springboot2.0 auto configuration自动配置

概念

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。

原理

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，会自动引入一个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-boot-autoconfigure.jar的spring.factories文件

 spring.factories文件内会有一个org.springframework.boot.autoconfigure.EnableAutoConfiguration的key

configure.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.cloud.CloudAutoConfiguration,
org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration,
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.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.ldap.LdapDataAutoConfiguration,
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.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.jest.JestAutoConfiguration,
org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration,
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.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.groovy.template.GroovyTemplateAutoConfiguration,
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.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.reactor.core.ReactorCoreAutoConfiguration,
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.sendgrid.SendGridAutoConfiguration,
org.springframework.boot.autoconfigure.session.SessionAutoConfiguration,
org.springframework.boot.autoconfigure.security.oauth2.client.OAuth2ClientAutoConfiguration,
org.springframework.boot.autoconfigure.solr.SolrAutoConfiguration,
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.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

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

@Configuration
@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(StringRedisTemplate.class)
    public StringRedisTemplate stringRedisTemplate(
            RedisConnectionFactory redisConnectionFactory) throws UnknownHostException {
        StringRedisTemplate template = new StringRedisTemplate();
        template.setConnectionFactory(redisConnectionFactory);
        return template;
    }

}

@ConditionalOnXXX：

• @ConditionalOnBean（仅仅在当前上下文中存在某个对象时，才会实例化一个Bean
• @ConditionalOnClass（某个class位于类路径上，才会实例化一个Bean）
• @ConditionalOnExpression（当表达式为true的时候，才会实例化一个Bean）
• @ConditionalOnMissingBean（仅仅在当前上下文中不存在某个对象时，才会实例化一个Bean）
• @ConditionalOnMissingClass（某个class类路径上不存在的时候，才会实例化一个Bean）
• @ConditionalOnProperty(value = “spring.cloud.config.enabled”, matchIfMissing = true)（当某个配置的值为一定条件时，才会实例化一个Bean）

5. 配置bean的时候，少不了要获取properties或者yml文件的属性

5.1 通过@ConfigurationProperties(prefix=”xxxx”)映射配置文件的值到POJO

application.yml

test:
  id: 1
  name: test

随意一个POJO类，例：Properties.java，类名随意，通过prefix指定配置属性的前缀

@ConfigurationProperties(prefix="test")
public class Properties {
    private int id;
    private String name;

    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

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(Properties.class)将其转化为spring的bean

@RestController
@EnableConfigurationProperties(Properties.class)
public class CommonController extends BaseController {
    //转化为spring的bean后，就可以注入使用了
    @Autowired
    private Properties properties;

    @RequestMapping(value = "/properties", method = RequestMethod.GET)
    public Properties getProperties() {

        log.info(properties.toString());

        return properties;
    }

}

如果直接写@EnableConfigurationProperties不指定Properties类的话，必须在同一目录或者子目录下才行。

5.2.2. 通过@Bean配置将其转化为spring的bean

@Configuration
public class MyConfiguration {

    @Bean
    public Properties properties() {
        return new Properties();
    }

}

5.2.3. 通过@Component配置将其转化为spring的bean

@Component
@ConfigurationProperties(prefix="test")
public class Properties {
    private int id;
    private String name;

    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

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

原文地址：https://blog.csdn.net/ifrozen/article/details/79931143

实战--springboot配置 rocketmq

starters项目

1.pom.xml

<dependency>
      <groupId>com.aliyun.openservices</groupId>
      <artifactId>ons-client</artifactId>
      <version>1.8.4.Final</version>
    </dependency>

2.resources->META-INF->spring.factories

org.springframework.boot.autoconfigure.EnableAutoConfiguration=
  com.bjgxzd.boot.config.MqAutoConfiguration

3.MqAutoConfiguration

@Configuration
@ImportAutoConfiguration(value = {MqConfiguration.class})
public class MqAutoConfiguration {

  @Bean
  public  CommandLineRunner logRunner (){
    return args -> {
      System.out.println("==== GX rocket MQ loaded ====");
    };
  }

}

4.MqConfiguration

@Configuration
@EnableConfigurationProperties({MqProperties.class})
public class MqConfiguration {

  @Autowired
  private MqProperties mqProperties;

  @Bean(initMethod = "start", destroyMethod = "shutdown")
  @ConditionalOnMissingBean(ProducerBean.class)
  public ProducerBean buildProducer() {
    ProducerBean producer = new ProducerBean();
    producer.setProperties(getMqProperties());
    return producer;
  }

  private Properties getMqProperties(){
    Properties properties = new Properties();
    properties.setProperty(PropertyKeyConst.AccessKey, mqProperties.getAccessKey());
    properties.setProperty(PropertyKeyConst.SecretKey, mqProperties.getSecretKey());
    properties.setProperty(PropertyKeyConst.ONSAddr, mqProperties.getOnsAddr());
    return properties;
  }

  @ConditionalOnMissingBean(OrderProducerBean.class)
  @Bean(initMethod = "start", destroyMethod = "shutdown")
  public OrderProducerBean buildOrderProducer() {
    OrderProducerBean orderProducerBean = new OrderProducerBean();
    orderProducerBean.setProperties(getMqProperties());
    return orderProducerBean;
  }

}

5.MqProperties

@Data
@ConfigurationProperties(prefix = "mq.rocketmq")
public class MqProperties {
  private String accessKey;
  private String secretKey;
  private String onsAddr;
}

syncsrv项目

application.yml

mq:
  rocketmq:
    access-key: 62f49160c57b4f158a8ab3ebd2ff66cc
    secret-key: J8H3v+Go55DIimy6gbKu3Bbnc0U=
    ons-addr: http://172.169.101.121:8080/rocketmq/nsaddr4broker-internal

pom.xml

mq 集成好了，直接依赖
<dependency>
  <groupId>com.bjgxzd</groupId>
  <artifactId>gx-mq-spring-boot-starter</artifactId>
  <version>1.0-SNAPSHOT</version>
</dependency>

启动类 QfjsSyncApplication

@SpringBootApplication
public class QfjsSyncApplication implements CommandLineRunner {

  public static void main(String[] args) {
    SpringApplication.run(QfjsSyncApplication.class, args);
  }


  @Override
  public void run(String... args) throws Exception {

  }
}

使用

直接注入就可以发消息了
private final ProducerBean producer;

public TestController(ProducerBean producer) {
  this.producer = producer;
}