命令查詢職責分離模式(Command Query Responsibility Segregation，CQRS)從業(yè)務上分離修改 (Command，增，刪，改，會對系統(tǒng)狀態(tài)進行修改)和查詢（Query，查，不會對系統(tǒng)狀態(tài)進行修改)的行為。從而使得邏輯更加清晰，便于對不同部分進行針對性的優(yōu)化。
CQRS有以下幾點有點：
1.分工明確，可以負責不同的部分；
2.將業(yè)務上的命令和查詢的職責分離能夠提高系統(tǒng)的性能、可擴展性和安全性。并且在系統(tǒng)的演化中能夠保持高度的靈活性，能夠防止出現(xiàn)CRUD模式中，對查詢或者修改中的某一方進行改動，導致另一方出現(xiàn)問題的情況；
3.邏輯清晰，能夠看到系統(tǒng)中的那些行為或者操作導致了系統(tǒng)的狀態(tài)變化；
4.可以從數(shù)據(jù)驅動(Data-Driven) 轉到任務驅動(Task-Driven)以及事件驅動(Event-Driven)。
因此Command使用數(shù)據(jù)庫，Query使用效率查詢效率更高的Elasticsearch。
如何確保數(shù)據(jù)庫和Elasticsearch的數(shù)據(jù)的一致性？
我們可以使用事件驅動(Event-Driven)即Spring Data的Domain Event同步數(shù)據(jù)，可參考文章：http://www.zmynmublwnt.cn/article/154225.html 。
當老數(shù)據(jù)庫有大量數(shù)據(jù)需要導入Elasticsearch時，可參考文章：http://www.zmynmublwnt.cn/article/153563.html
Spring Data Elasticsearch使用的是transport client，而Elasticsearch官網(wǎng)推薦使用REST client。阿里云的Elasticsearch使用transport client目前還在存在問題，阿里云推薦使用REST client。
本示例使用的是Spring Data Jest鏈接Elasticsearch（目前只有spring boot2.0以上版本支持），Elasticsearch的版本為：5.5.3
1.項目構建
1.pom依賴如下：
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<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
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spring: data: jest: uri: http://127.0.0.1:9200 username: elastic password: changeme |
2.構造查詢條件
以簡單的實體類為例
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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@Datapublic 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;} |
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package com.hfcsbc.esetl.domain;import lombok.Data;import javax.persistence.Entity;import javax.persistence.Id;/** * Create by pengchao on 2018/2/23 */@Entity@Datapublic class Address { @Id private Long id; private String name; private Integer number;} |
1.根據(jù)多個狀態(tài)查詢(類似于sql的in)
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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鏈接查詢(類似于sql的and)
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BoolQueryBuilder queryBuilder = QueryBuilders.boolQuery();queryBuilder .must(queryBuilder1) .must(queryBuilder2) .must(queryBuilder3); |
3.range查詢（類似于sql的between .. and ..)
QueryBuilder rangeQuery = QueryBuilders.rangeQuery("birthDay").from(yesterday).to(today);
4.嵌套對象查詢
QueryBuilder queryBuilder = QueryBuilders.nestedQuery("nested", QueryBuilders.termQuery("address.id", 100001), ScoreMode.None);
ScoreMode: 定義other join side中score是如何被使用的。如果不關注scoring，我們只需要設置成ScoreMode.None，此種方式會忽略評分因此會更高效和節(jié)約內存
3.獲取統(tǒng)計數(shù)據(jù)
1.非嵌套獲取數(shù)據(jù)求和
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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.嵌套數(shù)據(jù)求和
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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(); |
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持服務器之家。
原文鏈接：http://www.wisely.top/2018/02/27/spring-data-jest-elasticsarch/
