SpringFactoriesLoader

  • Author: HuiFer

  • 源码阅读仓库: SourceHot-spring-boot

  • 全路径 : org.springframework.core.io.support.SpringFactoriesLoader

  • 测试类 : org.springframework.core.io.support.SpringFactoriesLoaderTests

loadFactories

  • 加载并实例化工厂
  1. public static <T> List<T> loadFactories(Class<T> factoryType, @Nullable ClassLoader classLoader) {
  2.         Assert.notNull(factoryType, "'factoryType' must not be null");
  3.         ClassLoader classLoaderToUse = classLoader;
  4.         if (classLoaderToUse == null) {
  5.             classLoaderToUse = SpringFactoriesLoader.class.getClassLoader();
  6.         }
  7.         // 工厂实现类名称
  8.         List<String> factoryImplementationNames = loadFactoryNames(factoryType, classLoaderToUse);
  9.         if (logger.isTraceEnabled()) {
  10.             logger.trace("Loaded [" + factoryType.getName() + "] names: " + factoryImplementationNames);
  11.         }
  12.         List<T> result = new ArrayList<>(factoryImplementationNames.size());
  13.         for (String factoryImplementationName : factoryImplementationNames) {
  14.             // 将实例化的工厂放入结果集合
  15.             result.add(instantiateFactory(factoryImplementationName, factoryType, classLoaderToUse));
  16.         }
  17.         // 排序
  18.         AnnotationAwareOrderComparator.sort(result);
  19.         return result;
  20.     }

loadSpringFactories

  • 获取接口的实现类名
  1.     private static Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader) {
  2.         MultiValueMap<String, String> result = cache.get(classLoader);
  3.         if (result != null) {
  4.             return result;
  5.         }
  7.         try {
  8.             // 找 META-INF/spring.factories
  9.             Enumeration<URL> urls = (classLoader != null ?
  10.                     classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :
  11.                     ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));
  12.             result = new LinkedMultiValueMap<>();
  13.             while (urls.hasMoreElements()) {
  14.                 // 获取 路由地址
  15.                 URL url = urls.nextElement();
  16.                 // url 解析
  17.                 UrlResource resource = new UrlResource(url);
  18.                 // Properties 解析
  19.                 Properties properties = PropertiesLoaderUtils.loadProperties(resource);
  20.                 // 循环解析结果
  21.                 for (Map.Entry<?, ?> entry : properties.entrySet()) {
  22.                     String factoryTypeName = ((String) entry.getKey()).trim();
  23.                     for (String factoryImplementationName : StringUtils.commaDelimitedListToStringArray((String) entry.getValue())) {
  24.                         // 放入list
  25.                         result.add(factoryTypeName, factoryImplementationName.trim());
  26.                     }
  27.                 }
  28.             }
  29.             // 放入缓存
  30.             cache.put(classLoader, result);
  31.             return result;
  32.         }
  33.         catch (IOException ex) {
  34.             throw new IllegalArgumentException("Unable to load factories from location [" +
  35.                                                        FACTORIES_RESOURCE_LOCATION + "]", ex);
  36.         }
  37.     }

  • 存放在 测试目录下的META-INF/spring.factories

    1. org.springframework.core.io.support.DummyFactory =\
    2. org.springframework.core.io.support.MyDummyFactory2, \
    3. org.springframework.core.io.support.MyDummyFactory1
    5. java.lang.String=\
    6. org.springframework.core.io.support.MyDummyFactory1
    8. org.springframework.core.io.support.DummyPackagePrivateFactory=\
    9. org.springframework.core.io.support.DummyPackagePrivateFactory

  • Enumeration<URL> urls 变量存放的是 扫描到的META-INF/spring.factories 路径

  • while 代码简单描述

    1. 获取文件路径
    2. 文件路径解析
    3. 读取文件 Properties 解析
    4. 放入返回结果
    5. 放入缓存

instantiateFactory

  1. @SuppressWarnings("unchecked")
  2. private static <T> T instantiateFactory(String factoryImplementationName, Class<T> factoryType, ClassLoader classLoader) {
  3.    try {
  4.       Class<?> factoryImplementationClass = ClassUtils.forName(factoryImplementationName, classLoader);
  5.       if (!factoryType.isAssignableFrom(factoryImplementationClass)) {
  6.          throw new IllegalArgumentException(
  7.                "Class [" + factoryImplementationName + "] is not assignable to factory type [" + factoryType.getName() + "]");
  8.       }
  9.       return (T) ReflectionUtils.accessibleConstructor(factoryImplementationClass).newInstance();
  10.    }
  11.    catch (Throwable ex) {
  12.       throw new IllegalArgumentException(
  13.             "Unable to instantiate factory class [" + factoryImplementationName + "] for factory type [" + factoryType.getName() + "]",
  14.             ex
  15.       );
  16.    }
  17. }
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