JackSon是解析JSON和XML的一个框架，优点是简单易用，性能较高。
SpringBoot使用Jackson序列化时将null转成空字符串
简介
大家知道很多情况下，我们的API中数据交换都用JSON数据，这种数据格式简单、易读写、且轻量。在SpringBoot中默认使用jackson帮助我们进行序列化与反序列化的操作。
在控制层将我们的对象序列化返回给前端时，有些字段为null，序列化后的值也是null，如果前端直接展示的话，对用户不够友好，这里我们可以对jackson稍加修改，将值为null的转换成空字符串""。
不要使用继承MappingJackson2HttpMessageConverter的方式进行编写,可能会导致无法访问swgger文档的情况,但是接口是可以正常调用的
使用以下方式
可以根据不同类型的null转换成指定的值
package com.fish.config.jackson;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;
import java.io.IOException;
public class CustomizeNullJsonSerializer {
public static class NullArrayJsonSerializer extends JsonSerializer
package com.fish.config.jackson;
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;
public class MyBeanSerializerModifier extends BeanSerializerModifier {
@Override
public List changeProperties(SerializationConfig config,
BeanDescription beanDesc,
List beanProperties) {
// 循环所有的beanPropertyWriter
for (int i = 0; i < beanProperties.size(); i++) {
BeanPropertyWriter writer = beanProperties.get(i);
// 判断字段的类型，如果是数组或集合则注册nullSerializer
if (isStringType(writer)) {
writer.assignNullSerializer(new CustomizeNullJsonSerializer.NullStringJsonSerializer());
}
}
return beanProperties;
}
private boolean isArrayType(BeanPropertyWriter writer) {
Class clazz = writer.getType().getRawClass();
return clazz.isArray() || Collection.class.isAssignableFrom(clazz);
}
private boolean isStringType(BeanPropertyWriter writer) {
Class clazz = writer.getType().getRawClass();
return CharSequence.class.isAssignableFrom(clazz) || Character.class.isAssignableFrom(clazz);
}
private boolean isNumberType(BeanPropertyWriter writer) {
Class clazz = writer.getType().getRawClass();
return Number.class.isAssignableFrom(clazz);
}
private boolean isBooleanType(BeanPropertyWriter writer) {
Class clazz = writer.getType().getRawClass();
return clazz.equals(Boolean.class);
}
}
package com.fish.config.jackson;
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;
@Configuration
public class JacksonConfig {
@Bean
@Primary
@ConditionalOnMissingBean(ObjectMapper.class)
public ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder) {
ObjectMapper objectMapper = builder.createXmlMapper(false).build();
objectMapper.setSerializerFactory(objectMapper.getSerializerFactory()
.withSerializerModifier(new MyBeanSerializerModifier()));
SerializerProvider serializerProvider = objectMapper.getSerializerProvider();
//serializerProvider.setNullValueSerializer(new CustomizeNullJsonSerializer.NullObjectJsonSerializer());
return objectMapper;
}
}
格式化date类型可以在properties或者yml中进行配置
全局统一
#date类型时间格式化 #pring.jackson.date-format=yyyy-MM-dd HH:mm:ss #spring.jackson.joda-date-time-format=yyyy-MM-dd HH:mm:ss #spring.jackson.time-zone=GMT+8 #date类型转换时间戳 spring.jackson.serialization.write-dates-as-timestamps=true
