BeanFactory接口与ApplicationContext接口功能介绍

类关系结构

BeanFactory 功能介绍

BeanFactory 是核心容器，负责管理 Bean 对象

• BeanFactory 接口的功能只有一个 getBean() 方法

• BeanFactory 的实现类（DefaultListableBeanFactory）包含：控制反转、基本的依赖注入、Bean 生命周期的各种功能，不能只考虑接口功能

  import lombok.SneakyThrows;
  import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
  import org.springframework.beans.factory.support.DefaultSingletonBeanRegistry;
  import org.springframework.boot.SpringApplication;
  import org.springframework.boot.autoconfigure.SpringBootApplication;
  import org.springframework.context.ConfigurableApplicationContext;
  
  import java.lang.reflect.Field;
  import java.util.Locale;
  import java.util.Map;
  
  @SpringBootApplication
  public class SpringApplicationMain {
      @SneakyThrows
      public static void main(String[] args) {
          ConfigurableApplicationContext context = SpringApplication.run(SpringApplicationMain.class, args);
          ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
  
          // 通过反射方式来获取私有成员变量
          Field singletonObjectsField = DefaultSingletonBeanRegistry.class.getDeclaredField("singletonObjects");
          singletonObjectsField.setAccessible(true);
          Map<String, Object> singletonObjects = (Map<String, Object>) singletonObjectsField.get(beanFactory);
  
          // 事先已经通过注解为Spring容器中注入两个以"component_"开头的组件, 这里过滤得到
          singletonObjects.entrySet().stream()
                  .filter(e -> e.getKey().startsWith("component_"))
                  .forEach(e -> System.out.println(e.getKey() + " = " + e.getValue()));
      }
  }

  

  

ApplicationContext 功能介绍

接口	功能
MessageSource	国际化的能力
ResourcePatternResolve	根据通配符去匹配文件资源（磁盘路径、类路径等）
ApplicationEventPublisher	发布事件对象（ApplicationEvent）
EnvironmentCapable	读取系统环境变量或配置文件中的信息，定义获取 Environment 方法

MessageSource 接口

使用方法

提供了 getMessage() 方法，以实现国际化的能力

1. 需要准备各种不同语言的资源，例如 messages_en.properties 和 messages_zh.properties 文件

   hi=Hello
   user=user

   hi=嗨
   user=用户

2. 提供 resource_en.properties 和 resource_zh.properties 文件

   username=username
   password=password

   username=用户名
   password=密码

3. 通过调用 getMessage() 来获取资源

   import lombok.SneakyThrows;
   import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
   import org.springframework.beans.factory.support.DefaultSingletonBeanRegistry;
   import org.springframework.boot.SpringApplication;
   import org.springframework.boot.autoconfigure.SpringBootApplication;
   import org.springframework.context.ConfigurableApplicationContext;
   
   import java.lang.reflect.Field;
   import java.util.Locale;
   import java.util.Map;
   
   @SpringBootApplication
   public class SpringApplicationMain {
       @SneakyThrows
       public static void main(String[] args) {
           ConfigurableApplicationContext context = SpringApplication.run(SpringApplicationMain.class, args);
   
           // 默认情况下, 文件必须以"messages.properties"命名
           String hiZh = context.getMessage("hi", null, Locale.CHINA);
           String hiEn = context.getMessage("hi", null, Locale.ENGLISH);
           System.out.println(hiZh);
           System.out.println(hiEn);
   
           // 默认情况下会报错, 希望正常运行需要进行一些配置
           String usernameZh = context.getMessage("username", null, Locale.CHINA);
           String passwordEn = context.getMessage("password", null, Locale.ENGLISH);
           System.out.println("usernameZh = " + usernameZh);
           System.out.println("passwordEn = " + passwordEn);
   }

4. 额外对Spring配置文件 application.properties 进行修改

   spring.messages.basename=messages,resource

源码解析

1. 找到自动配置类 MessageSourceAutoConfiguration

   @Configuration(proxyBeanMethods = false)
   // 1. 自动配置类标配@ConditionalOnMissingBean注解
   @ConditionalOnMissingBean(name = AbstractApplicationContext.MESSAGE_SOURCE_BEAN_NAME, search = SearchStrategy.CURRENT)
   @AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
   // 2. @Conditional注解, 在ResourceBundleCondition注入之后进行注入, 指定前置依赖项
   @Conditional(ResourceBundleCondition.class)
   // 3. @EnableConfigurationProperties搭配@ConfigurationProperties使用
   @EnableConfigurationProperties
   public class MessageSourceAutoConfiguration {
   
       private static final Resource[] NO_RESOURCES = {};
   
       // 4. MessageSourceProperties配置类, 对应一些默认配置项
       @Bean
       @ConfigurationProperties(prefix = "spring.messages")
       public MessageSourceProperties messageSourceProperties() {
           return new MessageSourceProperties();
       }
   
       @Bean
       public MessageSource messageSource(MessageSourceProperties properties) {
           ResourceBundleMessageSource messageSource = new ResourceBundleMessageSource();
           if (StringUtils.hasText(properties.getBasename())) {
               messageSource.setBasenames(StringUtils
                       .commaDelimitedListToStringArray(StringUtils.trimAllWhitespace(properties.getBasename())));
           }
           if (properties.getEncoding() != null) {
               messageSource.setDefaultEncoding(properties.getEncoding().name());
           }
           messageSource.setFallbackToSystemLocale(properties.isFallbackToSystemLocale());
           Duration cacheDuration = properties.getCacheDuration();
           if (cacheDuration != null) {
               messageSource.setCacheMillis(cacheDuration.toMillis());
           }
           messageSource.setAlwaysUseMessageFormat(properties.isAlwaysUseMessageFormat());
           messageSource.setUseCodeAsDefaultMessage(properties.isUseCodeAsDefaultMessage());
           return messageSource;
       }
   
       protected static class ResourceBundleCondition extends SpringBootCondition {
   
           private static ConcurrentReferenceHashMap<String, ConditionOutcome> cache = new ConcurrentReferenceHashMap<>();
   
           @Override
           public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
               String basename = context.getEnvironment().getProperty("spring.messages.basename", "messages");
               ConditionOutcome outcome = cache.get(basename);
               if (outcome == null) {
                   outcome = getMatchOutcomeForBasename(context, basename);
                   cache.put(basename, outcome);
               }
               return outcome;
           }
   
           private ConditionOutcome getMatchOutcomeForBasename(ConditionContext context, String basename) {
               ConditionMessage.Builder message = ConditionMessage.forCondition("ResourceBundle");
               for (String name : StringUtils.commaDelimitedListToStringArray(StringUtils.trimAllWhitespace(basename))) {
                   for (Resource resource : getResources(context.getClassLoader(), name)) {
                       if (resource.exists()) {
                           return ConditionOutcome.match(message.found("bundle").items(resource));
                       }
                   }
               }
               return ConditionOutcome.noMatch(message.didNotFind("bundle with basename " + basename).atAll());
           }
   
           private Resource[] getResources(ClassLoader classLoader, String name) {
               String target = name.replace('.', '/');
               try {
                   return new PathMatchingResourcePatternResolver(classLoader)
                           .getResources("classpath*:" + target + ".properties");
               }
               catch (Exception ex) {
                   return NO_RESOURCES;
               }
           }
   
       }
   
   }

2. 查看配置文件类 MessageSourceProperties

   // 这里使用lombok注解对一些冗余代码进行修改
   @Getter
   @Setter
   public class MessageSourceProperties {
   
       /**
        * Comma-separated list of basenames (essentially a fully-qualified classpath
        * location), each following the ResourceBundle convention with relaxed support for
        * slash based locations. If it doesn't contain a package qualifier (such as
        * "org.mypackage"), it will be resolved from the classpath root.
        */
       private String basename = "messages";
   
       /**
        * Message bundles encoding.
        */
       private Charset encoding = StandardCharsets.UTF_8;
   
       /**
        * Loaded resource bundle files cache duration. When not set, bundles are cached
        * forever. If a duration suffix is not specified, seconds will be used.
        */
       @DurationUnit(ChronoUnit.SECONDS)
       private Duration cacheDuration;
   
       /**
        * Whether to fall back to the system Locale if no files for a specific Locale have
        * been found. if this is turned off, the only fallback will be the default file (e.g.
        * "messages.properties" for basename "messages").
        */
       private boolean fallbackToSystemLocale = true;
   
       /**
        * Whether to always apply the MessageFormat rules, parsing even messages without
        * arguments.
        */
       private boolean alwaysUseMessageFormat = false;
   
       /**
        * Whether to use the message code as the default message instead of throwing a
        * "NoSuchMessageException". Recommended during development only.
        */
       private boolean useCodeAsDefaultMessage = false;
   
   

     public boolean isFallbackToSystemLocale() {
         return this.fallbackToSystemLocale;
     }
     public boolean isAlwaysUseMessageFormat() {
         return this.alwaysUseMessageFormat;
     }
     public boolean isUseCodeAsDefaultMessage() {
         return this.useCodeAsDefaultMessage;
     }
 }
 ```

ApplicationEventPublisher 接口

使用方法

1. 自定义一类事件

   import org.springframework.context.ApplicationEvent;
   
   public class MyEvent extends ApplicationEvent {
   
       // source代表事件源, 即谁发送的事件
       public MyEvent(Object source) {
           super(source);
       }
   }

2. 自定义一个或多个事件监听器（任意一个Spring组件即可）

   import com.example.event.MyEvent;
   import org.springframework.context.event.EventListener;
   import org.springframework.stereotype.Component;
   
   // 任意一个Spring组件都可以作为事件监听器
   @Component
   public class MyEventListenerComponent {
   
       // 方法参数需要和监听的事件类型保持一致, 例如发送的事件类型是String.class, 那么方法参数中也应该是String.class
       @EventListener
       public void getStringEvent(String message){
           System.out.println("String Event");
           System.out.println(message);
       }
   
       @EventListener
       public void getMyEvent(MyEvent myEvent){
           System.out.println("MyClass Event");
           System.out.println(myEvent);
       }
   }

3. 使用 ApplicationContext 中的功能进行事件发布

   import lombok.SneakyThrows;
   import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
   import org.springframework.boot.SpringApplication;
   import org.springframework.boot.autoconfigure.SpringBootApplication;
   import org.springframework.context.ConfigurableApplicationContext;
   
   @SpringBootApplication
   public class SpringApplicationV5Main {
       @SneakyThrows
       public static void main(String[] args) {
           ConfigurableApplicationContext context = SpringApplication.run(SpringApplicationV5Main.class, args);
           ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
   
           context.publishEvent("Hello Event");
           context.publishEvent(new MyEvent(context));
       }
   }

ResourcePatternResolve 接口

EnvironmentCapable 接口