如何在Apache Tomcat的单个JS文件上设置Expires HTTP标头？

问题描述

我有一个 js 文件，这个文件会在5-10分钟之间缓存，这取决于我是使用eclipse中的tomcat（通过GWT插件）还是将tomcat作为启动文件独立。

这很奇怪，因为我使用 GWT 作为我的框架，并且该文件根本不应该被缓存（这是一个nocache.js文件对那些了解GWT的人）。
我阅读过，这是一个容器配置问题，并在别的地方，这是我需要在包含HTML文件中定义的东西。

基本上，我现在很困惑，因为我不知道如何得到这个文件不缓存。
请注意这个js是由 GWT 产生的，我无法修改它。

帮助，
Ittai

解决方案

使用javax。 servlet.Filter

使用过滤器可以以便携的方式（跨不同的应用程序服务器）执行此操作的一种方法。在您的web.xml中添加以下内容：

 < filter> 
< filter-name> headersFilter< / filter-name> 
< filter-class> MyHeadersFilter< / filter-class> 
< / filter> 
< filter-mapping> 
< filter-name> headersFilter< / filter-name> 
< url-pattern> / *< / url-pattern> 
< / filter-mapping> 
  

然后执行您的MyHeadersFilter：

 public class MyHeadersFilter implements Filter {
 
 @Override $ b $ public void doFilter（final ServletRequest request，$ b $ final ServletResponse response，final FilterChain chain）
抛出IOException，ServletException {
 
 final HttpServletRequest httpRequest =（HttpServletRequest）请求; 
 final String requestUri = httpRequest.getRequestURI（）; 
 
 final HttpServletResponse httpResponse =（HttpServletResponse）响应; 
 
 
 if（requestUri.contains（.nocache。））{
 httpResponse.addHeader（Cache-Control，no-cache）; 
 ... 
 
} else if（...）{
 ... 
} 
 
 chain.doFilter（request，响应）; 
 
 
 $ / code $ / pre 
 
 $ hr 
 
 
可选：可配置的过滤器
 
 
 
您还可以使用< init-param>  s：
 < filter> 
< filter-name> headersFilter< / filter-name> 
< filter-class> MyHeadersFilter< / filter-class> 
< init-param> 
< param-name> myParam< / param-name> 
<参数值> myValue< /参数值> 
< / init-param> 
< / filter> 
  
将以下内容添加到MyHeadersFilter中： 
 
 
  private FilterConfig filterConfig; 
 
 @Override 
 public void init（final FilterConfig filterConfig）throws ServletException {
 this.filterConfig = filterConfig; 
} 
 
 @Override 
 public void destroy（）{
 this.filterConfig = null; 
 
 
 
 $ b $ p 
 $ b 
这样可以使用以下方法访问init-param： / p> 
 
 
  filterConfig.getInitParameter（myParam）
  
 
I have a js file which is cached between 5-10 minutes, depending on whether I'm using tomcat from the eclipse (via GWT plugin) or starting tomcat as standalone.
This is strange as I'm using GWT as my framework and this file should not be cached at all (it's a nocache.js file to those of you who know GWT).I've read on a GWT Google group thread that it's a container configuration issue, and somewhere else that it's something I need to define in the containing HTML file.
Basically, I'm confused right now as I have no clue on how to get this file to not cache.Please note that this js is generated by GWT and I cannot modify it.
Thanks for any help,Ittai
 解决方案 
Using a javax.servlet.Filter
One way to do this in a portable way (across different app servers), is using Filters. In your web.xml add the following:
  <filter>
    <filter-name>headersFilter</filter-name>
    <filter-class>MyHeadersFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>headersFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
Then implement your MyHeadersFilter like:
public class MyHeadersFilter implements Filter {

  @Override
  public void doFilter(final ServletRequest request,
         final ServletResponse response, final FilterChain chain)
         throws IOException, ServletException {

      final HttpServletRequest httpRequest = (HttpServletRequest) request;
      final String requestUri = httpRequest.getRequestURI();

      final HttpServletResponse httpResponse = (HttpServletResponse) response;


      if (requestUri.contains(".nocache.")) {
        httpResponse.addHeader("Cache-Control", "no-cache");
        ...

      } else if (...) {
        ...
      }

      chain.doFilter(request, response);
  }
}
Optional: Configurable Filters
You can also make your filter configurable from your web.xml, by using <init-param>s:
  <filter>
    <filter-name>headersFilter</filter-name>
    <filter-class>MyHeadersFilter</filter-class>
    <init-param>
        <param-name>myParam</param-name>
        <param-value>myValue</param-value>
    </init-param>
  </filter>
Add the following to MyHeadersFilter:
    private FilterConfig filterConfig;

    @Override
    public void init(final FilterConfig filterConfig) throws ServletException {
        this.filterConfig = filterConfig;
    }

    @Override
    public void destroy() {
        this.filterConfig = null;
    }
That makes it possible to access your init-param(s) using:
filterConfig.getInitParameter("myParam")
                        
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