使用NEST调用ElasticSearch

前言

ElasticSearch（以后简称ES）是一个稳定可靠快速的分布式文档存储（内存+本地持久化）和搜索引擎

本文使用.NetCore3.1调用ES作为示例。ES的.NET SDK采用NEST

注意：ES版本与NEST版本需要匹配，否则会造成”Invalid NEST response built from a unsuccessful () low level call on POST“。示例使用elasticsearch:7.16.1+NEST:7.17.0

ElasticSearch安装部署

# ElasticSearch安装手册

## 拉取镜像
```
docker pull elasticsearch:7.16.1
```
## 创建本地映射
```
mkdir -p /elasticsearch/data
chmod -R 777 /elasticsearch/data
```
## 开启容器
```
docker run --name es -p 9200:9200 -p 9300:9300  -e "discovery.type=single-node" -e ES_JAVA_OPTS="-Xms256m -Xmx256m" -v /elasticsearch/data:/usr/share/elasticsearch/data -d elasticsearch:7.16.1
```
## 修改配置
```
docker exec -it es /bin/bash
ls
cd config
ls
vi elasticsearch.yml

# 加入跨域配置
http.cors.enabled: true
http.cors.allow-origin: "*"
http.cors.allow-headers: Authorization
xpack.security.enabled: true
xpack.security.transport.ssl.enabled: true

# 设置密码(如果运行以下命令提示不成功，exit退出容器后restart再进入)
bin/elasticsearch-setup-passwords interactive
```
## 重启容器
```
docker restart es
```

 .NETCORE3.1调用

1.Nuget中获取NEST(v7.17.0)

2.appsettings.json中配置ES地址

"EsUrl": "http://192.168.1.10:9200/"

3.增加ES操作服务

IEsClientProvider.cs

using Nest;

namespace Elasticsearch.Service
{
    public interface IEsClientProvider
    {
        ElasticClient GetClient();
    }
}

EsClientProvider.cs

using Microsoft.Extensions.Configuration;
using Nest;
using System;

namespace Elasticsearch.Service
{
    public class EsClientProvider : IEsClientProvider
    {
        private readonly IConfiguration _configuration;
        private ElasticClient _client;
        public EsClientProvider(IConfiguration configuration)
        {
            _configuration = configuration;
        }

        public ElasticClient GetClient()
        {
            if (_client != null)
                return _client;

            InitClient();
            return _client;
        }

        private void InitClient()
        {
            var node = new Uri(_configuration["EsUrl"]);
            _client = new ElasticClient(new ConnectionSettings(node).DefaultIndex("tracks"));
        }
    }
}

4.Startup.ConfigureServices中注册服务

services.AddSingleton<IEsClientProvider, EsClientProvider>();

5.Controller中获取注入的服务

using Elasticsearch.Service;
using Microsoft.AspNetCore.Mvc;
using Nest;
using System.Collections.Generic;

namespace Elasticsearch.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class ValueController : ControllerBase
    {
        private readonly ElasticClient _client;

        public ValueController(IEsClientProvider clientProvider)
        {
            _client = clientProvider.GetClient();
        }

        /// <summary>
        /// 提交数据
        /// </summary>
        /// <param name="post"></param>
        /// <returns></returns>
        [HttpPost("[action]")]
        public Post Submit(Post post)
        {
            IndexResponse res=_client.IndexDocument(post);
            if (res.IsValid)
            {
                return post;
            }
            else
            {
                return null;
            }
        }

        /// <summary>
        /// 查询数据
        /// </summary>
        /// <param name="shipguid"></param>
        /// <returns></returns>
        [HttpGet("[action]")]
        public IReadOnlyCollection<Post> Search(string shipguid)
        {
            return _client.Search<Post>(s => s
                .From(0)
                .Size(10)
                .Query(q => q.Match(m => m.Field(f => f.shipGuid).Query(shipguid)))).Documents;
        }
    }
}