diff --git a/.gitignore b/.gitignore
index cf70988..13d81d6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 **/node_modules
+docker/mongodb/data
\ No newline at end of file
diff --git a/docker/docker-compose.yml b/docker/docker-compose.yml
index 9de7b71..f125b0a 100644
--- a/docker/docker-compose.yml
+++ b/docker/docker-compose.yml
@@ -4,4 +4,11 @@ services:
     container_name: "mongo"
     image: "mongo:latest"
     ports:
-     - "27017:27017"
\ No newline at end of file
+     - "27017:27017"
+    environment:
+     - "MONGO_INITDB_DATABASE=express-test"
+     - "MONGO_INITDB_ROOT_USERNAME=god"
+     - "MONGO_INITDB_ROOT_PASSWORD=P@ssword"
+    volumes:
+     - "./mongodb/docker-entrypoint-initdb.d:/docker-entrypoint-initdb.d/:ro"
+     - "./mongodb/data:/data/db"
\ No newline at end of file
diff --git a/docker/mongodb/docker-entrypoint-initdb.d/initDatabase.js b/docker/mongodb/docker-entrypoint-initdb.d/initDatabase.js
new file mode 100644
index 0000000..7aa3d49
--- /dev/null
+++ b/docker/mongodb/docker-entrypoint-initdb.d/initDatabase.js
@@ -0,0 +1,12 @@
+db.test.insert({id: 'test'});
+
+db.createUser(
+    {
+      user: "application_user",
+      pwd: "Password1",
+      roles:
+        [
+          { role: "readWrite", db: "db_application" }
+        ]
+    }
+)
\ No newline at end of file
diff --git a/src/js/controller/applicationCtrl.js b/src/js/controller/applicationCtrl.js
index d366b1c..416394d 100644
--- a/src/js/controller/applicationCtrl.js
+++ b/src/js/controller/applicationCtrl.js
@@ -1,6 +1,8 @@
 const Repository = require('../repository/repository');
-const router = require('express').Router();
+const authenticationFilter = require('../filter/authenticationFilter');
+const express = require('express');
 
+const router = express.Router();
 const applicationRepository = new Repository('applications');
 
 router.get('/', (request, response) => {
@@ -36,7 +38,7 @@ router.put('/:applicationId', (request, response) => {
     });
 });
 
-router.delete('/:applicationId', (request, response) => {
+router.delete('/:applicationId', authenticationFilter, (request, response) => {
     const applicationId = request.params.applicationId;
     applicationRepository.find({_id: applicationId}, entity => {
         if (entity.length === 0) {
diff --git a/src/js/controller/templateCtrl.js b/src/js/controller/templateCtrl.js
index 6ea9355..df9e75e 100644
--- a/src/js/controller/templateCtrl.js
+++ b/src/js/controller/templateCtrl.js
@@ -1,4 +1,3 @@
-const Repository = require('../repository/repository');
 const router = require('express').Router();
 
 // Develop routes here
diff --git a/src/js/controller/userCtrl.js b/src/js/controller/userCtrl.js
index c5cd1c7..9a2dc25 100644
--- a/src/js/controller/userCtrl.js
+++ b/src/js/controller/userCtrl.js
@@ -8,10 +8,12 @@ router.post('/login', (request, response) => {
     if (!loginRequest) {
         response.status(403).send();
     } else {
-        userService.checkCredentials(loginRequest.login, loginRequest.password, () => {
-            const tokenPayload = { login: loginRequest.login };
-            response.json(tokenService.build(tokenPayload));
-        }, () => response.status(403).send());
+        userService.checkCredentials(loginRequest.login, loginRequest.password,
+            () => {
+                const tokenPayload = { login: loginRequest.login };
+                response.json(tokenService.build(tokenPayload));
+            },
+            () => response.status(403).send());
     }
 });
 
diff --git a/src/js/filter/authenticationFilter.js b/src/js/filter/authenticationFilter.js
new file mode 100644
index 0000000..8295da5
--- /dev/null
+++ b/src/js/filter/authenticationFilter.js
@@ -0,0 +1,17 @@
+const tokenService = require('../service/tokenService');
+
+module.exports = (request, response, next) => {
+    const authenticationHeader = request.headers.authorization;
+
+    if (authenticationHeader) {
+        const token = authenticationHeader.split(' ')[1];
+        
+        if (tokenService.isValid(token)) {
+            next();
+        } else {
+            response.status(403).send();
+        }
+    } else {
+        response.status(401).send();
+    }
+};
\ No newline at end of file
diff --git a/src/js/repository/mongoClient.js b/src/js/repository/mongoClient.js
index 2024f2e..2a3bb10 100644
--- a/src/js/repository/mongoClient.js
+++ b/src/js/repository/mongoClient.js
@@ -2,9 +2,18 @@ const mongodb = require('mongodb');
 const configuration = require('../configuration');
 const mongoConfig = configuration.mongodb;
 
+function buildDatabaseUrl() {
+    const username = mongoConfig.username;
+    const password = encodeURIComponent(mongoConfig.password);
+    const url = `${mongoConfig.url}:${mongoConfig.port}`;
+    const test = `mongodb://${username}:${password}@${url}`;
+    console.log(test);
+    return test;
+}
+
 class MongoClient {
     constructor() {
-        mongodb.MongoClient.connect(mongoConfig.url, (error, client) => {
+        mongodb.MongoClient.connect(buildDatabaseUrl(), (error, client) => {
             if (error !== null) {
                 throw new Error(`Unable de connect to Mongo database: ${error}`);
             }
@@ -61,6 +70,5 @@ class MongoClient {
     }
 }
 
-// Define a singleton of class "MongoClient".
-const mongoClient = new MongoClient();
-module.exports = mongoClient;
\ No newline at end of file
+const singleton = new MongoClient();
+module.exports = singleton;
\ No newline at end of file
diff --git a/src/js/repository/repository.js b/src/js/repository/repository.js
index 44de763..a47d580 100644
--- a/src/js/repository/repository.js
+++ b/src/js/repository/repository.js
@@ -13,7 +13,7 @@ function convertIdToMongodbFormat(entity) {
 module.exports = class Repository {
     /**
      * Creates a new repository which read and write into the {@code collectionName} collection in database.
-     * @param {*} collectionName 
+     * @param {String} collectionName 
      */
     constructor(collectionName) {
         this.collectionName = collectionName;
@@ -22,8 +22,9 @@ module.exports = class Repository {
 
     /**
      * Returns the entities that matches criteria in {@code query}.
-     * @param {*} query The query which contains criteria to find some entities.
-     * @param {*} onSuccess The function to execute after getting entities.
+     * @param {Object} query The query which contains criteria to find some entities.
+     * @param {Function} onSuccess The function to execute after getting entities.
+     * @param {Function} onError  The function to execute if entity finding failed.
      */
     find(query, onSuccess, onError) {
         convertIdToMongodbFormat(query);
diff --git a/src/js/service/passwordService.js b/src/js/service/passwordService.js
index 397c8ed..3d3c902 100644
--- a/src/js/service/passwordService.js
+++ b/src/js/service/passwordService.js
@@ -2,11 +2,22 @@ const bcrypt = require('bcrypt');
 const saltRounds = 10;
 
 class PasswordService {
+    /**
+     * Hashes the password in parameters.
+     * @param {String} password The plain text password.
+     * @returns The hashed password.
+     */
     hashPassword(password) {
         const salt = bcrypt.genSaltSync(saltRounds);
         return bcrypt.hashSync(password, salt);
     }
 
+    /**
+     * Checks if the {@code plainTextPassword} matches the hashed password.
+     * @param {String} plainTextPassword The plain text password.
+     * @param {String} hashedPassword The hashed password.
+     * @returns A boolean.
+     */
     areSamePasswords(plainTextPassword, hashedPassword) {
         return bcrypt.compareSync(plainTextPassword, hashedPassword);
     }
diff --git a/src/js/service/tokenService.js b/src/js/service/tokenService.js
index 5160ec9..17180d9 100644
--- a/src/js/service/tokenService.js
+++ b/src/js/service/tokenService.js
@@ -3,10 +3,20 @@ const configuration = require('../configuration');
 const securityConfig = configuration.security;
 
 class TokenService {
+    /**
+     * Builds a JWT token.
+     * @param {Object} tokenPayload The JWT payload.
+     * @returns {String} The JWT token.
+     */
     build(tokenPayload) {
         return jwt.sign(tokenPayload, securityConfig.jwt.secret, {expiresIn: securityConfig.jwt.validity});
     }
 
+    /**
+     * Checks if the given token is valid, and provides from this application or not.
+     * @param {String} token The JWT token to check.
+     * @returns A boolean.
+     */
     isValid(token) {
         try {
             jwt.verify(token, securityConfig.jwt.secret);
@@ -17,5 +27,5 @@ class TokenService {
     }
 }
 
-const jwtInstance = new TokenService();
-module.exports = jwtInstance;
\ No newline at end of file
+const singleton = new TokenService();
+module.exports = singleton;
\ No newline at end of file
diff --git a/src/js/service/userService.js b/src/js/service/userService.js
index d8cfdb6..b8c5a95 100644
--- a/src/js/service/userService.js
+++ b/src/js/service/userService.js
@@ -15,14 +15,7 @@ class UserService {
     }
 
     /**
-     * 
-     */
-    isAuthenticated() {
-        return false;
-    }
-
-    /**
-     * 
+     * Checks if credentials matches to an existing user, that have this password.
      * @param {String} login User login.
      * @param {String} password User password, in plain text.
      * @param {Function} onSuccess Callback function to execute if a user exists with this login.
diff --git a/src/mongodb/initDatabase.js b/src/mongodb/initDatabase.js
deleted file mode 100644
index 1675e61..0000000
--- a/src/mongodb/initDatabase.js
+++ /dev/null
@@ -1,14 +0,0 @@
-use express-test;
-
-db.collection.test.insert({id: 'test'});
-
-db.createUser(
-    {
-      user: "express-user",
-      pwd: "P@ssword1",
-      roles:
-        [
-          { role: "readWrite", db: "express-test" }
-        ]
-    }
-)
\ No newline at end of file
diff --git a/src/resources/application.yml b/src/resources/application.yml
index ce52fa2..f189a13 100644
--- a/src/resources/application.yml
+++ b/src/resources/application.yml
@@ -1,8 +1,9 @@
 mongodb:
-  url: 'mongodb://localhost:27017'
-  username: 'express-user'
-  password: 'P@ssword1'
-  database: 'express-test'
+  url: 'localhost'
+  port: 27017
+  username: 'application_user'
+  password: 'Password1'
+  database: 'db_application'
 security:
   jwt:
     secret: 5ubtcCCo7hWBqjNGtzzVKnLT1KxN9uS4D6kRZowCunZAYPmxtKy6mvgoxANe4WqLVfiVI7AZSVqZCtvlSWFwIsnXGH6lxeKG0U8Wu7Kw0jwfFOGLvlO8bXaB