Elastic实战：彻底解决spring-data-elasticsearch日期、时间类型数据读取报错问题

0. 引言
在使用spring-data-elasticsearch读取es中时间类型的数据时出现了日期转换报错，不少初学者会在这里困惑很久，所以今天我们专门来解读该问题的几种解决方案。

1. 问题分析
该问题的报错形式一般是：

Failed to convert from type [java.lang.String] to type [java.util.Date] for value '2022-03-15T14:31:55+08:00';
nested exception is java.lang.IllegalArgumentException"

当然时间类型的表现形式不一定是我这里的2022-03-15T14:31:55+08:00，可能多种多样，但解决办法都是一致的。

该问题的原因很简单，就是es中存储的时间格式是该种类型的，使用java client去获取时，无法直接转换为时间类型

2. 问题解决
这里演示的环境版本是如下所示。如果在实操时发现部分代码不可用，注意检查版本

spring-data-elasticsearch3.2.12.RELEASE

2.1 es mapping与实体类中声明相同的时间格式
第一种方案，是我们应该在实体类和索引mapping创建前就做好的，将es mapping中的时间字段的格式与实体类中保持统一
1、es mapping中设置时间格式，如果有多种格式中间用||隔开

PUT date_custom
{
"mappings": {
"properties": {
"create_time": {
"type": "date",
"format": "yyyy-MM-dd HH:mm:ss || yyyy-MM-dd'T'HH:mm:ss'+08:00' || strict_date_optional_time || epoch_millis"
}
}
}
}

2、实体类中同样声明该时间格式

@Data
@Document(indexName = "date_custom",shards = 1, replicas = 0)
public class DateTest implements Serializable {

@Field(type = FieldType.Date, name = "create_time",format = {},
pattern = "yyyy-MM-dd HH:mm:ss || yyyy-MM-dd'T'HH:mm:ss'+08:00' || strict_date_optional_time || epoch_millis")
private Date createTime;

// 旧版本
// @Field(type = FieldType.Date, name = "create_time",format = DateFormat.custom, pattern = "yyyy-MM-dd HH:mm:ss || yyyy-MM-dd'T'HH:mm:ss'+08:00' || strict_date_optional_time || epoch_millis")
// private Date createTime;
}

es自带的时间格式，可以在官方文档中找到

2.2 配置日期格式转换器
1、ElasticsearchRestTemplate的构造方法中提供了一个构造方法，可以传入指定的EntityMapper

@Bean
public ElasticsearchRestTemplate elasticsearchRestTemplate(RestHighLevelClient elasticsearchClient,EntityMapper entityMapper){
return new ElasticsearchRestTemplate(elasticsearchClient,entityMapper);
}

2、EntityMapper有两个实现类，其中ElasticsearchEntityMapper实现类提供了一个自定义转换器的方法setConversions

@Bean
@Override
public EntityMapper entityMapper() {
ElasticsearchEntityMapper entityMapper = new ElasticsearchEntityMapper(elasticsearchMappingContext(), new DefaultConversionService());
entityMapper.setConversions(elasticsearchCustomConversions());
return entityMapper;
}

3、通过该方法我们可以将我们自定义的转换器StringToDateConverter传入进去

@Override
public ElasticsearchCustomConversions elasticsearchCustomConversions(){
List<Converter<?,?>> converterList = Lists.newArrayList(StringToDateConverter.INSTANT);
return new ElasticsearchCustomConversions(converterList);
}

4、完整代码

import com.google.common.collect.Lists;
import org.elasticsearch.client.RestHighLevelClient;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.convert.support.DefaultConversionService;
import org.springframework.core.convert.converter.Converter;
import org.springframework.data.elasticsearch.client.ClientConfiguration;
import org.springframework.data.elasticsearch.client.RestClients;
import org.springframework.data.elasticsearch.config.AbstractElasticsearchConfiguration;
import org.springframework.data.elasticsearch.core.ElasticsearchEntityMapper;
import org.springframework.data.elasticsearch.core.ElasticsearchRestTemplate;
import org.springframework.data.elasticsearch.core.EntityMapper;
import org.springframework.data.elasticsearch.core.convert.ElasticsearchCustomConversions;
import org.springframework.data.elasticsearch.repository.config.EnableElasticsearchRepositories;
import org.springframework.http.HttpHeaders;
import org.springframework.lang.NonNull;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.List;

@Configuration
@EnableElasticsearchRepositories(basePackages = "com.example.datedemo")
public class ElasticRestClientConfig extends AbstractElasticsearchConfiguration {

@Value("${spring.elasticsearch.rest.uris}")
private String url;
@Value("${spring.elasticsearch.rest.username}")
private String username;
@Value("${spring.elasticsearch.rest.password}")
private String password;

@Override
@Bean
public RestHighLevelClient elasticsearchClient() {
url = url.replace("http://","");
HttpHeaders headers = new HttpHeaders();
headers.setBasicAuth(username,password);
final ClientConfiguration clientConfiguration = ClientConfiguration.builder()
.connectedTo(url)
.withDefaultHeaders(headers)
.build();
return RestClients.create(clientConfiguration).rest();
}

@Bean
public ElasticsearchRestTemplate elasticsearchRestTemplate(RestHighLevelClient elasticsearchClient,EntityMapper entityMapper){
return new ElasticsearchRestTemplate(elasticsearchClient,entityMapper);
}

/**
* 指定EntityMapper为ElasticsearchEntityMapper
* 解决es mapper映射实体类问题
* @return
*/
@Bean
@Override
public EntityMapper entityMapper() {
ElasticsearchEntityMapper entityMapper = new ElasticsearchEntityMapper(elasticsearchMappingContext(), new DefaultConversionService());
entityMapper.setConversions(elasticsearchCustomConversions());
return entityMapper;
}

/**
* 指定日期转换器，解决日期转换错误问题
* @return
*/
@Override
public ElasticsearchCustomConversions elasticsearchCustomConversions(){
List<Converter<?,?>> converterList = Lists.newArrayList(StringToDateConverter.INSTANT);
return new ElasticsearchCustomConversions(converterList);
}

/**
* 字符串转换日期
*/
private enum StringToDateConverter implements Converter<String, java.util.Date> {
/**
* 转换器实例
*/
INSTANT;

@Override
public Date convert(@NonNull String source) {
try {
return new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'+08:00'").parse(source);
} catch (ParseException e) {
e.printStackTrace();
}
return null;
}
}

}

2.3 @DateTimeFormat注解声明格式（不生效）
首先说明一下这种方式并不生效，这里单独说明是为了列举出来，让大家避免走弯路。

该种方法的原理是通过在注解中声明自定义格式来实现格式转换，但实际上这并不起作用，因为spring-data-elasticsearch会忽略@DateTimeFormat注解

@JsonFormat(pattern="yyyy-MM-dd HH:mm:ss",timezone = "GMT+8") //返回时间类型
@DateTimeFormat(pattern="yyyy-MM-dd HH:mm:ss") //接收时间类型
private Date startTime;

================
1、my es mapping

PUT test001
{
  "mappings": {
    "properties": {
      "order_count": {
        "type": "long"
      },
      "pay_amount_sum": {
        "type": "double"
      },
      "shop_id": {
        "type": "long"
      },
      "statistic_time": {
        "type": "date",
         "format": "yyyy-MM-dd HH:mm:ss || strict_date_optional_time || epoch_millis"
      }
    }
  }
}

2、my java model code

   @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss", timezone = "GMT+8")
    @Field(value = "create_time", type = FieldType.Date, format = DateFormat.epoch_millis)
    private Date createTime;

3、my exception

Unable to convert value '2022-05-23 14:49:24' to java.util.Date for property 'createTime'

4、my change

 @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss", timezone = "GMT+8")
    @Field(value = "create_time", type = FieldType.Date, format = {},
            pattern = "yyyy-MM-dd HH:mm:ss || strict_date_optional_time || epoch_millis")
    private Date createTime;