Elasticsearch(ES 8.x) 自动补全java代码

当使用Elasticsearch进行自动补全时，可以使用Elasticsearch的Completion Suggester功能。Completion Suggester是一种特殊类型的字段，它可以用于实现自动补全功能。下面是使用Java代码实现Elasticsearch自动补全的示例：

1. 首先，你需要在Java项目中添加Elasticsearch的Java客户端库。你可以在Maven或Gradle中添加以下依赖项：

<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-high-level-client</artifactId>
    <version>8.0.0</version>
</dependency>

2. 创建Elasticsearch的Java客户端：

RestHighLevelClient client = new RestHighLevelClient(
        RestClient.builder(new HttpHost("localhost", 9200, "http")));

3. 创建索引和映射：

CreateIndexRequest request = new CreateIndexRequest("my_index");
client.indices().create(request, RequestOptions.DEFAULT);

PutMappingRequest mappingRequest = new PutMappingRequest("my_index");
mappingRequest.source("{\"properties\":{\"suggest\":{\"type\":\"completion\"}}}", XContentType.JSON);
client.indices().putMapping(mappingRequest, RequestOptions.DEFAULT);

4. 添加文档：

IndexRequest indexRequest = new IndexRequest("my_index");
indexRequest.id("1");
indexRequest.source("{\"suggest\":{\"input\":[\"apple\", \"banana\", \"orange\"]}}", XContentType.JSON);
client.index(indexRequest, RequestOptions.DEFAULT);

5. 执行自动补全查询：

SearchRequest searchRequest = new SearchRequest("my_index");
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
SuggestionBuilder suggestionBuilder = SuggestBuilders.completionSuggestion("suggest").prefix("app");
SuggestBuilder suggestBuilder = new SuggestBuilder();
suggestBuilder.addSuggestion("my-suggestion", suggestionBuilder);
searchSourceBuilder.suggest(suggestBuilder);
searchRequest.source(searchSourceBuilder);

SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);
CompletionSuggestion suggestion = searchResponse.getSuggest().getSuggestion("my-suggestion");
List<CompletionSuggestion.Entry.Option> options = suggestion.getOptions();

for (CompletionSuggestion.Entry.Option option : options) {
    String text = option.getText().string();
    System.out.println(text);
}

这是一个简单的示例，演示了如何使用Elasticsearch的Java客户端实现自动补全功能。你可以根据自己的需求进行修改和扩展。