.class)private Date date;public class ClientStringSerialize extends JsonSerializer<String> { @Override public void serialize(String string, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException { if(string == null){ jsonGenerator.writeString(string + '[NULL]'); }else{ jsonGenerator.writeString(string); } }}public class ClientDtaeSerialize extends JsonSerializer<Date> { @Override public void serialize(Date createDate, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException { jsonGenerator.writeString(new SimpleDateFormat('yyyy-MM-dd HH:mm:ss').format(createDate)); }}

實(shí)踐總結(jié)：

一當(dāng)全局配置了NULL字段過濾的配置，但有的實(shí)體對(duì)象需要序列化出NULL的字段值，如何處理？

答：

1. 直接在對(duì)象上增加 @JsonInclude(JsonInclude.Include.ALWAYS) 類上的注解優(yōu)先級(jí)比較高，會(huì)覆蓋全局的配置

2.用自定義的類序列化注解（同上）

二直接在字段上加自定義序列化類會(huì)覆蓋全局配置嗎？

答：不會(huì)，有默認(rèn)的 public class NullSerializer extends StdSerializer<Object> 來(lái)處理，當(dāng)值不為Null的時(shí)候才會(huì)執(zhí)行自定義字段上的序列化注解實(shí)現(xiàn)類

補(bǔ)充知識(shí)：SpringBoot中Jackson返回null處理,字符串類型轉(zhuǎn)空串,數(shù)組集合轉(zhuǎn)[],對(duì)象轉(zhuǎn){}

SpringBoot返回Json數(shù)據(jù)中null值處理，將字符串類型null值轉(zhuǎn)換為''，將集合數(shù)組類型null值轉(zhuǎn)換為[]，將原始數(shù)據(jù)類型null值轉(zhuǎn)換為0，將布爾類型null值轉(zhuǎn)換為false，將實(shí)體對(duì)象null值轉(zhuǎn)換為{}。

1.自定義null值序列化處理器

import com.fasterxml.jackson.core.JsonGenerator;import com.fasterxml.jackson.databind.JsonSerializer;import com.fasterxml.jackson.databind.SerializerProvider;import java.io.IOException;/** * 自定義null值序列化處理器 */public class CustomizeNullJsonSerializer { /** * 處理數(shù)組集合類型的null值 */ public static class NullArrayJsonSerializer extends JsonSerializer<Object> { @Override public void serialize(Object value, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException { jsonGenerator.writeStartArray(); jsonGenerator.writeEndArray(); } } /** * 處理字符串類型的null值 */ public static class NullStringJsonSerializer extends JsonSerializer<Object> { @Override public void serialize(Object value, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException { jsonGenerator.writeString(''); } } /** * 處理數(shù)值類型的null值 */ public static class NullNumberJsonSerializer extends JsonSerializer<Object> { @Override public void serialize(Object value, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException { jsonGenerator.writeNumber(0); } } /** * 處理boolean類型的null值 */ public static class NullBooleanJsonSerializer extends JsonSerializer<Object> { @Override public void serialize(Object value, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException { jsonGenerator.writeBoolean(false); } } /** * 處理實(shí)體對(duì)象類型的null值 */ public static class NullObjectJsonSerializer extends JsonSerializer<Object> { @Override public void serialize(Object value, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException { jsonGenerator.writeStartObject(); jsonGenerator.writeEndObject(); } }}

2.序列化程序修改器

import com.fasterxml.jackson.databind.BeanDescription;import com.fasterxml.jackson.databind.SerializationConfig;import com.fasterxml.jackson.databind.ser.BeanPropertyWriter;import com.fasterxml.jackson.databind.ser.BeanSerializerModifier;import java.util.Collection;import java.util.List;/** * <pre> * 此modifier主要做的事情為： * 1.當(dāng)序列化類型為數(shù)組集合時(shí)，當(dāng)值為null時(shí)，序列化成[] * 2.String類型值序列化為'' * * </pre> */public class MyBeanSerializerModifier extends BeanSerializerModifier { @Override public List<BeanPropertyWriter> changeProperties(SerializationConfig config, BeanDescription beanDesc, List<BeanPropertyWriter> beanProperties) { // 循環(huán)所有的beanPropertyWriter for (int i = 0; i < beanProperties.size(); i++) { BeanPropertyWriter writer = beanProperties.get(i); // 判斷字段的類型，如果是數(shù)組或集合則注冊(cè)nullSerializer if (isArrayType(writer)) { // 給writer注冊(cè)一個(gè)自己的nullSerializer writer.assignNullSerializer(new CustomizeNullJsonSerializer.NullArrayJsonSerializer()); } if (isStringType(writer)) { writer.assignNullSerializer(new CustomizeNullJsonSerializer.NullStringJsonSerializer()); } } return beanProperties; } /** * 是否是數(shù)組 */ private boolean isArrayType(BeanPropertyWriter writer) { Class<?> clazz = writer.getType().getRawClass(); return clazz.isArray() || Collection.class.isAssignableFrom(clazz); } /** * 是否是String */ private boolean isStringType(BeanPropertyWriter writer) { Class<?> clazz = writer.getType().getRawClass(); return CharSequence.class.isAssignableFrom(clazz) || Character.class.isAssignableFrom(clazz); } /** * 是否是數(shù)值類型 */ private boolean isNumberType(BeanPropertyWriter writer) { Class<?> clazz = writer.getType().getRawClass(); return Number.class.isAssignableFrom(clazz); } /** * 是否是boolean */ private boolean isBooleanType(BeanPropertyWriter writer) { Class<?> clazz = writer.getType().getRawClass(); return clazz.equals(Boolean.class); }}

3.配置Jackson實(shí)體

import com.fasterxml.jackson.databind.ObjectMapper;import com.fasterxml.jackson.databind.SerializerProvider;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;/** * 配置Jackson實(shí)體 */@Configurationpublic class JacksonConfig { @Bean @Primary @ConditionalOnMissingBean(ObjectMapper.class) public ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder) { ObjectMapper objectMapper = builder.createXmlMapper(false).build(); /** 為objectMapper注冊(cè)一個(gè)帶有SerializerModifier的Factory */ objectMapper.setSerializerFactory(objectMapper.getSerializerFactory() .withSerializerModifier(new MyBeanSerializerModifier())); SerializerProvider serializerProvider = objectMapper.getSerializerProvider(); serializerProvider.setNullValueSerializer(new CustomizeNullJsonSerializer .NullObjectJsonSerializer()); return objectMapper; }}

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