之前一直在用SpringBoot框架，一直感覺SpringBoot框架自動(dòng)配置的功能很強(qiáng)大，但是并沒有明白它是怎么實(shí)現(xiàn)自動(dòng)配置的，現(xiàn)在有空研究了一下，大概明白了SpringBoot框架是怎么實(shí)現(xiàn)自動(dòng)配置的功能，我們編寫一個(gè)最簡(jiǎn)單的自動(dòng)配置功能，大概的總結(jié)一下.
一,配置屬性類
其實(shí)就是值對(duì)象注入的方式去配置一些Spring常用的配置，我們編寫一個(gè)最簡(jiǎn)單的配置對(duì)象。
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@ConfigurationProperties(prefix = "hello")//@Component //如果這里添加了注解那么在自動(dòng)配置類的時(shí)候就不用添加@enableConfigurationProperties(HelloProperties.class)注解.public class HelloProperties { private String msg="default";//現(xiàn)在我們?cè)谂渲梦募慼ello.msg=world,因?yàn)楹?jiǎn)單就不再展示;如果那么默認(rèn)為default. public String getMsg() { return msg; } public void setMsg(String msg) { this.msg = msg; }} |
這是一個(gè)簡(jiǎn)單的屬性值對(duì)象，那么相當(dāng)于寫死的字段就是SpringBoot為我們自動(dòng)配置的配置，那么我們很多時(shí)候可以自己在application.properties中修改某些配置就是這樣的道理，我們不設(shè)置就是默認(rèn)的，設(shè)置了就是我們?cè)O(shè)置的屬性。
二,自動(dòng)配置類
上面已經(jīng)構(gòu)建了我們簡(jiǎn)單的屬性對(duì)象，那么現(xiàn)在我們要通過屬性對(duì)象得到相應(yīng)的屬性值將其注入到我們的Bean中，這些Bean也就是一些SpringBoot啟動(dòng)后為我們自動(dòng)配置生成的Bean，當(dāng)然SpringBoot優(yōu)先使用我們配置的Bean這個(gè)功能是如何實(shí)現(xiàn)的,我們往下看一下就明白了。
首先我們需要一個(gè)功能Bean，可以把這個(gè)Bean看做是SpringBoot框架啟動(dòng)后在容器里面生成的為我們服務(wù)的內(nèi)置Bean,簡(jiǎn)單的寫一個(gè)。
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//@Component 這里很重要，如果我們添加了這個(gè)注解那么，按照我們下面的設(shè)置SpringBoot會(huì)優(yōu)先使用我們配置的這個(gè)Bean，這是符合SpringBoot框架優(yōu)先使用自定義Bean的原則的。public class HelloService { private String msg = "service";//如果自動(dòng)配置沒有讀入成功，那么為默認(rèn)值 public String say() { return "hello " + msg; }//為我們服務(wù)的方法 public String getMsg() { return msg; } public void setMsg(String msg) { this.msg = msg; }} |
現(xiàn)在編寫我們的自動(dòng)配置類。
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@Configuration //配置類@EnableConfigurationProperties(HelloProperties.class)//這里就是前面說的，這個(gè)注解讀入我們的配置對(duì)象類@ConditionalOnClass(HelloService.class)//當(dāng)類路徑存在這個(gè)類時(shí)才會(huì)加載這個(gè)配置類，否則跳過,這個(gè)很有用比如不同jar包間類依賴，依賴的類不存在直接跳過，不會(huì)報(bào)錯(cuò)public class HelloAutoConfiguration { @Autowired private HelloProperties helloProperties; @Bean @ConditionalOnMissingBean(HelloService.class)//這個(gè)配置就是SpringBoot可以優(yōu)先使用自定義Bean的核心所在，如果沒有我們的自定義Bean那么才會(huì)自動(dòng)配置一個(gè)新的Bean public HelloService auto(){ HelloService helloService =new HelloService(); helloService.setMsg(helloProperties.getMsg()); return helloService; }} |
好了現(xiàn)在自動(dòng)配置的類也寫好了，我們可以啟動(dòng)一下SpringBoot應(yīng)用，測(cè)試一下。
三,測(cè)試自動(dòng)配置
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@SpringBootApplication@RestControllerpublic class MyRun { @Autowired private HelloService helloService; @RequestMapping("/auto/home") public String home(){ return helloService.say(); } public static void main(String[] args) { SpringApplication.run(MyRun.class,args); }} |
ok ,運(yùn)行后訪問你會(huì)看到：
hello world
代表我們的自動(dòng)配置功能成功。
四,SpringBoot管理自動(dòng)配置
其實(shí)在很多時(shí)候我們的配置是在很多jar包里的，那么我們新的應(yīng)用該怎么讀入這些jar包里的配置文件呢，SpringBoot是這樣管理的。
最主要的注解就是@enableAutoConfiguration,而這個(gè)注解會(huì)導(dǎo)入一個(gè)EnableAutoConfigurationImportSelector的類,而這個(gè)類會(huì)去讀取一個(gè)spring.factories下key為EnableAutoConfiguration全限定名對(duì)應(yīng)值.
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# Auto Configureorg.springframework.boot.autoconfigure.EnableAutoConfiguration=\org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,\org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,\org.springframework.boot.autoconfigure.amqp.RabbitAutoConfiguration,\org.springframework.boot.autoconfigure.MessageSourceAutoConfiguration,\org.springframework.boot.autoconfigure.PropertyPlaceholderAutoConfiguration,\org.springframework.boot.autoconfigure.batch.BatchAutoConfiguration,\org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration,\org.springframework.boot.autoconfigure.cassandra.CassandraAutoConfiguration,\org.springframework.boot.autoconfigure.cloud.CloudAutoConfiguration,\org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration,\org.springframework.boot.autoconfigure.couchbase.CouchbaseAutoConfiguration,\org.springframework.boot.autoconfigure.dao.PersistenceExceptionTranslationAutoConfiguration,\org.springframework.boot.autoconfigure.data.cassandra.CassandraDataAutoConfiguration,\org.springframework.boot.autoconfigure.data.cassandra.CassandraRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.couchbase.CouchbaseDataAutoConfiguration,\org.springframework.boot.autoconfigure.data.couchbase.CouchbaseRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchAutoConfiguration,\org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchDataAutoConfiguration,\org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.mongo.MongoDataAutoConfiguration,\org.springframework.boot.autoconfigure.data.mongo.MongoRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.neo4j.Neo4jDataAutoConfiguration,\org.springframework.boot.autoconfigure.data.neo4j.Neo4jRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.solr.SolrRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration,\org.springframework.boot.autoconfigure.data.redis.RedisRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.rest.RepositoryRestMvcAutoConfiguration,\org.springframework.boot.autoconfigure.data.web.SpringDataWebAutoConfiguration,\org.springframework.boot.autoconfigure.elasticsearch.jest.JestAutoConfiguration,\org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration,\org.springframework.boot.autoconfigure.gson.GsonAutoConfiguration,\org.springframework.boot.autoconfigure.h2.H2ConsoleAutoConfiguration,\org.springframework.boot.autoconfigure.hateoas.HypermediaAutoConfiguration,\org.springframework.boot.autoconfigure.hazelcast.HazelcastAutoConfiguration,\org.springframework.boot.autoconfigure.hazelcast.HazelcastJpaDependencyAutoConfiguration,\org.springframework.boot.autoconfigure.info.ProjectInfoAutoConfiguration,\org.springframework.boot.autoconfigure.integration.IntegrationAutoConfiguration,\org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration,\org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration,\org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration,\org.springframework.boot.autoconfigure.jdbc.JndiDataSourceAutoConfiguration,\org.springframework.boot.autoconfigure.jdbc.XADataSourceAutoConfiguration,\org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration,\org.springframework.boot.autoconfigure.jms.JmsAutoConfiguration,\org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration,\org.springframework.boot.autoconfigure.jms.JndiConnectionFactoryAutoConfiguration,\org.springframework.boot.autoconfigure.jms.activemq.ActiveMQAutoConfiguration,\org.springframework.boot.autoconfigure.jms.artemis.ArtemisAutoConfiguration,\org.springframework.boot.autoconfigure.jms.hornetq.HornetQAutoConfiguration,\org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration,\org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration,\org.springframework.boot.autoconfigure.jersey.JerseyAutoConfiguration,\org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration,\org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration,\org.springframework.boot.autoconfigure.mail.MailSenderAutoConfiguration,\org.springframework.boot.autoconfigure.mail.MailSenderValidatorAutoConfiguration,\org.springframework.boot.autoconfigure.mobile.DeviceResolverAutoConfiguration,\org.springframework.boot.autoconfigure.mobile.DeviceDelegatingViewResolverAutoConfiguration,\org.springframework.boot.autoconfigure.mobile.SitePreferenceAutoConfiguration,\org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration,\org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration,\org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration,\org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration,\org.springframework.boot.autoconfigure.reactor.ReactorAutoConfiguration,\org.springframework.boot.autoconfigure.security.SecurityAutoConfiguration,\org.springframework.boot.autoconfigure.security.SecurityFilterAutoConfiguration,\org.springframework.boot.autoconfigure.security.FallbackWebSecurityAutoConfiguration,\org.springframework.boot.autoconfigure.security.oauth2.OAuth2AutoConfiguration,\org.springframework.boot.autoconfigure.sendgrid.SendGridAutoConfiguration,\org.springframework.boot.autoconfigure.session.SessionAutoConfiguration,\org.springframework.boot.autoconfigure.social.SocialWebAutoConfiguration,\org.springframework.boot.autoconfigure.social.FacebookAutoConfiguration,\org.springframework.boot.autoconfigure.social.LinkedInAutoConfiguration,\org.springframework.boot.autoconfigure.social.TwitterAutoConfiguration,\org.springframework.boot.autoconfigure.solr.SolrAutoConfiguration,\org.springframework.boot.autoconfigure.velocity.VelocityAutoConfiguration,\org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration,\org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration,\org.springframework.boot.autoconfigure.transaction.jta.JtaAutoConfiguration,\org.springframework.boot.autoconfigure.web.DispatcherServletAutoConfiguration,\org.springframework.boot.autoconfigure.web.EmbeddedServletContainerAutoConfiguration,\org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration,\org.springframework.boot.autoconfigure.web.HttpEncodingAutoConfiguration,\org.springframework.boot.autoconfigure.web.HttpMessageConvertersAutoConfiguration,\org.springframework.boot.autoconfigure.web.MultipartAutoConfiguration,\org.springframework.boot.autoconfigure.web.ServerPropertiesAutoConfiguration,\org.springframework.boot.autoconfigure.web.WebClientAutoConfiguration,\org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration,\org.springframework.boot.autoconfigure.websocket.WebSocketAutoConfiguration,\org.springframework.boot.autoconfigure.websocket.WebSocketMessagingAutoConfiguration,\org.springframework.boot.autoconfigure.webservices.WebServicesAutoConfiguration 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所以如果需要我們可以在我們的resources目錄下創(chuàng)建spring.factories下添加類似的配置即可。。
以上所述是小編給大家介紹的SpringBoot自動(dòng)配置的實(shí)現(xiàn)原理，希望對(duì)大家有所幫助，如果大家有任何疑問歡迎給我留言，小編會(huì)及時(shí)回復(fù)大家的！
