Source Code of com.googlecode.richrest.server.ActionServlet$ActionInterceptorChain

package com.googlecode.richrest.server;


import java.io.IOException;
import java.io.Serializable;
import java.util.Iterator;
import java.util.List;
import java.util.Map;


import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


import com.googlecode.richrest.Action;
import com.googlecode.richrest.server.mapper.DefaultActionMapper;
import com.googlecode.richrest.server.provider.SpringActionProvider;
import com.googlecode.richrest.util.BeanUtils;
import com.googlecode.richrest.util.ClassUtils;
import com.googlecode.richrest.util.ExceptionUtils;
import com.googlecode.richrest.util.logger.Logger;
import com.googlecode.richrest.util.logger.LoggerFactory;


/**
 * Action请求Servlet接收器.
 * <p>
 * web.xml配置：
 * <pre>
 * &lt;servlet&gt;
 *     &lt;servlet-name&gt;actionServlet&lt;/servlet-name&gt;
 *     &lt;servlet-class&gt;com.googlecode.richrest.server.ActionServlet&lt;/servlet-class&gt;
 *     &lt;init-param&gt;
 *         &lt;param-name&gt;actionProvider&lt;/param-name&gt;
 *         &lt;param-value&gt;
 *             com.googlecode.richrest.server.factory.SpringActionProvider
 *         &lt;/param-value&gt;
 *     &lt;/init-param&gt;
 *     &lt;init-param&gt;
 *         &lt;param-name&gt;actionMapper&lt;/param-name&gt;
 *         &lt;param-value&gt;
 *             com.googlecode.richrest.server.mapper.DefaultActionMapper
 *         &lt;/param-value&gt;
 *     &lt;/init-param&gt;
 *     &lt;load-on-startup&gt;1&lt;/load-on-startup&gt;
 * &lt;/servlet&gt;
 * &lt;servlet-mapping&gt;
 *     &lt;servlet-name&gt;actionServlet&lt;/servlet-name&gt;
 *     &lt;url-pattern&gt;*.data&lt;/url-pattern&gt;
 * &lt;/servlet-mapping&gt;
 * </pre>
 * @author <a href="mailto:liangfei0201@gmail.com">liangfei</a>
 */
public class ActionServlet extends HttpServlet {


  private static final long serialVersionUID = 5273076711496326339L;


  /**
   * 日志输出接口
   */
  protected final Logger logger = LoggerFactory.getLogger(getClass());


  protected ActionServletContext actionServletContext;


  // 初始化
  @Override
  public void init() throws ServletException {
    super.init();
    actionServletContext = new ActionServletContext(getServletContext(), getServletConfig());
    ActionServletContext.init(actionServletContext); // 初始化上下文
    try {
      // 加载Action工厂
      ActionProvider actionProvider = getActionProvider();
      if (actionProvider == null)// 缺省使用SpringActionProvider
        actionProvider = new SpringActionProvider();
      ActionServletContext.getContext().setActionProvider(actionProvider);
      actionInterceptor = reduceActionInterceptorChain(actionProvider.getActionInterceptors());


      // 加载Action接收器
      ActionMapper actionMapper = getActionMapper();
      if (actionMapper == null) // 缺省使用ActionMapper
        actionMapper = new DefaultActionMapper();
      ActionServletContext.getContext().setActionMapper(actionMapper);
    } catch (ServletException e) {
      logger.error(e.getMessage(), e);
      throw e;
    } catch (Exception e) {
      logger.error(e.getMessage(), e);
      throw new ServletException(e.getMessage(), e);
    } finally {
      ActionServletContext.destroy();
    }
  }


  // 销毁
  @Override
  public void destroy() {
    super.destroy();
  }


  // 请求适配
  @Override
  protected void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    doPost(request, response);
  }


  @Override
  protected void doPut(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    doPost(request, response);
  }


  @Override
  protected void doDelete(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    doPost(request, response);
  }


  @Override
  protected void doHead(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    doPost(request, response);
  }


  // 请求处理
  @SuppressWarnings("unchecked")
  @Override
  protected void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    ActionServletContext.init(actionServletContext); // 初始化上下文
    try {
      ServletSerializer serializer = ActionServletContext.getContext().getActionMapper().getSerializer(request);
      response.setContentType(serializer.getContentType());


      String actionName = ActionServletContext.getContext().getActionMapper().getActionName(request); // 获取Action名称
      if (actionName == null) // action名称不允许为空
        throw new NullPointerException("Can not resolve action name by request: " + request.getRequestURI());


      Action<Serializable, Serializable> action = ActionServletContext.getContext().getActionProvider().getAction(actionName); // 获取Action实例
      if (action == null) // action实例不允许为空
        throw new NullPointerException("Not existed action: " + actionName);
      ActionDelegate delegate = new ActionDelegate(actionInterceptor, action);
      Class<? extends Serializable> modelClass = getModelClass(action);


      ActionContext.init(request, response, actionName, action); // 初始化上下文
      try {
        // 接收客户端传过来的对象
        Serializable model = serializer.deserialize(modelClass, request);
        Serializable result;
        try {
          result = doExceute(actionName, delegate, model);
        } catch (ServletForwardException e) {
          throw e;
        } catch (Exception e) { // 从Action中抛出的业务性异常，直接序列化到客户端
          result = e;
        }
        serializer.serialize(result, response);
      } finally {
        ActionContext.destroy(); // 销毁上下文
      }
    } catch (ServletForwardException e) {
      Serializable forwardModel = e.getModel();
      request.setAttribute("model", forwardModel);
      if (forwardModel instanceof Map) {
        Map map = (Map)forwardModel;
        for (Iterator iterator = map.entrySet().iterator(); iterator.hasNext();) {
          Map.Entry entry = (Map.Entry)iterator.next();
          request.setAttribute(String.valueOf(entry.getKey()), entry.getValue());
        }
      } else {
        Map<String, Object> map = BeanUtils.getProperties(forwardModel);
        for (Map.Entry<String, Object> entry : map.entrySet()) {
          request.setAttribute(entry.getKey(), entry.getValue());
        }
      }
      request.getRequestDispatcher(e.getTarget()).forward(request, response);
      return;
    } catch (Throwable e) { // 服务器错误
      logger.error(e.getMessage(), e);
      String msg = ExceptionUtils.getDetailMessage(e);
      response.sendError(500, msg); // 不能序列化则发送HTTP错误信息报头
    } finally {
      ActionServletContext.destroy();
    }
  }


  protected Serializable doExceute(String actionName, Action<Serializable, Serializable> action, Serializable model) throws Exception {
    Serializable result; // 返回结果
    try {
      result = action.execute(model); // 执行
    } catch (ActionForwardException e) {
      String forwardActionName = e.getTarget(); // 不为空
      Serializable forwardModel = e.getModel();
      Action<Serializable, Serializable> forwardAction = ActionServletContext.getContext().getActionProvider().getAction(forwardActionName); // 获取Action实例
      if (forwardAction == null) // action实例不允许为空
        throw new NullPointerException("Not existed action: " + forwardActionName);
      ActionDelegate forwardActionDelegate = new ActionDelegate(actionInterceptor, forwardAction);
      ActionContext.getContext().pushAction(forwardActionName, forwardAction);
      try {
        return doExceute(forwardActionName, forwardActionDelegate, forwardModel);
      } finally {
        ActionContext.getContext().popAction();
      }
    }
    return result;
  }


  @SuppressWarnings("unchecked")
  protected Class<? extends Serializable> getModelClass(Action<Serializable, Serializable> action) throws Exception {
    return (Class<? extends Serializable>) ClassUtils.getMethod(action.getClass(), "execute").getParameterTypes()[0];
  }


  /**
   * ActionProvider的配置参数名
   */
  protected static final String ACTION_PROVIDER_PARAM_NAME = "actionProvider";


  /**
   * 加载Action实例化工厂，子类可通过覆写该方法，拦截加载方式
   * @return Action实例化工厂
   * @throws Exception 异常均向上抛出，由框架统一处理
   */
  protected ActionProvider getActionProvider() throws Exception {
    // 加载Action工厂
    String actionProviderClassName = super.getInitParameter(ACTION_PROVIDER_PARAM_NAME);
    if (actionProviderClassName != null && actionProviderClassName.trim().length() > 0) {
      try {
        Class<?> actionProviderClass = ClassUtils.forName(actionProviderClassName.trim());
        if (ActionProvider.class.isAssignableFrom(actionProviderClass)) {
          return (ActionProvider)actionProviderClass.newInstance();
        } else {
          logger.error(actionProviderClass.getName() + " unimplementet interface " + ActionProvider.class.getName());
        }
      } catch (Exception e) {
        logger.error(e.getMessage(), e);
      }
    }
    return null;
  }


  /**
   * ActionMapper的配置参数名
   */
  protected static final String ACTION_MAPPER_PARAM_NAME = "actionMapper";


  /**
   * 加载Action接收决策器，子类可通过覆写该方法，拦截加载方式
   * @return Action接收决策器
   * @throws Exception 异常均向上抛出，由框架统一处理
   */
  protected ActionMapper getActionMapper() throws Exception {
    // 加载模型转换器
    String actionMapperClassName = super.getInitParameter(ACTION_MAPPER_PARAM_NAME);
    if (actionMapperClassName != null && actionMapperClassName.trim().length() > 0) {
      try {
        Class<?> actionMapperClass = ClassUtils.forName(actionMapperClassName.trim());
        if (ActionMapper.class.isAssignableFrom(actionMapperClass)) {
          return (ActionMapper)actionMapperClass.newInstance();
        } else {
          logger.error(actionMapperClass.getName() + " unimplementet interface " + ActionMapper.class.getName());
        }
      } catch (Exception e) {
        logger.error(e.getMessage(), e);
      }
    }
    return null;
  }


  protected ActionInterceptor actionInterceptor;


  /**
   * 将拦截器列表归约成链
   * @param sctionInterceptors 拦截器列表
   * @return 拦截器链的第一个拦截器
   */
  protected ActionInterceptor reduceActionInterceptorChain(List<ActionInterceptor> actionInterceptors) {
    if (actionInterceptors == null || actionInterceptors.size() == 0)
      return null;
    ActionInterceptor lastActionInterceptor = null;
    for (int i = actionInterceptors.size() - 1; i >= 0; i --) { // 倒序拼装拦截器链
      ActionInterceptor actionInterceptor = (ActionInterceptor)actionInterceptors.get(i);
      if (actionInterceptor != null)
        lastActionInterceptor = new ActionInterceptorChain(actionInterceptor, lastActionInterceptor);
    }
    return lastActionInterceptor;
  }


  // 拦截器链
  protected static final class ActionInterceptorChain implements ActionInterceptor {


    // 当前拦截器
    private final ActionInterceptor currentActionInterceptor;


    // 下一拦截器
    private final ActionInterceptor nextActionInterceptor;


    /**
     * 构造拦截器链
     * @param currentActionInterceptor 当前拦截器
     * @param nextActionInterceptor 下一拦截器
     */
    ActionInterceptorChain(ActionInterceptor currentActionInterceptor, ActionInterceptor nextActionInterceptor) {
      if (currentActionInterceptor == null)
        throw new NullPointerException("currentActionInterceptor == null");
      this.currentActionInterceptor = currentActionInterceptor;
      this.nextActionInterceptor = nextActionInterceptor;
    }


    public Serializable intercept(Action<Serializable, Serializable> action, Serializable object) throws Exception {
      if (nextActionInterceptor == null)
        return currentActionInterceptor.intercept(action, object); // 如果没有下一拦载器，传入实际Action实例
      return currentActionInterceptor.intercept(new ActionDelegate(nextActionInterceptor, action), object); // 如果有下一拦载器，则代理下一拦截器
    }


  }


  /**
   * Action委托于拦截器调用
   * @author <a href="mailto:liangfei0201@gmail.com">liangfei</a>
   */
  protected static final class ActionDelegate implements Action<Serializable, Serializable> {


    private final ActionInterceptor actionInterceptor;


    private final Action<Serializable, Serializable> action;


    ActionDelegate(ActionInterceptor actionInterceptor, Action<Serializable, Serializable> action) {
      if (action == null)
        throw new NullPointerException("action == null!");
      this.actionInterceptor = actionInterceptor;
      this.action = action;
    }


    public Serializable execute(Serializable object) throws Exception {
      if (actionInterceptor != null)
        return actionInterceptor.intercept(action, object); // 如果有拦截器，则执行拦截器
      return action.execute(object); // 否则，直接执行Action实例
    }


  }


}
Source Code of com.googlecode.richrest.server.ActionServlet$ActionInterceptorChain

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