When working with static resources like CSS and HTML files in Tomcat, you might encounter frustrating caching behavior where changes don't appear even after:

• Browser cache clearing
• Different browser testing
• Different machine testing
• Hard refreshes (Ctrl+F5)

Tomcat implements caching through its DefaultServlet with these default settings:

<!-- In conf/web.xml -->
<init-param>
    <param-name>fileCaching</param-name>
    <param-value>true</param-value>
</init-param>
<init-param>
    <param-name>cacheTTL</param-name>
    <param-value>5000</param-value>
</init-param>

1. Modify web.xml Configuration

Update your application's web.xml:

<servlet>
    <servlet-name>default</servlet-name>
    <servlet-class>org.apache.catalina.servlets.DefaultServlet</servlet-class>
    <init-param>
        <param-name>cachingAllowed</param-name>
        <param-value>false</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>

2. Version Your Static Files

Add version parameter to resource URLs:

<link rel="stylesheet" href="/styles/main.css?v=1.0.23">

3. Use Cache-Control Headers

Create a filter to set headers:

public class NoCacheFilter implements Filter {
    public void doFilter(ServletRequest req, ServletResponse res, 
                         FilterChain chain) throws IOException, ServletException {
        HttpServletResponse response = (HttpServletResponse) res;
        response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate");
        response.setHeader("Pragma", "no-cache");
        response.setHeader("Expires", "0");
        chain.doFilter(req, res);
    }
    // init() and destroy() methods...
}

4. Development-Specific Configuration

For Maven projects, add to pom.xml:

<build>
    <resources>
        <resource>
            <directory>src/main/resources</directory>
            <filtering>true</filtering>
        </resource>
    </resources>
</build>

Confirm caching is disabled by:

1. Checking response headers in browser dev tools
2. Using curl: curl -I http://yourserver/static/style.css
3. Adding timestamp logging in your application

For complete control, serve static files through a custom servlet:

@WebServlet("/static/*")
public class StaticServlet extends HttpServlet {
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) 
        throws ServletException, IOException {
        // Your custom implementation without caching
    }
}

---

Working with static files during web development can become frustrating when Tomcat's caching behavior prevents changes from appearing immediately. Many developers encounter situations where updated CSS/HTML files don't reflect changes until after a server restart - even across different browsers and machines.

Tomcat implements caching for static resources by default to improve performance in production environments. The default cache settings include:

- Static resource caching enabled
- Cache TTL (Time-To-Live) of 5000ms (5 seconds)
- Maximum cache size of 10240KB

For development environments, you can completely disable caching by modifying your context.xml file:

<Context>
    <Resources cachingAllowed="false" />
</Context>

Alternatively, add this to your web.xml:

<filter>
    <filter-name>NoCacheFilter</filter-name>
    <filter-class>org.apache.catalina.filters.RestExpiresFilter</filter-class>
    <init-param>
        <param-name>ExpiresByType text/css</param-name>
        <param-value>access plus 0 seconds</param-value>
    </init-param>
</filter>

For production environments where you want some caching but still need control:

<Context>
    <Resources 
        cachingAllowed="true"
        cacheMaxSize="102400"
        cacheTtl="60000"
        cacheObjectMaxSize="51200" />
</Context>

Even after configuring Tomcat, browsers might still cache resources. Implement versioning for your static files:

<link rel="stylesheet" href="/css/styles.css?v=1.0.1">

To confirm caching is disabled, check HTTP headers in browser dev tools. You should see:

Cache-Control: no-cache, no-store, must-revalidate
Pragma: no-cache
Expires: 0