鲁春利的工作笔记,好记性不如烂笔头
web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0"> <display-name>Invicme</display-name> <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> </context-param> <context-param> <param-name>shiroConfigLocations</param-name> <param-value>classpath:shiro/shiro-form-filter.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> <session-config> <session-timeout>30</session-timeout> </session-config> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>
web.xml的配置中<context-param>的作用
1. 启动一个WEB项目的时候,容器(如:Tomcat)会去读它的配置文件web.xml
读两个节点: <listener></listener> 和 <context-param></context-param>
2. 紧接着,容器创建一个ServletContext(上下文),这个WEB项目所有部分都将共享这个上下文
3. 容器将<context-param></context-param>转化为键值对,并交给ServletContext
4. 容器创建<listener></listener>中的类实例,即创建监听
5. 在监听中会有contextInitialized(ServletContextEvent args)初始化方法
在这个方法中获得ServletContext = ServletContextEvent.getServletContext();
context-param的值 = ServletContext.getInitParameter(“context-param的键”);
6. 得到这个context-param的值之后,可以做一些其他操作了
ShiroFilter
package org.apache.shiro.web.servlet; import org.apache.shiro.web.env.WebEnvironment; import org.apache.shiro.web.filter.mgt.FilterChainResolver; import org.apache.shiro.web.util.WebUtils; /** * @see org.apache.shiro.web.env.EnvironmentLoader EnvironmentLoader * @see org.apache.shiro.web.env.EnvironmentLoaderListener EnvironmentLoaderListener * @see <a href="http://shiro.apache.org/web.html">Apache Shiro Web Documentation</a> * @since 1.2 */ public class ShiroFilter extends AbstractShiroFilter { /** * @see org.apache.shiro.web.env.EnvironmentLoaderListener * @since 1.2 */ @Override public void init() throws Exception { // WebEnvironment env = WebUtils.getRequiredWebEnvironment(getServletContext()); setSecurityManager(env.getWebSecurityManager()); FilterChainResolver resolver = env.getFilterChainResolver(); if (resolver != null) { setFilterChainResolver(resolver); } } }
辅助工具类WebUtils
package org.apache.shiro.web.util; public class WebUtils { public static WebEnvironment getRequiredWebEnvironment(ServletContext sc) throws IllegalStateException { WebEnvironment we = getWebEnvironment(sc); if (we == null) { throw new IllegalStateException("No WebEnvironment found: no EnvironmentLoaderListener registered?"); } return we; } public static WebEnvironment getWebEnvironment(ServletContext sc) { return getWebEnvironment(sc, EnvironmentLoader.ENVIRONMENT_ATTRIBUTE_KEY); } public static WebEnvironment getWebEnvironment(ServletContext sc, String attrName) { if (sc == null) { // 异常 } Object attr = sc.getAttribute(attrName); if (attr == null) { // 返回null(ServletContext中无该属性) return null; } if (attr instanceof RuntimeException) { // 异常 } if (attr instanceof Error) { // 异常 } if (attr instanceof Exception) { // 异常 } if (!(attr instanceof WebEnvironment)) { // 异常 } // 获取到实际的值 return (WebEnvironment) attr; } }
ServletContext中的EnvironmentLoader.ENVIRONMENT_ATTRIBUTE_KEY属性是在什么时候设置的呢?
WebEnvironment的类图结构
EnvironmentLoaderListener
package org.apache.shiro.web.env; public class EnvironmentLoaderListener extends EnvironmentLoader implements ServletContextListener { // Web应用被初始化时默认调用的方法 public void contextInitialized(ServletContextEvent sce) { // 调用父类EnvironmentLoader的initEnvironment方法 initEnvironment(sce.getServletContext()); } // Web应用被销毁时默认调用的方法(reload时是会调用该方法) public void contextDestroyed(ServletContextEvent sce) { destroyEnvironment(sce.getServletContext()); } }
EnvironmentLoader
package org.apache.shiro.web.env; public class EnvironmentLoader { // 在web.xml文件中指定WebEnvironment的实现类 public static final String ENVIRONMENT_CLASS_PARAM = "shiroEnvironmentClass"; // 在web.xml文件中指定ini文件路径(不指定则默认加载/WEB-INF/shiro.ini) public static final String CONFIG_LOCATIONS_PARAM = "shiroConfigLocations"; // 初始化Environment实例 public WebEnvironment initEnvironment(ServletContext servletContext) throws IllegalStateException { if (servletContext.getAttribute(ENVIRONMENT_ATTRIBUTE_KEY) != null) { // 第一次Web应用启动时上下文中已经存在该KEY的属性,说明web.xml文件配置有问题,可能有多个EnvironmentLoader*的定义 // 异常 } // 记录日志 servletContext.log("Initializing Shiro environment"); log.info("Starting Shiro environment initialization."); // 记录当前时间 long startTime = System.currentTimeMillis(); try { // 获取WebEnvironment类的实例 WebEnvironment environment = createEnvironment(servletContext); // 在ServletContext中设置KEY,设置完成后在WebUtils中就可以获取到了 servletContext.setAttribute(ENVIRONMENT_ATTRIBUTE_KEY, environment); // 在日志中输出ServletContext中设置WebEnvironment耗费的时间(毫秒) if (log.isInfoEnabled()) { long elapsed = System.currentTimeMillis() - startTime; log.info("Shiro environment initialized in {} ms.", elapsed); } return environment; } catch (RuntimeException ex) { // 异常 } catch (Error err) { // 异常 } } // 在给定的ServletContext中设置WebEnvironment protected WebEnvironment createEnvironment(ServletContext sc) { Class<?> clazz = determineWebEnvironmentClass(sc); if (!MutableWebEnvironment.class.isAssignableFrom(clazz)) { // native方法,底层JVM实现 // 异常 } // 从ServletContext中获取shiroConfigLocations属性的值(classpath:shiro/shiro-form-filter.ini) String configLocations = sc.getInitParameter(CONFIG_LOCATIONS_PARAM); boolean configSpecified = StringUtils.hasText(configLocations); if (configSpecified && !(ResourceConfigurable.class.isAssignableFrom(clazz))) { // 异常 } // 获取类的实例(ClassUtils.newInstance(clazz) ==> return clazz.newInstance();) MutableWebEnvironment environment = (MutableWebEnvironment) ClassUtils.newInstance(clazz); // 调用父类DefaultWebEnvironment的setServletContext environment.setServletContext(sc); if (configSpecified && (environment instanceof ResourceConfigurable)) { // 调用父类ResourceBasedWebEnvironment的setConfigLocations ((ResourceConfigurable) environment).setConfigLocations(configLocations); } customizeEnvironment(environment); // LifecycleUtils.init中会调用environment.init方法(IniWebEnvironment.init()) LifecycleUtils.init(environment); // 返回得到的WebEnvironment类的实例(IniWebEnvironment的实例) return environment; } // 获取WebEnvironment的Class类对象 protected Class<?> determineWebEnvironmentClass(ServletContext servletContext) { // ENVIRONMENT_CLASS_PARAM = "shiroEnvironmentClass";获取web.xml文件中声明的属性值 String className = servletContext.getInitParameter(ENVIRONMENT_CLASS_PARAM); if (className != null) { try { // web.xml配置的参数对应className=org.apache.shiro.web.env.IniWebEnvironment return ClassUtils.forName(className); } catch (UnknownClassException ex) { // 异常 } } else { // 如果未配置则使用该IniWebEnvironment类 return IniWebEnvironment.class; } } // 空的方法体,可以实现自定义的逻辑 protected void customizeEnvironment(WebEnvironment environment) { // ...... } }