jenkins/core/src/main/java/hudson/DependencyRunner.java

package hudson;

import hudson.model.AbstractProject;
import hudson.model.Hudson;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.logging.Logger;

/**
 * Runs a job on all projects in the order of dependencies
 */
public class DependencyRunner implements Runnable {

    private static final Logger LOGGER = Logger.getLogger(DependencyRunner.class.getName());
	
    ProjectRunnable runnable;

    List<AbstractProject> polledProjects = new ArrayList<AbstractProject>();

    public DependencyRunner(ProjectRunnable runnable) {
        this.runnable = runnable;
    }

    public void run() {
        Set<AbstractProject> topLevelProjects = new HashSet<AbstractProject>();
        // Get all top-level projects
    	LOGGER.fine("assembling top level projects");
        for (AbstractProject p : Hudson.getInstance().getAllItems(
                    AbstractProject.class))
            if (p.getUpstreamProjects().size() == 0) {
            	LOGGER.fine("adding top level project " + p.getName());
                topLevelProjects.add(p);
            } else { 
            	LOGGER.fine("skipping project since not a top level project: " 
            			+ p.getName());
            }
        populate(topLevelProjects);
        for (AbstractProject p : polledProjects) {
        	LOGGER.fine("running project in correct dependency order: " + p.getName());
            runnable.run(p);
        }
    }

    private void populate(Set<AbstractProject> projectList) {
        for (AbstractProject p : projectList) {
            if (polledProjects.contains(p)) {
                // Project will be readded at the queue, so that we always use
                // the longest path
            	LOGGER.fine("removing project " + p.getName() + " for re-add");
                polledProjects.remove(p);
            }

        	LOGGER.fine("adding project " + p.getName());
            polledProjects.add(p);

            // Add all downstream dependencies
            populate(new HashSet<AbstractProject>(p.getDownstreamProjects()));
        }
    }

    public interface ProjectRunnable {
        void run(AbstractProject p);
    }
}