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Elasticsearch能支持动态的DSL

丁D
学无止境
2020-12-09 14:46
31187已阅读

Elasticsearch DSL

摘要本文介绍如何让Elasticsearch能像Mybatis一样支持动态的SQL.

### 背景
当我们使用了Elasticsearch，我们就需要考虑如何去访问Elasticsearch上面的数据，目前官方推荐RestHighLevelClient SDK去操作es数据，但是使用过的同学的知道，要构造这个这个请求对象很麻烦，特别是当我们的查询复杂的时候。
下面有一段本blog使用Sdk去访问es的代码，看起来就知道构造一个查询对象麻烦。

```java
		RestHighLevelClient client = new RestHighLevelClient(restClient);

// 创建并设置SearchSourceBuilder对象
		SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
		BoolQueryBuilder  boolQueryBuilder = new BoolQueryBuilder();
		BoolQueryBuilder  filterQueryBuilder = new BoolQueryBuilder();

if(categoryId != null && categoryId != Category.INDEX_0){//首页查询所有
			TermQueryBuilder termQueryBuilder = QueryBuilders.termQuery("category_id",categoryId);
			filterQueryBuilder.must(termQueryBuilder);
		}
		filterQueryBuilder.must(QueryBuilders.termQuery("states",1));//已发布的
		//filterQueryBuilder.should(QueryBuilders.matchQuery("title",searchKey));
		//filterQueryBuilder.should(QueryBuilders.matchQuery("summary",searchKey));
		HasChildQueryBuilder hasChildQueryBuilder = new HasChildQueryBuilder(
				"t_article_contents",QueryBuilders.matchQuery("contents",searchKey).boost(1), ScoreMode.None);
		//filterQueryBuilder.should(hasChildQueryBuilder);
		//这里的should是放在 bool query中的原本是没有作用的只有提升相关度的作用，，，但是使用.minimumShouldMatch(1);  至少匹配一个
		boolQueryBuilder.should(QueryBuilders.matchQuery("title",searchKey).boost(5)).minimumShouldMatch(1);
		boolQueryBuilder.should(QueryBuilders.matchQuery("summary",searchKey).boost(3)).minimumShouldMatch(1);
		boolQueryBuilder.should(hasChildQueryBuilder.boost(1)).minimumShouldMatch(1);
		
		boolQueryBuilder.filter(filterQueryBuilder);
		searchSourceBuilder.query(boolQueryBuilder);
		searchSourceBuilder.from(0);
		// 每页多少条数据
		searchSourceBuilder.size(1000);
		// 设置排序规则
		searchSourceBuilder.sort(new ScoreSortBuilder().order(SortOrder.DESC));  // 按_score降序排序（默认值）
		searchSourceBuilder.sort("publish_time", SortOrder.DESC);
		// 设置超时时间为2s
		searchSourceBuilder.timeout(new TimeValue(2000));

//高亮
		HighlightBuilder highlightBuilder = new HighlightBuilder();//Creates a new HighlightBuilder
		highlightBuilder.preTags("<span class=\"highlight-es\">").postTags("</span>");
		HighlightBuilder.Field highlightTitle =
				new HighlightBuilder.Field("title");//Create a field highlighter for the title field
		highlightTitle.highlighterType("unified");  //Set the field highlighter type
		highlightBuilder.field(highlightTitle);  //Add the field highlighter to the highlight builder
		HighlightBuilder.Field highlightSummary = new HighlightBuilder.Field("summary");
		highlightBuilder.field(highlightSummary);
		searchSourceBuilder.highlighter(highlightBuilder);

// 创建并设置SearchRequest对象
		SearchRequest searchRequest = new SearchRequest();
		// 设置request要搜索的索引和类型
		searchRequest.indices("blog").types("t_article");
		searchRequest.source(searchSourceBuilder);
		SearchResponse searchResponse = client.search(searchRequest);
		System.out.printf(searchResponse.toString());
		SearchHits hits = searchResponse.getHits();

List<Article> publishList = new ArrayList<>();
		for(SearchHit hit : hits){
			Article article = new Article();
			Map<String, Object> sourceAsMap = hit.getSourceAsMap();
			article.setId(Long.parseLong(hit.getId()));
			article.setTitle((String)sourceAsMap.get("title"));
			article.setThumbUrl((String)sourceAsMap.get("thumb_url"));
			article.setSummary((String)sourceAsMap.get("summary"));
			article.setClickNum(Integer.valueOf(sourceAsMap.get("click_num")+""));
			article.setPublishTime((String)sourceAsMap.get("publish_time"));
			article.setCreator((String)sourceAsMap.get("creator"));

Map<String, HighlightField>  highMap = hit.getHighlightFields();
			if(highMap!=null && !highMap.isEmpty()){
				if(highMap.get("title")!=null){
					article.setTitle(highMap.get("title").getFragments()[0].string());
				}
				if(highMap.get("summary")!=null){
					article.setSummary(highMap.get("summary").getFragments()[0].string());
				}
			}
			publishList.add(article);
		}
		mv.addObject("publishList",publishList);
		List<Article> mostClickList = this.findMostClickArticle();
		mv.addObject("mostClickList",mostClickList);
		client.close();
```

使用过mybatis和hibernate的同学都知道，mybatis简单，易学，那么我们也可以使用elasticsearch的语法DSL来查询。

### 动态DSL
我们可以建一个文件我们的dsl放在resource下面，customer_dsl.xml
```xml
<?xml version="1.0" encoding="UTF-8"?>
<dsls>
	
	<dsl id="customer.calcCustomerCount">
		{
			"size": 0,
			"query": {
				"bool": {
					"must": [
						{
							"term": {
								"type": "customer"
							}
						},
						{
							"term": {
								"group_id": {
									"value": "${#groupId}"
								}
							}
						},
						。。。。
						。。。。。
						。。。。。
						。。。。。
						<if test="#brandId == null and #isCustomer != null and #isCustomer">
						,{
							"range": {
								"first_pay_time": {
									"gte": "${#startTimeUtc}",
									"lte": "${#endTimeUtc}"
								}
							}
						}
						</if>
					]
				}
			}
		}
	</dsl>
</dsls>

```
解析动态的dsl语句，这里我为了简单将customer_dsl，放在c盘，这个可以转成dsl，然后使用RestHighLevelClient来直接执行DSL.
```java

public static void main(String[] args) throws Exception {
        DefaultQueryDSLFactory dslFactory = new DefaultQueryDSLFactory("file:c:/customer_dsl.xml");
        Map<String, Object> searchMap = new HashMap<>();
        searchMap.put("groupId",123);
        String s = dslFactory.getQueryDsl("customer.calcCustomerCount", searchMap);
        System.out.println(s);
    }
```

上面看到这个语法${#groupId}，可能会觉得很奇怪，不像mybatis啊，这个是使用SpEl语法#groupId，然后我们又重写了前缀，和后缀的方法
```java
		private final String expressionPrefix = "${";

private final String expressionSuffix = "}";
		
				@Override
		public final String getExpressionPrefix() {
			return this.expressionPrefix;
		}

@Override
		public final String getExpressionSuffix() {
			return this.expressionSuffix;
		}
```

可以配置项目启动的创建bean会自动加载dsl.xml文件放在缓存中
```java
@Configuration
public class DefaultQueryDSLFactoryConfig {

@Bean
    public DefaultQueryDSLFactory createDefaultQueryDSLFactory() throws Exception {
        DefaultQueryDSLFactory defaultQueryDSLFactory = new DefaultQueryDSLFactory("classpath*:**/*_dsl.xml");
        return defaultQueryDSLFactory;
    }
}
```

[代码](https://github.com/348786639/dynamicDSL.git "代码")

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