Struts2源码阅读
2016-05-20 21:11
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Struts2源码阅读(一)_Struts2框架流程概述
博客分类:Struts2
框架ServletHTML
1. Struts2架构图
请求首先通过Filter chain,Filter主要包括ActionContextCleanUp,它主要清理当前线程的ActionContext和Dispatcher;FilterDispatcher主要通过AcionMapper来决定需要调用哪个Action。
ActionMapper取得了ActionMapping后,在Dispatcher的serviceAction方法里创建ActionProxy,ActionProxy创建ActionInvocation,然后ActionInvocation调用Interceptors,执行Action本身,创建Result并返回,当然,如果要在返回之前做些什么,可以实现PreResultListener。
2. Struts2部分类介绍
这部分从Struts2参考文档中翻译就可以了。
ActionMapper
ActionMapper其实是HttpServletRequest和Action调用请求的一个映射,它屏蔽了Action对于Request等java Servlet类的依赖。Struts2中它的默认实现类是DefaultActionMapper,ActionMapper很大的用处可以根据自己的需要来设计url格式,它自己也有Restful的实现,具体可以参考文档的docs\actionmapper.html。
ActionProxy&ActionInvocation
Action的一个代理,由ActionProxyFactory创建,它本身不包括Action实例,默认实现DefaultActionProxy是由ActionInvocation持有Action实例。ActionProxy作用是如何取得Action,无论是本地还是远程。而ActionInvocation的作用是如何执行Action,拦截器的功能就是在ActionInvocation中实现的。
ConfigurationProvider&Configuration
ConfigurationProvider就是Struts2中配置文件的解析器,Struts2中的配置文件主要是尤其实现类XmlConfigurationProvider及其子类StrutsXmlConfigurationProvider来解析。
3. Struts2请求流程
1、客户端发送请求
2、请求先通过ActionContextCleanUp-->FilterDispatcher
3、FilterDispatcher通过ActionMapper来决定这个Request需要调用哪个Action
4、如果ActionMapper决定调用某个Action,FilterDispatcher把请求的处理交给ActionProxy,这儿已经转到它的Delegate--Dispatcher来执行
5、ActionProxy根据ActionMapping和ConfigurationManager找到需要调用的Action类
6、ActionProxy创建一个ActionInvocation的实例
7、ActionInvocation调用真正的Action,当然这涉及到相关拦截器的调用
8、Action执行完毕,ActionInvocation创建Result并返回,当然,如果要在返回之前做些什么,可以实现PreResultListener。添加PreResultListener可以在Interceptor中实现。
Struts2源码阅读(二)_ActionContext及CleanUP Filter
博客分类:Struts2
ServletWebworkJSP
1. ActionContext
ActionContext是被存放在当前线程中的,获取ActionContext也是从ThreadLocal中获取的。所以在执行拦截器、 action和result的过程中,由于他们都是在一个线程中按照顺序执行的,所以可以可以在任意时候在ThreadLocal中获取 ActionContext。
ActionContext包括了很多信息,比如Session、Application、Request、Locale、ValueStack等,其中 ValueStack可以解析ognl表达式,来动态后去一些值,同时可以给表达式提供对象。
ActionContext(com.opensymphony.xwork.ActionContext)是Action执行时的上下文,上下文可以看作是一个容器 (其实我们这里的容器就是一个Map而已),它存放的是Action在执行时需要用到的对象. 一般情况, 我们的ActionContext都是通过: ActionContext context = (ActionContext) actionContext.get(); 来获取的.我们再来看看这里的actionContext对象的创建:
static ThreadLocal actionContext = new ActionContextThreadLocal();
ActionContextThreadLocal是实现ThreadLocal的一个内部类.ThreadLocal可以命名为"线程局部变量",它为每一个使用该变量的线程都提供一个变量值的副本,使每一个线程都可以独立地改变自己的副本,而不会和其它线程的副本冲突.这样,我们 ActionContext里的属性只会在对应的当前请求线程中可见,从而保证它是线程安全的.
通过ActionContext取得HttpSession: Map session = ActionContext.getContext().getSession(); (通过Map模拟HttpServlet的对象,操作更方便)
2. ServletActionContext
ServletActionContext(com.opensymphony.webwork. ServletActionContext),这个类直接继承了我们上面介绍的ActionContext,它提供了直接与Servlet相关对象访问的功能,它可以取得的对象有:
(1)javax.servlet.http.HttpServletRequest : HTTPservlet请求对象
(2)javax.servlet.http.HttpServletResponse : HTTPservlet相应对象
(3)javax.servlet.ServletContext : Servlet上下文信息
(4)javax.servlet.ServletConfig : Servlet配置对象
(5)javax.servlet.jsp.PageContext : Http页面上下文
如何从ServletActionContext里取得Servlet的相关对象:
<1>取得HttpServletRequest对象: HttpServletRequest request = ServletActionContext. getRequest();
<2>取得HttpSession对象: HttpSession session = ServletActionContext. getRequest().getSession();
3. ServletActionContext和ActionContext联系
ServletActionContext和ActionContext有着一些重复的功能,在我们的Action中,该如何去抉择呢?我们遵循的原则是:如果ActionContext能够实现我们的功能,那最好就不要使用ServletActionContext,让我们的Action尽量不要直接去访问Servlet的相关对象.
注意:在使用ActionContext时有一点要注意: 不要在Action的构造函数里使用ActionContext.getContext(), 因为这个时候ActionContext里的一些值也许没有设置,这时通过ActionContext取得的值也许是null;同样,HttpServletRequest req = ServletActionContext.getRequest()也不要放在构造函数中,也不要直接将req作为类变量给其赋值。 至于原因,我想是因为前面讲到的static ThreadLocal
actionContext = new ActionContextThreadLocal(),从这里我们可以看出ActionContext是线程安全的,而 ServletActionContext继承自ActionContext,所以ServletActionContext也线程安全,线程安全要求每个线程都独立进行,所以req的创建也要求独立进行,所以ServletActionContext.getRequest()这句话不要放在构造函数中,也不要直接放在类中,而应该放在每个具体的方法体中(eg:login()、queryAll()、insert()等),这样才能保证每次产生对象时独立的建立了一个req。
4.ActionContextClearUp
ActionContextClearUp其实是Defer ClearUP.作用就是延长action中属性的生命周期,包括自定义属性,以便在jsp页面中进行访问,让actionContextcleanup过滤器来清除属性,不让action自己清除。具体看下面的代码,代码很简单:
Java代码
public void doFilter(...){
...
try{
...
//继续执行所配置的chain中的Filter
chain.doFilter(request, response);
}finally{
//保证在所有动作执行完之后,调用cleanUp
...
cleanUp(request);
}
}
protected static void cleanUp(ServletRequest req) {
...
ActionContext.setContext(null);//清除ActionContext实例
Dispatcher.setInstance(null);//清除Dispatcher实例(Dispatcher主要是完成将url解析成对应的Action)
}
另外注明一下UtilTimerStack的push和pop是用来计算调用方法所执行的开始和结束时间,用来做性能测试的。用法如下:
Java代码
String timerKey = "ActionContextCleanUp_doFilter: ";
UtilTimerStack.setActive(true);
UtilTimerStack.push(timerKey);
//调用要测试的方法。
UtilTimerStack.pop(timerKey);
Struts2源码阅读(三)_Dispatcher&ConfigurationProvider
博客分类:Struts2
StrutsXMLBeanApacheWebwork
首先强调一下struts2的线程程安全,在Struts2中大量采用ThreadLocal线程局部变量的方法来保证线程的安全,像Dispatcher等都是通过ThreadLocal来保存变量值,使得每个线程都有自己独立的实例变量,互不相干.
接下来就从Dispatcher开始看起,先看其构造函数:
Java代码
//创建Dispatcher,此类是一个Delegate,它是真正完成根据url解析转向,读取对应Action的地方
public Dispatcher(ServletContext servletContext, Map<String, String> initParams) {
this.servletContext = servletContext;
//配置在web.xml中的param参数
this.initParams = initParams;
}
我们再看在FilterDispatcher创建Dispatcher的:
Java代码
protected Dispatcher createDispatcher(FilterConfig filterConfig) {
Map<String, String> params = new HashMap<String, String>();
for (Enumeration e = filterConfig.getInitParameterNames(); e.hasMoreElements();) {
String name = (String) e.nextElement();
String value = filterConfig.getInitParameter(name);
params.put(name, value);
}
都可以从FilterConfig中得到
return new Dispatcher(filterConfig.getServletContext(), params);
}
创建Dispatcher之后,来看init()方法
init()方法是用来Load用户配置文件,资源文件以及默认的配置文件.
主要分七步走,看下面注释
Java代码
public void init() {
if (configurationManager == null) {
//设置ConfigurationManager的defaultFrameworkBeanName.
//这里DEFAULT_BEAN_NAME为struts,这是xwork框架的内容,Framework可以是xwork,struts,webwork等
configurationManager = new ConfigurationManager(BeanSelectionProvider.DEFAULT_BEAN_NAME);
}
//读取properties信息,默认的default.properties,
init_DefaultProperties(); // [1]
//读取xml配置文件
init_TraditionalXmlConfigurations(); // [2]
//读取用户自定义的struts.properties
init_LegacyStrutsProperties(); // [3]
//自定义的configProviders
init_CustomConfigurationProviders(); // [5]
//载入FilterDispatcher传进来的initParams
init_FilterInitParameters() ; // [6]
//将配置文件中的bean与具体的类映射
init_AliasStandardObjects() ; // [7]
//构建一个用于依赖注射的Container对象
//在这里面会循环调用上面七个ConfigurationProvider的register方法
//其中的重点就是DefaultConfiguration的#reload()方法
Container container = init_PreloadConfiguration();
container.inject(this);
init_CheckConfigurationReloading(container);
init_CheckWebLogicWorkaround(container);
if (!dispatcherListeners.isEmpty()) {
for (DispatcherListener l : dispatcherListeners) {
l.dispatcherInitialized(this);
}
}
}
分七步载入各种配置属性,都是通过ConfigurationProvider接口进行的,这个接口提供init(),destroy(),register()等方法.
将各种ConfigurationProvider初始化之后将实例添加到ConfigurationManager的List里面.
最后通过循环调用List里的这些destroy(),register()等方法实现对配置文件的属性进行注册和销毁等功能.
下面将分析这七层功夫是怎样一步步练成的.
首先是init_DefaultProperties()
Java代码
private void init_DefaultProperties() {
configurationManager.addConfigurationProvider(new DefaultPropertiesProvider());
}
接来看DefaultPropertiesProvider好了,DefaultPropertiesProvider实际上只是实现了register()方法
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);
}
Java代码
//PropertiesSettings构造方法
//读取org/apache/struts2/default.properties的配置信息,如果项目中需要覆盖,可以在classpath里的struts.properties里覆写
public PropertiesSettings(String name) {
URL settingsUrl = ClassLoaderUtils.getResource(name + ".properties", getClass());
if (settingsUrl == null) {
LOG.debug(name + ".properties missing");
settings = new LocatableProperties();
return;
}
settings = new LocatableProperties(new LocationImpl(null, settingsUrl.toString()));
// Load settings
InputStream in = null;
try {
in = settingsUrl.openStream();
settings.load(in);
} catch (IOException e) {
throw new StrutsException("Could not load " + name + ".properties:" + e, e);
} finally {
if(in != null) {
try {
in.close();
} catch(IOException io) {
LOG.warn("Unable to close input stream", io);
}
}
}
}
//loadSettings主要是将progerty的value和Locale从上面PropertiesSettings中取得并存放到LocatableProperties props
//这个props是register的一个入参.
protected void loadSettings(LocatableProperties props, final Settings settings) {
// We are calling the impl methods to get around the single instance of Settings that is expected
for (Iterator i = settings.listImpl(); i.hasNext(); ) {
String name = (String) i.next();
props.setProperty(name, settings.getImpl(name), settings.getLocationImpl(name));
}
}
再来看第二步:init_TraditionalXmlConfigurations()
Java代码
private void init_TraditionalXmlConfigurations() {
//首先读取web.xml中的config初始参数值
//如果没有配置就使用默认的DEFAULT_CONFIGURATION_PATHS:"struts-default.xml,struts-plugin.xml,struts.xml",
//这儿就可以看出为什么默认的配置文件必须取名为这三个名称了
//如果不想使用默认的名称,直接在web.xml中配置config初始参数即可
String configPaths = initParams.get("config");
if (configPaths == null) {
configPaths = DEFAULT_CONFIGURATION_PATHS;
}
String[] files = configPaths.split("\\s*[,]\\s*");
for (String file : files) {
if (file.endsWith(".xml")) {
if ("xwork.xml".equals(file)) {
//XmlConfigurationProvider负责解析xwork.xml
configurationManager.addConfigurationProvider(new XmlConfigurationProvider(file, false));
} else {
//其它xml都是由StrutsXmlConfigurationProvider来解析
configurationManager.addConfigurationProvider(new StrutsXmlConfigurationProvider(file, false, servletContext));
}
} else {
throw new IllegalArgumentException("Invalid configuration file name");
}
}
}
对于其它配置文件只用StrutsXmlConfigurationProvider,此类继承XmlConfigurationProvider,而XmlConfigurationProvider又实现ConfigurationProvider接口。
类XmlConfigurationProvider负责配置文件的读取和解析,
首先通过init()中的loadDocuments(configFileName);利用DomHelper中的
public static Document parse(InputSource inputSource, Map<String, String> dtdMappings) 将configFileName配置文件通过SAX解析方式按照DtdMappings解析成Document对象.
然后通过Provider的register()方法加载"bean"和"constant"属性,再通过loadPackages()加载package及package中的属性
addAction()方法负责读取<action>标签,并将数据保存在ActionConfig中;
addResultTypes()方法负责将<result-type>标签转化为ResultTypeConfig对象;
loadInterceptors()方法负责将<interceptor>标签转化为InterceptorConfi对象;
loadInterceptorStack()方法负责将<interceptor-ref>标签转化为InterceptorStackConfig对象;
loadInterceptorStacks()方法负责将<interceptor-stack>标签转化成InterceptorStackConfig对象。
而上面的方法最终会被addPackage()方法调用,addPackage又会被Provider的loadPackages()调用,将所读取到的数据汇集到PackageConfig对象中。
Java代码
protected PackageConfig addPackage(Element packageElement) throws ConfigurationException {
PackageConfig.Builder newPackage = buildPackageContext(packageElement);
if (newPackage.isNeedsRefresh()) {
return newPackage.build();
}
// add result types (and default result) to this package
addResultTypes(newPackage, packageElement);
// load the interceptors and interceptor stacks for this package
loadInterceptors(newPackage, packageElement);
// load the default interceptor reference for this package
loadDefaultInterceptorRef(newPackage, packageElement);
// load the default class ref for this package
loadDefaultClassRef(newPackage, packageElement);
// load the global result list for this package
loadGlobalResults(newPackage, packageElement);
// load the global exception handler list for this package
loadGobalExceptionMappings(newPackage, packageElement);
// get actions
NodeList actionList = packageElement.getElementsByTagName("action");
for (int i = 0; i < actionList.getLength(); i++) {
Element actionElement = (Element) actionList.item(i);
addAction(actionElement, newPackage);
}
// load the default action reference for this package
loadDefaultActionRef(newPackage, packageElement);
PackageConfig cfg = newPackage.build();
configuration.addPackageConfig(cfg.getName(), cfg);
return cfg;
}
loadConfigurationFiles解析读取xml中的内容
private List<Document> loadConfigurationFiles(String fileName, Element includeElement) {
...
//通过DomHelper调用SAX进行解析xml
doc = DomHelper.parse(in, dtdMappings);
...
Element rootElement = doc.getDocumentElement();
NodeList children = rootElement.getChildNodes();
int childSize = children.getLength();
for (int i = 0; i < childSize; i++) {
Node childNode = children.item(i);
if (childNode instanceof Element) {
Element child = (Element) childNode;
final String nodeName = child.getNodeName();
if ("include".equals(nodeName)) {
String includeFileName = child.getAttribute("file");
//解析每个action配置是,对于include文件可以使用通配符*来进行配置
//如Struts.xml中可配置成<include file="actions_*.xml"/>
if (includeFileName.indexOf('*') != -1) {
ClassPathFinder wildcardFinder = new ClassPathFinder();
wildcardFinder.setPattern(includeFileName);
Vector<String> wildcardMatches = wildcardFinder.findMatches();
for (String match : wildcardMatches) {
//递归Load子file中的<include/>
docs.addAll(loadConfigurationFiles(match, child));
}
} else {
docs.addAll(loadConfigurationFiles(includeFileName, child));
}
}
}
}
docs.add(doc);
loadedFileUrls.add(url.toString());
...
return docs;
}
Struts2源码阅读(四)_Dispatcher&ConfigurationProvider续
博客分类:Struts2
StrutsBeanApacheXMLWeb
接下来第三步:init_LegacyStrutsProperties()
调用的是调用的是LegacyPropertiesConfigurationProvider
通过比较前面DefaultPropertiesProvider与调用的是LegacyPropertiesConfigurationProvider.
发现DefaultPropertiesProvider继承自后者,但重写了register()方法,主要是生成PropertiesSetting的不同,前者是根据org/apache/struts2/default.properties
后者是根据struts.properties
我们展开register()中的Settings.getInstance(),最后是调用getDefaultInstance()
Java代码
private static Settings getDefaultInstance() {
if (defaultImpl == null) {
// Create bootstrap implementation
//不带参数的DefaultSettings(),区别与DefaultPropertiesProvider中直接带default.properties参数
//不带参数就是默认为struts.propertes,并且加载struts.custom.properties所定义的properties文件
defaultImpl = new DefaultSettings();
// Create default implementation
try {
//STRUTS_CONFIGURATION为:struts.configuration
//在struts.proterties中查找struts.configuration的值,这个值必须是org.apache.struts2.config.Configuration接口的实现类
//所以我有个困惑就是在下面的转换当中怎么将Configuration转换成Setting类型的...
//这一点先放下了,有时间再研究
String className = get(StrutsConstants.STRUTS_CONFIGURATION);
if (!className.equals(defaultImpl.getClass().getName())) {
try {
// singleton instances shouldn't be built accessing request or session-specific context data
defaultImpl = (Settings) ObjectFactory.getObjectFactory().buildBean(Thread.currentThread().getContextClassLoader().loadClass(className), null);
} catch (Exception e) {
LOG.error("Settings: Could not instantiate the struts.configuration object, substituting the default implementation.", e);
}
}
} catch (IllegalArgumentException ex) {
// ignore
在2.1.6中去掉了第四步:init_ZeroConfiguration();
第五步是自定义的configProviders
Java代码
private void init_CustomConfigurationProviders() {
//从这里可以看到可以将自定义的Provider定义在web.xml中FilterDispatcher的param中:configProviders
String configProvs = initParams.get("configProviders");
if (configProvs != null) {
String[] classes = configProvs.split("\\s*[,]\\s*");
for (String cname : classes) {
try {
Class cls = ClassLoaderUtils.loadClass(cname, this.getClass());
ConfigurationProvider prov = (ConfigurationProvider)cls.newInstance();
configurationManager.addConfigurationProvider(prov);
}
...
}
}
}
第六步:init_FilterInitParameters
Java代码
//从这里可以看出struts.properties中的属性不仅可以在struts.xml中以constant形式定义,而且可以在FilterDispatcher的param中定义
private void init_FilterInitParameters() {
configurationManager.addConfigurationProvider(new ConfigurationProvider() {
public void destroy() {}
public void init(Configuration configuration) throws ConfigurationException {}
public void loadPackages() throws ConfigurationException {}
public boolean needsReload() { return false; }
public void register(ContainerBuilder builder, LocatableProperties props) throws ConfigurationException {
props.putAll(initParams);//在这里实现滴~
}
});
}
第七步:init_AliasStandardObjects,使用BeanSelectionProvider
这是将配置文件中定义的<bean>与实际的类相映射,就是注入bean的依赖关系,这部分以后有时候再研究Container
接下来是看怎样调用这些ConfigurationProviders
展开init_PreloadConfiguration()
Java代码
private Container init_PreloadConfiguration() {
Configuration config = configurationManager.getConfiguration();
Container container = config.getContainer();
boolean reloadi18n = Boolean.valueOf(container.getInstance(String.class, StrutsConstants.STRUTS_I18N_RELOAD));
LocalizedTextUtil.setReloadBundles(reloadi18n);
return container;
}
//再看getConfiguration()
public synchronized Configuration getConfiguration() {
if (configuration == null) {
setConfiguration(new DefaultConfiguration(defaultFrameworkBeanName));
try {
//重点就是这个reloadContainer
configuration.reloadContainer(getContainerProviders());
} catch (ConfigurationException e) {
setConfiguration(null);
throw new ConfigurationException("Unable to load configuration.", e);
}
} else {
conditionalReload();
}
return configuration;
}
展开DefaultConfiguration中的reloadContainer
Java代码
public synchronized List<PackageProvider> reloadContainer(List<ContainerProvider> providers) throws ConfigurationException {
packageContexts.clear();
loadedFileNames.clear();
List<PackageProvider> packageProviders = new ArrayList<PackageProvider>();
//Struts2(xwork2)用Container来完成依赖注入的功能
//首先初始化一个ContainerBuilder,再由builder来保存接口与实现类或工厂类的对应关系
//然后通过builder.create(boolean)方法产生container
//由container.getInstance(Class);就可以得到接口的实现实例了
//这一部分比较复杂,后面研究完成了,会单独拿出来讲,这里先弄清楚Xwork依赖注入的实现步骤就可以了
ContainerProperties props = new ContainerProperties();
ContainerBuilder builder = new ContainerBuilder();
for (final ContainerProvider containerProvider : providers)
{
//循环调用ConfigurationProvider的init和register方法,明白了吧,在这里统一循环调用
containerProvider.init(this);
containerProvider.register(builder, props);
}
props.setConstants(builder);
//注入依赖关系,在这里并不产生实例
builder.factory(Configuration.class, new Factory<Configuration>() {
public Configuration create(Context context) throws Exception {
return DefaultConfiguration.this;
}
});
ActionContext oldContext = ActionContext.getContext();
try {
// Set the bootstrap container for the purposes of factory creation
Container bootstrap = createBootstrapContainer();
setContext(bootstrap);
//create已经注入依赖关系的Container
container = builder.create(false);
setContext(container);
objectFactory = container.getInstance(ObjectFactory.class);
// Process the configuration providers first
for (final ContainerProvider containerProvider : providers)
{
if (containerProvider instanceof PackageProvider) {
container.inject(containerProvider);
//调用PackageProvider的loadPackages()方法,这里主要是针对XmlConfigurationProvider和StrutsXmlConfigurationProvider
((PackageProvider)containerProvider).loadPackages();
packageProviders.add((PackageProvider)containerProvider);
}
}
// Then process any package providers from the plugins
Set<String> packageProviderNames = container.getInstanceNames(PackageProvider.class);
if (packageProviderNames != null) {
for (String name : packageProviderNames) {
PackageProvider provider = container.getInstance(PackageProvider.class, name);
provider.init(this);
provider.loadPackages();
packageProviders.add(provider);
}
}
rebuildRuntimeConfiguration();
} finally {
if (oldContext == null) {
ActionContext.setContext(null);
}
}
return packageProviders;
}
Struts2源码阅读(五)_FilterDispatcher核心控制器
博客分类:Struts2
StrutsApacheJSPBeanGo
Dispatcher已经在之前讲过,这就好办了。FilterDispatcher是Struts2的核心控制器,首先看一下init()方法。
Java代码
public void init(FilterConfig filterConfig) throws ServletException {
try {
this.filterConfig = filterConfig;
initLogging();
//创建dispatcher,前面都已经讲过啰
dispatcher = createDispatcher(filterConfig);
dispatcher.init();
//注入将FilterDispatcher中的变量通过container注入,如下面的staticResourceLoader
dispatcher.getContainer().inject(this);
//StaticContentLoader在BeanSelectionProvider中已经被注入了依赖关系:DefaultStaticContentLoader
//可以在struts-default.xml中的<bean>可以找到
staticResourceLoader.setHostConfig(new FilterHostConfig(filterConfig));
} finally {
ActionContext.setContext(null);
}
}
Java代码
//下面来看DefaultStaticContentLoader的setHostConfig
public void setHostConfig(HostConfig filterConfig) {
//读取初始参数pakages,调用parse(),解析成类似/org/apache/struts2/static,/template的数组
String param = filterConfig.getInitParameter("packages");
//"org.apache.struts2.static template org.apache.struts2.interceptor.debugging static"
String packages = getAdditionalPackages();
if (param != null) {
packages = param + " " + packages;
}
this.pathPrefixes = parse(packages);
initLogging(filterConfig);
}
现在回去doFilter的方法,每当有一个Request,都会调用这些Filters的doFilter方法
Java代码
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) res;
ServletContext servletContext = getServletContext();
String timerKey = "FilterDispatcher_doFilter: ";
try {
// FIXME: this should be refactored better to not duplicate work with the action invocation
//先看看ValueStackFactory所注入的实现类OgnlValueStackFactory
//new OgnlValueStack
ValueStack stack = dispatcher.getContainer().getInstance(ValueStackFactory.class).createValueStack();
ActionContext ctx = new ActionContext(stack.getContext());
ActionContext.setContext(ctx);
UtilTimerStack.push(timerKey);
//如果是multipart/form-data就用MultiPartRequestWrapper进行包装
//MultiPartRequestWrapper是StrutsRequestWrapper的子类,两者都是HttpServletRequest实现
//此时在MultiPartRequestWrapper中就会把Files给解析出来,用于文件上传
//所有request都会StrutsRequestWrapper进行包装,StrutsRequestWrapper是可以访问ValueStack
//下面是参见Dispatcher的wrapRequest
// String content_type = request.getContentType();
//if(content_type!= null&&content_type.indexOf("multipart/form-data")!=-1){
//MultiPartRequest multi =getContainer().getInstance(MultiPartRequest.class);
//request =new MultiPartRequestWrapper(multi,request,getSaveDir(servletContext));
//} else {
// request = new StrutsRequestWrapper(request);
// }
request = prepareDispatcherAndWrapRequest(request, response);
ActionMapping mapping;
try {
//根据url取得对应的Action的配置信息
//看一下注入的DefaultActionMapper的getMapping()方法.Action的配置信息存储在 ActionMapping对象中
mapping = actionMapper.getMapping(request, dispatcher.getConfigurationManager());
} catch (Exception ex) {
log.error("error getting ActionMapping", ex);
dispatcher.sendError(request, response, servletContext, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, ex);
return;
}
//如果找不到对应的action配置,则直接返回。比如你输入***.jsp等等
//这儿有个例外,就是如果path是以“/struts”开头,则到初始参数packages配置的包路径去查找对应的静态资源并输出到页面流中,当然.class文件除外。如果再没有则跳转到404
if (mapping == null) {
// there is no action in this request, should we look for a static resource?
String resourcePath = RequestUtils.getServletPath(request);
if ("".equals(resourcePath) && null != request.getPathInfo()) {
resourcePath = request.getPathInfo();
}
if (staticResourceLoader.canHandle(resourcePath)) {
// 在DefaultStaticContentLoader中:return serveStatic && (resourcePath.startsWith("/struts") || resourcePath.startsWith("/static"));
staticResourceLoader.findStaticResource(resourcePath, request, response);
} else {
// this is a normal request, let it pass through
chain.doFilter(request, response);
}
// The framework did its job here
return;
}
//正式开始Action的方法
dispatcher.serviceAction(request, response, servletContext, mapping);
} finally {
try {
ActionContextCleanUp.cleanUp(req);
} finally {
UtilTimerStack.pop(timerKey);
}
}
}
Java代码
//下面是ActionMapper接口的实现类 DefaultActionMapper的getMapping()方法的源代码:
public ActionMapping getMapping(HttpServletRequest request,
ConfigurationManager configManager) {
ActionMapping mapping = new ActionMapping();
String uri = getUri(request);//得到请求路径的URI,如:testAtcion.action或testAction.do
int indexOfSemicolon = uri.indexOf(";");//修正url的带;jsessionid 时找不到而且的bug
uri = (indexOfSemicolon > -1) ? uri.substring(0, indexOfSemicolon) : uri;
uri = dropExtension(uri, mapping);//删除扩展名,默认扩展名为action
if (uri == null) {
return null;
}
parseNameAndNamespace(uri, mapping, configManager);//匹配Action的name和namespace
handleSpecialParameters(request, mapping);//去掉重复参数
//如果Action的name没有解析出来,直接返回
if (mapping.getName() == null) {
returnnull;
}
//下面处理形如testAction!method格式的请求路径
if (allowDynamicMethodCalls) {
// handle "name!method" convention.
String name = mapping.getName();
int exclamation = name.lastIndexOf("!");//!是Action名称和方法名的分隔符
if (exclamation != -1) {
mapping.setName(name.substring(0, exclamation));//提取左边为name
mapping.setMethod(name.substring(exclamation + 1));//提取右边的method
}
}
return mapping;
}
从代码中看出,getMapping()方法返回ActionMapping类型的对象,该对象包含三个参数:Action的name、namespace和要调用的方法method。
如果getMapping()方法返回ActionMapping对象为null,则FilterDispatcher认为用户请求不是Action,自然另当别论,FilterDispatcher会做一件非常有意思的事:如果请求以/struts开头,会自动查找在web.xml文件中配置的 packages初始化参数,就像下面这样(注意粗斜体部分):
Xml代码
<filter>
<filter-name>struts2</filter-name>
<filter-class>
org.apache.struts2.dispatcher.FilterDispatcher
</filter-class>
<init-param>
<param-name>packages</param-name>
<param-value>com.lizanhong.action</param-value>
</init-param>
lt;/filter>
FilterDispatcher会将com.lizanhong.action包下的文件当作静态资源处理,即直接在页面上显示文件内容,不过会忽略扩展名为class的文件。比如在com.lizanhong.action包下有一个aaa.txt的文本文件,其内容为“中华人民共和国”,访问 http://localhost:8081/Struts2Demo/struts/aaa.txt时会输出txt中的内容
FilterDispatcher.findStaticResource()方法
Java代码
protectedvoid findStaticResource(String name, HttpServletRequest request, HttpServletResponse response) throws IOException {
if (!name.endsWith(".class")) {//忽略class文件
//遍历packages参数
for (String pathPrefix : pathPrefixes) {
InputStream is = findInputStream(name, pathPrefix);//读取请求文件流
if (is != null) {
...
// set the content-type header
String contentType = getContentType(name);//读取内容类型
if (contentType != null) {
response.setContentType(contentType);//重新设置内容类型
}
...
try {
//将读取到的文件流以每次复制4096个字节的方式循环输出
copy(is, response.getOutputStream());
} finally {
is.close();
}
return;
}
}
}
}
如果用户请求的资源不是以/struts开头——可能是.jsp文件,也可能是.html文件,则通过过滤器链继续往下传送,直到到达请求的资源为止。
如果getMapping()方法返回有效的ActionMapping对象,则被认为正在请求某个Action,将调用 Dispatcher.serviceAction(request, response, servletContext, mapping)方法,该方法是处理Action的关键所在。
下面就来看serviceAction,这又回到全局变量dispatcher中了
Java代码
//Load Action class for mapping and invoke the appropriate Action method, or go directly to the Result.
public void serviceAction(HttpServletRequest request, HttpServletResponse response, ServletContext context,
ActionMapping mapping) throws ServletException {
//createContextMap方法主要把Application、Session、Request的key value值拷贝到Map中
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);
String namespace = mapping.getNamespace();
String name = mapping.getName();
String method = mapping.getMethod();
Configuration config = configurationManager.getConfiguration();
//创建一个Action的代理对象,ActionProxyFactory是创建ActionProxy的工厂
//参考实现类:DefaultActionProxy和DefaultActionProxyFactory
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!
//如果是Result,则直接转向,关于Result,ActionProxy,ActionInvocation下一讲中再分析
if (mapping.getResult() != null) {
Result result = mapping.getResult();
result.execute(proxy.getInvocation());
} else {
//执行Action
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) {
LOG.error("Could not find action or result", 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);
}
}
Struts2源码阅读(六)_ActionProxy&ActionInvocation
博客分类:Struts2
SpringStrutsBeanAccess
下面开始讲一下主菜ActionProxy了.在这之前最好先去了解一下动态Proxy的基本知识.
ActionProxy是Action的一个代理类,也就是说Action的调用是通过ActionProxy实现的,其实就是调用了ActionProxy.execute()方法,而该方法又调用了ActionInvocation.invoke()方法。归根到底,最后调用的是DefaultActionInvocation.invokeAction()方法。
DefaultActionInvocation()->init()->createAction()。
最后通过调用ActionProxy.exute()-->ActionInvocation.invoke()-->Intercepter.intercept()-->ActionInvocation.invokeActionOnly()-->invokeAction()
这里的步骤是先由ActionProxyFactory创建ActionInvocation和ActionProxy.
Java代码
public ActionProxy createActionProxy(String namespace, String actionName, String methodName, Map<String, Object> extraContext, boolean executeResult, boolean cleanupContext) {
ActionInvocation inv = new DefaultActionInvocation(extraContext, true);
container.inject(inv);
return createActionProxy(inv, namespace, actionName, methodName, executeResult, cleanupContext);
}
下面先看DefaultActionInvocation的init方法
Java代码
public void init(ActionProxy proxy) {
this.proxy = proxy;
Map<String, Object> contextMap = createContextMap();
// Setting this so that other classes, like object factories, can use the ActionProxy and other
// contextual information to operate
ActionContext actionContext = ActionContext.getContext();
if (actionContext != null) {
actionContext.setActionInvocation(this);
}
//创建Action,struts2中每一个Request都会创建一个新的Action
createAction(contextMap);
if (pushAction) {
stack.push(action);
contextMap.put("action", action);
}
invocationContext = new ActionContext(contextMap);
invocationContext.setName(proxy.getActionName());
// get a new List so we don't get problems with the iterator if someone changes the list
List<InterceptorMapping> interceptorList = new ArrayList<InterceptorMapping>(proxy.getConfig().getInterceptors());
interceptors = interceptorList.iterator();
}
protected void createAction(Map<String, Object> contextMap) {
// load action
String timerKey = "actionCreate: " + proxy.getActionName();
try {
UtilTimerStack.push(timerKey);
//默认为SpringObjectFactory:struts.objectFactory=spring.这里非常巧妙,在struts.properties中可以重写这个属性
//在前面BeanSelectionProvider中通过配置文件为ObjectFactory设置实现类
//这里以Spring为例,这里会调到SpringObjectFactory的buildBean方法,可以通过ApplicationContext的getBean()方法得到Spring的Bean
action = objectFactory.buildAction(proxy.getActionName(), proxy.getNamespace(), proxy.getConfig(), contextMap);
} catch (InstantiationException e) {
throw new XWorkException("Unable to intantiate Action!", e, proxy.getConfig());
} catch (IllegalAccessException e) {
throw new XWorkException("Illegal access to constructor, is it public?", e, proxy.getConfig());
} catch (Exception e) {
...
} finally {
UtilTimerStack.pop(timerKey);
}
if (actionEventListener != null) {
action = actionEventListener.prepare(action, stack);
}
}
//SpringObjectFactory
public Object buildBean(String beanName, Map<String, Object> extraContext, boolean injectInternal) throws Exception {
Object o = null;
try {
//SpringObjectFactory会通过web.xml中的context-param:contextConfigLocation自动注入ClassPathXmlApplicationContext
o = appContext.getBean(beanName);
} catch (NoSuchBeanDefinitionException e) {
Class beanClazz = getClassInstance(beanName);
o = buildBean(beanClazz, extraContext);
}
if (injectInternal) {
injectInternalBeans(o);
}
return o;
}
Java代码
//接下来看看DefaultActionInvocation 的invoke方法
public String invoke() throws Exception {
String profileKey = "invoke: ";
try {
UtilTimerStack.push(profileKey);
if (executed) {
throw new IllegalStateException("Action has already executed");
}
//递归执行interceptor
if (interceptors.hasNext()) {
//interceptors是InterceptorMapping实际上是像一个像FilterChain一样的Interceptor链
//通过调用Invocation.invoke()实现递归牡循环
final InterceptorMapping interceptor = (InterceptorMapping) interceptors.next();
String interceptorMsg = "interceptor: " + interceptor.getName();
UtilTimerStack.push(interceptorMsg);
try {
//在每个Interceptor的方法中都会return invocation.invoke()
resultCode = interceptor.getInterceptor().intercept(DefaultActionInvocation.this);
}
finally {
UtilTimerStack.pop(interceptorMsg);
}
} else {
//当所有interceptor都执行完,最后执行Action,invokeActionOnly会调用invokeAction()方法
resultCode = invokeActionOnly();
}
// this is needed because the result will be executed, then control will return to the Interceptor, which will
// return above and flow through again
//在Result返回之前调用preResultListeners
//通过executed控制,只执行一次
if (!executed) {
if (preResultListeners != null) {
for (Object preResultListener : preResultListeners) {
PreResultListener listener = (PreResultListener) preResultListener;
String _profileKey = "preResultListener: ";
try {
UtilTimerStack.push(_profileKey);
listener.beforeResult(this, resultCode);
}
finally {
UtilTimerStack.pop(_profileKey);
}
}
}
// now execute the result, if we're supposed to
//执行Result
if (proxy.getExecuteResult()) {
executeResult();
}
executed = true;
}
return resultCode;
}
finally {
UtilTimerStack.pop(profileKey);
}
}
//invokeAction
protected String invokeAction(Object action,ActionConfig actionConfig)throws Exception{
String methodName = proxy.getMethod();
String timerKey = "invokeAction: " + proxy.getActionName();
try {
UtilTimerStack.push(timerKey);
boolean methodCalled = false;
Object methodResult = null;
Method method = null;
try {
//java反射机制得到要执行的方法
method = getAction().getClass().getMethod(methodName, new Class[0]);
} catch (NoSuchMethodException e) {
// hmm -- OK, try doXxx instead
//如果没有对应的方法,则使用do+Xxxx来再次获得方法
try {
String altMethodName = "do" + methodName.substring(0, 1).toUpperCase() + methodName.substring(1);
method = getAction().getClass().getMethod(altMethodName, new Class[0]);
} catch (NoSuchMethodException e1) {
// well, give the unknown handler a shot
if (unknownHandlerManager.hasUnknownHandlers()) {
try {
methodResult = unknownHandlerManager.handleUnknownMethod(action, methodName);
methodCalled = true;
} catch (NoSuchMethodException e2) {
// throw the original one
throw e;
}
} else {
throw e;
}
}
}
//执行Method
if (!methodCalled) {
methodResult = method.invoke(action, new Object[0]);
}
//从这里可以看出可以Action的方法可以返回String去匹配Result,也可以直接返回Result类
if (methodResult instanceof Result) {
this.explicitResult = (Result) methodResult;
// Wire the result automatically
container.inject(explicitResult);
return null;
} else {
return (String) methodResult;
}
} catch (NoSuchMethodException e) {
throw new IllegalArgumentException("The " + methodName + "() is not defined in action " + getAction().getClass() + "");
} catch (InvocationTargetException e) {
// We try to return the source exception.
Throwable t = e.getTargetException();
if (actionEventListener != null) {
String result = actionEventListener.handleException(t, getStack());
if (result != null) {
return result;
}
}
if (t instanceof Exception) {
throw (Exception) t;
} else {
throw e;
}
} finally {
UtilTimerStack.pop(timerKey);
}
}
action执行完了,还要根据ResultConfig返回到view,也就是在invoke方法中调用executeResult方法。
Java代码
private void executeResult() throws Exception {
//根据ResultConfig创建Result
result = createResult();
String timerKey = "executeResult: " + getResultCode();
try {
UtilTimerStack.push(timerKey);
if (result != null) {
//开始执行Result,
//可以参考Result的实现,如用了比较多的ServletDispatcherResult,ServletActionRedirectResult,ServletRedirectResult
result.execute(this);
} else if (resultCode != null && !Action.NONE.equals(resultCode)) {
throw new ConfigurationException("No result defined for action " + getAction().getClass().getName()
+ " and result " + getResultCode(), proxy.getConfig());
} else {
if (LOG.isDebugEnabled()) {
LOG.debug("No result returned for action " + getAction().getClass().getName() + " at " + proxy.getConfig().getLocation());
}
}
} finally {
UtilTimerStack.pop(timerKey);
}
}
public Result createResult() throws Exception {
//如果Action中直接返回的Result类型,在invokeAction()保存在explicitResult
if (explicitResult != null) {
Result ret = explicitResult;
explicitResult = null;
return ret;
}
//返回的是String则从config中得到当前Action的Results列表
ActionConfig config = proxy.getConfig();
Map<String, ResultConfig> results = config.getResults();
ResultConfig resultConfig = null;
synchronized (config) {
try {
//通过返回的String来匹配resultConfig
resultConfig = results.get(resultCode);
} catch (NullPointerException e) {
// swallow
}
if (resultConfig == null) {
// If no result is found for the given resultCode, try to get a wildcard '*' match.
//如果找不到对应name的ResultConfig,则使用name为*的Result
//说明可以用*通配所有的Result
resultConfig = results.get("*");
}
}
if (resultConfig != null) {
try {
//创建Result
return objectFactory.buildResult(resultConfig, invocationContext.getContextMap());
} catch (Exception e) {
LOG.error("There was an exception while instantiating the result of type " + resultConfig.getClassName(), e);
throw new XWorkException(e, resultConfig);
}
} else if (resultCode != null && !Action.NONE.equals(resultCode) && unknownHandlerManager.hasUnknownHandlers()) {
return unknownHandlerManager.handleUnknownResult(invocationContext, proxy.getActionName(), proxy.getConfig(), resultCode);
}
return null;
}
public Result buildResult(ResultConfig resultConfig, Map<String, Object> extraContext) throws Exception {
String resultClassName = resultConfig.getClassName();
Result result = null;
if (resultClassName != null) {
//buildBean中会用反射机制Class.newInstance来创建bean
result = (Result) buildBean(resultClassName, extraContext);
Map<String, String> params = resultConfig.getParams();
if (params != null) {
for (Map.Entry<String, String> paramEntry : params.entrySet()) {
try {
//reflectionProvider参见OgnlReflectionProvider;
//resultConfig.getParams()就是result配置文件里所配置的参数<param></param>
//setProperties方法最终调用的是Ognl类的setValue方法
//这句其实就是把param名值设置到根对象result上
reflectionProvider.setProperty(paramEntry.getKey(), paramEntry.getValue(), result, extraContext, true);
} catch (ReflectionException ex) {
if (LOG.isErrorEnabled())
LOG.error("Unable to set parameter [#0] in result of type [#1]", ex,
paramEntry.getKey(), resultConfig.getClassName());
if (result instanceof ReflectionExceptionHandler) {
((ReflectionExceptionHandler) result).handle(ex);
}
}
}
}
}
return result;
}
最后看一张在网上看到的一个调用流程图作为参考:
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