使用filter实现url级别内存缓存示例

用到了fastjson用来解析配置,原理是通过自己实现response类来得到输出的内容

package saleandbuy.freemodule.web.filter;

import java.io.ioexception;
import java.io.printwriter;
import java.io.stringwriter;
import java.util.arrays;
import java.util.hashmap;
import java.util.list;
import java.util.map;
import javax.servlet.filterchain;
import javax.servlet.servletexception;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import javax.servlet.http.httpservletresponsewrapper;

import com.alibaba.fastjson.json;
import com.alibaba.fastjson.jsonarray;
import com.alibaba.fastjson.jsonobject;

public class cacheresp {
 private long waittime=1000*3;

 private static map<string,cacheinfo> cfgmap=new hashmap<string, cacheresp.cacheinfo>();

 public static final string query_strings="querystrings";
 public static final string cached_time="cachedtime";
 public static final string cache_config="cacheconfig";

 public static void config(string cfgjson) {
  jsonobject cfg=json.parseobject(cfgjson);
  for (map.entry<string, object> entry : cfg.entryset()) {
   string key=entry.getkey();
   map<string, object> value=(map<string, object>) entry.getvalue();
   list querystrings= (jsonarray)value.get(query_strings);
   integer cachedtime=(integer) value.get(cached_time);
   cacheinfo cacheinfo=new cacheinfo(querystrings,cachedtime);
   cfgmap.put(key, cacheinfo);
  }
 }

 public static void cacheddo(httpservletrequest request, httpservletresponse response,filterchain chain) throws ioexception, servletexception {
  cacheinfo cacheinfo=getcacheinfo(request);
  string querystring=request.getquerystring();
  //cacheinfo为空则不需要缓存，不为空则需要缓存
  if(cacheinfo!=null){
   long now=system.currenttimemillis();
   synchronized (cacheresp.class) {
    if(now-cacheinfo.lastupdatetime>cacheinfo.cachedtime){
     system.out.println("not use cache:"); 
     proxyresponse proxyresponse=new proxyresponse(response);
     chain.dofilter(request, proxyresponse);
     cacheinfo.cachemap.put(querystring, proxyresponse.getbuffer());
     cacheinfo.lastupdatetime=now;
    }else {
     system.out.println("use cache");
    }
   }
   string cachestr=cacheinfo.cachemap.get(querystring).tostring();
   response.getwriter().write(cachestr);
  }else {
   chain.dofilter(request, response);
  }
 }

 private static cacheinfo getcacheinfo(httpservletrequest request){
  string key=request.getrequesturi().replace(request.getcontextpath(), "");
  cacheinfo cacheinfo=cfgmap.get(key);
  if(cacheinfo!=null&&
    cacheinfo.needcache(request.getquerystring())){
   return cacheinfo;
  }
  return null;
 }

 public static class cacheinfo{
  public list querystrings=arrays.aslist(new string[]{"list","index"});
  public long cachedtime=1000;
  public long lastupdatetime=0;
  public map<string, stringbuffer> cachemap=new hashmap<string, stringbuffer>();

  public cacheinfo(list querystrings, integer cachedtime) {
   super();
   if(cachedtime!=null){
    this.cachedtime = cachedtime;
   }
   this.querystrings = querystrings;
  }

  /**
   *
   * @param querystrings request.getquerystring
   * @return
   */
  public boolean needcache(string querystrings) {
   if(querystrings==null){//querystrings为空时默认缓存所有的查询
    return true;
   }
   return querystrings.contains(querystrings);
  }

 }

 private static class proxyresponse extends httpservletresponsewrapper{

  private stringwriter sw=new stringwriter();

//  private bytearrayoutputstream baos=new bytearrayoutputstream();

  public proxyresponse(httpservletresponse response) {
   super(response);
  }

  @override
  public printwriter getwriter() throws ioexception {
   return new printwriter(sw);
  }

  public stringbuffer getbuffer() {
   return sw.getbuffer();
  }
 }
}