项目启动时shiro加载过程

<!--- shiro 1.2 -->
    <listener>
        <listener-class>org.apache.shiro.web.env.EnvironmentLoaderListener</listener-class>
    </listener>
    <context-param>
        <param-name>shiroEnvironmentClass</param-name>
        <param-value>org.apache.shiro.web.env.IniWebEnvironment</param-value><!-- 默认先从/WEB-INF/shiro.ini，如果没有找classpath:shiro.ini -->
    </context-param>
    <context-param>
        <param-name>shiroConfigLocations</param-name>
        <param-value>classpath:shiro.ini</param-value>
    </context-param>
    <filter>
        <filter-name>shiroFilter</filter-name>
        <filter-class>org.apache.shiro.web.servlet.ShiroFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>shiroFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

public class EnvironmentLoaderListener extends EnvironmentLoader implements ServletContextListener {

   //servlet容器启动的时候调用
    public void contextInitialized(ServletContextEvent sce) {
        initEnvironment(sce.getServletContext());
    }

    //servlet容器销毁的时候调用
    public void contextDestroyed(ServletContextEvent sce) {
        destroyEnvironment(sce.getServletContext());
    }
}

    public WebEnvironment initEnvironment(ServletContext servletContext) throws IllegalStateException {

        //防止已经被初始化过了，这里做个校验
        if (servletContext.getAttribute(ENVIRONMENT_ATTRIBUTE_KEY) != null) {
            String msg = "There is already a Shiro environment associated with the current ServletContext.  " +
                    "Check if you have multiple EnvironmentLoader* definitions in your web.xml!";
            throw new IllegalStateException(msg);
        }

        servletContext.log("Initializing Shiro environment");
        log.info("Starting Shiro environment initialization.");

        long startTime = System.currentTimeMillis();

        try {
　　　　　　　//重点是这，创建WebEnvironment
            WebEnvironment environment = createEnvironment(servletContext);
            servletContext.setAttribute(ENVIRONMENT_ATTRIBUTE_KEY, environment);

            log.debug("Published WebEnvironment as ServletContext attribute with name [{}]",
                    ENVIRONMENT_ATTRIBUTE_KEY);

            if (log.isInfoEnabled()) {
                long elapsed = System.currentTimeMillis() - startTime;
                log.info("Shiro environment initialized in {} ms.", elapsed);
            }

            return environment;
        } catch (RuntimeException ex) {
            log.error("Shiro environment initialization failed", ex);
            servletContext.setAttribute(ENVIRONMENT_ATTRIBUTE_KEY, ex);
            throw ex;
        } catch (Error err) {
            log.error("Shiro environment initialization failed", err);
            servletContext.setAttribute(ENVIRONMENT_ATTRIBUTE_KEY, err);
            throw err;
        }
    }

    protected WebEnvironment createEnvironment(ServletContext sc) {
        
        //加载IniWebEnvironment
        Class<?> clazz = determineWebEnvironmentClass(sc);
        if (!MutableWebEnvironment.class.isAssignableFrom(clazz)) {
            throw new ConfigurationException("Custom WebEnvironment class [" + clazz.getName() +
                    "] is not of required type [" + WebEnvironment.class.getName() + "]");
        }

        //获取shiro配置路径
        String configLocations = sc.getInitParameter(CONFIG_LOCATIONS_PARAM);
        boolean configSpecified = StringUtils.hasText(configLocations);

        if (configSpecified && !(ResourceConfigurable.class.isAssignableFrom(clazz))) {
            String msg = "WebEnvironment class [" + clazz.getName() + "] does not implement the " +
                    ResourceConfigurable.class.getName() + "interface.  This is required to accept any " +
                    "configured " + CONFIG_LOCATIONS_PARAM + "value(s).";
            throw new ConfigurationException(msg);
        }

        MutableWebEnvironment environment = (MutableWebEnvironment) ClassUtils.newInstance(clazz);

        environment.setServletContext(sc);

        if (configSpecified && (environment instanceof ResourceConfigurable)) {
            ((ResourceConfigurable) environment).setConfigLocations(configLocations);
        }

        customizeEnvironment(environment);

        //重点是初始化过程
        LifecycleUtils.init(environment);

        return environment;
    }

    protected Class<?> determineWebEnvironmentClass(ServletContext servletContext) {
        String className = servletContext.getInitParameter(ENVIRONMENT_CLASS_PARAM);
        if (className != null) {
            try {
                return ClassUtils.forName(className);
            } catch (UnknownClassException ex) {
                throw new ConfigurationException(
                        "Failed to load custom WebEnvironment class [" + className + "]", ex);
            }
        } else {
            return IniWebEnvironment.class;
        }
    }

    public void init() {
        //这里暂时还没有配置文件，需要从前面加载的configLocations路径中加载
        Ini ini = getIni();

        String[] configLocations = getConfigLocations();

        if (log.isWarnEnabled() && !CollectionUtils.isEmpty(ini) &&
                configLocations != null && configLocations.length > 0) {
            log.warn("Explicit INI instance has been provided, but configuration locations have also been " +
                    "specified.  The {} implementation does not currently support multiple Ini config, but this may " +
                    "be supported in the future. Only the INI instance will be used for configuration.",
                    IniWebEnvironment.class.getName());
        }

        if (CollectionUtils.isEmpty(ini)) {
            log.debug("Checking any specified config locations.");
            //从配置路径下加载shiro配置
            ini = getSpecifiedIni(configLocations);
        }

        if (CollectionUtils.isEmpty(ini)) {
            log.debug("No INI instance or config locations specified.  Trying default config locations.");
            ini = getDefaultIni();
        }

        if (CollectionUtils.isEmpty(ini)) {
            String msg = "Shiro INI configuration was either not found or discovered to be empty/unconfigured.";
            throw new ConfigurationException(msg);
        }

        setIni(ini);

        //重点又来了，shiro需要的类是从这里开始加载的
        configure();
    }

    protected void configure() {

        this.objects.clear();

        WebSecurityManager securityManager = createWebSecurityManager();
        setWebSecurityManager(securityManager);

        FilterChainResolver resolver = createFilterChainResolver();
        if (resolver != null) {
            setFilterChainResolver(resolver);
        }
    }