一.Spring Boot Starter简介
Starter是Spring Boot中的一个非常重要的概念，Starter相当于模块，它能将模块所需的依赖整合起来并对模块内的Bean根据环境（ 条件）进行自动配置。使用者只需要依赖相应功能的Starter，无需做过多的配置和依赖，Spring Boot就能自动扫描并加载相应的模块。
例如在Maven的依赖中加入spring-boot-starter-web就能使项目支持Spring MVC，并且Spring Boot还为我们做了很多默认配置，无需再依赖spring-web、spring-webmvc等相关包及做相关配置就能够立即使用起来。
二.Starter的开发步骤
编写Starter非常简单，与编写一个普通的Spring Boot应用没有太大区别，总结如下：
1.新建Maven项目，在项目的POM文件中定义使用的依赖；
2.新建配置类，写好配置项和默认的配置值，指明配置项前缀；
3.新建自动装配类，使用@Configuration和@Bean来进行自动装配；
4.新建spring.factories文件，指定Starter的自动装配类；
三.Starter的开发示例
下面，我就以创建一个自动配置并连接ElasticSearch的Starter来讲一下各个步骤及细节。 1.新建Maven项目，在项目的POM文件中定义使用的依赖。
<?xml version="1.0" encoding="UTF-8"?><project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.0.4.RELEASE</version></parent><modelVersion>4.0.0</modelVersion><artifactId>es-starter</artifactId><version>1.0.0.SNAPSHORT</version><dependencies><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>1.16.18</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId><version>2.0.4.RELEASE</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-configuration-processor</artifactId><optional>true</optional></dependency><dependency><groupId>org.elasticsearch.client</groupId><artifactId>x-pack-transport</artifactId><version>5.6.4</version></dependency></dependencies></project>
由于本starter主要是与ElasticSearch建立连接，获得TransportClient对象，所以需要依赖
x-pack-transport包。
2.新建配置类，写好配置项和默认的配置值，指明配置项前缀。
package cn.sxw.commons.data.es.starter;import org.springframework.boot.context.properties.ConfigurationProperties;import lombok.Data;/*** Created by William on 2018/8/7.*/
@Data
@ConfigurationProperties(prefix = "sxw.elasticsearch")
public class ElasticSearchProperties {private String clusterName = "elasticsearch";private String clusterNodes = "127.0.0.1:9300";private String userName = "elastic";private String password = "changeme";}
指定配置项前缀为
sxw.elasticsearch，各配置项均有默认值，默认值可以通过模块使用者的配置文件进行覆盖。
3.新建自动装配类，使用@Configuration和@Bean来进行自动装配。
package cn.sxw.commons.data.es.starter;import org.elasticsearch.client.transport.TransportClient;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.transport.InetSocketTransportAddress;
import org.elasticsearch.common.transport.TransportAddress;
import org.elasticsearch.xpack.client.PreBuiltXPackTransportClient;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Arrays;
import java.util.stream.Collectors;import javax.annotation.Resource;import lombok.extern.slf4j.Slf4j;/*** Created by William on 2018/8/7.*/
@Slf4j
@Configuration
@EnableConfigurationProperties(ElasticSearchProperties.class)
public class ElasticSearchAutoConfiguration implements DisposableBean{private TransportClient transportClient;@Resourceprivate ElasticSearchProperties properties;@Bean@ConditionalOnMissingBean(TransportClient.class)public TransportClient transportClient() {log.debug("=======" + properties.getClusterName());log.debug("=======" + properties.getClusterNodes());log.debug("=======" + properties.getUserName());log.debug("=======" + properties.getPassword());log.info("开始建立es连接");transportClient = new PreBuiltXPackTransportClient(settings());TransportAddress[] transportAddresses= Arrays.stream(properties.getClusterNodes().split(",")).map (t->{String[] addressPortPairs = t.split(":");String address = addressPortPairs[0];Integer port = Integer.valueOf(addressPortPairs[1]);try {return new InetSocketTransportAddress(InetAddress.getByName(address), port);} catch (UnknownHostException e) {log.error("连接ElasticSearch失败", e);throw new RuntimeException ("连接ElasticSearch失败",e);}}).collect (Collectors.toList ()).toArray (new TransportAddress[0]);transportClient.addTransportAddresses(transportAddresses);return transportClient;}private Settings settings() {return Settings.builder().put("cluster.name", properties.getClusterName()).put("xpack.security.user", properties.getUserName() +":" + properties.getPassword()).build();}@Overridepublic void destroy() throws Exception {log.info("开始销毁Es的连接");if (transportClient != null) {transportClient.close();}}
}
本类主要对TransportClient类进行自动配置;
@ConditionalOnMissingBean当Spring容器中没有TransportClient类的对象时，调用transportClient()创建对象; 关于更多Bean的条件装配用法请自行查阅Spring Boot相关文档;
4.新建spring.factories文件，指定Starter的自动装配类。
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\cn.sxw.commons.data.es.starter.ElasticSearchAutoConfiguration
spring.factories文件位于resources/META-INF目录下，需要手动创建;
org.springframework.boot.autoconfigure.EnableAutoConfiguration后面的类名说明了自动装配类，如果有多个 ，则用逗号分开; 使用者应用（SpringBoot）在启动的时候，会通过org.springframework.core.io.support.SpringFactoriesLoader读取classpath下每个Starter的spring.factories文件，加载自动装配类进行Bean的自动装配；
至此，整个Starter开发完毕，Deploy到中央仓库或Install到本地仓库后即可使用。
四.Starter的使用
1.创建Maven项目，依赖刚才发布的es-starter包。
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><parent><artifactId>spring-boot-parent</artifactId><groupId>org.springframework.boot</groupId><version>2.0.4.RELEASE</version></parent><modelVersion>4.0.0</modelVersion><artifactId>es-example</artifactId><version>1.0.0-SNAPSHOT</version><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>es-starter</artifactId><version>1.0.0.SNAPSHORT</version></dependency></dependencies><build><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><configuration><source>1.8</source><target>1.8</target></configuration></plugin></plugins></build> </project>
只需依赖刚才开发的es-starter即可
2.编写应用程序启动类。
package cn.sxw.commons.data.es.example;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;/*** Created by William on 2018/8/7.*/
@SpringBootApplication
@ComponentScan("cn.sxw.commons.data.es.example")
public class ExampleApplication {public static void main(String[] args) {SpringApplication.run(ExampleApplication.class, args);}
}
3.编写查询ElasticSearch的使用类
package cn.sxw.commons.data.es.example;import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.client.transport.TransportClient;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.search.SearchHit;
import org.elasticsearch.search.SearchHits;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.stereotype.Component;import java.util.Map;import lombok.extern.slf4j.Slf4j;/*** Created by William on 2018/8/7.*/
@Slf4j
@Component
public class ExampleRunner implements ApplicationRunner {private static final String INDEX_NAME = "tb_question";@Autowiredprivate TransportClient transportClient;@Overridepublic void run(ApplicationArguments applicationArguments) throws Exception {SearchResponse response = transportClient.prepareSearch(INDEX_NAME).setTypes(INDEX_NAME).setQuery(QueryBuilders.matchAllQuery()).setFrom(0).setSize(5).execute().actionGet();SearchHits hits = response.getHits();log.info(String.format("=======总共找到%d条记录", hits.getTotalHits()));log.info("=======第一页数据：");for (SearchHit searchHit : hits) {Map<String, Object> source = searchHit.getSource();String question = source.get("question").toString();log.info(question);}}
}
通过实现ApplicationRunner或CommandLineRunner接口，可以实现应用程序启动完成后自动运行run方法，达到测试es-starter模块目的。 索引名称tb_question是公司测试环境ElasticSearch中的索引，已存在数据。
4.应用程序配置
sxw:elasticsearch:cluster-name: docker-clustercluster-nodes: 192.168.2.180:9300,192.168.2.181:9300user-name: elasticpassword: changeme
在application.yml文件中配置es-starter需要的配置信息，这里连接公司测试环境中的ElasticSearch。 这里配置的值可以覆盖es-starter中默认值，也就是之前ElasticSearchProperties文件中的默认值。
5.运行程序测试
/Library/Java/JavaVirtualMachines/jdk1.8.0_25.jdk/Contents/Home/bin/java "-javaagent:/Applications/开发/IntelliJ IDEA.app/Contents/lib/idea_rt.jar=52434:/Applications/开发/IntelliJ IDEA.app/Contents/bin" -Dfile.encoding=UTF-8 -classpath cn.sxw.commons.data.es.example.ExampleApplication
objc[2017]: Class JavaLaunchHelper is implemented in both /Library/Java/JavaVirtualMachines/jdk1.8.0_25.jdk/Contents/Home/bin/java (0x1022a24c0) and /Library/Java/JavaVirtualMachines/jdk1.8.0_25.jdk/Contents/Home/jre/lib/libinstrument.dylib (0x1023254e0). One of the two will be used. Which one is undefined.. ____ _ __ _ _/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \\\/ ___)| |_)| | | | | || (_| | ) ) ) )' |____| .__|_| |_|_| |_\__, | / / / /=========|_|==============|___/=/_/_/_/:: Spring Boot :: (v2.0.4.RELEASE)2018-08-08 16:26:43.161 INFO 2017 --- [ main] c.s.c.d.es.example.ExampleApplication : Starting ExampleApplication on William.local with PID 2017 (/Users/William/Git/sxw-java/es-spring-boot-starter/es-example/target/classes started by William in /Users/William/Git/sxw-java/es-spring-boot-starter)
2018-08-08 16:26:43.167 INFO 2017 --- [ main] c.s.c.d.es.example.ExampleApplication : No active profile set, falling back to default profiles: default
2018-08-08 16:26:43.365 INFO 2017 --- [ main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@635eaaf1: startup date [Wed Aug 08 16:26:43 CST 2018]; root of context hierarchy
2018-08-08 16:26:45.078 INFO 2017 --- [ main] s.c.d.e.s.ElasticSearchAutoConfiguration : =======docker-cluster
2018-08-08 16:26:45.079 INFO 2017 --- [ main] s.c.d.e.s.ElasticSearchAutoConfiguration : =======192.168.2.180:9300,192.168.2.181:9300
2018-08-08 16:26:45.081 INFO 2017 --- [ main] s.c.d.e.s.ElasticSearchAutoConfiguration : =======elastic
2018-08-08 16:26:45.081 INFO 2017 --- [ main] s.c.d.e.s.ElasticSearchAutoConfiguration : =======changeme
2018-08-08 16:26:45.082 INFO 2017 --- [ main] s.c.d.e.s.ElasticSearchAutoConfiguration : 开始建立es连接
2018-08-08 16:26:46.200 INFO 2017 --- [ main] o.elasticsearch.plugins.PluginsService : no modules loaded
2018-08-08 16:26:46.201 INFO 2017 --- [ main] o.elasticsearch.plugins.PluginsService : loaded plugin [org.elasticsearch.index.reindex.ReindexPlugin]
2018-08-08 16:26:46.202 INFO 2017 --- [ main] o.elasticsearch.plugins.PluginsService : loaded plugin [org.elasticsearch.join.ParentJoinPlugin]
2018-08-08 16:26:46.202 INFO 2017 --- [ main] o.elasticsearch.plugins.PluginsService : loaded plugin [org.elasticsearch.percolator.PercolatorPlugin]
2018-08-08 16:26:46.202 INFO 2017 --- [ main] o.elasticsearch.plugins.PluginsService : loaded plugin [org.elasticsearch.script.mustache.MustachePlugin]
2018-08-08 16:26:46.202 INFO 2017 --- [ main] o.elasticsearch.plugins.PluginsService : loaded plugin [org.elasticsearch.transport.Netty3Plugin]
2018-08-08 16:26:46.202 INFO 2017 --- [ main] o.elasticsearch.plugins.PluginsService : loaded plugin [org.elasticsearch.transport.Netty4Plugin]
2018-08-08 16:26:46.202 INFO 2017 --- [ main] o.elasticsearch.plugins.PluginsService : loaded plugin [org.elasticsearch.xpack.XPackPlugin]
2018-08-08 16:26:49.137 INFO 2017 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup
2018-08-08 16:26:49.157 INFO 2017 --- [ main] c.s.c.d.es.example.ExampleApplication : Started ExampleApplication in 6.6 seconds (JVM running for 7.915)
2018-08-08 16:26:49.215 INFO 2017 --- [ main] c.s.c.data.es.example.ExampleRunner : =======总共找到907条记录
2018-08-08 16:26:49.215 INFO 2017 --- [ main] c.s.c.data.es.example.ExampleRunner : =======第一页数据：
2018-08-08 16:26:49.230 INFO 2017 --- [ main] c.s.c.data.es.example.ExampleRunner : <p>下列诗句朗读节奏有错误的一项是( )</p>
2018-08-08 16:26:49.230 INFO 2017 --- [ main] c.s.c.data.es.example.ExampleRunner : <p><span style=";font-family:宋体;color:rgb(0,0,0);font-size:14px"><span style="font-family:宋体">《卧薪尝胆》这个故事出自于（</span> A <span style="font-family:宋体">）</span></span></p><p><span style=";font-family:宋体;color:rgb(0,0,0);font-size:14px">A<span style="font-family:宋体">、司马迁《史记》 </span><span style="font-family:Times New Roman">B</span><span style="font-family:宋体">、司马光 《资治通鉴》</span></span></p><p><span style=";font-family:宋体;color:rgb(0,0,0);font-size:14px">C<span style="font-family:宋体">、孔子 《论语》 </span><span style="font-family:Times New Roman">D</span><span style="font-family:宋体">、司马迁《春秋》</span></span></p><p><br/></p>
2018-08-08 16:26:49.230 INFO 2017 --- [ main] c.s.c.data.es.example.ExampleRunner : <p style="margin-bottom:7px;margin-bottom:auto;vertical-align:middle"><span style=";font-family:'Cambria Math';font-size:14pxfont-family:宋体,新宋体">填空题</span></p><p style="margin-bottom:7px;margin-bottom:auto;vertical-align:middle"><span style=";font-family:'Cambria Math';font-size:14pxfont-family:宋体,新宋体">该模式给当地带来的主要影响是 </span><span style=";font-family:'Cambria Math';font-size:14px"><br/></span><br/></p><p><br/></p>
2018-08-08 16:26:49.231 INFO 2017 --- [ main] c.s.c.data.es.example.ExampleRunner : <p>下列词语没有错别字的一项是( )</p>
2018-08-08 16:26:49.231 INFO 2017 --- [ main] c.s.c.data.es.example.ExampleRunner : <p>语文第16题</p>
2018-08-08 16:26:49.232 INFO 2017 --- [ Thread-2] s.c.a.AnnotationConfigApplicationContext : Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@635eaaf1: startup date [Wed Aug 08 16:26:43 CST 2018]; root of context hierarchy
2018-08-08 16:26:49.234 INFO 2017 --- [ Thread-2] o.s.j.e.a.AnnotationMBeanExporter : Unregistering JMX-exposed beans on shutdown
2018-08-08 16:26:49.328 INFO 2017 --- [ Thread-2] s.c.d.e.s.ElasticSearchAutoConfiguration : 开始销毁Es的连接Process finished with exit code 0
运行程序，观察控制台输出，es-starter成功与ElasticSearch建立连接，且应用程序启动完后ExampleRunner的run方法查询出5条数据。