Tomcat - starting webapps in a specific order

Question

I know that Tomcat and the Servlet spec do not support starting webapps in a particular order.

However, this seems to me like a common use case, and I\'m wondering i

Answer 1

Since none of the options worked for Tomcat 9.0.19 (the one mentioned by @Luiz also) we used the code approach and replaced the Tomcat StandardHost and HostConfig with minimal custom implementations:

public class CustomTomcatHost extends StandardHost {

    public CustomTomcatHost() {
        super();
    }

    @Override
    public void addLifecycleListener(LifecycleListener listener) {
        if (listener instanceof HostConfig) {
            listener = new OrderedHostConfig();
        }
        super.addLifecycleListener(listener);
    }
}

The deployApps function in HostConfig had to be overriden for sorting to work for everything (incl. WAR files in /webapps folder and also for descriptor XML files in configbase folder (e.g. conf/Catalina/localhost)):

public class OrderedHostConfig extends HostConfig {

    public OrderedHostConfig() {
        super();
    }

    public String[] prioritySort(String[] paths) {
        if (paths == null) return null;

        Arrays.sort(paths, new Comparator() {
            @Override
            public int compare(String a, String b) {
                return a.compareTo(b); //TODO: sort paths based on your criteria
            }
        });

        return paths;
    }

    @Override
    protected void deployApps() {

        File appBase = host.getAppBaseFile();
        File configBase = host.getConfigBaseFile();

        String[] apps = prioritySort(filterAppPaths(appBase.list()));

        // Deploy XML descriptors from configBase
        deployDescriptors(configBase, prioritySort(configBase.list()));
        // Deploy WARs
        deployWARs(appBase, apps);
        // Deploy expanded folders
        deployDirectories(appBase, apps);
    }
}

Then we placed the new classes in a new jar file in Tomcat /lib directory and modified conf/server.xml file to replace the host class with our own implementation:

During start Tomcat loaded all components in the required order.