对handlerexecutionchain类的深入理解

handlerexecutionchain类比较简单，好理解。

/*
 * 处理器执行链由处理器对象和拦截器组成。
 */
public class handlerexecutionchain {

下面是类的部分属性。

private final object handler; //处理器对象。

  private handlerinterceptor[] interceptors; //拦截器数组

  private list<handlerinterceptor> interceptorlist; //拦截器列表

/**
   * apply prehandle methods of registered interceptors.
   * @return {@code true} if the execution chain should proceed with the
   * next interceptor or the handler itself. else, dispatcherservlet assumes
   * that this interceptor has already dealt with the response itself.
   * 执行已经注册的拦截的 prehandle()方法。如果返回true,则执行链可以执行下一个拦截器的prehandle()方法或 handler 自身。
   * 否则，
   */
  boolean applyprehandle(httpservletrequest request, httpservletresponse response) throws exception {
    handlerinterceptor[] interceptors = getinterceptors();
    if (!objectutils.isempty(interceptors)) {
      for (int i = 0; i < interceptors.length; i++) {
        handlerinterceptor interceptor = interceptors[i];
        if (!interceptor.prehandle(request, response, this.handler)) {
          triggeraftercompletion(request, response, null);
          return false;
        }
        this.interceptorindex = i;
      }
    }
    return true;
  }

/*
   * 执行已经注册的拦截器 posthandle()方法。
   */
  void applyposthandle(httpservletrequest request, httpservletresponse response, modelandview mv) throws exception {
    handlerinterceptor[] interceptors = getinterceptors();
    if (!objectutils.isempty(interceptors)) {
      for (int i = interceptors.length - 1; i >= 0; i--) {
        handlerinterceptor interceptor = interceptors[i];
        interceptor.posthandle(request, response, this.handler, mv);
      }
    }
  }

/**
   * 这个方法只会执行prehandle()方法已经成功执行并且返回true的拦截器中的posthandle()方法。
   */
  void triggeraftercompletion(httpservletrequest request, httpservletresponse response, exception ex)
      throws exception {

    handlerinterceptor[] interceptors = getinterceptors();
    if (!objectutils.isempty(interceptors)) {
      for (int i = this.interceptorindex; i >= 0; i--) {
        handlerinterceptor interceptor = interceptors[i];
        try {
          interceptor.aftercompletion(request, response, this.handler, ex);
        }
        catch (throwable ex2) {
          logger.error("handlerinterceptor.aftercompletion threw exception", ex2);
        }
      }
    }
  }

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