@GetMapping("/test")
    public Map<LocalDateTime, LocalDateTime> fetchEvents() {
        Map<LocalDateTime,LocalDateTime> map = new HashMap<>();
        map.put(LocalDateTime.now(),LocalDateTime.now());
        return map;
    }

以上接口默认返回格式为 ISO-8601 格式，例如 2022-02-23T14:30:00.000

以下代码来修改springboot web应该LocalDatetime的返回格式，如果：LocalDateTime要作为Map的key时要单独添加module进行格式化处理

import java.io.IOException;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;

public class LocalDateTimeKeySerializer extends JsonSerializer<LocalDateTime> {
    private static final String PATTERN = "yyyy-MM-dd HH:mm:ss";
    private static final DateTimeFormatter FORMATTER = DateTimeFormatter.ofPattern(PATTERN);

    @Override
    public void serialize(LocalDateTime value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
        gen.writeFieldName(FORMATTER.format(value));
    }
}

@Configuration
public class JacksonConfiguration {
    private static final String PATTERN = "yyyy-MM-dd HH:mm:ss";
    @Bean
    public Jackson2ObjectMapperBuilderCustomizer jackson2ObjectMapperBuilderCustomizer() {
        return builder -> {
            builder.serializerByType(LocalDateTime.class, new LocalDateTimeSerializer(DateTimeFormatter.ofPattern(PATTERN)));
            builder.deserializerByType(LocalDateTime.class, new LocalDateTimeDeserializer(DateTimeFormatter.ofPattern(PATTERN)));
            SimpleModule module = new SimpleModule();
            //添加对Map key的序列化
            module.addKeySerializer(LocalDateTime.class, new LocalDateTimeKeySerializer());
            builder.modules(module);
        };

    }
}