一、基礎API簡介1、RestHighLevelClient

RestHighLevelClient的API作為ElasticSearch備受推薦的客戶端元件，其封裝系統操作ES的方法，包括索引結構管理，資料增刪改查管理，常用查詢方法，並且可以結合原生ES查詢原生語法，功能十分強大。

在使用RestHighLevelClient的語法時，通常涉及上面幾個方面，在掌握基礎用法之上可以根據業務特點進行一些自定義封裝，這樣可以更優雅的解決業務需求。

使用RestHighLevelClient需要依賴rest-high-level-client包，和ES相關基礎依賴。

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

這裡不做過多描述，注意一點：因為ES的資料結構特點，所以不需要索引更新方法，新的欄位在更新資料時直接寫入即可，不需要提前更新索引結構。

@Servicepublic class EsIndexOperation {    @Resource    private RestHighLevelClient client ;    private final RequestOptions options = RequestOptions.DEFAULT;    /**     * 判斷索引是否存在     */    public boolean checkIndex (String index) {        try {            return client.indices().exists(new GetIndexRequest(index), options);        } catch (IOException e) {            e.printStackTrace();        }        return Boolean.FALSE ;    }    /**     * 建立索引     */    public boolean createIndex (String indexName ,Map<String, Object> columnMap){        try {            if(!checkIndex(indexName)){                CreateIndexRequest request = new CreateIndexRequest(indexName);                if (columnMap != null && columnMap.size()>0) {                    Map<String, Object> source = new HashMap<>();                    source.put("properties", columnMap);                    request.mapping(source);                }                this.client.indices().create(request, options);                return Boolean.TRUE ;            }        } catch (IOException e) {            e.printStackTrace();        }        return Boolean.FALSE;    }    /**     * 刪除索引     */    public boolean deleteIndex(String indexName) {        try {            if(checkIndex(indexName)){                DeleteIndexRequest request = new DeleteIndexRequest(indexName);                AcknowledgedResponse response = client.indices().delete(request, options);                return response.isAcknowledged();            }        } catch (Exception e) {            e.printStackTrace();        }        return Boolean.FALSE;    }}

這裡在更新資料時，可以直接修改索引結構，在dataMap中放進新的欄位即可。

@Servicepublic class EsDataOperation {    @Resource    private RestHighLevelClient client ;    private final RequestOptions options = RequestOptions.DEFAULT;    /**     * 寫入資料     */    public boolean insert (String indexName, Map<String,Object> dataMap){        try {            BulkRequest request = new BulkRequest();            request.add(new IndexRequest(indexName,"doc").id(dataMap.remove("id").toString())                    .opType("create").source(dataMap,XContentType.JSON));            this.client.bulk(request, options);            return Boolean.TRUE ;        } catch (Exception e){            e.printStackTrace();        }        return Boolean.FALSE;    }    /**     * 批次寫入資料     */    public boolean batchInsert (String indexName, List<Map<String,Object>> userIndexList){        try {            BulkRequest request = new BulkRequest();            for (Map<String,Object> dataMap:userIndexList){                request.add(new IndexRequest(indexName,"doc").id(dataMap.remove("id").toString())                        .opType("create").source(dataMap,XContentType.JSON));            }            this.client.bulk(request, options);            return Boolean.TRUE ;        } catch (Exception e){            e.printStackTrace();        }        return Boolean.FALSE;    }    /**     * 更新資料，可以直接修改索引結構     */    public boolean update (String indexName, Map<String,Object> dataMap){        try {            UpdateRequest updateRequest = new UpdateRequest(indexName,"doc", dataMap.remove("id").toString());            updateRequest.setRefreshPolicy(WriteRequest.RefreshPolicy.IMMEDIATE);            updateRequest.doc(dataMap) ;            this.client.update(updateRequest, options);            return Boolean.TRUE ;        } catch (Exception e){            e.printStackTrace();        }        return Boolean.FALSE;    }    /**     * 刪除資料     */    public boolean delete (String indexName, String id){        try {            DeleteRequest deleteRequest = new DeleteRequest(indexName,"doc", id);            this.client.delete(deleteRequest, options);            return Boolean.TRUE ;        } catch (Exception e){            e.printStackTrace();        }        return Boolean.FALSE;    }}

注意：查詢總數的CountRequest語法，SearchRequest查詢結果中資料轉換語法，分頁查詢中需要指定偏移位置和分頁大小。

@Servicepublic class EsQueryOperation {    @Resource    private RestHighLevelClient client ;    private final RequestOptions options = RequestOptions.DEFAULT;    /**     * 查詢總數     */    public Long count (String indexName){        // 指定建立時間        BoolQueryBuilder queryBuilder = QueryBuilders.boolQuery();        queryBuilder.must(QueryBuilders.termQuery("createTime", 1611378102795L));        SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();        sourceBuilder.query(queryBuilder);        CountRequest countRequest = new CountRequest(indexName);        countRequest.source(sourceBuilder);        try {            CountResponse countResponse = client.count(countRequest, options);            return countResponse.getCount();        } catch (Exception e) {            e.printStackTrace();        }        return 0L;    }    /**     * 查詢集合     */    public List<Map<String,Object>> list (String indexName) {        // 查詢條件,指定時間並過濾指定欄位值        SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();        BoolQueryBuilder queryBuilder = QueryBuilders.boolQuery();        queryBuilder.must(QueryBuilders.termQuery("createTime", 1611378102795L));        queryBuilder.mustNot(QueryBuilders.termQuery("name","北京-李四"));        sourceBuilder.query(queryBuilder);        SearchRequest searchRequest = new SearchRequest(indexName);        searchRequest.source(sourceBuilder);        try {            SearchResponse searchResp = client.search(searchRequest, options);            List<Map<String,Object>> data = new ArrayList<>() ;            SearchHit[] searchHitArr = searchResp.getHits().getHits();            for (SearchHit searchHit:searchHitArr){                Map<String,Object> temp = searchHit.getSourceAsMap();                temp.put("id",searchHit.getId()) ;                data.add(temp);            }            return data;        } catch (Exception e) {            e.printStackTrace();        }        return null ;    }    /**     * 分頁查詢     */    public List<Map<String,Object>> page (String indexName,Integer offset,Integer size) {        // 查詢條件,指定時間並過濾指定欄位值        SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();        sourceBuilder.from(offset);        sourceBuilder.size(size);        sourceBuilder.sort("createTime", SortOrder.DESC);        SearchRequest searchRequest = new SearchRequest(indexName);        searchRequest.source(sourceBuilder);        try {            SearchResponse searchResp = client.search(searchRequest, options);            List<Map<String,Object>> data = new ArrayList<>() ;            SearchHit[] searchHitArr = searchResp.getHits().getHits();            for (SearchHit searchHit:searchHitArr){                Map<String,Object> temp = searchHit.getSourceAsMap();                temp.put("id",searchHit.getId()) ;                data.add(temp);            }            return data;        } catch (Exception e) {            e.printStackTrace();        }        return null ;    }}

排序除了常規的指定欄位升序降序規則之外，還可以基於原生的指令碼語法，基於自定義規則排序讓一些特定的資料沉底或者置頂。