Elasticsearch High Level REST Client 經常使用 Java API

Elasticsearch(ES)有兩種鏈接方式：transport、rest。transport經過TCP方式訪問ES(只支持java),rest方式經過http API 訪問ES(沒有語言限制)。ES官方建議使用rest方式, transport 將計劃在後面的版本中廢棄。

官方提供low-level rest client(支持5.0及之後版本) 和high-level rest client(支持版本爲 5.6及之後版本)。須要java版本爲1.8。 High level rest client 接受和Transport Client相同的請求參數，並返回相同的響應對象。本文主要介紹High level rest client 經常使用的 Java api。

引入maven jar包

<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-high-level-client</artifactId>
    <version>6.1.4</version>
</dependency>
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初始化客戶端

RestHighLevelClient client = new RestHighLevelClient(
        RestClient.builder(
                new HttpHost("localhost", 9200, "http"),
                new HttpHost("localhost", 9201, "http")));
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關閉客戶端

client.close();
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文檔格式

ES容許咱們存儲一個JSON格式的文檔,能夠經過如下幾種不一樣方式產生JSON格式的文檔。

• 1.手動方式，使用原生的byte[]或者String

String json = "{" +
        "\"user\":\"kimchy\"," +
        "\"postDate\":\"2013-01-30\"," +
        "\"message\":\"trying out Elasticsearch\"" +
    "}";
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• 2. 使用Map方式，會自動轉換成與之等價的JSON

Map<String, Object> json = new HashMap<String, Object>();
json.put("user","kimchy");
json.put("postDate",new Date());
json.put("message","trying out Elasticsearch");
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• 3. 使用第三方庫來序列化beans，如Jackson

ObjectMapper mapper = new ObjectMapper(); 
byte[] json = mapper.writeValueAsBytes(yourbean);
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• 4. 使用內置的幫助類 XContentFactory.jsonBuilder()

XContentBuilder builder = XContentFactory.jsonBuilder()  
            .startObject()  
                .field("user", "ccse")  
                .field("postDate", new Date())  
                .field("message", "this is Elasticsearch")  
            .endObject();  
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index api

新建文檔，若文檔已經存在，會覆蓋以前的文檔

IndexRequest request = new IndexRequest(
        "posts", 
        "doc",  
        "1");   
String jsonString = "{" +
        "\"user\":\"kimchy\"," +
        "\"postDate\":\"2013-01-30\"," +
        "\"message\":\"trying out Elasticsearch\"" +
        "}";
request.source(jsonString, XContentType.JSON); 
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update api

更新文檔，文檔不存在時，返回document missing

UpdateRequest request = new UpdateRequest("posts", "doc", "1")
        .doc(builder);
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upsert api

文檔存在則進行更新，不存在則新建

UpdateRequest request = new UpdateRequest("posts", "doc", "1")
.doc(builder);
 UpdateRequest updateRequest = new UpdateRequest(posts", "doc", "1") .doc(builder).upsert(indexRequest); 複製代碼

也能夠根據腳本進行更新

Map<String, Object> parameters = singletonMap("count", 4); 
Script inline = new Script(ScriptType.INLINE, "painless", "ctx._source.field += params.count", parameters);  
request.script(inline);  
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Bulk api

批量api能夠一次執行多個請求，包括 index,update,upsert,delete等請求。

BulkRequest request = new BulkRequest(); 
request.add(new IndexRequest("posts", "doc", "1")  
        .source(XContentType.JSON,"field", "foo"));
request.add(new IndexRequest("posts", "doc", "2")  
        .source(XContentType.JSON,"field", "bar"));
request.add(new IndexRequest("posts", "doc", "3")  
        .source(XContentType.JSON,"field", "baz"));
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