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struts 2丢弃缓存头

struts2 caching

Dewfy · 技术社区 · 15 年前

我在为我的图像设置缓存选项时有奇怪的struts2丢弃行为。

我正在尝试将数据库中的图像缓存到客户端渲染我使用的图像( http://struts.apache.org/2.x/docs/how-can-we-display-dynamic-or-static-images-that-can-be-provided-as-an-array-of-bytes.html )其中特殊结果类型呈现如下:

public void execute(ActionInvocation invocation) throws Exception {
     ...//some preparation
    HttpServletResponse response = ServletActionContext.getResponse();
    HttpServletRequest request = ServletActionContext.getRequest();
    ServletOutputStream os = response.getOutputStream();
    try
    {
        byte[] imageBytes = action.getImage();
        response.setContentType("image/gif");
        response.setContentLength(imageBytes.length);
        //I want cache up to 10 min
        Date future = new Date(((new Date()).getTime() + 1000 * 10*60l));
        ;
        response.addDateHeader("Expires", future.getTime());
      response.setHeader("Cache-Control", "max-age=" + 10*60 + "");
        response.addHeader("cache-Control", "public"); 
        response.setHeader("ETag", request.getRequestURI());
        os.write(imageBytes);
    }
    catch(Exception e)
    {
        response.sendError(HttpServletResponse.SC_NOT_FOUND);
    }

    os.flush();
    os.close();
}

但是当图像嵌入到页面中时,它总是被重新加载(firebug显示代码200),并且头中既不显示过期,也不显示最长期限。

Host    localhost:9090
Accept  image/png,image/*;q=0.8,*/*;q=0.5
Accept-Language en-us,en;q=0.5
Accept-Encoding gzip,deflate
Accept-Charset  ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive  300
Connection  keep-alive
Referer http://localhost:9090/web/result?matchId=1
Cookie  JSESSIONID=4156BEED69CAB0B84D950932AB9EA1AC; 
If-None-Match   /web/_srv/teamcolor
Cache-Control   max-age=0

我不知道它为什么会被破坏,可能是在网址的问题?它是带有参数的窗体:

 http://localhost:9090/web/_srv/teamcolor?loginId=3

2 回复 | 直到 15 年前

Dewfy 15 年前

最后,我发现了我的代码有什么问题,这是相当奇怪的,因为它是部分工作(图像显示)。

罪魁祸首如下:

HttpServletResponse response = ServletActionContext.getResponse();

必须用以下内容替换:

HttpServletResponse response = (HttpServletResponse)
    invocation.getInvocationContext().get(StrutsStatics.HTTP_RESPONSE);

这看起来有点神奇,但显然两个响应共享相同的输出流,但不共享头声明的容器。

Tommi 15 年前

不确定这是否会更好,但你可以试试。创建修改响应头的自定义拦截器。类似这样的事情(注意,我没有测试过这个):

package com.yourpackage.interceptor;

import java.util.Date;

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

import org.apache.struts2.StrutsStatics;

import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.interceptor.AbstractInterceptor;

public class ResponseHeadersInterceptor extends AbstractInterceptor {

    @Override
    public String intercept(ActionInvocation invocation) throws Exception {

        ActionContext context = invocation.getInvocationContext();
        HttpServletResponse response = (HttpServletResponse)context.get(StrutsStatics.HTTP_RESPONSE);
        HttpServletRequest request = (HttpServletRequest)context.get(StrutsStatics.HTTP_REQUEST);

        if (response!=null) {
            Date future = new Date(((new Date()).getTime() + 1000 * 10*60l));
            response.addDateHeader("Expires", future.getTime());
            response.setHeader("Cache-Control", "max-age=" + 10*60 + "");
            response.addHeader("cache-Control", "public");
            if (request!=null)
                response.setHeader("ETag", request.getRequestURI());
        }

        return invocation.invoke();
    }

}

然后在struts.xml中,定义拦截器和一个新的拦截器堆栈:

<interceptors>
    <interceptor name="responseHeaders" class="com.yourpackage.interceptor.ResponseHeadersInterceptor" />       
    <interceptor-stack name="extendedStack">
        <interceptor-ref name="defaultStack" />
        <interceptor-ref name="responseHeaders" />
    </interceptor-stack>        
</interceptors>

然后修改动作定义以使用 extendedStack .