JSF and cache-control

最新推荐文章于 2021-02-24 06:46:16 发布

最新推荐文章于 2021-02-24 06:46:16 发布 · 226 阅读

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#Cache #JSF #ITeye #Bean #Servlet

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本文探讨了IFrame缓存导致的数据不更新问题，并提出了三种解决方案：修改头部元信息、使用过滤器及清理Bean数据。这些方法能确保每次请求都获取最新的服务器数据。

进行的项目中遇到这样的问题，我的每一个连接都是连接一台服务器，点击一个连接时候刷新Iframe里页面配置一些参数，切换到另一个服务器连接的时候，Iframe里面列表依然显示着上一台服务器数据列表情况，bean数据没有清空。
在网上查了些资料，方法大概如下：
[b]方案一[/b]
在head里添加信息，好像不起作用，可能和bean范围有关，没有细究


<meta http-equiv="pragma" content="no-cache" />
<meta http-equiv="Cache-Control" content="no-cache,must-revalidate" />
<meta http-equiv="expires" content="Wed,26 Feb 1997 08:21:57 GMT" />

[b]方案二[/b]
利用filter，很好的思路
One of the most annoying problems with building dynamic websites is how to control page cache.

The most used solution is to use a <meta content=”no-cache” http-equiv=”Pragma”/> tag inside the <HEAD> tag. Voilà, problem solved. Wrong! For two reasons:
1. It’s HTML, (most) proxy servers will still cache your pages since they don’t read HTML
2. The HTTP specification does not set any guidelines for Pragma response headers; instead, Pragma request headers are discussed.
Although a few caches may honor this header, the majority won’t, and it won’t have any effect.

However, true HTTP headers are almost always obeyed by any cache. With ADF Faces / JSF it is quite easy to gain control over your caching strategies with a phaselistener:


package nl.iteye.utils;
import javax.faces.context.FacesContext;
import javax.faces.event.PhaseEvent;
import javax.faces.event.PhaseId;
import javax.faces.event.PhaseListener;
import javax.servlet.http.HttpServletResponse;

public class NoCachePhaseListener implements PhaseListener {

    public PhaseId getPhaseId() {
        return PhaseId.RENDER_RESPONSE;
    }

    public void afterPhase(PhaseEvent phaseEvent) {
    }

    public void beforePhase(PhaseEvent phaseEvent) {
        FacesContext facesContext = phaseEvent.getFacesContext();
        HttpServletResponse response = (HttpServletResponse) facesContext.getExternalContext().getResponse();
        response.addHeader(“Pragma”, “no-cache”);
        response.addHeader(“Cache-Control”, “no-cache”);
        response.addHeader(“Cache-Control”, “no-store”);
        response.addHeader(“Cache-Control”, “must-revalidate”);
        response.addHeader(“Expires”, “Mon, 1 Jan 2006 05:00:00 GMT”);//in the past
    }
}

And don’t forget to add the viewhandler to the faces-config.xml within the <lifecycle> tag : <phase-listener>nl.iteye.utils.NoCachePhaseListener</phase-listener> to make this magic work!

[b]方案三[/b]
每次连接之前，代码清除bean


TestBean tBean=((TestBean)FacesUtils.getManagedBean("testBean"));
tBean.tlists = null;