springboot auto configuration的本质就是自动配置spring的各种bean。然后使应用可以通过@Autowired等注入方式来直接使用bean。
比如自动配置redisTemplate,jdbcTemplate等bean。
1. 开启@EnableAutoConfiguration注解
如果写了@SpringBootApplication注解,不必再写@EnableAutoConfiguration。
@SpringBootApplication = @Configuration + @EnableAutoConfiguration + @ComponentScan
@SpringCloudApplication = @SpringBootApplication + @EnableDiscoveryClient + @EnableCircuitBreaker
2. 开启@EnableAutoConfiguration注解后,会引入一个AutoConfigurationImportSelector类
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import(AutoConfigurationImportSelector.class)
public @interface EnableAutoConfiguration {
String ENABLED_OVERRIDE_PROPERTY = "spring.boot.enableautoconfiguration";
/**
* Exclude specific auto-configuration classes such that they will never be applied.
* @return the classes to exclude
*/
Class<?>[] exclude() default {};
/**
* Exclude specific auto-configuration class names such that they will never be
* applied.
* @return the class names to exclude
* @since 1.3.0
*/
String[] excludeName() default {};
}
其会去扫描classpath下所有jar包内的META-INF/spring.factories文件.
3. spring.factories文件
spring.factories文件路径是
spring-boot-autoconfigure-2.3.4.RELEASE.jar下的META-INFspring.factories,spring.factories文件内容:
# Initializers
org.springframework.context.ApplicationContextInitializer=
org.springframework.boot.autoconfigure.SharedMetadataReaderFactoryContextInitializer,
org.springframework.boot.autoconfigure.logging.ConditionEvaluationReportLoggingListener
# Application Listeners
org.springframework.context.ApplicationListener=
org.springframework.boot.autoconfigure.BackgroundPreinitializer
# Auto Configuration Import Listeners
org.springframework.boot.autoconfigure.AutoConfigurationImportListener=
org.springframework.boot.autoconfigure.condition.ConditionEvaluationReportAutoConfigurationImportListener
# Auto Configuration Import Filters
org.springframework.boot.autoconfigure.AutoConfigurationImportFilter=
org.springframework.boot.autoconfigure.condition.OnBeanCondition,
org.springframework.boot.autoconfigure.condition.OnClassCondition,
org.springframework.boot.autoconfigure.condition.OnWebApplicationCondition
# Auto Configure
org.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.batch.BatchAutoConfiguration,
org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration,
org.springframework.boot.autoconfigure.cassandra.CassandraAutoConfiguration,
org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration,
org.springframework.boot.autoconfigure.context.LifecycleAutoConfiguration,
org.springframework.boot.autoconfigure.context.MessageSourceAutoConfiguration,
org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration,
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.CassandraReactiveDataAutoConfiguration,
org.springframework.boot.autoconfigure.data.cassandra.CassandraReactiveRepositoriesAutoConfiguration,
org.springframework.boot.autoconfigure.data.cassandra.CassandraRepositoriesAutoConfiguration,
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseDataAutoConfiguration,
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveDataAutoConfiguration,
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveRepositoriesAutoConfiguration,
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseRepositoriesAutoConfiguration,
org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchDataAutoConfiguration,
org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchRepositoriesAutoConfiguration,
org.springframework.boot.autoconfigure.data.elasticsearch.ReactiveElasticsearchRepositoriesAutoConfiguration,
org.springframework.boot.autoconfigure.data.elasticsearch.ReactiveElasticsearchRestClientAutoConfiguration,
org.springframework.boot.autoconfigure.data.jdbc.JdbcRepositoriesAutoConfiguration,
org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration,
org.springframework.boot.autoconfigure.data.ldap.LdapRepositoriesAutoConfiguration,
org.springframework.boot.autoconfigure.data.mongo.MongoDataAutoConfiguration,
org.springframework.boot.autoconfigure.data.mongo.MongoReactiveDataAutoConfiguration,
org.springframework.boot.autoconfigure.data.mongo.MongoReactiveRepositoriesAutoConfiguration,
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.r2dbc.R2dbcDataAutoConfiguration,
org.springframework.boot.autoconfigure.data.r2dbc.R2dbcRepositoriesAutoConfiguration,
org.springframework.boot.autoconfigure.data.r2dbc.R2dbcTransactionManagerAutoConfiguration,
org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration,
org.springframework.boot.autoconfigure.data.redis.RedisReactiveAutoConfiguration,
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.ElasticsearchRestClientAutoConfiguration,
org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration,
org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration,
org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration,
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.http.HttpMessageConvertersAutoConfiguration,
org.springframework.boot.autoconfigure.http.codec.CodecsAutoConfiguration,
org.springframework.boot.autoconfigure.influx.InfluxDbAutoConfiguration,
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.jersey.JerseyAutoConfiguration,
org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration,
org.springframework.boot.autoconfigure.jsonb.JsonbAutoConfiguration,
org.springframework.boot.autoconfigure.kafka.KafkaAutoConfiguration,
org.springframework.boot.autoconfigure.avAIlability.ApplicationAvailabilityAutoConfiguration,
org.springframework.boot.autoconfigure.ldap.embedded.EmbeddedLdapAutoConfiguration,
org.springframework.boot.autoconfigure.ldap.LdapAutoConfiguration,
org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration,
org.springframework.boot.autoconfigure.mail.MailSenderAutoConfiguration,
org.springframework.boot.autoconfigure.mail.MailSenderValidatorAutoConfiguration,
org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration,
org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration,
org.springframework.boot.autoconfigure.mongo.MongoReactiveAutoConfiguration,
org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration,
org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration,
org.springframework.boot.autoconfigure.quartz.QuartzAutoConfiguration,
org.springframework.boot.autoconfigure.r2dbc.R2dbcAutoConfiguration,
org.springframework.boot.autoconfigure.rsocket.RSocketMessagingAutoConfiguration,
org.springframework.boot.autoconfigure.rsocket.RSocketRequesterAutoConfiguration,
org.springframework.boot.autoconfigure.rsocket.RSocketServerAutoConfiguration,
org.springframework.boot.autoconfigure.rsocket.RSocketStrategiesAutoConfiguration,
org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration,
org.springframework.boot.autoconfigure.security.servlet.UserDetailsServiceAutoConfiguration,
org.springframework.boot.autoconfigure.security.servlet.SecurityFilterAutoConfiguration,
org.springframework.boot.autoconfigure.security.reactive.ReactiveSecurityAutoConfiguration,
org.springframework.boot.autoconfigure.security.reactive.ReactiveUserDetailsServiceAutoConfiguration,
org.springframework.boot.autoconfigure.security.rsocket.RSocketSecurityAutoConfiguration,
org.springframework.boot.autoconfigure.security.saml2.Saml2RelyingPartyAutoConfiguration,
org.springframework.boot.autoconfigure.sendgrid.SendGridAutoConfiguration,
org.springframework.boot.autoconfigure.session.SessionAutoConfiguration,
org.springframework.boot.autoconfigure.security.oauth2.client.servlet.OAuth2ClientAutoConfiguration,
org.springframework.boot.autoconfigure.security.oauth2.client.reactive.ReactiveOAuth2ClientAutoConfiguration,
org.springframework.boot.autoconfigure.security.oauth2.resource.servlet.OAuth2ResourceServerAutoConfiguration,
org.springframework.boot.autoconfigure.security.oauth2.resource.reactive.ReactiveOAuth2ResourceServerAutoConfiguration,
org.springframework.boot.autoconfigure.solr.SolrAutoConfiguration,
org.springframework.boot.autoconfigure.task.TaskExecutionAutoConfiguration,
org.springframework.boot.autoconfigure.task.TaskSchedulingAutoConfiguration,
org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration,
org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration,
org.springframework.boot.autoconfigure.transaction.jta.JtaAutoConfiguration,
org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration,
org.springframework.boot.autoconfigure.web.client.RestTemplateAutoConfiguration,
org.springframework.boot.autoconfigure.web.embedded.EmbeddedWebServerFactoryCustomizerAutoConfiguration,
org.springframework.boot.autoconfigure.web.reactive.HttpHandlerAutoConfiguration,
org.springframework.boot.autoconfigure.web.reactive.ReactiveWebServerFactoryAutoConfiguration,
org.springframework.boot.autoconfigure.web.reactive.WebFluxAutoConfiguration,
org.springframework.boot.autoconfigure.web.reactive.error.ErrorWebFluxAutoConfiguration,
org.springframework.boot.autoconfigure.web.reactive.function.client.ClientHttpConnectorAutoConfiguration,
org.springframework.boot.autoconfigure.web.reactive.function.client.WebClientAutoConfiguration,
org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration,
org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration,
org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration,
org.springframework.boot.autoconfigure.web.servlet.HttpEncodingAutoConfiguration,
org.springframework.boot.autoconfigure.web.servlet.MultipartAutoConfiguration,
org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration,
org.springframework.boot.autoconfigure.websocket.reactive.WebSocketReactiveAutoConfiguration,
org.springframework.boot.autoconfigure.websocket.servlet.WebSocketServletAutoConfiguration,
org.springframework.boot.autoconfigure.websocket.servlet.WebSocketMessagingAutoConfiguration,
org.springframework.boot.autoconfigure.webservices.WebServicesAutoConfiguration,
org.springframework.boot.autoconfigure.webservices.client.WebServiceTemplateAutoConfiguration
# Failure analyzers
org.springframework.boot.diagnostics.FailureAnalyzer=
org.springframework.boot.autoconfigure.data.redis.RedisUrlSyntaxFailureAnalyzer,
org.springframework.boot.autoconfigure.diagnostics.analyzer.NoSuchBeanDefinitionFailureAnalyzer,
org.springframework.boot.autoconfigure.flyway.FlywayMigrationScriptMissingFailureAnalyzer,
org.springframework.boot.autoconfigure.jdbc.DataSourceBeanCreationFailureAnalyzer,
org.springframework.boot.autoconfigure.jdbc.HikariDriverConfigurationFailureAnalyzer,
org.springframework.boot.autoconfigure.r2dbc.ConnectionFactoryBeanCreationFailureAnalyzer,
org.springframework.boot.autoconfigure.session.NonUniqueSessionRepositoryFailureAnalyzer
# Template availability providers
org.springframework.boot.autoconfigure.template.TemplateAvailabilityProvider=
org.springframework.boot.autoconfigure.freemarker.FreeMarkerTemplateAvailabilityProvider,
org.springframework.boot.autoconfigure.mustache.MustacheTemplateAvailabilityProvider,
org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAvailabilityProvider,
org.springframework.boot.autoconfigure.thymeleaf.ThymeleafTemplateAvailabilityProvider,
org.springframework.boot.autoconfigure.web.servlet.JspTemplateAvailabilityProvider
spring boot 会自动配置
org.springframework.boot.autoconfigure.EnableAutoConfiguration的key下所有自动配置类。可以看到这里面包含RabbitMq,MongoDB,Redis,JdbcTemplate,Thymeleaf,WebFlux,WebSocket等等模块的自动配置类。
4. 一般自动配置类都有@Configuration注解,相当于一个spring的xml文件,里面可以通过@Bean注解配置bean。具体例子见org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration类。
package org.springframework.boot.autoconfigure.data.redis;
import JAVA.NET.UnknownHostException;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
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 org.springframework.context.annotation.Import;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.RedisOperations;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.StringRedisTemplate;
/**
* {@link EnableAutoConfiguration Auto-configuration} for Spring Data's Redis support.
*
* @author Dave Syer
* @author Andy Wilkinson
* @author Christian Dupuis
* @author Christoph Strobl
* @author Phillip Webb
* @author Eddú Meléndez
* @author Stephane Nicoll
* @author Marco Aust
* @author Mark Paluch
* @since 1.0.0
*/
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(RedisOperations.class)
@EnableConfigurationProperties(RedisProperties.class)
@Import({ LettuceConnectionConfiguration.class, JedisConnectionConfiguration.class })
public class RedisAutoConfiguration {
@Bean
@ConditionalOnMissingBean(name = "redisTemplate")
public RedisTemplate<Object, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory)
throws UnknownHostException {
RedisTemplate<Object, Object> template = new RedisTemplate<>();
template.setConnectionFactory(redisConnectionFactory);
return template;
}
@Bean
@ConditionalOnMissingBean
public StringRedisTemplate stringRedisTemplate(RedisConnectionFactory redisConnectionFactory)
throws UnknownHostException {
StringRedisTemplate template = new StringRedisTemplate();
template.setConnectionFactory(redisConnectionFactory);
return template;
}
}
@ConditionalOnXXX:
5. 配置bean的时候,少不了要获取properties或者yml文件的属性值
5.1 通过@ConfigurationProperties(prefix=”xxxx”)映射配置文件的值到POJO
application.yml
定义一个POJO类,例:ZookeeperProperties.java,通过prefix指定配置属性的前缀,加上@Component,这可以变成spring bean,可以直接用@Autowired注入。
spring:
zookeeper:
address: 172.16.0.100:2181
timeout: 4000
@ConfigurationProperties(prefix = "spring.zookeeper")
public class ZookeeperProperties {
RedisAutoConfiguration redisAutoConfiguration;
private String address;
private Integer timeout;
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public Integer getTimeout() {
return timeout;
}
public void setTimeout(Integer timeout) {
this.timeout = timeout;
}
}
5.2 将配置文件的POJO类转化为spring的bean
5.2.1. 在要使用配置的地方使用@EnableConfigurationProperties(ZookeeperProperties.class)将其转化为spring的bean,也可以使用@component,二选一。
我们使用EnableConfigurationProperties模式:
import org.Apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import java.util.concurrent.CountDownLatch;
@Configuration
@EnableConfigurationProperties(ZookeeperProperties.class)
public class ZookeeperConfig {
private static final Logger logger = LoggerFactory.getLogger(ZookeeperConfig.class);
@Autowired
ZookeeperProperties zookeeperProperties;
@Bean(name = "zkClient")
public ZooKeeper zkClient(){
ZooKeeper zooKeeper=null;
try {
final CountDownLatch countDownLatch = new CountDownLatch(1);
//连接成功后,会回调watcher监听,此连接操作是异步的,执行完new语句后,直接调用后续代码
// 可指定多台服务地址 127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183
zooKeeper = new ZooKeeper(zookeeperProperties.getAddress() , zookeeperProperties.getTimeout(), new Watcher() {
@Override
public void process(WatchedEvent event) {
if(Event.KeeperState.SyncConnected==event.getState()){
//如果收到了服务端的响应事件,连接成功
countDownLatch.countDown();
}
}
});
countDownLatch.await();
logger.info("【初始化ZooKeeper连接状态....】={}",zooKeeper.getState());
}catch (Exception e){
logger.error("初始化ZooKeeper连接异常....】={}",e);
}
return zooKeeper;
}
}
5.2.2. 通过@Bean配置将其转化为spring的bean
@Configuration
public class ZKConfiguration {
@Bean
public ZookeeperProperties zookeeperProperties() {
return new ZookeeperProperties();
}
}
5.2.3. 通过@Component配置将其转化为spring的bean
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;
@Component
@ConfigurationProperties(prefix = "spring.zookeeper")
public class ZookeeperProperties {
private String address;
private Integer timeout;
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public Integer getTimeout() {
return timeout;
}
public void setTimeout(Integer timeout) {
this.timeout = timeout;
}
}
转化为spring的bean后,就可以在想用的地方通过任意注入方式注入bean来使用了。
5.2.4. 总结
在写spring boot starter的时候,因为所有类都不在启动的@ComponentScan目录下,所以使用一般使用 5.2.1 或者 5.2.2 的方式获取配置文件信息。在写具体的spring boot应用服务时,配置类都在启动的@ComponentScan目录下,使用 5.2.3 的方式比较方便