sprint data elasticsearch rest client無法處理localdatetime格式的問題

在使用HighLevelRestClient的時候，如果Document對象有LocalDateTime類的屬性，那么在搜索結果轉換為對象的時候就會報錯，無法將long型轉換為localdatetime，這時因為默認的elasticsearch converters里面不提供，所以需要我們自己添加。

@Configuration
public class ESConfiguration extends AbstractElasticsearchConfiguration {

    @Value("${elasticsearch.config.hosts}")
    private String hosts;

    @Bean
    public RestHighLevelClient elasticsearchClient() {
        ClientConfiguration configuration = ClientConfiguration.builder()
                .connectedTo(this.hosts)
                .build();

        return RestClients.create(configuration).rest();
    }

    @Bean
    @Override
    public EntityMapper entityMapper() {

        ElasticsearchEntityMapper entityMapper = new ElasticsearchEntityMapper(
                elasticsearchMappingContext(), new DefaultConversionService()
        );
        entityMapper.setConversions(elasticsearchCustomConversions());

        return entityMapper;
    }

    /**
     * 默認的converter不支持long到localdatime的轉換，從elasticsearch讀取的時候會報錯，所以在這里添加一個。
     */
    @Bean
    @Override
    public ElasticsearchCustomConversions elasticsearchCustomConversions() {
        List<Converter> converters= new ArrayList<>();
        converters.add(LongToLocalDateTimeConverter.INSTANCE);
        return new ElasticsearchCustomConversions(converters);
    }

    @ReadingConverter
    static enum LongToLocalDateTimeConverter implements Converter<Long, LocalDateTime> {
        INSTANCE;

        private LongToLocalDateTimeConverter() {
        }

        public LocalDateTime convert(Long source) {
            return Instant.ofEpochMilli(source).atZone(ZoneId.systemDefault()).toLocalDateTime();
        }
    }
}