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StrutsPrepareAndExecuteFilter(转)
http://www.iteye.com/topic/829843
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。
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 >
- <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:
属性摘要 | |
---|---|
protected List<Pattern > | excludedPatterns |
protected ExecuteOperations | execute |
protected PrepareOperations | prepare |
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。
方法摘要 | |
---|---|
void | destroy () 继承自Filter,用于资源释放 |
void | doFilter (ServletRequest req, ServletResponse res, FilterChain chain) 继承自Filter,执行方法 |
void | init (FilterConfig filterConfig) 继承自Filter,初始化参数 |
protected void | postInit (Dispatcher dispatcher, FilterConfig filterConfig) Callback for post initialization(一个空的方法,用于方法回调初始化) |
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);
- //<strong>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</strong>
- 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();
- }
- }
- 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);
- //<strong>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</strong>
- 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();
- }
- }
- 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;
- }
- 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);
- }
- 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());
- }
- 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);
- }
- 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
3、doFilter方法
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);
- }
- }
- 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);
- }
- /**
- * 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
- }
- }
- 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;
- static ThreadLocal actionContext = new ThreadLocal();
- Map<String, Object> context;
下面我们看下如何创建action上下文的,代码如下:
- /**
- *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;
- }
- /**
- *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;
- }
- 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;
- }
- //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);
- }
- }
- 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);
- }
- 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
- >
- <!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);
- }
- }
- 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。
StrutsPrepareAndExecuteFilter(转)