基于Spring Data Jest的Elasticsearch数据查询与统计

CQRS有以下几点有点：

• 1.分工明确，可以负责不同的部分；
• 2.将业务上的命令和查询的职责分离能够提高系统的性能、可扩展性和安全性。并且在系统的演化中能够保持高度的灵活性，能够防止出现CRUD模式中，对查询或者修改中的某一方进行改动，导致另一方出现问题的情况；
• 3.逻辑清晰，能够看到系统中的那些行为或者操作导致了系统的状态变化；
• 4.可以从数据驱动(Data-Driven) 转到任务驱动(Task-Driven)以及事件驱动(Event-Driven)。

因此Command使用普通数据库（关系型数据库或非关系型数据库），Query使用效率查询效率更高的Elasticsearch。

如何确保数据库和Elasticsearch的数据的一致性？

• 我们可以使用事件驱动(Event-Driven)即Spring Data的Domain Event同步数据，可参考博客：http://www.wisely.top/2017/06/20/spring-data-domain-event-usage/ 。

当老数据库有大量数据需要导入Elasticsearch时，可参考博客：http://www.wisely.top/2018/02/24/spring-batch-elasticsearch/

Spring Data Elasticsearch使用的是transport client，而Elasticsearch官网推荐使用REST client。阿里云的Elasticsearch使用transport client目前还在存在问题，阿里云推荐使用REST client。

本示例使用的是Spring Data Jest链接Elasticsearch，Elasticsearch的版本为：5.5.3（目前只有spring boot 2.0以上版本支持）

1.项目构建

• 1.pom依赖如下：

<dependency>
    <groupId>com.github.vanroy</groupId>
    <artifactId>spring-boot-starter-data-jest</artifactId>
    <version>3.0.0.RELEASE</version>
</dependency>

<dependency>
    <groupId>io.searchbox</groupId>
    <artifactId>jest</artifactId>
    <version>5.3.2</version>
</dependency>

• 2.配置文件

spring:
  data:
    jest:
      uri: http://127.0.0.1:9200
      username: elastic
      password: changeme

2.构造查询条件

以简单的实体类为例

package com.hfcsbc.esetl.domain;

import lombok.Data;
import org.springframework.data.elasticsearch.annotations.Document;
import org.springframework.data.elasticsearch.annotations.Field;
import org.springframework.data.elasticsearch.annotations.FieldType;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import java.util.Date;
import java.util.List;

/**
 * Create by pengchao on 2018/2/23
 */
@Document(indexName = "person", type = "person", shards = 1, replicas = 0, refreshInterval = "-1")
@Entity
@Data
public class Person {
    @Id
    private Long id;
    private String name;
    @OneToOne
    @Field(type = FieldType.Nested)
    private List<Address> address;
    private Integer number;
    private Integer status;
    private Date birthDay;
}

package com.hfcsbc.esetl.domain;

import lombok.Data;

import javax.persistence.Entity;
import javax.persistence.Id;

/**
 * Create by pengchao on 2018/2/23
 */
@Entity
@Data
public class Address {
    @Id
    private Long id;
    private String name;
    private Integer number;
}

• 1.根据多个状态查询(类似于sql的in)

BoolQueryBuilder orderStatusCondition = QueryBuilders.boolQuery()
        .should(QueryBuilders.termQuery("status", 1))
        .should(QueryBuilders.termQuery("status", 2))
        .should(QueryBuilders.termQuery("status", 3))
        .should(QueryBuilders.termQuery("status", 4))
        .should(QueryBuilders.termQuery("status", 5));

• 2.and链接查询(类似于sql的and)

BoolQueryBuilder queryBuilder = QueryBuilders.boolQuery();
queryBuilder
        .must(queryBuilder1)
        .must(queryBuilder2)
        .must(queryBuilder3);

• 3.range查询（类似于sql的between .. and ..)

QueryBuilder rangeQuery = QueryBuilders.rangeQuery("birthDay").from(yesterday).to(today);

• 4.嵌套对象查询

QueryBuilder queryBuilder = QueryBuilders.nestedQuery("nested", QueryBuilders.termQuery("address.id", 100001), ScoreMode.None);

ScoreMode: 定义other join side中score是如何被使用的。如果不关注scoring，我们只需要设置成ScoreMode.None，此种方式会忽略评分因此会更高效和节约内存

3.获取统计数据

• 1.非嵌套获取数据求和

SumAggregationBuilder sumBuilder = AggregationBuilders.sum("sum").field("number");
SearchQuery searchQuery = new NativeSearchQueryBuilder()
        .withIndices(QUERY_INDEX)
        .withTypes(QUERY_TYPE)
        .withQuery(boolQueryBuilder)
        .addAggregation(sumBuilder).build();
        
AggregatedPage<ParkingOrder> account = (AggregatedPage<ParkingOrder>) esParkingOrderRepository.search(EsQueryBuilders.buildYesterdayArrearsSumQuery(employeeId));

int sum = account.getAggregation("sum", SumAggregation.class).getSum().intValue();

• 2.嵌套数据求和

SumAggregationBuilder sumBuilder = AggregationBuilders.sum("sum").field("adress.num");
AggregationBuilder aggregationBuilder = AggregationBuilders.nested("nested", "adress").subAggregation(sumBuilder);
SearchQuery searchQuery = new NativeSearchQueryBuilder()
        .withIndices(QUERY_INDEX)
        .withTypes(QUERY_TYPE)
        .withQuery(boolQueryBuilder)
        .addAggregation((AbstractAggregationBuilder) aggregationBuilder).build();
AggregatedPage<ParkingOrder> account = (AggregatedPage<ParkingOrder>) esParkingOrderRepository.search(EsQueryBuilders.buildYesterdayArrearsSumQuery(employeeId));
int sum = account.getAggregation("nested", SumAggregation.class).getAggregation("sum", SumAggregation.class).getSum().intValue();