springboot自动装配原理-以redis为例

约定不等于承诺〃 2022-02-19 10:18 630阅读 0赞

# springboot自动装配原理 #

每天多学一点点~  
话不多说，这就开始吧…

### 文章目录 ###

*  springboot自动装配原理
 *   *  1.传统的ssm项目配置redis上
     *  2.springboot自动装配redis
     *  3.自动装配原理，从@SpringbootApplication入手分析
     *  4.结语

## 1.传统的ssm项目配置redis上 ##

1.  加入pom依赖

<dependency>
    	<groupId>org.springframework.data</groupId>
    	<artifactId>spring-data-redis</artifactId>
    	<version>2.0.9.RELEASE</version>
    </dependency>
    
    <dependency>
    	<groupId>redis.clients</groupId>
    	<artifactId>jedis</artifactId>
    	<version>2.9.0</version>
    </dependency>

1.  配置xml的bean的配置

//配置连接池
        <bean id="poolConfig" class="redis.clients.jedis.JedisPoolConfig">
            <property name="minIdle" value="10"></property>
            <property name="maxTotal" value="20"></property>
        </bean>
        
        //配置连接工厂
        <bean id="jedisConnectionFactory" class="org.springframework.data.redis.connection.jedis.JedisConnectionFactory">
            <property name="hostName" value="47.104.128.12"></property>
            <property name="password" value="123456"></property>
            <property name="database" value="0"></property>
            <property name="poolConfig" ref="poolConfig"></property>
        </bean>
    
    
        //配置 redisTemplate 模版类
        <bean id="redisTemplate" class="org.springframework.data.redis.core.RedisTemplate">
            <property name="connectionFactory"  ref="jedisConnectionFactory"/>
            
            <property name="keySerializer">
                <bean class="org.springframework.data.redis.serializer.StringRedisSerializer"/>
            </property>
            <property name="valueSerializer">
                <bean class="org.springframework.data.redis.serializer.GenericJackson2JsonRedisSerializer"/>
            </property>
            <property name="hashKeySerializer">
                <bean class="org.springframework.data.redis.serializer.StringRedisSerializer"/>
            </property>
            <property name="hashValueSerializer">
             <bean class="org.springframework.data.redis.serializer.GenericJackson2JsonRedisSerializer"/>
            </property>
        </bean>

1.  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

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

1.  修改yml配置文件  
    spring.redis.host=47.104.128.12  
    spring.redis.port=6379  
    spring.redis.password=123456
2.  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<String,Object>      
    	 * @throws
    	 */
        public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory){
    		RedisTemplate<String, Object> redisTemplate = new RedisTemplate<String, Object>();
    		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 ##

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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<String> 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<String> 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<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader) {
    		MultiValueMap<String, String> result = cache.get(classLoader);
    		if (result != null) {
    			return result;
    		}
    
    		try {
    			Enumeration<URL> 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<String> 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);
    		}
    	}

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjQzNzYzMw_size_16_color_FFFFFF_t_70 1]

1.  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<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;
    	}
    
    }
    
    =====================================JedisConnectionConfiguration==========================================
    
    @Configuration
    @ConditionalOnClass({ GenericObjectPool.class, JedisConnection.class, Jedis.class })
    class JedisConnectionConfiguration extends RedisConnectionConfiguration {
    
    	private final RedisProperties properties;
    
    	private final List<JedisClientConfigurationBuilderCustomizer> builderCustomizers;
    
    	JedisConnectionConfiguration(RedisProperties properties,
    			ObjectProvider<RedisSentinelConfiguration> sentinelConfiguration,
    			ObjectProvider<RedisClusterConfiguration> clusterConfiguration,
    			ObjectProvider<List<JedisClientConfigurationBuilderCustomizer>> 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！！！**

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