Apache Static/Dynamic File Separation

In Apache+Tomcat integrations, having Apache serve static files (CSS, JS, images) directly while forwarding only dynamic requests (JSP, servlets) to Tomcat significantly improves performance. This page covers how to implement this separation for each integration method.

Separation Principle

[Client]
     ↓
[Apache HTTPD]
     ├── /static/, /images/, /css/, /js/  → Apache direct serving (fast)
     └── /api/, /app/, *.do, *.jsp        → Forwarded to Tomcat (dynamic)

Benefits of direct serving:

Reduces Tomcat load (saves threads)
Easier to control caching headers
Minimal disk I/O using sendfile() system calls
Compression (gzip) can be applied at the Apache level

mod_jk — JkUnMount Method

Forward everything to Tomcat with JkMount, then define exceptions with JkUnMount.

<VirtualHost *:80>
    ServerName example.com

    # Static file directories
    DocumentRoot /var/www/myapp
    Alias /static  /var/www/myapp/static
    Alias /images  /var/www/myapp/images

    # Forward all to Tomcat
    JkMount /* worker1

    # Exception paths (served directly by Apache)
    JkUnMount /static/*   worker1
    JkUnMount /images/*   worker1
    JkUnMount /css/*      worker1
    JkUnMount /js/*       worker1
    JkUnMount /fonts/*    worker1
    JkUnMount /favicon.ico worker1
    JkUnMount /robots.txt  worker1

    <Directory "/var/www/myapp/static">
        Options -Indexes
        AllowOverride None
        Require all granted

        # Cache headers
        <IfModule mod_expires.c>
            ExpiresActive On
            ExpiresByType text/css             "access plus 1 year"
            ExpiresByType application/javascript "access plus 1 year"
            ExpiresByType image/png            "access plus 6 months"
            ExpiresByType image/jpeg           "access plus 6 months"
            ExpiresByType image/svg+xml        "access plus 6 months"
            ExpiresByType font/woff2           "access plus 1 year"
        </IfModule>
    </Directory>

    CustomLog ${APACHE_LOG_DIR}/myapp_access.log combined
    ErrorLog  ${APACHE_LOG_DIR}/myapp_error.log
</VirtualHost>

Extension-Based JkUnMount

You can also exclude static files based on file extension patterns.

# Extension-based exclusions (mod_jk)
JkUnMount /*.css   worker1
JkUnMount /*.js    worker1
JkUnMount /*.png   worker1
JkUnMount /*.jpg   worker1
JkUnMount /*.gif   worker1
JkUnMount /*.ico   worker1
JkUnMount /*.woff  worker1
JkUnMount /*.woff2 worker1
JkUnMount /*.ttf   worker1
JkUnMount /*.svg   worker1
JkUnMount /*.map   worker1

Note: Extension patterns can be combined with path patterns (/static/*) and work as OR conditions.

mod_proxy_http — ProxyPass Exclusion Method

Use the ! exclusion in ProxyPass directives to exclude static files.

<VirtualHost *:443>
    ServerName example.com
    DocumentRoot /var/www/myapp

    SSLEngine on
    SSLCertificateFile    /etc/letsencrypt/live/example.com/fullchain.pem
    SSLCertificateKeyFile /etc/letsencrypt/live/example.com/privkey.pem

    # Map static file directories
    Alias /static /var/www/myapp/static
    Alias /images /var/www/myapp/images

    # Exclude static paths (! = do not proxy)
    ProxyPass /static      !
    ProxyPass /images      !
    ProxyPass /css         !
    ProxyPass /js          !
    ProxyPass /fonts       !
    ProxyPass /favicon.ico !
    ProxyPass /robots.txt  !

    # Forward only dynamic requests to Tomcat
    ProxyRequests Off
    ProxyPreserveHost On
    ProxyPass        / http://127.0.0.1:8080/ connectiontimeout=10 timeout=60
    ProxyPassReverse / http://127.0.0.1:8080/

    # Static file directory settings
    <Directory "/var/www/myapp/static">
        Options -Indexes
        AllowOverride None
        Require all granted
    </Directory>

    <Directory "/var/www/myapp/images">
        Options -Indexes
        AllowOverride None
        Require all granted
    </Directory>

    # Static file cache + compression
    <IfModule mod_expires.c>
        ExpiresActive On
        ExpiresByType text/css               "access plus 1 year"
        ExpiresByType application/javascript  "access plus 1 year"
        ExpiresByType image/png              "access plus 6 months"
        ExpiresByType image/jpeg             "access plus 6 months"
        ExpiresByType image/webp             "access plus 6 months"
        ExpiresByType font/woff2             "access plus 1 year"
    </IfModule>

    <IfModule mod_deflate.c>
        AddOutputFilterByType DEFLATE text/css application/javascript
        AddOutputFilterByType DEFLATE image/svg+xml application/json
    </IfModule>

    CustomLog ${APACHE_LOG_DIR}/myapp_access.log combined
    ErrorLog  ${APACHE_LOG_DIR}/myapp_error.log
</VirtualHost>

Extension-Based Routing — Using RewriteRule

mod_rewrite provides finer-grained control.

sudo a2enmod rewrite

<VirtualHost *:443>
    ServerName example.com
    DocumentRoot /var/www/myapp

    RewriteEngine On

    # Static file extensions served by Apache (skip Tomcat)
    RewriteRule \.(css|js|png|jpg|jpeg|gif|ico|woff|woff2|ttf|svg|webp|map)$ - [L]

    # Everything else forwarded to Tomcat
    RewriteRule ^/(.*)$ http://127.0.0.1:8080/$1 [P,L]
    ProxyPassReverse / http://127.0.0.1:8080/
</VirtualHost>

SetHandler — Force Handler for Specific Paths

SetHandler forces a specific handling method for a given path. Useful for status pages and health check endpoints.

# Server status page (internal network only)
<Location /server-status>
    SetHandler server-status
    Require ip 127.0.0.1 10.0.0.0/8
</Location>

# Server info page
<Location /server-info>
    SetHandler server-info
    Require ip 127.0.0.1
</Location>

# mod_proxy_balancer management page
<Location /balancer-manager>
    SetHandler balancer-manager
    Require ip 127.0.0.1
</Location>

# Health check endpoint (for load balancer probes)
<Location /health>
    SetHandler default-handler
    # Responds with static file (no Tomcat needed)
</Location>

# Enable mod_status
sudo a2enmod status
sudo systemctl reload apache2

Preventing Tomcat Double-Serving

When Apache serves static files, prevent Tomcat's DefaultServlet from double-serving the same files.

<!-- web.xml — Restrict DefaultServlet static path -->
<servlet-mapping>
    <servlet-name>default</servlet-name>
    <url-pattern>/dynamic-static/*</url-pattern>
    <!-- /static/* is handled by Apache, not mapped to Tomcat -->
</servlet-mapping>

Or place static files outside the WAR:

<!-- server.xml — Add external path to Context -->
<Context path="/myapp" docBase="/opt/tomcat/webapps/myapp">
    <!-- /static is outside the Context -->
</Context>

Build Artifact Deployment Structure

A common structure for serving SPA (Vue/React) builds directly from Apache:

/var/www/myapp/
├── static/          ← React/Vue build (Apache serving)
│   ├── css/
│   ├── js/
│   └── media/
├── index.html       ← SPA entry point (Apache serving)
└── api/             ← Only API requests go to Tomcat (ProxyPass)

<VirtualHost *:443>
    ServerName example.com
    DocumentRoot /var/www/myapp

    # Only API goes to Tomcat
    ProxyPass /api/ http://127.0.0.1:8080/api/
    ProxyPassReverse /api/ http://127.0.0.1:8080/api/

    # SPA routing — unknown paths fall back to index.html
    RewriteEngine On
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteCond %{REQUEST_URI} !^/api/
    RewriteRule ^ /index.html [L]

    <Directory "/var/www/myapp">
        Options -Indexes
        AllowOverride None
        Require all granted
    </Directory>
</VirtualHost>

Performance Comparison

Method	Static File Handling	Tomcat Load	Cache Control
All forwarded to Tomcat	Tomcat DefaultServlet	High	Difficult
Apache direct serving	Apache mod_static	Low	Easy
CDN offloading	CDN	None	CDN config

Summary

Item	Method
mod_jk	`JkUnMount /static/* worker1`
mod_proxy	`ProxyPass /static !`
Extension-based	`RewriteRule \.(css\|js\|...)$ - [L]`
Handler assignment	`SetHandler balancer-manager`
Cache headers	`mod_expires` + `ExpiresActive On`
SPA support	`RewriteRule ^ /index.html [L]`

Separation Principle​

mod_jk — JkUnMount Method​

Extension-Based JkUnMount​

mod_proxy_http — ProxyPass Exclusion Method​

Extension-Based Routing — Using RewriteRule​

SetHandler — Force Handler for Specific Paths​

Preventing Tomcat Double-Serving​

Build Artifact Deployment Structure​

Performance Comparison​

Summary​