Struts2 之 Validation 拦截器 基于XML配置方式实现(验证框架)

补充理解小点：

I:系统加载验证的XML文件  读取到DefaultActionValidatorManager类中的ValidatorConfig进行使用

II：<result name="input">/WEB-INF/page/addUser.jsp</result>在struts2中这个input怎么返回的。
查看源码：
在ValidationInterceptor 验证拦截器查看得知：

public class ValidationInterceptor extends MethodFilterInterceptor {  
    private boolean alwaysInvokeValidate = true; 
    public void setAlwaysInvokeValidate(String alwaysInvokeValidate) {
            this.alwaysInvokeValidate = Boolean.parseBoolean(alwaysInvokeValidate);
    } 
    protected void doBeforeInvocation(ActionInvocation invocation) throws Exception {
        
        if (action instanceof Validateable && programmatic) {
            
            Validateable validateable = (Validateable) action;  
            try {
               
               //把验证错误信息添加在fieldErrors Map集合中 但并没有返回 “input”
                PrefixMethodInvocationUtil.invokePrefixMethod(
                                invocation,
                                new String[] { VALIDATE_PREFIX, ALT_VALIDATE_PREFIX });
            }  
          //这个默认为true
            if (alwaysInvokeValidate ) {
               //以上是把验证错误信息放入到一个fieldErrors Map集合中后继续执行
                validateable.validate();
            }
            
        }
    } 
    protected String doIntercept(ActionInvocation invocation) throws Exception {
          //方法执行完成 继续执行下一个拦截器  DefaultWorkflowInterceptor
        doBeforeInvocation(invocation); 
        return invocation.invoke();
    } 
}
在DefaultWorkflowInterceptor拦截器中可以查看源码得知input返回值在这里进行返回


public class DefaultWorkflowInterceptor extends MethodFilterInterceptor {

    private static final long serialVersionUID = 7563014655616490865L;

    private static final Logger LOG = LoggerFactory.getLogger(DefaultWorkflowInterceptor .class );

    private static final Class[] EMPTY_CLASS_ARRAY = new Class[0];
   
    private String inputResultName = Action.INPUT;
 
    public void setInputResultName(String inputResultName) {
        this.inputResultName = inputResultName;
    } 
    @Override
    protected String doIntercept(ActionInvocation invocation) throws Exception {
        Object action = invocation.getAction();
          //首先盘对请求的action是否实现了 ValidationAware的接口
        if (action instanceof ValidationAware) {
            ValidationAware validationAwareAction = (ValidationAware) action;
            //这一步 判断fieldErrors Map集合中是否有错误 
            if (validationAwareAction.hasErrors()) {
                 //如果Map集合不为空就赋值resultName 为input
                String resultName = inputResultName;

                if (action instanceof ValidationWorkflowAware) {
                    resultName = ((ValidationWorkflowAware) action).getInputResultName();
                } 
                
                if (annotation != null) {
                    if (!annotation.methodName().equals("" )) {
                        Method method = action.getClass().getMethod(annotation.methodName());
                        resultName = (String) method.invoke(action);
                    } else {
                        resultName = annotation.resultName();
                    }
                } 
               //在这里返回 input；
                return resultName;
            }
        }
     //如果Map集合 为空就继续执行
        return invocation.invoke();
    }

}

//DefaultWorkflowInterceptor类继承自MethodFilterInterceptor  实现了doIntercept方法
//当doIntercept返回input时进行接收
public abstract class MethodFilterInterceptor extends AbstractInterceptor { 
    
    @Override
    public String intercept(ActionInvocation invocation) throws Exception {
        if (applyInterceptor(invocation)) {
          //接收到 input 进行向上返回
            return doIntercept(invocation);
        }
        return invocation.invoke();
    }
 
    protected abstract String doIntercept(ActionInvocation invocation) throws Exception;
   
}
//DefaultActionInvocation 管理调度拦截器的执行和返回值（个人理解）
public class DefaultActionInvocation implements ActionInvocation {
  
    public String invoke() throws Exception {
        String profileKey = "invoke: ";
        try {
            UtilTimerStack.push(profileKey);
           //执行拦截器 
            if (interceptors .hasNext()) {
               
                String interceptorMsg = "interceptor: " + interceptor.getName();
                UtilTimerStack. push(interceptorMsg);
                try {
     //在这里进行最终的接受拦截器的返回值 “input”
   resultCode     =interceptor.getInterceptor().intercept(DefaultActionInvocation. this);
                            }
                finally {
                    UtilTimerStack. pop(interceptorMsg);
                }
            } else {
                resultCode = invokeActionOnly();
            } 
              
                 
                if (proxy .getExecuteResult()) {
                    //执行<result name="input">/WEB-INF/page/addUser.jsp</result>
                    executeResult();
                }

                executed = true;
            }

            return resultCode ;
        }
        finally {
            UtilTimerStack. pop(profileKey);
        }
    }
 private void executeResult() throws Exception {
        result = createResult(); 
         // getResultCode也就是获取到了input
        String timerKey = "executeResult: " + getResultCode();
        try {
            UtilTimerStack. push(timerKey);
            if (result != null) {
                result.execute( this);
            }  
        }  
    }
} 

以上都是个人单步调试看到的 能力有限 仅限个人理解