Struts2源码浅析-请求处理(转)

本文转自/article/1599555.html

StrutsPrepareAndExecuteFilter doFilter方法为请求的入口

doFilter方法主要做以下几件事

一： 根据配置的常量 设置当前request 字符编码 response国际化Locale信息

二： 创建ActionContext数据对象

三： 请求处理

1.分析url 根据url 创建ActionMapping对象 这些操作主要由ActionMapper接口实现类完成

2. 执行请求逻辑动作

①.根据请求映射对象ActionMapping 创建ActionProxy 主要由ActionProxyFactory接口完成

②.执行Action 逻辑(拦截器,Action对应方法)

四：清理ActionContext数据对象

流程分析

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public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {

HttpServletRequest request = (HttpServletRequest) req;

HttpServletResponse response = (HttpServletResponse) res;

try {

//根据struts2常量配置 设置当前request Encoding 即request.setCharacterEncoding(encoding)

//当前 response 设置国际化Locale信息 即response.setLocale(locale);

prepare.setEncodingAndLocale(request, response);

//创建ActionContext数据对象 包括ValueStack

prepare.createActionContext(request, response);

//将当前的Dispatcher保存到ThreadLocal中

prepare.assignDispatcherToThread();

if ( excludedPatterns != null && prepare.isUrlExcluded(request, excludedPatterns)) {

chain.doFilter(request, response);

} else {

//包装request 返回StrutsRequestWrapper

//StrutsRequestWrapper继承了HttpServletRequestWrapper

request = prepare.wrapRequest(request);

//创建ActionMapping

ActionMapping mapping = prepare.findActionMapping(request, response, true);

if (mapping == null) {

boolean handled = execute.executeStaticResourceRequest(request, response);

if (!handled) {

chain.doFilter(request, response);

}

} else {

//真正执行Action的地方

execute.executeAction(request, response, mapping);

}

}

} finally {

//清除ActionContext

prepare.cleanupRequest(request);

}

}

一：设置编码字符 国际化Locale信息，PrepareOperations#setEncodingAndLocale方法 调用了 Dispatcher#prepare方法 真正做事的还是Dispatcher

PrepareOperations类的setEncodingAndLocale 方法

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public void setEncodingAndLocale(HttpServletRequest request, HttpServletResponse response) {

dispatcher.prepare(request, response);

}

Dispatcher的prepare方法

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public void prepare(HttpServletRequest request, HttpServletResponse response) {

//struts.i18n.encoding 常量

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);

}

}

二：创建ActionContext数据对象 由PrepareOperations#createActionContext方法完成

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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;

}

//ActionContext与 ValueStack 是主从关系

//ActionContext中持有ValueStack

ActionContext oldContext = ActionContext.getContext();

if (oldContext != null) {

ctx = new ActionContext(new HashMap<String, Object>(oldContext.getContextMap()));

} else {

//ValueStack是由ValueStackFactory 创建

ValueStack stack = dispatcher.getContainer().getInstance(ValueStackFactory.class).createValueStack();

stack.getContext().putAll(dispatcher.createContextMap(request, response, null, servletContext));

//将创建的ValueStack 保存到ActionContext

ctx = new ActionContext(stack.getContext());

}

request.setAttribute(CLEANUP_RECURSION_COUNTER, counter);

//将当前ActionContext 保存到ThreadLocal中

ActionContext.setContext(ctx);

return ctx;

}

三： 请求处理

1.创建ActionMapping对象 一个ActionMapping对象 对应一次请求,

ActionMapping定义

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public class ActionMapping {

private String name;

private String namespace;

private String method;

private String extension;

private Map<String, Object> params;

private Result result;

}

PrepareOperations findActionMapping方法 创建ActionMaping对象的动作转交给ActionMapper接口的getMapping方法完成

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public ActionMapping findActionMapping(HttpServletRequest request, HttpServletResponse response, boolean forceLookup) {

ActionMapping mapping = (ActionMapping) request.getAttribute(STRUTS_ACTION_MAPPING_KEY);

if (mapping == null || forceLookup) {

try {

//ActionMapper 默认实现DefaultActionMapper

//getMapping方法主要负责 查找对应的ActionConfig对象 根据ActionConfig对象创建 ActionMapping

mapping = dispatcher.getContainer().getInstance(ActionMapper.class).getMapping(request, dispatcher.getConfigurationManager());

if (mapping != null) {

request.setAttribute(STRUTS_ACTION_MAPPING_KEY, mapping);

}

} catch (Exception ex) {

//错误信息

dispatcher.sendError(request, response, servletContext, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, ex);

}

}

return mapping;

}

ActionMapper 的实现类 DefaultActionMapper , getMapping方法 分析url ,根据url查找到的ActionConfig对象 创建ActionMapping

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public ActionMapping getMapping(HttpServletRequest request,

ConfigurationManager configManager) {

//实例化ActionMapping

ActionMapping mapping = new ActionMapping();

String uri = getUri(request);

int indexOfSemicolon = uri.indexOf(";");

uri = (indexOfSemicolon > -1) ? uri.substring(0, indexOfSemicolon) : uri;

uri = dropExtension(uri, mapping);

if (uri == null) {

return null;

}

// name, namspace处理

parseNameAndNamespace(uri, mapping, configManager);

handleSpecialParameters(request, mapping);

if (mapping.getName() == null) {

return null;

}

//处理action!menthod 形式

parseActionName(mapping);

return mapping;

}

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protected void parseNameAndNamespace(String uri, ActionMapping mapping,

ConfigurationManager configManager) {

String namespace, name;

int lastSlash = uri.lastIndexOf("/");

if (lastSlash == -1) {

namespace = "";

name = uri;

} else if (lastSlash == 0) {

namespace = "/";

name = uri.substring(lastSlash + 1);

} else if (alwaysSelectFullNamespace) {

// Simply select the namespace as everything before the last slash

namespace = uri.substring(0, lastSlash);

name = uri.substring(lastSlash + 1);

} else {

//配置元素管理器

Configuration config = configManager.getConfiguration();

String prefix = uri.substring(0, lastSlash);

namespace = "";

boolean rootAvailable = false;

//config.getPackageConfigs()

for (Object cfg : config.getPackageConfigs().values()) {

String ns = ((PackageConfig) cfg).getNamespace();

//匹配nameSpace

if (ns != null && prefix.startsWith(ns) && (prefix.length() == ns.length() || prefix.charAt(ns.length()) == '/')) {

if (ns.length() > namespace.length()) {

namespace = ns;

}

}

if ("/".equals(ns)) {

rootAvailable = true;

}

}

name = uri.substring(namespace.length() + 1);

if (rootAvailable && "".equals(namespace)) {

namespace = "/";

}

}

if (!allowSlashesInActionNames && name != null) {

int pos = name.lastIndexOf('/');

if (pos > -1 && pos < name.length() - 1) {

name = name.substring(pos + 1);

}

}

//TODO

mapping.setNamespace(namespace);

mapping.setName(name);

}

处理action!menthod 形式

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protected ActionMapping parseActionName(ActionMapping mapping) {

if (mapping.getName() == null) {

return mapping;

}

if (allowDynamicMethodCalls) {

String name = mapping.getName();

int exclamation = name.lastIndexOf("!");

if (exclamation != -1) {

mapping.setName(name.substring(0, exclamation));

mapping.setMethod(name.substring(exclamation + 1));

}

}

return mapping;

}

ActionMapping创建 时序图



2.1根据请求映射对象ActionMapping 创建ActionProxy

回到StrutsPrepareAndExecuteFilter doFilter方法

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//执行Action 方法入口

execute.executeAction(request, response, mapping);

ExecuteOperations 的 executeAction方法 把处理逻辑转交给了 Dispatcher的serviceAction方法

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public void executeAction(HttpServletRequest request, HttpServletResponse response, ActionMapping mapping) throws ServletException {

dispatcher.serviceAction(request, response, servletContext, mapping);

}

Dispatcher的serviceAction方法主要完成 1.创建ActionProxy，ActionInvocation，Action对象 2.执行对应的方法

ActionProxy是个接口 接口定义

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public interface ActionProxy {

/**

* 我们定义的Action

* ActionInvocation 中也持有Action引用

* <br>------------------------------<br>

* @return

*/

Object getAction();

String getActionName();

/**

* 初始化阶段 包装的对象

* <br>------------------------------<br>

* @return

*/

ActionConfig getConfig();

/**

* 该值决定 执行完Action对应的方法后 是否执行Result相关操作

*/

void setExecuteResult(boolean executeResult);

/**

*

* @return the status

*/

boolean getExecuteResult();

/**

* 执行器

*/

ActionInvocation getInvocation();

String getNamespace();

String execute() throws Exception;

/**

* Action 对应的方法

*/

String getMethod();

}

ActionInvocation 负责执行所有的拦截器Interceptor和我们定义的Action方法

ActionInvocation接口定义

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/**

* Action 执行器

*/

public interface ActionInvocation extends Serializable {

/**

* 我们定义的Action

* <br>------------------------------<br>

* @return

*/

Object getAction();

boolean isExecuted();

ActionContext getInvocationContext();

ActionProxy getProxy();

Result getResult() throws Exception;

/**

* Action 对应方法执行完成后 返回的Result

* <br>------------------------------<br>

* @return

*/

String getResultCode();

void setResultCode(String resultCode);

ValueStack getStack();

void addPreResultListener(PreResultListener listener);

/**

* 执行所有操作

* 1.执行拦截器

* 2.调用invokeActionOnly方法执行 action对应方法

* <br>------------------------------<br>

* @return

* @throws Exception

*/

String invoke() throws Exception;

/**

* 执行我们定义的Action 方法 在invoke方法中调用

* <br>------------------------------<br>

* @return

* @throws Exception

*/

String invokeActionOnly() throws Exception;

void setActionEventListener(ActionEventListener listener);

/**

* 这个方法会创建我们定义的Action

* <br>------------------------------<br>

* @param proxy

*/

void init(ActionProxy proxy) ;

}

Dispatcher的serviceAction方法

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public void serviceAction(HttpServletRequest request, HttpServletResponse response, ServletContext context, ActionMapping mapping) throws ServletException {

//1.保存request, session, 等web元素到map中

Map<String, Object> extraContext = createContextMap(request, response, mapping, context);

// 省略

//TODO

String namespace = mapping.getNamespace();

String name = mapping.getName();

String method = mapping.getMethod();

//2.初始化完成之后 解析的xml数据对象 会保存到 Configuration#runtimeConfiguration变量中

Configuration config = configurationManager.getConfiguration();

//3.创建ActionProxy,ActionInvocation 返回StrutsActionProxy

ActionProxy proxy = config.getContainer().getInstance(ActionProxyFactory.class).createActionProxy(namespace, name, method, extraContext, true, false);

request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, proxy.getInvocation().getStack());

//执行Action 对应方法入口

if (mapping.getResult() != null) {

Result result = mapping.getResult();

result.execute(proxy.getInvocation());

} else {

//StrutsActionProxy#execute()方法

//4.实际是转到了ActionInvocation#invoke方法

proxy.execute();

}

}

createContextMap 方法 保存web元素 最终已map的形式返回

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public Map<String, Object> createContextMap(HttpServletRequest request, HttpServletResponse response, ActionMapping mapping, ServletContext context) {

Map requestMap = new RequestMap(request);

Map params = new HashMap(request.getParameterMap());

Map session = new SessionMap(request);

Map application = new ApplicationMap(context);

//包装成map集合

Map<String, Object> extraContext = createContextMap(requestMap, params, session, application, request, response, context);

if (mapping != null) {

extraContext.put(ServletActionContext.ACTION_MAPPING, mapping);

}

return extraContext;

}

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public HashMap<String, Object> createContextMap(Map requestMap, Map parameterMap, Map sessionMap, Map applicationMap, HttpServletRequest request, HttpServletResponse response, ServletContext servletContext) {

HashMap<String, Object> extraContext = new HashMap<String, Object>();

extraContext.put(ActionContext.PARAMETERS, new HashMap(parameterMap));

extraContext.put(ActionContext.SESSION, sessionMap);

extraContext.put(ActionContext.APPLICATION, applicationMap);

Locale locale;

if (defaultLocale != null) {

locale = LocalizedTextUtil.localeFromString(defaultLocale, request.getLocale());

} else {

locale = request.getLocale();

}

extraContext.put(ActionContext.LOCALE, locale);

//extraContext.put(ActionContext.DEV_MODE, Boolean.valueOf(devMode));

// value为HttpServletRequest

//HttpServletRequest = extraContext.get('StrutsStatics.HTTP_REQUEST')

extraContext.put(StrutsStatics.HTTP_REQUEST, request);

extraContext.put(StrutsStatics.HTTP_RESPONSE, response);

extraContext.put(StrutsStatics.SERVLET_CONTEXT, servletContext);

//value为包装过的 元素map

//获取方式extraContext.get('request').requestMap.get('key')

extraContext.put("request", requestMap);

extraContext.put("session", sessionMap);

extraContext.put("application", applicationMap);

extraContext.put("parameters", parameterMap);

AttributeMap attrMap = new AttributeMap(extraContext);

extraContext.put("attr", attrMap);

return extraContext;

}

创建ActionProxy,ActionInvocation 是由ActionProxyFactory实现类完成

DefaultActionProxyFactory createActionProxy方法

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public ActionProxy createActionProxy(String namespace, String actionName, String methodName, Map<String, Object> extraContext, boolean executeResult, boolean cleanupContext) {

//创建ActionInvocation

ActionInvocation inv = new DefaultActionInvocation(extraContext, true);

//对该ActionInvocation 实例 进行依赖注入 即引用了@Inject注解的 方法 变量..

container.inject(inv);

//创建ActionProxy

//ActionProxy,ActionInvocation都互相持有对方的引用

//子类StrutsActionProxyFactory 重写了该方法

return createActionProxy(inv, namespace, actionName, methodName, executeResult, cleanupContext);

}

StrutsActionProxyFactory 的createActionProxy方法, StrutsActionProxyFactory是DefaultActionProxyFactory的子类

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public ActionProxy createActionProxy(ActionInvocation inv, String namespace, String actionName, String methodName, boolean executeResult, boolean cleanupContext) {

StrutsActionProxy proxy = new StrutsActionProxy(inv, namespace, actionName, methodName, executeResult, cleanupContext);

container.inject(proxy);

//这里会创建action

proxy.prepare();

return proxy;

}

StrutsActionProxyFactory 的prepare方法 主要完成调用ActionInvocation init方法 创建我们定义的Action 也可能是从Spring容器获得

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protected void prepare() {

//从configuration runtimeConfiguration对象中获取ActionConfig

config = configuration.getRuntimeConfiguration().getActionConfig(namespace, actionName);

//...略

//ActionConfig method为空 默认设置为"execute"

resolveMethod();

//检查method 在Action是否存在

if (!config.isAllowedMethod(method)) {

throw new ConfigurationException("Invalid method: "+method+" for action "+actionName);

}

//创建Action 可能是从spring容器中获得

invocation.init(this);

}

DefaultActionInvocation init方法

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public void init(ActionProxy proxy) {

this.proxy = proxy;

Map<String, Object> contextMap = createContextMap();

ActionContext actionContext = ActionContext.getContext();

if (actionContext != null) {

actionContext.setActionInvocation(this);

}

// 创建Action

createAction(contextMap);

if (pushAction) {

stack.push(action);

contextMap.put("action", action);

}

invocationContext = new ActionContext(contextMap);

invocationContext.setName(proxy.getActionName());

//从当前mapping对应的ActionConfig获得拦截器

List<InterceptorMapping> interceptorList = new ArrayList<InterceptorMapping>(proxy.getConfig().getInterceptors());

interceptors = interceptorList.iterator();

}

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protected void createAction(Map<String, Object> contextMap) {

//省略...

// load action

//Action的创建在此发生

action = objectFactory.buildAction(proxy.getActionName(), proxy.getNamespace(), proxy.getConfig(), contextMap);

//省略...

if (actionEventListener != null) {

action = actionEventListener.prepare(action, stack);

}

}

ObjectFactory 主要负责bean 的创建 继承关系：



以spring为例 StrutsSpringObjectFactory

ObjectFactory bulidAction方法 转到bulidBean方法

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public Object buildAction(String actionName, String namespace, ActionConfig config, Map<String, Object> extraContext) throws Exception {

return buildBean(config.getClassName(), extraContext);

}

SpringObjectFactory 重写了ObjectFactory 的buildBean方法

主要从spring容器中获得bean 这里使用的是spring 的AutowireCapableBeanFactory容器 具有自动装配特性

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public Object buildBean(Class clazz, Map<String, Object> extraContext) throws Exception {

Object bean;

try {

// Decide to follow autowire strategy or use the legacy approach which mixes injection strategies

if (alwaysRespectAutowireStrategy) {

// Leave the creation up to Spring

bean = autoWiringFactory.createBean(clazz, autowireStrategy, false);

injectApplicationContext(bean);

return injectInternalBeans(bean);

} else {

bean = autoWiringFactory.autowire(clazz, AutowireCapableBeanFactory.AUTOWIRE_CONSTRUCTOR, false);

bean = autoWiringFactory.applyBeanPostProcessorsBeforeInitialization(bean, bean.getClass().getName());

// We don't need to call the init-method since one won't be registered.

bean = autoWiringFactory.applyBeanPostProcessorsAfterInitialization(bean, bean.getClass().getName());

return autoWireBean(bean, autoWiringFactory);

}

} catch (UnsatisfiedDependencyException e) {

if (LOG.isErrorEnabled())

LOG.error("Error building bean", e);

// Fall back

return autoWireBean(super.buildBean(clazz, extraContext), autoWiringFactory);

}

}

ActionProxy, ActionInvocation创建过程结束了

当前的ActionInvocation对象中 持有当前映射匹配的拦截器集合interceptors,ActionProxy和我们定义的action对象

目前还没有执行Action对应方法 万事俱备只欠东风了。

ActionProxy创建时序图



2.2 执行Action逻辑 真正执行逻辑是在ActionInvocation的invoke方法中发生

回到Dispatcher 的serviceAction方法

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//StrutsActionProxy#execute()方法

//实际是转到了ActionInvocation#invoke方法

proxy.execute();

StrutsActionProxy的 execute方法调用ActionInvocation invoke方法

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public String execute() throws Exception {

ActionContext previous = ActionContext.getContext();

ActionContext.setContext(invocation.getInvocationContext());

try {

return invocation.invoke();

} finally {

if (cleanupContext)

ActionContext.setContext(previous);

}

}

ActionInvocation invoke方法

大致执行步骤1.执行所有的拦截器 2.执行Action对应的Method 3.根据Action执行结果 再执行Result

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public String invoke() throws Exception {

//...省略

//1.先执行所有拦截器

if (interceptors.hasNext()) {

//这里类似一个递归调用

//intercept方法中 invocation.invoke();

final InterceptorMapping interceptor = (InterceptorMapping) interceptors.next();

resultCode = interceptor.getInterceptor().intercept(DefaultActionInvocation.this);

} else {

//2.最后 执行Action对应方法 返回result字符串

resultCode = invokeActionOnly();

}

//...省略

if (proxy.getExecuteResult()) {

//3.实例化Result对象

executeResult();

}

return resultCode;

}

拦截器的执行 interceptors为一个迭代器Iterator 当执行完一个拦截器 拦截器中又会回调 invoke方法执行下一个 例如:

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public String intercept(ActionInvocation invocation) throws Exception {

String result = null;

//回调到DefaultActionInvocation#invoke方法

result = invocation.invoke();

return result;

}

拦截器执行完成 接着执行Action 对应方法 在invokeActionOnly发生

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public String invokeActionOnly() throws Exception {

return invokeAction(getAction(), proxy.getConfig());

}

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protected String invokeAction(Object action, ActionConfig actionConfig) throws Exception {

//要执行的方法

String methodName = proxy.getMethod();

try {

Object methodResult = null;

Method method = null;

//获得Method对象

method = getAction().getClass().getMethod(methodName, EMPTY_CLASS_ARRAY);

//执行Action 方法

methodResult = method.invoke(action, new Object[0]);

if (methodResult instanceof Result) {

this.explicitResult = (Result) methodResult;

container.inject(explicitResult);

return null;

} else {

//返回 result Str

return (String) methodResult;

}

} catch (NoSuchMethodException e) {

throw new IllegalArgumentException("The " + methodName + "() is not defined in action " + getAction().getClass() + "");

} catch (InvocationTargetException e) {

Throwable t = e.getTargetException();

if (actionEventListener != null) {

//异常处理

String result = actionEventListener.handleException(t, getStack());

if (result != null) {

return result;

}

}

}

}

执行Result 根据ResultConfig 中的calssName创建result对象 在执行execute

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private void executeResult() throws Exception {

//根据ResultConfig对象创建Result对象

result = createResult();

result.execute(this);

}

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public Result createResult() throws Exception {

if (explicitResult != null) {

Result ret = explicitResult;

explicitResult = null;

return ret;

}

ActionConfig config = proxy.getConfig();

Map<String, ResultConfig> results = config.getResults();

ResultConfig resultConfig = null;

try {

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.

resultConfig = results.get("*");

}

if (resultConfig != null) {

try {

//创建Result对象

//resultConfig中包含了 className 直

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;

}

执行Result execute方法 以ServletDispatcherResult为例

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public void execute(ActionInvocation invocation) throws Exception {

lastFinalLocation = conditionalParse(location, invocation);

doExecute(lastFinalLocation, invocation);

}

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public void doExecute(String finalLocation, ActionInvocation invocation) throws Exception {

PageContext pageContext = ServletActionContext.getPageContext();

if (pageContext != null) {

pageContext.include(finalLocation);

} else {

//...省略

if (!insideActionTag && !response.isCommitted() && (request.getAttribute("javax.servlet.include.servlet_path") == null)) {

request.setAttribute("struts.view_uri", finalLocation);

request.setAttribute("struts.request_uri", request.getRequestURI());

//转向

dispatcher.forward(request, response);

} else {

dispatcher.include(request, response);

}

}

}

请求时序图：



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