SpringBoot Starter介绍以及实例

墨蓝 2023-06-22 13:43 15阅读 0赞

# 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;
        @Resource
        private 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();
        }
    
        @Override
        public 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";
 
 @Autowired
 private TransportClient transportClient;
 
 @Override
 public 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-cluster
        cluster-nodes: 192.168.2.180:9300,192.168.2.181:9300
        user-name: elastic
        password: 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 : 下列诗句朗读节奏有错误的一项是( )
 2018-08-08 16:26:49.230 INFO 2017 --- [ main] c.s.c.data.es.example.ExampleRunner : 《卧薪尝胆》这个故事出自于（ A   ）A、司马迁《史记》           B、司马光 《资治通鉴》C、孔子   《论语》           D、司马迁《春秋》 
 2018-08-08 16:26:49.230 INFO 2017 --- [ main] c.s.c.data.es.example.ExampleRunner : 填空题该模式给当地带来的主要影响是 
 2018-08-08 16:26:49.231 INFO 2017 --- [ main] c.s.c.data.es.example.ExampleRunner : 下列词语没有错别字的一项是( )
 2018-08-08 16:26:49.231 INFO 2017 --- [ main] c.s.c.data.es.example.ExampleRunner : 语文第16题
 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。