Java Structs框架原理案例详解

<filter> 
    <filter-name>struts2</filter-name>  
    <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class> 
  </filter>  
  <filter-mapping> 
    <filter-name>struts2</filter-name>  
    <url-pattern>/*</url-pattern> 
  </filter-mapping>

public void init(FilterConfig filterConfig) throws ServletException {
        InitOperations init = new InitOperations();
        Dispatcher dispatcher = null;
        try {
            //封装filterConfig，其中有个主要方法getInitParameterNames将参数名字以String格式存储在List中
            FilterHostConfig config = new FilterHostConfig(filterConfig);
            //初始化struts内部日志
            init.initLogging(config);
            //创建dispatcher ，并初始化
            dispatcher = init.initDispatcher(config);
            init.initStaticContentLoader(config, dispatcher);
            //初始化类属性：prepare 、execute
            prepare = new PrepareOperations(filterConfig.getServletContext(), dispatcher);
            execute = new ExecuteOperations(filterConfig.getServletContext(), dispatcher);
            this.excludedPatterns = init.buildExcludedPatternsList(dispatcher);
            //回调空的postInit方法
            postInit(dispatcher, filterConfig);
        } finally {
            if (dispatcher != null) {
                dispatcher.cleanUpAfterInit();
            }
            init.cleanup();
        }
    }

public class FilterHostConfig implements HostConfig {
 
    private FilterConfig config;
    //构造方法
    public FilterHostConfig(FilterConfig config) {
        this.config = config;
    }
    //根据init-param配置的param-name获取param-value的值  
    public String getInitParameter(String key) {
        return config.getInitParameter(key);
    }
    //返回初始化参数名的迭代器 
    public Iterator<String> getInitParameterNames() {
        return MakeIterator.convert(config.getInitParameterNames());
    }
    //返回Servlet上下文
    public ServletContext getServletContext() {
        return config.getServletContext();
    }
}

public Dispatcher initDispatcher( HostConfig filterConfig ) {
         Dispatcher dispatcher = createDispatcher(filterConfig);
         dispatcher.init();
        return dispatcher;
    }

private Dispatcher createDispatcher( HostConfig filterConfig ) {
        //存放参数的Map
        Map<String, String> params = new HashMap<String, String>();
        //将参数存放到Map
        for ( Iterator e = filterConfig.getInitParameterNames(); e.hasNext(); ) {
            String name = (String) e.next();
            String value = filterConfig.getInitParameter(name);
            params.put(name, value);
        }
        //根据servlet上下文和参数Map构造Dispatcher 
        return new Dispatcher(filterConfig.getServletContext(), params);
    }

public void init() {
 
        if (configurationManager == null) {
            configurationManager = createConfigurationManager(BeanSelectionProvider.DEFAULT_BEAN_NAME);
        }
 
        try {
            init_FileManager();
            //加载org/apache/struts2/default.properties
            init_DefaultProperties(); // [1]
            //加载struts-default.xml,struts-plugin.xml,struts.xml
            init_TraditionalXmlConfigurations(); // [2]
            init_LegacyStrutsProperties(); // [3]
            //用户自己实现的ConfigurationProviders类 
            init_CustomConfigurationProviders(); // [5]
            //Filter的初始化参数 
            init_FilterInitParameters() ; // [6]
            init_AliasStandardObjects() ; // [7]
 
            Container container = init_PreloadConfiguration();
            container.inject(this);
            init_CheckWebLogicWorkaround(container);
 
            if (!dispatcherListeners.isEmpty()) {
                for (DispatcherListener l : dispatcherListeners) {
                    l.dispatcherInitialized(this);
                }
            }
        } catch (Exception ex) {
            if (LOG.isErrorEnabled())
                LOG.error("Dispatcher initialization failed", ex);
            throw new StrutsException(ex);
        }
    }