Spring中的策略模式简单实现与使用分析

public abstract class AbstractStrategy {
 
    /**
     *  抽象的策略接口
     */
    abstract void algorithm();
}

public class StrategyImplOne extends AbstractStrategy {
    @Override
    void algorithm() {
        System.out.println("我实现了策略（一）的方法！！！");
    }
}

public class StrategyImplTwo extends AbstractStrategy {
 
    @Override
    void algorithm() {
        System.out.println("我实现了策略（二）的方法！！！");
    }
}

public class Context {
 
    private AbstractStrategy strategy;
 
    public Context(AbstractStrategy strategy) {
        this.strategy = strategy;
    }
 
    /**
     *  触发策略执行
     */
    public void strategyImpl() {
        strategy.algorithm();
    }
}

public class StrategyTest {
    public static void main(String[] args) {
        // 执行策略一
        new Context(new StrategyImplOne()).strategyImpl();
        // 执行策略二
        new Context(new StrategyImplTwo()).strategyImpl();
    }
}

public class Properties extends Hashtable<Object, Object> {
    // ***
}

protected <T> T getDefaultStrategy(ApplicationContext context, Class<T> strategyInterface) {
        List<T> strategies = this.getDefaultStrategies(context, strategyInterface);
        if (strategies.size() != 1) {
            throw new BeanInitializationException("DispatcherServlet needs exactly 1 strategy for interface [" + strategyInterface.getName() + "]");
        } else {
            return strategies.get(0);
        }
    }

protected <T> List<T> getDefaultStrategies(ApplicationContext context, Class<T> strategyInterface) {
        String key = strategyInterface.getName();
        String value = defaultStrategies.getProperty(key);
        if (value == null) {
            return new LinkedList();
        } else {
            String[] classNames = StringUtils.commaDelimitedListToStringArray(value);
            List<T> strategies = new ArrayList(classNames.length);
            String[] var7 = classNames;
            int var8 = classNames.length;
 
            for(int var9 = 0; var9 < var8; ++var9) {
                String className = var7[var9];
 
                try {
                    Class<?> clazz = ClassUtils.forName(className, DispatcherServlet.class.getClassLoader());
                    Object strategy = this.createDefaultStrategy(context, clazz);
                    strategies.add(strategy);
                } catch (ClassNotFoundException var13) {
                    throw new BeanInitializationException("Could not find DispatcherServlet's default strategy class [" + className + "] for interface [" + key + "]", var13);
                } catch (LinkageError var14) {
                    throw new BeanInitializationException("Unresolvable class definition for DispatcherServlet's default strategy class [" + className + "] for interface [" + key + "]", var14);
                }
            }
 
            return strategies;
        }
    }

static {
        try {
            ClassPathResource resource = new ClassPathResource("DispatcherServlet.properties", DispatcherServlet.class);
            defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
        } catch (IOException var1) {
            throw new IllegalStateException("Could not load 'DispatcherServlet.properties': " + var1.getMessage());
        }
    }

# Default implementation classes for DispatcherServlet's strategy interfaces.
# Used as fallback when no matching beans are found in the DispatcherServlet context.
# Not meant to be customized by application developers.
org.springframework.web.servlet.LocaleResolver=org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver
org.springframework.web.servlet.ThemeResolver=org.springframework.web.servlet.theme.FixedThemeResolver
org.springframework.web.servlet.HandlerMapping=org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping,\
	org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping
org.springframework.web.servlet.HandlerAdapter=org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter,\
	org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter,\
	org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter
org.springframework.web.servlet.HandlerExceptionResolver=org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver,\
	org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver,\
	org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver
org.springframework.web.servlet.RequestToViewNameTranslator=org.springframework.web.servlet.view.DefaultRequestToViewNameTranslator
org.springframework.web.servlet.ViewResolver=org.springframework.web.servlet.view.InternalResourceViewResolver
org.springframework.web.servlet.FlashMapManager=org.springframework.web.servlet.support.SessionFlashMapManager