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作者 | 正文 | ||||||||||||||
发表时间:2010-11-30
最后修改:2011-05-31
作者:niumd blog:http://ari.iteye.com
一、概述 Struts2的核心是一个Filter,Action可以脱离web容器,那么是什么让http请求和action关联在一起的,下面我们深入源码来分析下Struts2是如何工作的。 FilterDispatcher API 写道
Deprecated. Since Struts 2.1.3, use StrutsPrepareAndExecuteFilter instead or StrutsPrepareFilter and StrutsExecuteFilter if needing using the ActionContextCleanUp filter in addition to this one
鉴于常规情况官方推荐使用StrutsPrepareAndExecuteFilter替代FilterDispatcher,我们此文将剖析StrutsPrepareAndExecuteFilter,其在工程中作为一个Filter配置在web.xml中,配置如下: <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>
二、源码属性方法简介 下面我们研究下StrutsPrepareAndExecuteFilter源码,类的主要信息如下:
StrutsPrepareAndExecuteFilter与普通的Filter并无区别,方法除继承自Filter外,仅有一个回调方法,第三部分我们将按照Filter方法调用顺序,由init—>doFilter—>destroy顺序地分析源码。
三、源码剖析
1、init方法 init是Filter第一个运行的方法,我们看下struts2的核心Filter在调用init方法初始化时做哪些工作: public void init(FilterConfig filterConfig) throws ServletException { InitOperations init = new InitOperations(); 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,这部分下面我们重点分析,初始化时加载那些资源 Dispatcher 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 { init.cleanup(); } }
首先看下FilterHostConfig ,源码如下:
public class FilterHostConfig implements HostConfig { private FilterConfig config; /** *构造函数 */ 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List */ public Iterator<String> getInitParameterNames() { return MakeIterator.convert(config.getInitParameterNames()); } public ServletContext getServletContext() { return config.getServletContext(); } } 只有短短的几行代码,getInitParameterNames是这个类的核心,将Filter初始化参数名称有枚举类型转为Iterator。此类的主要作为是对filterConfig 封装。
重点来了,创建并初始化Dispatcher public Dispatcher initDispatcher( HostConfig filterConfig ) { Dispatcher dispatcher = createDispatcher(filterConfig); dispatcher.init(); return dispatcher; } 创建Dispatcher,会读取 filterConfig 中的配置信息,将配置信息解析出来,封装成为一个Map,然后根绝servlet上下文和参数Map构造Dispatcher : private Dispatcher createDispatcher( HostConfig filterConfig ) { Map<String, String> params = new HashMap<String, String>(); for ( Iterator e = filterConfig.getInitParameterNames(); e.hasNext(); ) { String name = (String) e.next(); String value = filterConfig.getInitParameter(name); params.put(name, value); } return new Dispatcher(filterConfig.getServletContext(), params); } Dispatcher初始化,加载struts2的相关配置文件,将按照顺序逐一加载:default.properties,struts-default.xml,struts-plugin.xml,struts.xml,……
/** *初始化过程中依次加载如下配置文件 */ public void init() { if (configurationManager == null) { configurationManager = new ConfigurationManager(BeanSelectionProvider.DEFAULT_BEAN_NAME); } try { //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_CheckConfigurationReloading(container); 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); } }
初始化default.properties,具体的初始化操作在DefaultPropertiesProvider类中
private void init_DefaultProperties() { configurationManager.addConfigurationProvider(new DefaultPropertiesProvider()); }
下面我们看下DefaultPropertiesProvider类源码:
public void register(ContainerBuilder builder, LocatableProperties props) throws ConfigurationException { Settings defaultSettings = null; try { defaultSettings = new PropertiesSettings("org/apache/struts2/default"); } catch (Exception e) { throw new ConfigurationException("Could not find or error in org/apache/struts2/default.properties", e); } loadSettings(props, defaultSettings); }
其他的我们再次省略,大家可以浏览下各个初始化操作都加载了那些文件
doFilter是过滤器的执行方法,它拦截提交的HttpServletRequest请求,HttpServletResponse响应,作为strtus2的核心拦截器,在doFilter里面到底做了哪些工作,我们将逐行解读其源码,源码如下:
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException { //父类向子类转:强转为http请求、响应 HttpServletRequest request = (HttpServletRequest) req; HttpServletResponse response = (HttpServletResponse) res; try { //设置编码和国际化 prepare.setEncodingAndLocale(request, response); //创建Action上下文(重点) prepare.createActionContext(request, response); prepare.assignDispatcherToThread(); if ( excludedPatterns != null && prepare.isUrlExcluded(request, excludedPatterns)) { chain.doFilter(request, response); } else { request = prepare.wrapRequest(request); ActionMapping mapping = prepare.findActionMapping(request, response, true); if (mapping == null) { boolean handled = execute.executeStaticResourceRequest(request, response); if (!handled) { chain.doFilter(request, response); } } else { execute.executeAction(request, response, mapping); } } } finally { prepare.cleanupRequest(request); } }
setEncodingAndLocale调用了dispatcher方法的prepare方法:
/** * Sets the request encoding and locale on the response */ public void setEncodingAndLocale(HttpServletRequest request, HttpServletResponse response) { dispatcher.prepare(request, response); }
下面我们看下prepare方法,这个方法很简单只是设置了encoding 、locale ,做的只是一些辅助的工作: public void prepare(HttpServletRequest request, HttpServletResponse response) { String encoding = null; if (defaultEncoding != null) { encoding = defaultEncoding; } Locale locale = null; if (defaultLocale != null) { locale = LocalizedTextUtil.localeFromString(defaultLocale, request.getLocale()); } if (encoding != null) { try { request.setCharacterEncoding(encoding); } catch (Exception e) { LOG.error("Error setting character encoding to '" + encoding + "' - ignoring.", e); } } if (locale != null) { response.setLocale(locale); } if (paramsWorkaroundEnabled) { request.getParameter("foo"); // simply read any parameter (existing or not) to "prime" the request } }
Action上下文创建(重点)
ActionContext是一个容器,这个容易主要存储request、session、application、parameters等相关信息.ActionContext是一个线程的本地变量,这意味着不同的action之间不会共享ActionContext,所以也不用考虑线程安全问题。其实质是一个Map,key是标示request、session、……的字符串,值是其对应的对象: static ThreadLocal actionContext = new ThreadLocal(); Map<String, Object> context;
/** *创建Action上下文,初始化thread local */ public ActionContext createActionContext(HttpServletRequest request, HttpServletResponse response) { ActionContext ctx; Integer counter = 1; Integer oldCounter = (Integer) request.getAttribute(CLEANUP_RECURSION_COUNTER); if (oldCounter != null) { counter = oldCounter + 1; } //注意此处是从ThreadLocal中获取此ActionContext变量 ActionContext oldContext = ActionContext.getContext(); if (oldContext != null) { // detected existing context, so we are probably in a forward ctx = new ActionContext(new HashMap<String, Object>(oldContext.getContextMap())); } else { ValueStack stack = dispatcher.getContainer().getInstance(ValueStackFactory.class).createValueStack(); stack.getContext().putAll(dispatcher.createContextMap(request, response, null, servletContext)); //stack.getContext()返回的是一个Map<String,Object>,根据此Map构造一个ActionContext ctx = new ActionContext(stack.getContext()); } request.setAttribute(CLEANUP_RECURSION_COUNTER, counter); //将ActionContext存如ThreadLocal ActionContext.setContext(ctx); return ctx; }
上面代码中dispatcher.createContextMap,如何封装相关参数:
public Map<String,Object> createContextMap(HttpServletRequest request, HttpServletResponse response, ActionMapping mapping, ServletContext context) { // request map wrapping the http request objects Map requestMap = new RequestMap(request); // parameters map wrapping the http parameters. ActionMapping parameters are now handled and applied separately Map params = new HashMap(request.getParameterMap()); // session map wrapping the http session Map session = new SessionMap(request); // application map wrapping the ServletContext Map application = new ApplicationMap(context); //requestMap、params、session等Map封装成为一个上下文Map,逐个调用了map.put(Map p). Map<String,Object> extraContext = createContextMap(requestMap, params, session, application, request, response, context); if (mapping != null) { extraContext.put(ServletActionContext.ACTION_MAPPING, mapping); } return extraContext; }
我们简单看下RequestMap,其他的省略。RequestMap类实现了抽象Map,故其本身是一个Map,主要方法实现: //map的get实现 public Object get(Object key) { return request.getAttribute(key.toString()); } //map的put实现 public Object put(Object key, Object value) { Object oldValue = get(key); entries = null; request.setAttribute(key.toString(), value); return oldValue; }
下面是源码展示了如何执行Action控制器:
public void executeAction(HttpServletRequest request, HttpServletResponse response, ActionMapping mapping) throws ServletException { dispatcher.serviceAction(request, response, servletContext, mapping); } public void serviceAction(HttpServletRequest request, HttpServletResponse response, ServletContext context, ActionMapping mapping) throws ServletException { //封装执行的上下文环境,主要讲相关信息存储入map Map<String, Object> extraContext = createContextMap(request, response, mapping, context); // If there was a previous value stack, then create a new copy and pass it in to be used by the new Action ValueStack stack = (ValueStack) request.getAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY); boolean nullStack = stack == null; if (nullStack) { ActionContext ctx = ActionContext.getContext(); if (ctx != null) { stack = ctx.getValueStack(); } } if (stack != null) { extraContext.put(ActionContext.VALUE_STACK, valueStackFactory.createValueStack(stack)); } String timerKey = "Handling request from Dispatcher"; try { UtilTimerStack.push(timerKey); //获取命名空间 String namespace = mapping.getNamespace(); //获取action配置的name属性 String name = mapping.getName(); //获取action配置的method属性 String method = mapping.getMethod(); Configuration config = configurationManager.getConfiguration(); //根据执行上下文参数,命名空间,名称等创建用户自定义Action的代理对象 ActionProxy proxy = config.getContainer().getInstance(ActionProxyFactory.class).createActionProxy( namespace, name, method, extraContext, true, false); request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, proxy.getInvocation().getStack()); // if the ActionMapping says to go straight to a result, do it! //执行execute方法,并转向结果 if (mapping.getResult() != null) { Result result = mapping.getResult(); result.execute(proxy.getInvocation()); } else { proxy.execute(); } // If there was a previous value stack then set it back onto the request if (!nullStack) { request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, stack); } } catch (ConfigurationException e) { // WW-2874 Only log error if in devMode if(devMode) { String reqStr = request.getRequestURI(); if (request.getQueryString() != null) { reqStr = reqStr + "?" + request.getQueryString(); } LOG.error("Could not find action or result\n" + reqStr, e); } else { LOG.warn("Could not find action or result", e); } sendError(request, response, context, HttpServletResponse.SC_NOT_FOUND, e); } catch (Exception e) { sendError(request, response, context, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e); } finally { UtilTimerStack.pop(timerKey); } }
文中对如何解析Struts.xml,如何将URL与action映射匹配为分析,有需要的我后续补全,因为StrutsXmlConfigurationProvider继承XmlConfigurationProvider,并在register方法回调父类的register,有兴趣的可以深入阅读下下XmlConfigurationProvider源码:
public void register(ContainerBuilder containerBuilder, LocatableProperties props) throws ConfigurationException { if (servletContext != null && !containerBuilder.contains(ServletContext.class)) { containerBuilder.factory(ServletContext.class, new Factory<ServletContext>() { public ServletContext create(Context context) throws Exception { return servletContext; } }); } //调用父类的register,关键点所在 super.register(containerBuilder, props); }
struts2-core-2.2.1.jar包中struts-2.1.7.dtd对于Action的定义如下: <!ELEMENT action (param|result|interceptor-ref|exception-mapping)*> <!ATTLIST action name CDATA #REQUIRED class CDATA #IMPLIED method CDATA #IMPLIED converter CDATA #IMPLIED > 从上述DTD中可见Action元素可以含有name 、class 、method 、converter 属性。
XmlConfigurationProvider解析struts.xml配置的Action元素: protected void addAction(Element actionElement, PackageConfig.Builder packageContext) throws ConfigurationException { String name = actionElement.getAttribute("name"); String className = actionElement.getAttribute("class"); String methodName = actionElement.getAttribute("method"); Location location = DomHelper.getLocationObject(actionElement); if (location == null) { LOG.warn("location null for " + className); } //methodName should be null if it's not set methodName = (methodName.trim().length() > 0) ? methodName.trim() : null; // if there isnt a class name specified for an <action/> then try to // use the default-class-ref from the <package/> if (StringUtils.isEmpty(className)) { // if there is a package default-class-ref use that, otherwise use action support /* if (StringUtils.isNotEmpty(packageContext.getDefaultClassRef())) { className = packageContext.getDefaultClassRef(); } else { className = ActionSupport.class.getName(); }*/ } else { if (!verifyAction(className, name, location)) { if (LOG.isErrorEnabled()) LOG.error("Unable to verify action [#0] with class [#1], from [#2]", name, className, location.toString()); return; } } Map<String, ResultConfig> results; try { results = buildResults(actionElement, packageContext); } catch (ConfigurationException e) { throw new ConfigurationException("Error building results for action " + name + " in namespace " + packageContext.getNamespace(), e, actionElement); } List<InterceptorMapping> interceptorList = buildInterceptorList(actionElement, packageContext); List<ExceptionMappingConfig> exceptionMappings = buildExceptionMappings(actionElement, packageContext); ActionConfig actionConfig = new ActionConfig.Builder(packageContext.getName(), name, className) .methodName(methodName) .addResultConfigs(results) .addInterceptors(interceptorList) .addExceptionMappings(exceptionMappings) .addParams(XmlHelper.getParams(actionElement)) .location(location) .build(); packageContext.addActionConfig(name, actionConfig); if (LOG.isDebugEnabled()) { LOG.debug("Loaded " + (StringUtils.isNotEmpty(packageContext.getNamespace()) ? (packageContext.getNamespace() + "/") : "") + name + " in '" + packageContext.getName() + "' package:" + actionConfig); } }
工作中不涉及Struts2,本周工作有个2天的空档期,稍微看了下struts2的文档,写了个demo,从源码的角度研究了下运行原理,如有分析不当请指出,我后续逐步完善更正,大家共同提高。
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发表时间:2010-12-02
LZ真不错~
不知道LZ有没有关于struts1的源码讲解~ 如果有·· 不知道能不能弄个struts1源码与struts2源码的对比呢~ |
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发表时间:2010-12-02
1111111111111 写道 LZ真不错~
不知道LZ有没有关于struts1的源码讲解~ 如果有·· 不知道能不能弄个struts1源码与struts2源码的对比呢~ 等有时间吧;struts1网上应该有好像,我搜索了下struts2目前最新版本的源码没人分析,就分享了下 |
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发表时间:2010-12-03
1111111111111 写道 LZ真不错~
不知道LZ有没有关于struts1的源码讲解~ 如果有·· 不知道能不能弄个struts1源码与struts2源码的对比呢~ |
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发表时间:2010-12-05
楼主没有分析代理类的源码,希望楼主可以分析一下,谢谢
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发表时间:2010-12-05
nrxqq 写道 楼主没有分析代理类的源码,希望楼主可以分析一下,谢谢 后续补上 |
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发表时间:2011-01-10
我感觉很一般,就是吧struts2的源代码给贴出来了,也没说明什么,运行机制也没说清楚。LZ那点代码根本没抓到struts2的魂,我觉的,呵呵
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发表时间:2011-04-09
韩悠悠 写道 我感觉很一般,就是吧struts2的源代码给贴出来了,也没说明什么,运行机制也没说清楚。LZ那点代码根本没抓到struts2的魂,我觉的,呵呵
才疏学浅还得请您着资深人士指点 |
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