struts2 process

The work done by creating ActionContext
   * There is a Map<String, Object> in actionContext
   * ValueStack stack = dispatcher.getContainer().getInstance(ValueStackFactory.class).createValueStack();
         Create ValueStack implementation class by static injection: OgnlValueStack, also It means that when the actionContext is created, the value stack is created
   * The map stack in the ValueStack is the same as the Map in the
   ActionContext * Through ActionContext.setContext(ctx); put the actionContext into the ThreadLocal, so that the data is Safe
ActionProxy creation
    * ActionProxy proxy = config.getContainer().getInstance(ActionProxyFactory.class).createActionProxy(
                    namespace, name, method, extraContext, true, false);
    *
          ActionInvocation inv = new DefaultActionInvocation(extraContext, true);
          Created DefaultActionInvocation
          When creating ActionProxy, the init method of invocation has already been executed
          what the invocation init method does:
                Action creation and creation of all interceptors
          execute the inovke method in invocation
             * execute all interceptors
             * execute The currently requested action
             * executes the result set