springboot自动装配原理-以redis为例

springboot自动装配原理

每天多学一点点~
话不多说，这就开始吧…

1.传统的ssm项目配置redis上

1. 加入pom依赖

	org.springframework.data
	spring-data-redis
	2.0.9.RELEASE



	redis.clients
	jedis
	2.9.0


2. 配置xml的bean的配置

 //配置连接池
    
        
        
    
    
    //配置连接工厂
    
        
        
        
        
    


    //配置 redisTemplate 模版类
    
        
        
        
            
        
        
            
        
        
            
        
        
         
        
    

3. 导入配置
   @ImportResource(locations = “classpath:beans.xml”) 可以导入xml的配置文件

2.springboot自动装配redis

综上所述 我们发现，若整合redis的时候通过传统的整合，进行了大量的配置,那么我们来看下通过springboot自动装配整合的对比

1. 导入依赖

	
			org.springframework.boot
			spring-boot-starter-data-redis
		

2. 修改yml配置文件
   spring.redis.host=47.104.128.12
   spring.redis.port=6379
   spring.redis.password=123456

3. 修改序列化方式

@Configuration
public class RedisConfig {

	@Bean
	/**
	 * @Title: redisTemplate   
	 * @author: xuxiaoxiang 
	 * @Description: 初始化redis   
	 * @param redisConnectionFactory
	 * @return: RedisTemplate      
	 * @throws
	 */
    public RedisTemplate redisTemplate(RedisConnectionFactory redisConnectionFactory){
		RedisTemplate redisTemplate = new RedisTemplate();
		redisTemplate.setConnectionFactory(redisConnectionFactory);
		Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);
		/*通用的序列化和反序列化设置
        ObjectMapper类是Jackson库的主要类。它提供一些功能将转换成Java对象匹配JSON结构，反之亦然。*/
		ObjectMapper objectMapper = new ObjectMapper();
		objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
		objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
		jackson2JsonRedisSerializer.setObjectMapper(objectMapper);
		redisTemplate.setValueSerializer(jackson2JsonRedisSerializer);
        redisTemplate.setKeySerializer(new StringRedisSerializer());
        redisTemplate.afterPropertiesSet();
		return redisTemplate;
    }
	
}

3.自动装配原理，从@SpringbootApplication入手分析

1. AutoConfigurationImportSelector#selectImports方法

public class AutoConfigurationImportSelector
		implements DeferredImportSelector, BeanClassLoaderAware, ResourceLoaderAware,
		BeanFactoryAware, EnvironmentAware, Ordered {


	@Override
	public String[] selectImports(AnnotationMetadata annotationMetadata) {
		if (!isEnabled(annotationMetadata)) {
			return NO_IMPORTS;
		}
		AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader
				.loadMetadata(this.beanClassLoader);
		AnnotationAttributes attributes = getAttributes(annotationMetadata);
		//去mata-info/spring.factories文件中 查询 EnableAutoConfiguration对于值
		List configurations = getCandidateConfigurations(annotationMetadata,
				attributes);
		//去除重复的配置类，若我们自己写的starter 可能存主重复的
		configurations = removeDuplicates(configurations);
		Set exclusions = getExclusions(annotationMetadata, attributes);
		checkExcludedClasses(configurations, exclusions);
		configurations.removeAll(exclusions);
		//根据maven 导入的启动器过滤出 需要导入的配置类
		configurations = filter(configurations, autoConfigurationMetadata);
		fireAutoConfigurationImportEvents(configurations, exclusions);
		return StringUtils.toStringArray(configurations);
	}
}	
 
 //去spring.factories 中去查询EnableAutoConfirution类
 private static Map> loadSpringFactories(@Nullable ClassLoader classLoader) {
		MultiValueMap result = cache.get(classLoader);
		if (result != null) {
			return result;
		}

		try {
			Enumeration urls = (classLoader != null ?
					classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :
					ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));
			result = new LinkedMultiValueMap<>();
			while (urls.hasMoreElements()) {
				URL url = urls.nextElement();
				UrlResource resource = new UrlResource(url);
				Properties properties = PropertiesLoaderUtils.loadProperties(resource);
				for (Map.Entry entry : properties.entrySet()) {
					List factoryClassNames = Arrays.asList(
							StringUtils.commaDelimitedListToStringArray((String) entry.getValue()));
					result.addAll((String) entry.getKey(), factoryClassNames);
				}
			}
			cache.put(classLoader, result);
			return result;
		}
		catch (IOException ex) {
			throw new IllegalArgumentException("Unable to load factories from location [" +
					FACTORIES_RESOURCE_LOCATION + "]", ex);
		}
	}

2. RedisAutoConfiguration类
   导入了三个组件 RedisTemplate StringRedisTemplate JedisConnectionConfiguration

@Configuration
@ConditionalOnClass(RedisOperations.class)
@EnableConfigurationProperties(RedisProperties.class)
@Import({ LettuceConnectionConfiguration.class, JedisConnectionConfiguration.class })
public class RedisAutoConfiguration {
    
    //导入redisTemplate 
	@Bean
	@ConditionalOnMissingBean(name = "redisTemplate")
	public RedisTemplate redisTemplate(
			RedisConnectionFactory redisConnectionFactory) throws UnknownHostException {
		RedisTemplate 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;
	}

}

=====================================JedisConnectionConfiguration==========================================

@Configuration
@ConditionalOnClass({ GenericObjectPool.class, JedisConnection.class, Jedis.class })
class JedisConnectionConfiguration extends RedisConnectionConfiguration {

	private final RedisProperties properties;

	private final List builderCustomizers;

	JedisConnectionConfiguration(RedisProperties properties,
			ObjectProvider sentinelConfiguration,
			ObjectProvider clusterConfiguration,
			ObjectProvider> builderCustomizers) {
		super(properties, sentinelConfiguration, clusterConfiguration);
		this.properties = properties;
		this.builderCustomizers = builderCustomizers
				.getIfAvailable(Collections::emptyList);
	}

	@Bean
	@ConditionalOnMissingBean(RedisConnectionFactory.class)
	public JedisConnectionFactory redisConnectionFactory() throws UnknownHostException {
		return createJedisConnectionFactory();
	}

	private JedisConnectionFactory createJedisConnectionFactory() {
		JedisClientConfiguration clientConfiguration = getJedisClientConfiguration();
		if (getSentinelConfig() != null) {
			return new JedisConnectionFactory(getSentinelConfig(), clientConfiguration);
		}
		if (getClusterConfiguration() != null) {
			return new JedisConnectionFactory(getClusterConfiguration(),
					clientConfiguration);
		}
		return new JedisConnectionFactory(getStandaloneConfig(), clientConfiguration);
	}

	private JedisClientConfiguration getJedisClientConfiguration() {
		JedisClientConfigurationBuilder builder = applyProperties(
				JedisClientConfiguration.builder());
		RedisProperties.Pool pool = this.properties.getJedis().getPool();
		if (pool != null) {
			applyPooling(pool, builder);
		}
		if (StringUtils.hasText(this.properties.getUrl())) {
			customizeConfigurationFromUrl(builder);
		}
		customize(builder);
		return builder.build();
	}

	private JedisClientConfigurationBuilder applyProperties(
			JedisClientConfigurationBuilder builder) {
		if (this.properties.isSsl()) {
			builder.useSsl();
		}
		if (this.properties.getTimeout() != null) {
			Duration timeout = this.properties.getTimeout();
			builder.readTimeout(timeout).connectTimeout(timeout);
		}
		return builder;
	}

	private void applyPooling(RedisProperties.Pool pool,
			JedisClientConfiguration.JedisClientConfigurationBuilder builder) {
		builder.usePooling().poolConfig(jedisPoolConfig(pool));
	}

	private JedisPoolConfig jedisPoolConfig(RedisProperties.Pool pool) {
		JedisPoolConfig config = new JedisPoolConfig();
		config.setMaxTotal(pool.getMaxActive());
		config.setMaxIdle(pool.getMaxIdle());
		config.setMinIdle(pool.getMinIdle());
		if (pool.getMaxWait() != null) {
			config.setMaxWaitMillis(pool.getMaxWait().toMillis());
		}
		return config;
	}
}	

这里可以看到，spirngboot已经自动帮我们注入了redisTemplate和Jedis了，我们只需要直接用就可以；
注：springboot每个版本可能略有出入，但是整体都差不多，跟着流程走就可以

4.结语

世上无难事，只怕有心人，每天积累一点点，fighting！！！