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。 


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， 


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，不知道其它还有什么方式？ 


Struts2(2.1.2)部分源码阅读 
    从org.apache.struts2.dispatcher.FilterDispatcher开始 
    //创建Dispatcher，此类是一个Delegate，它是真正完成根据url解析，读取对应Action的地方 
  

public void init(FilterConfig filterConfig) throws ServletException {
       try {
           this.filterConfig = filterConfig;

           initLogging();

           dispatcher = createDispatcher(filterConfig);
           dispatcher.init();
           dispatcher.getContainer().inject(this);
           //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");
           String packages = "org.apache.struts2.static template org.apache.struts2.interceptor.debugging";
           if (param != null) {
               packages = param + " " + packages;
           }
           this.pathPrefixes = parse(packages);
       } finally {
           ActionContext.setContext(null);
       }
   }
    顺着流程我们看Disptcher的init方法。init方法里就是初始读取一些配置文件等，先看init_DefaultProperties，主要是读取properties配置文件。
   private void init_DefaultProperties() {
       configurationManager.addConfigurationProvider(new DefaultPropertiesProvider());
   }
   打开DefaultPropertiesProvider
   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);
   }

   //PropertiesSettings
   //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);
               }
           }
       }
   }

    再来看init_TraditionalXmlConfigurations方法，这个是读取struts-default.xml和Struts.xml的方法。 
    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"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*");
       //依次解析配置文件，xwork.xml单独解析
       for (String file : files) {
           if (file.endsWith(".xml")) {
               if ("xwork.xml".equals(file)) {
                   configurationManager.addConfigurationProvider(new XmlConfigurationProvider(file, false));
               } else {
                   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，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，将所读取到的数据汇集到PackageConfig对象中。来看XmlConfigurationProvider的源代码，详细的我自己也就大体浏览了一下，各位可以自己研读。 
  

protected PackageConfig addPackage(Element packageElement) throws ConfigurationException {
       PackageConfig.Builder newPackage = buildPackageContext(packageElement);

       if (newPackage.isNeedsRefresh()) {
           return newPackage.build();
       }
       .

       addResultTypes(newPackage, packageElement);
       loadInterceptors(newPackage, packageElement);
       loadDefaultInterceptorRef(newPackage, packageElement);
       loadDefaultClassRef(newPackage, packageElement);
       loadGlobalResults(newPackage, packageElement);
       loadGobalExceptionMappings(newPackage, packageElement);
       NodeList actionList = packageElement.getElementsByTagName("action");

       for (int i = 0; i  docs = new ArrayList<document>();
       if (!includedFileNames.contains(fileName)) {

               Element rootElement = doc.getDocumentElement();
               NodeList children = rootElement.getChildNodes();
               int childSize = children.getLength();

               for (int i = 0; i
                       if (nodeName.equals("include")) {
                           String includeFileName = child.getAttribute("file");
                           if(includeFileName.indexOf('*') != -1 ) {
                               ClassPathFinder wildcardFinder = new ClassPathFinder();
                               wildcardFinder.setPattern(includeFileName);
                               Vector<string> wildcardMatches = wildcardFinder.findMatches();
                               for (String match : wildcardMatches) {
                                   docs.addAll(loadConfigurationFiles(match, child));
                               }
                           }
                           else {

                               docs.addAll(loadConfigurationFiles(includeFileName, child));
                           }
                   }
               }
               }
               docs.add(doc);
               loadedFileUrls.add(url.toString());
           }
       }
       return docs;
   }
   init_CustomConfigurationProviders方式初始自定义的Provider，配置类全名和实现ConfigurationProvider接口，用逗号隔开即可。
   private void init_CustomConfigurationProviders() {
       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);
               }

           }
       }
   }
   好了，现在再回到FilterDispatcher，每次发送一个Request，FilterDispatcher都会调用doFilter方法。
   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 {
           ValueStack stack = dispatcher.getContainer().getInstance(ValueStackFactory.class).createValueStack();
           ActionContext ctx = new ActionContext(stack.getContext());
           ActionContext.setContext(ctx);

           UtilTimerStack.push(timerKey);
           //根据content type来使用不同的Request封装，可以参见Dispatcher的wrapRequest
           request = prepareDispatcherAndWrapRequest(request, response);
           ActionMapping mapping;
           try {
               //根据url取得对应的Action的配置信息--ActionMapping，actionMapper是通过Container的inject注入的
               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 (serveStatic && resourcePath.startsWith("/struts")) {
                   String name = resourcePath.substring("/struts".length());
                   findStaticResource(name, request, response);
               } else {
                   chain.doFilter(request, response);
               }
               return;
           }
           //正式开始Action的方法了
           dispatcher.serviceAction(request, response, servletContext, mapping);

       } finally {
           try {
               ActionContextCleanUp.cleanUp(req);
           } finally {
               UtilTimerStack.pop(timerKey);
           }
       }
   }
   Dispatcher类的serviceAction方法：
   public void serviceAction(HttpServletRequest request, HttpServletResponse response, ServletContext context,ActionMapping mapping) throws ServletException {

       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);
       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();
           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!
           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 (stack != null) {
               request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, stack);
           }
       } catch (ConfigurationException e) {
           LOG.error("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);
       }
   }
   第一句createContextMap()方法，该方法主要把Application、Session、Request的key value值拷贝到Map中，并放在HashMap<string>中，可以参见createContextMap方法：
   public Map<string> 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);
       Map<string> extraContext = createContextMap(requestMap, params, session, application, request, response, context);
       extraContext.put(ServletActionContext.ACTION_MAPPING, mapping);
       return extraContext;
   }
   后面才是最主要的--ActionProxy，ActionInvocation。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。先看DefaultActionInvocation的init方法。
   public void init(ActionProxy proxy) {
       this.proxy = proxy;
       Map 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，可Struts2里是每次请求都新建一个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 interceptorList = new ArrayList(proxy.getConfig().getInterceptors());
       interceptors = interceptorList.iterator();
   }

   protected void createAction(Map contextMap) {
       // load action
       String timerKey = "actionCreate: "+proxy.getActionName();
       try {
           UtilTimerStack.push(timerKey);
           //这儿默认建立Action是StrutsObjectFactory，实际中我使用的时候都是使用Spring创建的Action，这个时候使用的是SpringObjectFactory
           action = objectFactory.buildAction(proxy.getActionName(), proxy.getNamespace(), proxy.getConfig(), contextMap);
       }
       ..
       } finally {
           UtilTimerStack.pop(timerKey);
       }

       if (actionEventListener != null) {
           action = actionEventListener.prepare(action, stack);
       }
   }

   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");
           }
               //先执行interceptors
           if (interceptors.hasNext()) {
               final InterceptorMapping interceptor = (InterceptorMapping) interceptors.next();
               UtilTimerStack.profile("interceptor: "+interceptor.getName(),
                       new UtilTimerStack.ProfilingBlock<string>() {
                           public String doProfiling() throws Exception {
                               resultCode = interceptor.getInterceptor().intercept(DefaultActionInvocation.this);
                               return null;
                           }
               });
           } else {
                       //interceptor执行完了之后执行action
               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
           if (!executed) {
                       //在Result返回之前调用preResultListeners
               if (preResultListeners != null) {
                   for (Iterator iterator = preResultListeners.iterator();
                       iterator.hasNext();) {
                       PreResultListener listener = (PreResultListener) iterator.next();

                       String _profileKey="preResultListener: ";
                       try {
                           UtilTimerStack.push(_profileKey);
                           listener.beforeResult(this, resultCode);
                       }
                       finally {
                           UtilTimerStack.pop(_profileKey);
                       }
                   }
               }

               // now execute the result, if we're supposed to
               if (proxy.getExecuteResult()) {
                   executeResult();
               }

               executed = true;
           }

           return resultCode;
       }
       finally {
           UtilTimerStack.pop(profileKey);
       }
   }

    看程序中的if(interceptors.hasNext())语句，当然，interceptors里存储的是interceptorMapping列表（它包括一个Interceptor和一个name），所有的截拦器必须实现Interceptor的intercept方法，而该方法的参数恰恰又是ActionInvocation，在intercept方法中还是调用invocation.invoke()，从而实现了一个Interceptor链的调用。当所有的Interceptor执行完，最后调用invokeActionOnly方法来执行Action相应的方法。 
  

 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 {
                //获得需要执行的方法
                method = getAction().getClass().getMethod(methodName, new Class[0]);
            } catch (NoSuchMethodException e) {
                //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 (unknownHandler != null) {
                        try {
                            methodResult = unknownHandler.handleUnknownActionMethod(action, methodName);
                            methodCalled = true;
                        } catch (NoSuchMethodException e2) {
                            // throw the original one
                            throw e;
                        }
                    } else {
                        throw e;
                    }
                }
            }

            if (!methodCalled) {
                methodResult = method.invoke(action, new Object[0]);
            }
            //根据不同的Result类型返回不同值
            //如输出流Result
            if (methodResult instanceof Result) {
                this.explicitResult = (Result) methodResult;
                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);
        }
    }
    好了，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。
    private void executeResult() throws Exception {
        //根据ResultConfig创建Result
        result = createResult();
        String timerKey = "executeResult: "+getResultCode();
        try {
            UtilTimerStack.push(timerKey);
            if (result != null) {
                //这儿正式执行:)
                //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 {
        if (explicitResult != null) {
            Result ret = explicitResult;
            explicitResult = null;;
            return ret;
        }
        ActionConfig config = proxy.getConfig();
        Map results = config.getResults();
        ResultConfig resultConfig = null;
        synchronized (config) {
            try {
                //根据result名称获得ResultConfig，resultCode就是result的name
                resultConfig = (ResultConfig) results.get(resultCode);
            } catch (NullPointerException e) {
            }
            if (resultConfig == null) {
                //如果找不到对应name的ResultConfig，则使用name为*的Result
                resultConfig = (ResultConfig) results.get("*");
            }
        }
        if (resultConfig != null) {
            try {
                //参照StrutsObjectFactory的代码
                Result result = objectFactory.buildResult(resultConfig, invocationContext.getContextMap());
                return result;
            } 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) && unknownHandler != null) {
            return unknownHandler.handleUnknownResult(invocationContext, proxy.getActionName(), proxy.getConfig(), resultCode);
        }
        return null;
    }
    //StrutsObjectFactory
    public Result buildResult(ResultConfig resultConfig, Map extraContext) throws Exception {
        String resultClassName = resultConfig.getClassName();
        if (resultClassName == null)
            return null;
        //创建Result，因为Result是有状态的，所以每次请求都新建一个
        Object result = buildBean(resultClassName, extraContext);
        //这句很重要，后面将会谈到，reflectionProvider参见OgnlReflectionProvider；
        //resultConfig.getParams()就是result配置文件里所配置的参数<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.setProperties(resultConfig.getParams(), result, extraContext);
        if (result instanceof Result)
            return (Result) result;
        throw new ConfigurationException(result.getClass().getName() + " does not implement Result.");
    }
    最后补充一下，Struts2的查找值和设置值都是使用Ognl来实现的。关于Ognl的介绍可以到其官方网站查看http://www.ognl.org/，我在网上也找到另外一篇http://www.javaeye.com/topic/254684和http://www.javaeye.com/topic/223612。完了来看下面这段小测试程序（其它的Ognl的测试可以自己添加）。
public class TestOgnl {

    private User user;
    private Map context;

    @Before
    public void setUp() throws Exception {

    }

    @Test
    public void ognlGetValue() throws Exception {
    reset();
    Assert.assertEquals("myyate", Ognl.getValue("name", user));
    Assert.assertEquals("cares", Ognl.getValue("dept.name", user));
    Assert.assertEquals("myyate", Ognl.getValue("name", context, user));
    Assert.assertEquals("contextmap", Ognl.getValue("#name", context, user));
    Assert.assertEquals("parker", Ognl.getValue("#pen", context, user));
    }

    @Test
    public void ognlSetValue() throws Exception {
    reset();
    Ognl.setValue("name", user, "myyateC");
    Assert.assertEquals("myyateC", Ognl.getValue("name", user));

    Ognl.setValue("dept.name", user, "caresC");
    Assert.assertEquals("caresC", Ognl.getValue("dept.name", user));

    Assert.assertEquals("contextmap", Ognl.getValue("#name", context, user));
    Ognl.setValue("#name", context, user, "contextmapC");
    Assert.assertEquals("contextmapC", Ognl.getValue("#name", context, user));

    Assert.assertEquals("parker", Ognl.getValue("#pen", context, user));
    Ognl.setValue("#name", context, user, "parkerC");
    Assert.assertEquals("parkerC", Ognl.getValue("#name", context, user));
    }

    public static void main(String[] args) throws Exception {
    JUnitCore.runClasses(TestOgnl.class);
    }

    private void reset() {
    user = new User("myyate", new Dept("cares"));
    context = new OgnlContext();
    context.put("pen", "parker");
    context.put("name", "contextmap");
    }
}

class User {
    public User(String name, Dept dept) {
    this.name = name;
    this.dept = dept;
    }
    String name;
    private Dept dept;
    public Dept getDept() {
        return dept;
    }
    public String getName() {
        return name;
    }
    public void setDept(Dept dept) {
        this.dept = dept;
    }
    public void setName(String name) {
        this.name = name;
    }
}

class Dept {
    public Dept(String name) {
    this.name = name;
    }
    private String name;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}