Xwork2 源码阅读(二)

Dispatcher类

Dispatcher类是在struts2中定义的,在 webwork2 中叫DispatcherUtils，

 

作用相同:

1 初始化模块参数，

2 将 xwork 于 web层分离，

3 中转请求，进入xwork 的 action处理流程。

 

1 初始化，涉及方法 init()

在上一篇的 FilterDispatcher中的init() 方法，有这么两句:

 

 

dispatcher = createDispatcher(filterConfig);
dispatcher.init();

 

就是调用Dispatcher的初始化。

 

2  xwork 定义了一个类 : ActonContext，

ActonContext 有两个作用

 

 1) 线程安全，

 过这个类，xwork2 实现了 action 的线程安全，

 为每一次的action请求， 分配一个独立的ActonContext。

 

 2) 于 web 层分离，

xwork的做法，是把web层中组件中的变量

(主要是javax.servlet包中的类，如HttpServletRequest)

取出来,放入ActonContext。

这样xwork就不要在向外访问web层了。

 

 

涉及方法

 

public


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

 

Dispatcher  的这个方法，把web层的参数取出然后放入Map 中，(以备xwork构造ActionContext)。

 

 

3 中转请求，调action处理逻辑，这个是比较重要的一个地方， 

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.getFactory().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, extraContext, 
true


, 
false


);
        proxy.setMethod(method);
        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) {
        
throw


 
new


 ServletException(e);
    } 
finally


 {
        UtilTimerStack.pop(timerKey);
    }
}

 

 

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

得到框架的配置信息，得到框架的Container，构造出 ActionProxy。

这个过程中，涉及到几个xwork较核心的类，Configuration, ConfigurationManager, Container,

 

 

Configuration, ConfigurationManager 负责框架配置信息初始化的类

 

public


 
class


 DefaultConfiguration 
implements


 Configuration {

    
protected


 
static


 
final


 Logger LOG = LoggerFactory.getLogger(DefaultConfiguration.
class


);


    
// Programmatic Action Configurations
    
protected


 Map<String, PackageConfig> packageContexts = 
new


 LinkedHashMap<String, PackageConfig>();
    
protected


 RuntimeConfiguration runtimeConfiguration;
    
protected


 Container container;
    
protected


 String defaultFrameworkBeanName;
    
protected


 Set<String> loadedFileNames = 
new


 TreeSet<String>();


    ObjectFactory objectFactory;

 

这是描述框架总体配置信息的，其中，

Map<String, PackageConfig> 放的是package的config，对应struts2 配置文件中 package标签内容，

 

PackageConfig

 

public


 
class


 PackageConfig 
extends


 Located 
implements


 Comparable, Serializable, InterceptorLocator {

    
private


 
static


 
final


 Logger LOG = LoggerFactory.getLogger(PackageConfig.
class


);

    
private


 Map<String, ActionConfig> actionConfigs;
    
private


 Map<String, ResultConfig> globalResultConfigs;
    
private


 Map<String, Object> interceptorConfigs;
    
private


 Map<String, ResultTypeConfig> resultTypeConfigs;
    
private


 List<ExceptionMappingConfig> globalExceptionMappingConfigs;
    
private


 List<PackageConfig> parents;
    
private


 String defaultInterceptorRef;
    
private


 String defaultActionRef;
    
private


 String defaultResultType;
    
private


 String defaultClassRef;
    
private


 String name;
    
private


 String namespace = 
""

;
    
private


 
boolean


 isAbstract = 
false


;
    
private


 
boolean


 needsRefresh;

 

里边是一些package的信息，其中Map<String, ActionConfig> 放的就是action的描述类ActionConfig了

 

ActionConfig

 

 

public


 
class


 ActionConfig 
extends


 Located 
implements


 Serializable {

    
public


 
static


 
final


 String WILDCARD = 
"*"

;

    
protected


 List<InterceptorMapping> interceptors;
    
protected


 Map<String, String> params;
    
protected


 Map<String, ResultConfig> results;
    
protected


 List<ExceptionMappingConfig> exceptionMappings;
    
protected


 String className;
    
protected


 String methodName;
    
protected


 String packageName;
    
protected


 String name;
    
protected


 Set<String> allowedMethods;

 

 其中

interceptors : action的拦截器，


results: action执行后用来收尾的,如，跳到定义好的页面。
className 类名，packageName 包名，methodName 默认是 execute。


 

 

 

 

 

框架一般有个必须要做的活，就是把某配置文件的信息读到框架系统中来，

xwork2中，XMLConfigurationProvider 就是干这个的，

他读xml配置文件(就是我们定义action的配置的那个文件)，

然后把这些信息写到Configuration中。

ConfigurationManager 则负责调用适当的 ConfigurationProvider，

执行初始化逻辑，和返回具体的Configuration。

 

初始化等前期工作完毕后，则开始执行action的逻辑了，

xwork 使用了代理模式执行action，

   proxy.execute();

 

从这一句起， strust2 就把工作交接给了xwork了。

接着看Dispatcher 
 
ActionProxy proxy = config.getContainer().getInstance(ActionProxyFactory.
class


).createActionProxy(
         namespace, name, extraContext, 
true


, 
false


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

 

用Container 构造一个 ActionProxyFactory，在用ActionProxyFactory create一个 ActionProxy。

 

public


 ActionProxy createActionProxy(String namespace, String actionName, String methodName, Map extraContext, 
boolean


 executeResult, 
boolean


 cleanupContext) {

    ActionInvocation inv = 
new


 DefaultActionInvocation(extraContext, 
true


);
    container.inject(inv);
    
return


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

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

    ActionInvocation inv = new
 DefaultActionInvocation(extraContext, 
true
);
    container.inject(inv);
    return
 createActionProxy(inv, namespace, actionName, methodName, executeResult, cleanupContext);
}

 

 

xwork中，action的调用是借助 Proxy 模式，

Proxy 模式的实现，则是 DefaultActionProxy， Action， ActionInvocation 合伙完成的。

下边是一些关键代码

 

DefaultActionProxy

 

public


 String execute() 
throws


 Exception {
    ActionContext nestedContext = ActionContext.getContext();
    ActionContext.setContext(invocation.getInvocationContext());

    String retCode = 
null


;

    String profileKey = 
"execute: "

;
    
try


 {
        UtilTimerStack.push(profileKey);

       <SPAN style=
"COLOR: #ff0000"

> retCode = invocation.invoke();</SPAN>
    } 
finally


 {
        
if


 (cleanupContext) {
            ActionContext.setContext(nestedContext);
        }
        UtilTimerStack.pop(profileKey);
    }

    
return


 retCode;
}

public
 String execute() 
throws
 Exception {
    ActionContext nestedContext = ActionContext.getContext();
    ActionContext.setContext(invocation.getInvocationContext());

    String retCode = null
;

    String profileKey = "execute: "
;
    try
 {
        UtilTimerStack.push(profileKey);

       <span style="color: #ff0000;"
> retCode = invocation.invoke();</span>
    } finally
 {
        if
 (cleanupContext) {
            ActionContext.setContext(nestedContext);
        }
        UtilTimerStack.pop(profileKey);
    }

    return
 retCode;
}

 

 

 DefaultActionInvocation 得 invoke 方法。

 

public


 String invoke() 
throws


 Exception {
    String profileKey = 
"invoke: "

;
    
try


 {
        UtilTimerStack.push(profileKey);

        
if


 (executed) {
            
throw


 
new


 IllegalStateException(
"Action has already executed"

);
        }

        
if


 (interceptors.hasNext()) {
            
final


 InterceptorMapping interceptor = (InterceptorMapping) interceptors.next();
            UtilTimerStack.profile(
"interceptor: "

+interceptor.getName(),
                    
new


 UtilTimerStack.ProfilingBlock<String>() {
                        
public


 String doProfiling() 
throws


 Exception {
                            <SPAN style=
"COLOR: #ff0000"

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


);</SPAN>
                            
return


 
null


;
                        }
            });
        } 
else


 {
            <SPAN style=
"COLOR: #ff0000"

>resultCode = invokeActionOnly();</SPAN>
        }

        
// 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) {
            
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);
    }
   }

public
 String invoke() 
throws
 Exception {
    String profileKey = "invoke: "
;
    try
 {
        UtilTimerStack.push(profileKey);

        if
 (executed) {
            throw
 
new
 IllegalStateException(
"Action has already executed"
);
        }

        if
 (interceptors.hasNext()) {
            final
 InterceptorMapping interceptor = (InterceptorMapping) interceptors.next();
            UtilTimerStack.profile("interceptor: "
+interceptor.getName(),
                    new
 UtilTimerStack.ProfilingBlock<String>() {
                        public
 String doProfiling() 
throws
 Exception {
                            <span style="color: #ff0000;"
>resultCode = interceptor.getInterceptor().intercept(DefaultActionInvocation.
this
);</span>
                            return
 
null
;
                        }
            });
        } else
 {
            <span style="color: #ff0000;"
>resultCode = invokeActionOnly();</span>
        }

        // 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) {
            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);
    }
   }

 

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

是判断这个action是否有未被执行的拦截器，

 

resultCode = invokeActionOnly();


如没有或拦截器执行完毕，则执行invokeActionOnly


 

 invokeActionOnly方法

 

public


 String <SPAN style=
"COLOR: #ff0000"

>invokeActionOnly()</SPAN> 
throws


 Exception {
    
return


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

rotected String invokeAction(Object action, ActionConfig actionConfig) 
throws


 Exception {
    String methodName = proxy.getMethod();

    
if


 (LOG.isDebugEnabled()) {
        LOG.debug(
"Executing action method = "

 + actionConfig.getMethodName());
    }

    String timerKey = 
"invokeAction: "

+proxy.getActionName();
    
try


 {
        UtilTimerStack.push(timerKey);

        
boolean


 methodCalled = 
false


;
        Object methodResult = 
null


;
        Method method = 
null


;
        
try


 {
            <SPAN style=
"COLOR: #ff0000"

>method = getAction().getClass().getMethod(methodName, 
new


 Class[
0

]);</SPAN>
        } 
catch


 (NoSuchMethodException e) {
            
// hmm -- OK, try doXxx instead
            
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) {
            <SPAN style=
"COLOR: #ff0000"

>methodResult = method.invoke(action, 
new


 Object[
0

]);</SPAN>
        }

        
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);
    }
}

public
 String <span style=
"color: #ff0000;"
>invokeActionOnly()</span> 
throws
 Exception {
    return
 invokeAction(getAction(), proxy.getConfig());
}

rotected String invokeAction(Object action, ActionConfig actionConfig) throws
 Exception {
    String methodName = proxy.getMethod();

    if
 (LOG.isDebugEnabled()) {
        LOG.debug("Executing action method = "
 + actionConfig.getMethodName());
    }

    String timerKey = "invokeAction: "
+proxy.getActionName();
    try
 {
        UtilTimerStack.push(timerKey);

        boolean
 methodCalled = 
false
;
        Object methodResult = null
;
        Method method = null
;
        try
 {
            <span style="color: #ff0000;"
>method = getAction().getClass().getMethod(methodName, 
new
 Class[
0
]);</span>
        } catch
 (NoSuchMethodException e) {
            // hmm -- OK, try doXxx instead
            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) {
            <span style="color: #ff0000;"
>methodResult = method.invoke(action, 
new
 Object[
0
]);</span>
        }

        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);
    }
}

 

method = getAction().getClass().getMethod(methodName, new Class[0]);

取出需执行的action的方法，如 execute()

 

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

利用反射，执行action 方法

 

上边就是利用proxy模式，调用一个action的具体逻辑 的 过程。

 

一般的action里，都有一些变量，如从request中取出的参数等，

如要执行action 方法，如execute()，则必须先吧这些变量赋值 已供方法中使用，

这个工作，就是 拦截器(Interceptor) 的任务之一，

 

下篇探讨一下拦截器。