Apache Shiro学习笔记（七）EnvironmentLoaderListener
鲁春利的工作笔记，好记性不如烂笔头web.xml
Invicme
org.apache.shiro.web.env.EnvironmentLoaderListener
shiroEnvironmentClass
org.apache.shiro.web.env.IniWebEnvironment
shiroConfigLocations
classpath:shiro/shiro-form-filter.ini
ShiroFilter
org.apache.shiro.web.servlet.ShiroFilter
ShiroFilter
/*
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index.jsp
web.xml的配置中的作用
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:和
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. 容器将转化为键值对,并交给ServletContext
4. 容器创建中的类实例,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 Apache Shiro Web Documentation
* @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) {
// ......
}
}
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