springboot项目响应信息Jackson解析映射，key为null时抛异常解决办法

当使用@RestController注解时，会把响应信息自动解析成json格式，使用的是Jackson，但是Jackson默认不解析key为null的映射时会抛出异常，需要增加配置；

解决：

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializerProvider;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;

import java.io.IOException;

/**
 * Jackson解析配置
 * @author YanZhen
 * @date 2022/03/15 19:23
 */
@Configuration
public class JacksonConverterConfig {

    /**
     * @return 重写Jackson解析配置
     */
    @Bean
    public MappingJackson2HttpMessageConverter mappingJackson2HttpMessageConverter() {
        ObjectMapper objectMapper = new Jackson2ObjectMapperBuilder().build();
        // objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL); // 当值为null时舍弃序列化
        // 当Jackson解析map时，key为null转为空，防止com.fasterxml.jackson.databind.JsonMappingException异常
        objectMapper.getSerializerProvider().setNullKeySerializer(new JsonSerializer<Object>(){
            @Override
            public void serialize(Object o, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
                jsonGenerator.writeFieldName("");
            }
        });
        return new MappingJackson2HttpMessageConverter(objectMapper);
    }
}

可以设置成任何占位，只要你需要！！！