本文介绍spring-data-elasticsearch:jar:4.0.0.RELEASE版本completion suggest的使用。
主要用到CompletionSuggestionBuilder,SuggestBuilder这两个类
同QueryBuilders一样suggest也有一个SuggestBuilders用于构建term,phrase,completion三种类型的suggest构造器

CompletionSuggestionBuilder textBuilder = 
SuggestBuilders.completionSuggestion("goodsName.suggest")

而对于Completion的Context Suggest，我们就要用到CategoryQueryContext和GeoQueryContext
如下：

CategoryQueryContext categoryQueryContext = 
CategoryQueryContext.builder().setCategory(cityCode).build();

注意，这里的cityCode是从前端传递过来的一个动态参数，用于限定城市。
接下来将其封装到Map中

Map<String, List<? extends ToXContent>> contexts = new HashMap<>();
List<CategoryQueryContext> list = new ArrayList<>();
list.add(categoryQueryContext);
contexts.put("city", list); // 这里要和mapping中配置的name保持一致

最后我们把拼装好的contexts放到CompletionSuggestionBuilder中

textBuilder.contexts(contexts);

完整代码如下：

public List<String> suggest(String keyword, String cityCode) {
        HashSet<String> returnSet = new LinkedHashSet<>(); // 用于存储查询到的结果
        // 创建CompletionSuggestionBuilder
        CompletionSuggestionBuilder textBuilder = SuggestBuilders.completionSuggestion("goodsName.suggest") // 指定字段名
        .size(10) // 设定返回数量
        .skipDuplicates(true) // 去重
        // 配置context
        CategoryQueryContext categoryQueryContext = CategoryQueryContext.builder().setCategory(cityCode).build();
        Map<String, List<? extends ToXContent>> contexts = new HashMap<>();
        List<CategoryQueryContext> list = new ArrayList<>();
        list.add(categoryQueryContext);
        contexts.put("city", list);
        textBuilder.contexts(contexts); // 设置contexts
        // 创建suggestBuilder并将completionBuilder添加进去
        SuggestBuilder suggestBuilder = new SuggestBuilder();
        suggestBuilder.addSuggestion("suggest_text", textBuilder)
        .setGlobalText(keyword); 
        // 执行请求
        Suggest suggest = elasticsearchRestTemplate.suggest(suggestBuilder, elasticsearchRestTemplate.getIndexCoordinatesFor(Goods.class)).getSuggest();
        // 取出结果
        Suggest.Suggestion<Entry<Option>> textSuggestion = suggest.getSuggestion("suggest_text");
        for (Entry<Option> entry : textSuggestion.getEntries()) {
            List<Option> options = entry.getOptions();
            for (Suggest.Suggestion.Entry.Option option : options) {
                returnSet.add(option.getText().toString());
            }
        }
        return new ArrayList<>(returnSet);
    }

引入的相关类

import org.elasticsearch.search.suggest.Suggest;
import org.elasticsearch.search.suggest.Suggest.Suggestion.Entry;
import org.elasticsearch.search.suggest.Suggest.Suggestion.Entry.Option;
import org.elasticsearch.search.suggest.SuggestBuilder;
import org.elasticsearch.search.suggest.SuggestBuilders;
import org.elasticsearch.search.suggest.completion.CompletionSuggestionBuilder;
import org.elasticsearch.search.suggest.completion.context.CategoryQueryContext;

Goods.java

@Document(indexName = "goods", shards = 1, replicas = 0)
@Mapping(mappingPath = "/mappings/goods.json")
@Data
public class Goods {
    @Id
    private Long goodsId;
    private String goodsName;
    private String cityCode;
}

由于此版本中FieldType并没有提供Completion类型，使用@MultiField无法达到目的，因此用@Mapping方式进行配置
goods.json

{
  "properties": {
    "goodsName": {
      "type": "text",
      "analyzer": "ik_max_word", 
      "search_analyzer": "ik_smart",
      "fields": {
        "suggest": {
          "type": "completion",
          "analyzer": "standard",
          "contexts": [
            {                           
              "name": "city",
              "type": "category",
              "path": "cityCode"
            }
          ]
        }
      }
    }
  }
}

本文重点介绍4.x版本Completion Suggest的使用，如何做到更精确的查找，网上有很多，就不在这里介绍了。
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