@WebFilter different init param for different type

Question

I'm in the middle of migrating Servlet 2.5 based webapp to Servlet 3.0 and ran into this problem that I do not know how to squeeze these different filter-mappings into one @WebFilter annotation for the class.

Filters:

<!-- Day is 12 hours, so if we update at night the new content will be fetched first     thing in the morning -->
<filter>
    <filter-name>CacheForDay</filter-name>
    <filter-class>x.web.client.filter.CacheHeaderFilter</filter-class>
    <init-param>
        <param-name>CacheTime</param-name>
        <param-value>43200</param-value>
    </init-param>
</filter>

<filter>
    <filter-name>CacheForWeek</filter-name>
    <filter-class>x.web.client.filter.CacheHeaderFilter</filter-class>
    <init-param>
        <param-name>CacheTime</param-name>
        <param-value>604800</param-value>
    </init-param>
</filter>

<filter>
    <filter-name>CacheForMonth</filter-name>
    <filter-class>x.web.client.filter.CacheHeaderFilter</filter-class>
    <init-param>
        <param-name>CacheTime</param-name>
        <param-value>18144000</param-value>
    </init-param>
</filter>

<filter>
    <filter-name>noCache</filter-name>
    <filter-class>x.web.client.filter.CacheHeaderFilter</filter-class>
    <init-param>
        <param-name>CacheTime</param-name>
        <param-value>0</param-value>
    </init-param>
</filter> 

Filter-Mappings:

<filter-mapping>
    <filter-name>CacheForDay</filter-name>
    <url-pattern>*.png</url-pattern>
  </filter-mapping>

  <filter-mapping>
    <filter-name>CacheForDay</filter-name>
    <url-pattern>*.gif</url-pattern>
  </filter-mapping>

  <filter-mapping>
    <filter-name>CacheForDay</filter-name>
    <url-pattern>*.js</url-pattern>
  </filter-mapping>

  <filter-mapping>
    <filter-name>CacheForDay</filter-name>
    <url-pattern>*.css</url-pattern>
  </filter-mapping>

  <filter-mapping>
    <filter-name>CacheForMonth</filter-name>
    <url-pattern>*.ico</url-pattern>
  </filter-mapping>

How can I replace them by @WebFilter?

Answer 1

It is impossible with a single class annotated with @WebFilter. You wil have to either:

• Continue using the web.xml way; this is not bad considering the situation.
• Implement the logic in a base class and write trivial extensions, annotated with the appropriate @WebFilter. I think this wouldn't look nice.

Example of the later:

public class BaseCacheFilter implements Filter
{
    public void doFilter(...) {
        ...implementation here...
    }
    ....
}

@WebFilter(
    urlPatterns={"*.png","*.gif",...},
    initParams=@WebInitParam(name="CacheTime",value="43200")
)
public class CacheForDay extends BaseCacheFilter
{ /* EMPTY */ }