package com.slp.Decorator;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
public class SampleRequestWrapper extends HttpServletRequestWrapper {
private CacheManager cacheManager;
public SampleRequestWrapper(HttpServletRequest request) {
super(request);
// TODO Auto-generated constructor stub
}
/**
* 根据key值 首先在cache中查找，再调用基类方法查找
*/
public Object getAttribute(String s) {
if (s != null && s.startsWith("cacheable")) {
String cacheKey = s.substring("cacheable.".length());
return cacheManager.getValue(cacheKey);
} else {
return super.getAttribute(s);
}
}
}
有了这个类之后，我们就可以在处理URL请求的Filter中将原始的HttpServletRequest替换成这个装饰实现类。
package com.slp.Decorator;
import java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
public class SampleFilter {
public void doFilter(ServletRequest req,ServletResponse res,FilterChain chain) throws IOException, ServletException{
HttpServletRequest request=(HttpServletRequest)req;
request=new SampleRequestWrapper(request);
chain.doFilter(request, res);
}
}
这样的话，我们就在整个Request生命周期获得了HttpServletRequest的扩展：因为对于HttpServletRequest来说，其原生的getAttribute方法的行为被加入了从缓存中读取数据的新特性。
原文：http://www.cnblogs.com/dream-to-pku/p/5565763.html