Mongo wicket example connection provider. The MongoFilter was created as a servlet Filter because we also wanted to enable mongo through our rest api. A wicket filter would not be accessible through the rest api.

MongoFilter.java

package com.example.mongo;

import java.io.IOException;

import javax.inject.Inject;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class MongoFilter implements Filter {
  @Inject
    private MongoResource mongo;

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException,
            ServletException {
        try {
            mongo.beginRequest();
            chain.doFilter(request, response);
        } finally {
            mongo.endRequest();
        }
    }

    @Override
    public void destroy() {
    }
}

MongoResource.java

package com.example.mongo;

import java.io.PrintStream;

import javax.annotation.PostConstruct;
import javax.inject.Singleton;

import com.mongodb.DB;
import com.mongodb.MongoURI;

@Singleton
public class MongoResource {
    private static MongoURI mongoURI;

    private DB connectedDB;

    public MongoResource() {
    }

    @PostConstruct
    private void init() throws Exception {
        if (mongoURI == null)
            mongoURI = validateSettings();

        connectedDB = mongoURI.connectDB();
        if (mongoURI.getUsername() != null && !mongoURI.getUsername().isEmpty())
            connectedDB.authenticate(mongoURI.getUsername(), mongoURI.getPassword());
    }

    public DB getDB() {
        return connectedDB;
    }

    public static void validateSettings(String uri) {
        try {
            mongoURI = new MongoURI(uri);

            System.out.println("Connecting MongoDB using: " + mongoURI.getUsername() + "@" + mongoURI.getDatabase());
        } catch (Exception e) {
            System.err.println("Unable to connect to mongo: " + e);
            System.exit(1);
        }
    }

    public static MongoURI validateSettings() {
        String uri = System.getenv("MONGOLAB_URI");
        if (uri == null || uri.isEmpty()) {
            PrintStream err = System.err;
            err.printf(
                    "No %s has been set as an environment variable, format is: mongodb://user:password@hostname:port/databasename\n",
                    "MONGOLAB_URI");
            err.println();
            err.println("Without authentication:");
            err.printf("    export %s=mongodb://localhost:27017/topiconf\n", "MONGOLAB_URI");
            err.println();
            err.println("With authentication:");
            err.printf("    export %s=mongodb://john:doe@localhost:27017/topiconf", "MONGOLAB_URI");
            err.println();
            System.exit(1);
        }
        try {
            MongoURI mongoURI = new MongoURI(uri);
            System.out.println("Connecting MongoDB using: " + mongoURI.getUsername() + "@" + mongoURI.getDatabase());
            return mongoURI;

        } catch (Exception e) {
            System.err.println("Unable to connect to mongo: " + e);
            System.exit(1);
            return null;
        }
    }

    public void beginRequest() {
        connectedDB.requestStart();
    }

    public void endRequest() {
        connectedDB.requestDone();
    }
}