查看“Java Elasticsearch：查询”的源代码

[[category:ElasticSearch]]
[[category:Java]]

== 基本用法 ==
实现ES查询的关键步骤：
# 创建 RestHighLevelClient，Java ES Client对象；
# 创建 '''SearchRequest''' 对象：负责设置搜索参数；
# 通过 Client对象发送请求；
# 处理搜索结果；

=== 创建“RestHighLevelClient” ===
略（参考：[http://wiki.eijux.com/Java_Elasticsearch%EF%BC%9A%E5%9F%BA%E7%A1%80#.E8.BF.9E.E6.8E.A5.E9.85.8D.E7.BD.AE Java Elasticsearch：基础：连接配置]）

=== 创建“SearchRequest” ===
创建 '''SearchRequest''' 对象步骤如下：
# 创建 SearchRequest 对象；
# 通过 '''SearchSourceBuilder''' '''设置搜索参数'''；
# 将 SearchSourceBuilder 绑定到 SearchRequest 对象；


* 实际上大部分 SearchRequest 对象的搜索参数都是通过 SearchSourceBuilder 对象间接设置。

==== 初始化“SearchRequest” ====
SearchRequest 负责设置搜索参数，包括：ES Query、分页参数等等常用设置（通过 SearchSourceBuilder 对象间接设置）。

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// 创建SearchRequest对象，索引名=posts
SearchRequest searchRequest = new SearchRequest("posts"); 
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==== 创建“SearchSourceBuilder” ====
通过 SearchSourceBuilder 间接完成搜索参数的设置。

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// 创建SearchSourceBuilder，构建ES搜索
SearchSourceBuilder sourceBuilder = new SearchSourceBuilder(); 
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===== 构造查询条件 =====
Java ES 查询条件是通过 '''QueryBuilders''' 工具类构建的：
'''<pre>
QueryBuilder 是所有 Java ES 查询的基础接口；
</pre>'''

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// 例子-构建一个Match模糊查询
QueryBuilder matchQueryBuilder = QueryBuilders.matchQuery("user", "kimchy")
                         .fuzziness(Fuzziness.AUTO)
                         .prefixLength(3)
                         .maxExpansions(10);

// 将QueryBuilders构建的查询，绑定到SearchSourceBuilder对象
sourceBuilder.query(matchQueryBuilder);
</syntaxhighlight>
或：
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// 设置ES查询条件
sourceBuilder.query(QueryBuilders.termQuery("user", "kimchy")); 
</syntaxhighlight>

===== 设置分页参数 =====
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// 设置分页参数，偏移从0开始
sourceBuilder.from(0); 
// 设置分页参数，分页大小=5
sourceBuilder.size(5); 
</syntaxhighlight>

===== 设置排序参数 =====
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// 根据id字段，升序
sourceBuilder.sort("id", SortOrder.ASC);
</syntaxhighlight>

===== 设置请求超时时间 =====
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// 设置请求超时时间，60秒
sourceBuilder.timeout(new TimeValue(60, TimeUnit.SECONDS));
</syntaxhighlight>

==== 将 SearchSourceBuilder 绑定到 SearchRequest 对象 ====
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// 将 SearchSourceBuilder 绑定到 SearchRequest 对象
searchRequest.source(sourceBuilder);
</syntaxhighlight>

=== 执行请求 ===
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SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);
</syntaxhighlight>

=== 处理结果 ===
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RestStatus status = searchResponse.status(); // ES请求状态
TimeValue took = searchResponse.getTook(); // 执行时间
Boolean terminatedEarly = searchResponse.isTerminatedEarly();
Boolean timedOut = searchResponse.isTimedOut(); // 是否超时

// 获取hits，SearchHits对象包含搜索结果
SearchHits hits = searchResponse.getHits();

// 搜索结果总数
TotalHits totalHits = hits.getTotalHits();
long numHits = totalHits.value;

// 遍历搜索结果
SearchHit[] searchHits = hits.getHits();
for (SearchHit hit : searchHits) {
    // 获取文档内容，json字符串格式
    String sourceAsString = hit.getSourceAsString();
    // 获取文档内容，Map对象格式
    Map<String, Object> sourceAsMap = hit.getSourceAsMap();
}
</syntaxhighlight>

=== 完整示例 ===
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// 首先创建 RestClient，后续章节通过RestClient对象进行参数配置。
RestClientBuilder restClientBuilder = RestClient.builder(
                new HttpHost("localhost", 9200, "http"), // 设置ES服务地址，支持多个
                new HttpHost("localhost", 9201, "http"));

// 创建 RestHighLevelClient，请求都是通过 RestHighLevelClient 实例发出去的。
RestHighLevelClient client = new RestHighLevelClient(restClientBuilder);

// 创建 SearchRequest 对象
SearchRequest searchRequest = new SearchRequest();
// 通过 SearchSourceBuilder 构建搜索参数
SearchSourceBuilder builder = new SearchSourceBuilder();
// 通过 QueryBuilders 构建ES查询条件
builder.query(QueryBuilders.termsQuery("order_id", 1,2,3,4,5));
// 设置搜索参数
searchRequest.source(builder);

// 执行ES请求
SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);
// 获取搜索到的文档
SearchHits hits = searchResponse.getHits();
// 遍历搜索结果
SearchHit[] searchHits = hits.getHits();
for (SearchHit hit : searchHits) {
     // 获取文档内容，json字符串格式
     String sourceAsString = hit.getSourceAsString();
     // 获取文档内容，Map对象格式
     Map<String, Object> sourceAsMap = hit.getSourceAsMap();
}
</syntaxhighlight>

== 全文搜索（Match） ==
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