引入redis依赖

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

spring-boot-starter-data-redis

查看spring-boot-starter-data-redis jar包并无特殊内容，再查看依赖关系，引入了spring-data-redis 及lettuce-core, springboot2.x使用lettuce进行链接redis。

<dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter</artifactId>
      <version>2.2.5.RELEASE</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework.data</groupId>
      <artifactId>spring-data-redis</artifactId>
      <version>2.2.5.RELEASE</version>
      <scope>compile</scope>
      <exclusions>
        <exclusion>
          <artifactId>jcl-over-slf4j</artifactId>
          <groupId>org.slf4j</groupId>
        </exclusion>
      </exclusions>
    </dependency>
    <dependency>
      <groupId>io.lettuce</groupId>
      <artifactId>lettuce-core</artifactId>
      <version>5.2.2.RELEASE</version>
      <scope>compile</scope>
    </dependency>
  </dependencies>

查看 spring-data-redis下的spring.factories,仅有一个RepositoryFactorySupport并无自动装配。

org.springframework.data.repository.core.support.RepositoryFactorySupport=org.springframework.data.redis.repository.support.RedisRepositoryFactory

spring-boot-autoconfigure

redis自动装配由spring-boot-autoconfigure实现。

META-INF下spring.factories中自动配置关于redis的配置有

# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisReactiveAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisRepositoriesAutoConfiguration,\

META-INF下spring-autoconfigure-metadata.properties中关于redis的元数据配置

org.springframework.boot.autoconfigure.data.redis.LettuceConnectionConfiguration=
org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration.ConditionalOnClass=org.springframework.data.redis.core.RedisOperations
org.springframework.boot.autoconfigure.session.RedisReactiveSessionConfiguration.ConditionalOnBean=org.springframework.data.redis.connection.ReactiveRedisConnectionFactory
org.springframework.boot.autoconfigure.session.RedisSessionConfiguration=
org.springframework.boot.autoconfigure.cache.RedisCacheConfiguration.ConditionalOnBean=org.springframework.data.redis.connection.RedisConnectionFactory
org.springframework.boot.autoconfigure.cache.RedisCacheConfiguration=
org.springframework.boot.autoconfigure.cache.RedisCacheConfiguration.AutoConfigureAfter=org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration
org.springframework.boot.autoconfigure.data.redis.RedisRepositoriesAutoConfiguration.ConditionalOnClass=org.springframework.data.redis.repository.configuration.EnableRedisRepositories
org.springframework.boot.autoconfigure.data.redis.RedisRepositoriesAutoConfiguration=
org.springframework.boot.autoconfigure.data.redis.RedisRepositoriesAutoConfiguration.AutoConfigureAfter=org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration
org.springframework.boot.autoconfigure.data.redis.RedisReactiveAutoConfiguration=
org.springframework.boot.autoconfigure.data.redis.RedisReactiveAutoConfiguration.AutoConfigureAfter=org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration
org.springframework.boot.autoconfigure.data.redis.RedisRepositoriesAutoConfiguration.ConditionalOnBean=org.springframework.data.redis.connection.RedisConnectionFactory
org.springframework.boot.autoconfigure.session.RedisSessionConfiguration.ConditionalOnBean=org.springframework.data.redis.connection.RedisConnectionFactory
org.springframework.boot.autoconfigure.cache.RedisCacheConfiguration.ConditionalOnClass=org.springframework.data.redis.connection.RedisConnectionFactory
org.springframework.boot.autoconfigure.session.RedisSessionConfiguration.ConditionalOnClass=org.springframework.data.redis.core.RedisTemplate,org.springframework.session.data.redis.RedisIndexedSessionRepository
org.springframework.boot.autoconfigure.data.redis.RedisReactiveAutoConfiguration.ConditionalOnClass=reactor.core.publisher.Flux,org.springframework.data.redis.connection.ReactiveRedisConnectionFactory,org.springframework.data.redis.core.ReactiveRedisTemplate
org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration=
org.springframework.boot.autoconfigure.data.redis.LettuceConnectionConfiguration.ConditionalOnClass=io.lettuce.core.RedisClient
org.springframework.boot.autoconfigure.session.RedisReactiveSessionConfiguration.ConditionalOnClass=org.springframework.data.redis.connection.ReactiveRedisConnectionFactory,org.springframework.session.data.redis.ReactiveRedisSessionRepository
org.springframework.boot.autoconfigure.session.RedisReactiveSessionConfiguration=
org.springframework.boot.autoconfigure.data.redis.JedisConnectionConfiguration.ConditionalOnClass=org.apache.commons.pool2.impl.GenericObjectPool,redis.clients.jedis.Jedis,org.springframework.data.redis.connection.jedis.JedisConnection
org.springframework.boot.autoconfigure.data.redis.JedisConnectionConfiguration=
org.springframework.boot.autoconfigure.session.SessionAutoConfiguration.AutoConfigureAfter=org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration,org.springframework.boot.autoconfigure.hazelcast.HazelcastAutoConfiguration,org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration,org.springframework.boot.autoconfigure.data.mongo.MongoDataAutoConfiguration,org.springframework.boot.autoconfigure.data.mongo.MongoReactiveDataAutoConfiguration,org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration,org.springframework.boot.autoconfigure.data.redis.RedisReactiveAutoConfiguration
org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration.AutoConfigureAfter=org.springframework.boot.autoconfigure.couchbase.CouchbaseAutoConfiguration,org.springframework.boot.autoconfigure.hazelcast.HazelcastAutoConfiguration,org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration,org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration

RedisAutoConfiguration开启条件@ConditionalOnClass

metadata中也指定了配置 ConditionalOnClass开启条件指定的类RedisOperations

org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration.ConditionalOnClass=org.springframework.data.redis.core.RedisOperations

RedisAutoConfiguration类

配置类加载了配置属性类RedisProperties，导入了配置LettuceConnectionConfiguration、JedisConnectionConfiguration

通过使用@ConditionalOnMissingBean配置了默认的bean redisTemplate、StringRedisTemplate

@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;
 }

}

RedisReactiveAutoConfiguration

@AutoConfigureAfter(RedisAutoConfiguration.class) 在RedisAutoConfiguration自动配置完成后才会加载

@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({ ReactiveRedisConnectionFactory.class, ReactiveRedisTemplate.class, Flux.class })
@AutoConfigureAfter(RedisAutoConfiguration.class)
public class RedisReactiveAutoConfiguration {
  @Bean
    @ConditionalOnMissingBean(name = "reactiveRedisTemplate")
    @ConditionalOnBean(ReactiveRedisConnectionFactory.class)
    public ReactiveRedisTemplate<Object, Object> reactiveRedisTemplate(
            ReactiveRedisConnectionFactory reactiveRedisConnectionFactory, ResourceLoader resourceLoader) {
        JdkSerializationRedisSerializer jdkSerializer = new JdkSerializationRedisSerializer(
                resourceLoader.getClassLoader());
        RedisSerializationContext<Object, Object> serializationContext = RedisSerializationContext
                .newSerializationContext().key(jdkSerializer).value(jdkSerializer).hashKey(jdkSerializer)
                .hashValue(jdkSerializer).build();
        return new ReactiveRedisTemplate<>(reactiveRedisConnectionFactory, serializationContext);
    }

    @Bean
    @ConditionalOnMissingBean(name = "reactiveStringRedisTemplate")
    @ConditionalOnBean(ReactiveRedisConnectionFactory.class)
    public ReactiveStringRedisTemplate reactiveStringRedisTemplate(
            ReactiveRedisConnectionFactory reactiveRedisConnectionFactory) {
        return new ReactiveStringRedisTemplate(reactiveRedisConnectionFactory);
    }
}

RedisRepositoriesAutoConfiguration

@AutoConfigureAfter(RedisAutoConfiguration.class) 同样在RedisAutoConfiguration自动配置完成后才会加载

@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(EnableRedisRepositories.class)
@ConditionalOnBean(RedisConnectionFactory.class)
@ConditionalOnProperty(prefix = "spring.data.redis.repositories", name = "enabled", havingValue = "true",
  matchIfMissing = true)
@ConditionalOnMissingBean(RedisRepositoryFactoryBean.class)
@Import(RedisRepositoriesRegistrar.class)
@AutoConfigureAfter(RedisAutoConfiguration.class)
public class RedisRepositoriesAutoConfiguration {

}

总结

redis配置由springBoot集成，在spring-boot-autoconfigure中配置，spring.factories中EnableAutoConfiguration指定自动配置类
RedisAutoConfiguration进行自动配置，spring-configuration-metadata.properties指定了配置元数据RedisAutoConfiguration ConditionalOnClass配置条件RedisOperations，当引入spring-data-redis时存在类路径RedisOperations进行redis的自动加载。redis自动配置使用Lettuce作为client进行连接，配置了默认的bean redisTemplate、StringRedisTemplate。