至于Action是的创建则是由ActionProxy来完成的,来看一段简要的程序调用
ActionProxy proxy = ActionProxyFactory.getFactory().createActionProxy(namespace, actionName, extraContext);
request.setAttribute(ServletActionContext.WEBWORK_VALUESTACK_KEY, proxy.getInvocation().getStack()); //调用ActionInvocation
proxy.execute();
其实 ActionProxy是一个接口,而ActionProxyFactory则是一个抽象类,他们都是通过一个DefaultActionProxy和DefaultActionProxyFactory来完成操作的,且ActionProxy将调用ActionInvocation接口,由DefaultActionInvocation初始化的时候读取配置,然后由Invoke()方法来完成Action的调用及一些在Action被调用之前的Interceptor的操作.下面是关于DefaultActionInvocation的初始化和调用代码.
public class DefaultActionInvocation implements ActionInvocation {
private void init() throws Exception {
Map contextMap = createContextMap();
createAction(); //加载Action
if (pushAction) {
stack.push(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()); //获取配置
interceptors = interceptorList.iterator();
}
public String invoke() throws Exception {
if (executed) {
throw new IllegalStateException("Action has already executed");
}
//这里是执行拦截器的操作, 注: 拦截器本身就是AOP的一个特殊实现,Servlet2.3 中Filter就是一个特例啊
if (interceptors.hasNext()) {
Interceptor interceptor = (Interceptor) interceptors.next();
resultCode = interceptor.intercept(this);
} else {
resultCode = invokeAction(getAction(), proxy.getConfig());
}
// 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();
listener.beforeResult(this, resultCode);
}
}
// now execute the result, if we're supposed to
if (proxy.getExecuteResult()) {
executeResult();
}
executed = true;
}
…
}
下面再来说说Interceptor 的实现结构,刚开始我以为XWork1.x中Interceptor 应该是从Filter中继承下来的,后来看了源码,原来我的想法不对,想想也的确是不需要,也不应该从Filter下继承,因为Filter就是Servlet2.3的一个API,而XWork1.x设计目的就是要脱离Servlet API,且Interceptor的实现并非是少了Filter就不行,只是我们有了Filter将会来的更加方便!
对于WebWork2.x中的所有的拦截器,他们都有一个公共的接口Interceptor,在它当中定义了拦截器的一些基本操作方法,然后有一个AroundInterceptor抽象类,实现了该接口, AroundInterceptor的作用是组合拦截器的调用顺序,代码如下:
public String intercept(ActionInvocation invocation) throws Exception {
String result = null;
before(invocation); //这里是用于组合调用顺序
result = invocation.invoke();
after(invocation, result);
return result;
}
至于将Map 中的数据转换到我们的VO中,是通过ParametersInterceptor拦截器来完成操作的,这个拦截器是一个真正的实现类,他从AroundInterceptor抽象类下面继承
public class ParametersInterceptor extends AroundInterceptor {
//~ Methods ////////////////////////////////////////////////////////////////
protected void after(ActionInvocation dispatcher, String result) throws Exception {
}
protected void before(ActionInvocation invocation) throws Exception {
if (!(invocation.getAction() instanceof NoParameters)) {
final Map parameters = ActionContext.getContext().getParameters();
//用于获取Map 结构中的Parameters
if (log.isDebugEnabled()) {
log.debug("Setting params " + parameters);
}
ActionContext invocationContext = invocation.getInvocationContext();
try {
invocationContext.put(InstantiatingNullHandler.CREATE_NULL_OBJECTS, Boolean.TRUE);
invocationContext.put(XWorkMethodAccessor.DENY_METHOD_EXECUTION, Boolean.TRUE);
invocationContext.put(XWorkConverter.REPORT_CONVERSION_ERRORS, Boolean.TRUE);
if (parameters != null) {
final OgnlValueStack stack = ActionContext.getContext().getValueStack();
//用于获取OgnlValueStack操作,这个package没看过,具体听夏昕说是一套可读写对象属性的的类库,功能有些类似与Jakarta Commons BeanUtils ,及Spring Bean Wrapper
for (Iterator iterator = parameters.entrySet().iterator();
//遍历Parameters中的信息
iterator.hasNext();) {
Map.Entry entry = (Map.Entry) iterator.next();
String name = entry.getKey().toString();
//填充VO信息
if (acceptableName(name)) {
Object value = entry.getValue();
stack.setValue(name, value);
}
}
}
} finally {
invocationContext.put(InstantiatingNullHandler.CREATE_NULL_OBJECTS, Boolean.FALSE);
invocationContext.put(XWorkMethodAccessor.DENY_METHOD_EXECUTION, Boolean.FALSE);
invocationContext.put(XWorkConverter.REPORT_CONVERSION_ERRORS, Boolean.FALSE);
}
}
}
protected boolean acceptableName(String name) {
if (name.indexOf('=') != -1 || name.indexOf(',') != -1 || name.indexOf('#') != -1) {
return false;
} else {
return true;
}
}
}