一、下载安装
官网下载地址
https://www.elastic.co/cn/downloads/elasticsearch

解压
elasticsearch-8.2.3-windows-x86_64

修改配置
elasticsearch-8.2.3\config\elasticsearch.yml

# ======================== Elasticsearch Configuration =========================
#
# NOTE: Elasticsearch comes with reasonable defaults for most settings.
#       Before you set out to tweak and tune the configuration, make sure you
#       understand what are you trying to accomplish and the consequences.
#
# The primary way of configuring a node is via this file. This template lists
# the most important settings you may want to configure for a production cluster.
#
# Please consult the documentation for further information on configuration options:
# https://www.elastic.co/guide/en/elasticsearch/reference/index.html
#
# ---------------------------------- Cluster -----------------------------------
#
# Use a descriptive name for your cluster:
#
#cluster.name: my-application
#
# ------------------------------------ Node ------------------------------------
#
# Use a descriptive name for the node:
#
#node.name: node-1
#
# Add custom attributes to the node:
#
#node.attr.rack: r1
#
# ----------------------------------- Paths ------------------------------------
#
# Path to directory where to store the data (separate multiple locations by comma):
#
#path.data: /path/to/data
#
# Path to log files:
#
#path.logs: /path/to/logs
#
# ----------------------------------- Memory -----------------------------------
#
# Lock the memory on startup:
#
#bootstrap.memory_lock: true
#
# Make sure that the heap size is set to about half the memory available
# on the system and that the owner of the process is allowed to use this
# limit.
#
# Elasticsearch performs poorly when the system is swapping the memory.
#
# ---------------------------------- Network -----------------------------------
#
# By default Elasticsearch is only accessible on localhost. Set a different
# address here to expose this node on the network:
#
#network.host: 192.168.0.1
#
# By default Elasticsearch listens for HTTP traffic on the first free port it
# finds starting at 9200. Set a specific HTTP port here:
#
#http.port: 9200
#
# For more information, consult the network module documentation.
#
# --------------------------------- Discovery ----------------------------------
#
# Pass an initial list of hosts to perform discovery when this node is started:
# The default list of hosts is ["127.0.0.1", "[::1]"]
#
#discovery.seed_hosts: ["host1", "host2"]
#
# Bootstrap the cluster using an initial set of master-eligible nodes:
#
#cluster.initial_master_nodes: ["node-1", "node-2"]
#
# For more information, consult the discovery and cluster formation module documentation.
#
# --------------------------------- Readiness ----------------------------------
#
# Enable an unauthenticated TCP readiness endpoint on localhost
#
#readiness.port: 9399
#
# ---------------------------------- Various -----------------------------------
#
# Allow wildcard deletion of indices:
#
#action.destructive_requires_name: false

#----------------------- BEGIN SECURITY AUTO CONFIGURATION -----------------------
#
# The following settings, TLS certificates, and keys have been automatically      
# generated to configure Elasticsearch security features on 21-06-2022 06:14:38
#
# --------------------------------------------------------------------------------

# Enable security features
#xpack.security.enabled: true

#xpack.security.enrollment.enabled: true

# Enable encryption for HTTP API client connections, such as Kibana, Logstash, and Agents
#xpack.security.http.ssl:
#  enabled: true
#  keystore.path: certs/http.p12

# Enable encryption and mutual authentication between cluster nodes
#xpack.security.transport.ssl:
  #enabled: true
  #verification_mode: certificate
  #keystore.path: certs/transport.p12
  #truststore.path: certs/transport.p12
# Create a new cluster with the current node only
# Additional nodes can still join the cluster later
#cluster.initial_master_nodes: ["DESKTOP-22BJ4SG"]

# Allow HTTP API connections from anywhere
# Connections are encrypted and require user authentication
http.host: 0.0.0.0

# Allow other nodes to join the cluster from anywhere
# Connections are encrypted and mutually authenticated
#transport.host: 0.0.0.0


# 集群的名字
cluster.name: es-cluster

# 节点名字
node.name: es_node1

# ES的监听地址
network.host: 0.0.0.0

#设置对外服务的http端口，默认为9200
http.port: 9200

#设置索引数据的存储路径
path.data: D:/99-tools/elasticsearch-8.2.3-windows-x86_64/elasticsearch-8.2.3/data    
#设置日志文件的存储路径
path.logs: D:/99-tools/elasticsearch-8.2.3-windows-x86_64/elasticsearch-8.2.3/logs    

# 关闭http访问限制
xpack.security.enabled: false

# 增加新的参数，head插件可以访问es
http.cors.enabled: true
http.cors.allow-origin: "*"

# Enable security features
#xpack.security.enabled: false
xpack.security.enrollment.enabled: true

# Enable encryption for HTTP API client connections, such as Kibana, Logstash, and Agents
xpack.security.http.ssl:
  enabled: false
  keystore.path: certs/http.p12

# Enable encryption and mutual authentication between cluster nodes
xpack.security.transport.ssl:
  enabled: true
  verification_mode: certificate
  keystore.path: certs/transport.p12
  truststore.path: certs/transport.p12
# Create a new cluster with the current node only
# Additional nodes can still join the cluster later
cluster.initial_master_nodes: ["es_node1"]  #注意，这个要与node.name填写一致

#屏蔽自动下载geopip
ingest.geoip.downloader.enabled: false

启动服务
双击elasticsearch-8.2.3\bin\elasticsearch.bat 运行
9300：Java程序访问的端口
9200：浏览器、HTTP访问的端口

http://localhost:9200/

二、客户端elasticsearch-head安装
elasticsearch-head是一款专门针对于Elasticsearch的客户端工具

下载源码
https://github.com/mobz/elasticsearch-head](https://github.com/mobz/elasticsearch-head

加压后，在elasticsearch-head目录下执行命令
需要先安装nodejs，下载地址：http://nodejs.cn/download/

npm install
npm run start
安装成功
http://localhost:9100/

三、springboot 集成
依赖

  <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.13.2</version>
    </dependency>
    <dependency>
        <groupId>org.glassfish</groupId>
        <artifactId>jakarta.json</artifactId>
        <version>2.0.1</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/co.elastic.clients/elasticsearch-java -->
    <dependency>
        <groupId>co.elastic.clients</groupId>
        <artifactId>elasticsearch-java</artifactId>
        <version>8.2.3</version>
    </dependency>

配置

import co.elastic.clients.elasticsearch.ElasticsearchClient;
import co.elastic.clients.json.jackson.JacksonJsonpMapper;
import co.elastic.clients.transport.ElasticsearchTransport;
import co.elastic.clients.transport.rest_client.RestClientTransport;
import org.apache.http.HttpHost;
import org.elasticsearch.client.RestClient;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class ElasticSearchConfig {

    @Value("${elasticsearch.host-name}")
    private String hostName;

    @Value("${elasticsearch.port}")
    private int port;


    @Bean
    public ElasticsearchClient elasticsearchClient(){
        RestClient client = RestClient.builder(new HttpHost(hostName, port,"http")).build();
        ElasticsearchTransport transport = new RestClientTransport(client,new JacksonJsonpMapper());
        return new ElasticsearchClient(transport);
    }

}

index操作类

import co.elastic.clients.elasticsearch.ElasticsearchClient;
import co.elastic.clients.elasticsearch.indices.CreateIndexResponse;
import co.elastic.clients.elasticsearch.indices.DeleteIndexResponse;
import co.elastic.clients.elasticsearch.indices.GetIndexResponse;
import co.elastic.clients.transport.endpoints.BooleanResponse;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.io.IOException;

@Service
public class EsGpsIndexService {

    @Autowired
    private ElasticsearchClient client;

    public final static String INDEX_NAME = "gps";

    /**
     * 增加index
     * @throws IOException
     */
    public boolean create() throws IOException {
        CreateIndexResponse indexResponse = client.indices().create(c -> c.index(INDEX_NAME));
        System.out.println(indexResponse.toString());
        return indexResponse.acknowledged();
    }


    /**
     * 查询Index
     * @throws IOException
     */
    public void query() throws IOException {
        GetIndexResponse getIndexResponse = client.indices().get(i -> i.index(INDEX_NAME));
        System.out.println(getIndexResponse.toString());
    }

    /**
     * 判断index是否存在
     * @throws IOException
     */
    public boolean exists() throws IOException {
        BooleanResponse booleanResponse = client.indices().exists(e -> e.index(INDEX_NAME));
        System.out.println(booleanResponse.value());
        return booleanResponse.value();
    }


    /**
     * 删除index
     * @throws IOException
     */
    public void delete() throws IOException {
        DeleteIndexResponse deleteIndexResponse = client.indices().delete(d -> d.index(INDEX_NAME));
        System.out.println(deleteIndexResponse.toString());
    }

}
document 操作类

import co.elastic.clients.elasticsearch.ElasticsearchClient;
import co.elastic.clients.elasticsearch._types.SortOrder;
import co.elastic.clients.elasticsearch._types.query_dsl.QueryBuilders;
import co.elastic.clients.elasticsearch._types.query_dsl.RangeQuery;
import co.elastic.clients.elasticsearch.core.*;
import co.elastic.clients.elasticsearch.core.bulk.BulkOperation;
import co.elastic.clients.elasticsearch.core.search.Hit;
import co.elastic.clients.json.JsonData;
import co.elastic.clients.transport.endpoints.BooleanResponse;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

@Service
public class EsGpsDocumentService {

    @Autowired
    private ElasticsearchClient client;


    /**
     * 插入document
     * @throws IOException
     */
    public void add(GpsInfo gps) throws IOException {
        IndexResponse indexResponse = client.index(i -> i
                .index(EsGpsIndexService.INDEX_NAME)
                //设置id
                .id(gps.getId())
                //
                .document(gps));

    }

    /**
     * 更新Document
     * @throws IOException
     */
    public void update(GpsInfo gps) throws IOException {
        UpdateResponse<GpsInfo> updateResponse = client.update(u -> u
                        .index(EsGpsIndexService.INDEX_NAME)
                        .id(gps.getId())
                        .doc(gps)
                , GpsInfo.class);
    }

    /**
     * 判断Document是否存在
     * @throws IOException
     */
    public void exist(String id) throws IOException {
        BooleanResponse indexResponse = client.exists(e -> e.index(EsGpsIndexService.INDEX_NAME).id(id));
        System.out.println(indexResponse.value());
    }

    /**
     * 查询Document
     * @throws IOException
     */
    public void get(String id) throws IOException {
        GetResponse<GpsInfo> getResponse = client.get(g -> g
                        .index(EsGpsIndexService.INDEX_NAME)
                        .id("1")
                , GpsInfo.class
        );
        System.out.println(getResponse.source());


    }

    /**
     * 删除Document
     * @throws IOException
     */
    public void delete(String id) throws IOException {
        DeleteResponse deleteResponse = client.delete(d -> d
                .index(EsGpsIndexService.INDEX_NAME)
                .id("1")
        );
        System.out.println(deleteResponse.id());
    }

    /**
     * 批量插入Document
     * @throws IOException
     */
    public void bulk(List<GpsInfo> gpsList) throws IOException {

        List<BulkOperation> bulkOperationArrayList = new ArrayList<>();
        //遍历添加到bulk中
        for(GpsInfo gps : gpsList){
            bulkOperationArrayList.add(BulkOperation.of(o->o.index(i->i.document(gps).id(gps.getId()))));
            //bulkOperationArrayList.add(BulkOperation.of(x->x.create(d->d.document(gps).id(gps.getId()).index(EsGpsIndexService.INDEX_NAME))));
        }

        BulkResponse bulkResponse = client.bulk(b -> b.index(EsGpsIndexService.INDEX_NAME).operations(bulkOperationArrayList));

    }

    /**
     * 查询
     * @throws IOException
     * https://wenku.baidu.com/view/a8954a68862458fb770bf78a6529647d27283439.html
     */
    public void search(String vehicleId,long startTime,long endTime,int page,int pageSize) throws IOException {

        SearchResponse<GpsInfo> search = client.search(s -> s
                .index(EsGpsIndexService.INDEX_NAME)
                .query(q -> q
                        .bool(b -> b
                                .filter(m -> m.term(t -> t.field("vehicleId").value(vehicleId)))
                                .filter(f -> f.range(x-> x.field("gpsTime").gte(JsonData.of(startTime)).lte(JsonData.of(endTime))))
                         ))

                //分页查询，从第0页开始查询20个document
                .from(page)
                .size(pageSize)
                //按时间降序排序
                //.sort(f->f.field(o->o.field("gpsTime").order(SortOrder.Desc)))
                , GpsInfo.class
        );
        for (Hit<GpsInfo> hit : search.hits().hits()) {
            System.out.println(hit.source());
        }
    }
}

实体

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.Date;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class GpsInfo {

    private String id;
    private String vehicleId;
    private String deviceId;
    private String location;
    private Long gpsTime;
    private Long createTime;

}

测试例子

@RestController
@RequestMapping("/gps")
public class GpsController {

    @Autowired
    EsGpsIndexService esGpsIndexService;

    @Autowired
    EsGpsDocumentService esGpsDocumentService;

    @GetMapping("/test")
    public String test() throws IOException {

        boolean exist = esGpsIndexService.exists();
        if(!exist){
            esGpsIndexService.create();
        }

        esGpsIndexService.query();

        //
        /*GpsInfo gps = new GpsInfo();
        gps.setId("1");
        gps.setDeviceId("1111");
        gps.setVehicleId("123");
        gps.setLocation("12,33");
        gps.setCreateTime(System.currentTimeMillis());
        gps.setGpsTime(System.currentTimeMillis());
        esGpsDocumentService.add(gps);*/

        /*List<GpsInfo> gpsList =  new ArrayList<>();
        int i= 0;
        GpsInfo gps = null;
        long time = 1656041715000L;
        while (i < 10000){
            gps = new GpsInfo();
            gps.setId(String.valueOf(i*10000));
            gps.setDeviceId("1111");
            gps.setVehicleId("123456");
            gps.setLocation("12233.2232,33.2512235");
            gps.setCreateTime(time);
            gps.setGpsTime(time);
            gpsList.add(gps);
            //
            time += 1000;
            i += 1;
        }
        esGpsDocumentService.bulk(gpsList);*/


        long start = 1656041715000L;
        long end   = 1656041725000L;
        String v = "123456";
        esGpsDocumentService.search(v,start,end,0,20);


        return "elasticSearch test!!!!";
    }

}

现象
代码

Map<Long, Person> map = new HashMap<>();
Person person = new Person();
person.setName("Bruce");
map.put(1L, person);
List<ContainerClass> list = new ArrayList<>();
ContainerClass containerClass = new ContainerClass();
containerClass.setP1(map.get(1L));
containerClass.setP2(map.get(1L));
list.add(containerClass);
String s = JSON.toJSONString(list);
System.out.println(s);

结果

[{"p1":{"name":"Bruce"},"p2":{"$ref":"$[0].p1"}}]

解决
方案一

String s = JSON.toJSONString(list, SerializerFeature.DisableCircularReferenceDetect);

方案二

Person p2 = new Person();
BeanUtils.copyProperties(map.get(1L), p2);
containerClass.setP2(p2);

结果

[{"p1":{"name":"Bruce"},"p2":{"name":"Bruce"}}]

yaml配置如下：

objectConfig:
  object-map:
    1:
      name: "对象一"
      desc: "这是第一个对象"
      url: "https://abc.abc.abc"
    2:
      name: "对象二"
      desc: "这是第二个对象"
      url: "https://abc.abc.abc"

Java配置类代码如下：

@Configuration
@RefreshScope
@ConfigurationProperties(prefix = "objectConfig")
public class ObjectConfig {
  private Map<Integer, ObjectEntity> objectMap;
}

  public static class ObjectEntity{
    private String name;
    private String desc;
    private String url;
  }

Java使用代码如下：

 @Autowired
private ObjectConfig objectConfig;

ObjectConfig.ObjectEntity objectEntity = objectConfig.getObjectMap().get(1);
}

今天使用IDEA搭建项目的过程中，总是弹出Kotlin配置的对话框，之前一直使用19版的IDEA，没有这个东西，20版默认加了IDEA插件，让人头大。
在数次弹出配置对话框之后，无意点了“全部项目”，然后就导致所有项目报红，百度无结果，只能自己研究。
先是打开插件，把kotlin插件关掉，然后打开项目设置，把项目下面写着的kotlin删掉。
然后发现有些项目里面的target中存在kotlin关键字，于是把所有的target都删掉了（clean不掉，这个时候clean会报错，不能用）。
还是不行，然后就开始研究pom文件，报错的、能删的都删掉了，刷新一下maven，总算是搞定了。

说起来很简单，自己第一次摸索还是很耗费时间和经历的，希望后面的同学能顺利一点。

思路
选择排序，顾名思义，就是每次选出一个最小或最大的数，移动位置，直到整个数组完成排序。
有数组[26, -3, 14, -15, 0, 324, 98, 1, 22]
现对该数组进行排序，使用选择排序算法。
先来屡一下思路和步骤：

选出整个数组最小的数，记录它的下标；
将它和未排序的最左边数组进行交换（交换过就是排序了）；
直至整个数组排序完成。
讲解
首先声明出待排序下标、最小值和最小下标。最小值我们使用Integer.MAX_VALUE，来确保数组中肯定有值能够被排序：

@Test
public void sortTest() {
    int[] nums = new int[]{26, -3, 14, -15, 0, 324, 98, 1, 22};
    selectSort(nums);
    System.out.println(Arrays.toString(nums));
}

private void selectSort(int[] nums) {
    if (nums.length < 2) {
        return;
    }
    // 待排序下标，从0开始
    for (int i = 0; i < nums.length; i++) {
        // 初始化最小值和最小下标
        int minVal = Integer.MAX_VALUE;
        int minIndex = -1;
        // 遍历，寻找最小值
        for (int j = i; j < nums.length; j++) {
            // 如果元素小于minVal，则赋值minVal和minIndex
            if (nums[j] < minVal) {
                minVal = nums[j];
                minIndex = j;
            }
        }
        // 如果最小下标不等于-1，与待排序下表交换
        if (minIndex != -1) {
            int temp = nums[i];
            nums[i] = nums[minIndex];
            nums[minIndex] = temp;
        }
    }
}