CacheInterceptor.java

package cn.dreampie.route.cache;

import cn.dreampie.cache.SimpleCache;
import cn.dreampie.common.Constant;
import cn.dreampie.common.http.HttpMethod;
import cn.dreampie.common.http.HttpRequest;
import cn.dreampie.common.http.HttpResponse;
import cn.dreampie.common.http.result.HttpStatus;
import cn.dreampie.log.Logger;
import cn.dreampie.route.annotation.API;
import cn.dreampie.route.annotation.GET;
import cn.dreampie.route.core.RouteInvocation;
import cn.dreampie.route.core.RouteMatch;
import cn.dreampie.route.interceptor.Interceptor;

import java.util.Date;
import java.util.UUID;

/**
 * Created by Dreampie on 16/1/8.
 */
public class CacheInterceptor implements Interceptor {

  private final static Logger logger = Logger.getLogger(CacheInterceptor.class);
  public static final String HTTP_DEF_KEY = "_http";
  private int expired = -1;//-1 表示事件驱动缓存更新 缓存不会过期

  public CacheInterceptor() {

  }

  public CacheInterceptor(int expired) {
    this.expired = expired;
  }

  public void intercept(RouteInvocation ri) {
    if (Constant.cacheEnabled) {
      API apiAnno = (API) ri.getResourceClass().getAnnotation(API.class);
      String apiValue = apiAnno.value();
      RouteMatch routeMatch = ri.getRouteMatch();
      HttpRequest request = routeMatch.getRequest();
      HttpResponse response = routeMatch.getResponse();
      String method = request.getHttpMethod();
      String group = HTTP_DEF_KEY + Constant.CONNECTOR + apiValue;
      String uri = request.getRestUri();

      String version = SimpleCache.instance().get(group, apiValue);

      if (method.equals(HttpMethod.GET)) {
        GET getAnno = ri.getMethod().getAnnotation(GET.class);

        //缓存请求判断
        if (getAnno.cached()) {
          String previousToken = request.getHeader("If-None-Match");

          // compare previous token with current one
          if ((version != null) && (previousToken != null && previousToken.equals('"' + version + '"'))) {
            HttpStatus status = HttpStatus.NOT_MODIFIED;
            response.setStatus(status);
            // re-use original last modified timestamp
            response.setHeader("Last-Modified", request.getHeader("If-Modified-Since"));
            logger.info("Not modify '" + uri + "'");
            return; // no further processing required
          }

          //设置ETag
          setETag(apiValue, response, group, version);

          Object result = SimpleCache.instance().get(group, uri);
          if (result == null) {
            result = ri.invoke();
            SimpleCache.instance().add(group, uri, result, expired);
          } else {
            //not invoke render cache result
            ri.render(result);
          }
          return;
        }
      } else {
        //重置ETag
        setETag(apiValue, response, group, null);
        SimpleCache.instance().flush(group);//清楚 get 缓存
      }
    }
    //不缓存请求
    ri.invoke();
  }

  private void setETag(String apiValue, HttpResponse response, String group, String version) {
    // set header for the next time the client calls
    if (version == null) {
      version = UUID.randomUUID().toString();
      SimpleCache.instance().add(group, apiValue, version, expired);
    }
    // first time through - set last modified time to now
    response.setHeader("Last-Modified", new Date().toString());
    response.setHeader("ETag", '"' + version + '"');
  }
}