diff --git a/src/js/controller/applicationCtrl.js b/src/js/controller/applicationCtrl.js
index 92e3f2c..d366b1c 100644
--- a/src/js/controller/applicationCtrl.js
+++ b/src/js/controller/applicationCtrl.js
@@ -1,4 +1,3 @@
-const ObjectId = require('mongodb').ObjectId;
 const Repository = require('../repository/repository');
 const router = require('express').Router();
 
@@ -10,6 +9,12 @@ router.get('/', (request, response) => {
     });
 });
 
+router.get('/:applicationId', (request, response) => {
+    applicationRepository.find({_id: request.params.applicationId}, (result) => {
+        response.json(result[0]);
+    });
+});
+
 router.post('/', (request, response) => {
     applicationRepository.insert(request.body, (result) => {
         response.json(result);
@@ -17,7 +22,7 @@ router.post('/', (request, response) => {
 });
 
 router.put('/:applicationId', (request, response) => {
-    const applicationId = ObjectId(request.params.applicationId);
+    const applicationId = request.params.applicationId;
     applicationRepository.find({_id: applicationId}, entity => {
         if (entity.length === 0) {
             response.status(404).send();
@@ -32,7 +37,7 @@ router.put('/:applicationId', (request, response) => {
 });
 
 router.delete('/:applicationId', (request, response) => {
-    const applicationId = ObjectId(request.params.applicationId);
+    const applicationId = request.params.applicationId;
     applicationRepository.find({_id: applicationId}, entity => {
         if (entity.length === 0) {
             response.status(404).send();
diff --git a/src/js/controller/templateCtrl.js b/src/js/controller/templateCtrl.js
new file mode 100644
index 0000000..6ea9355
--- /dev/null
+++ b/src/js/controller/templateCtrl.js
@@ -0,0 +1,6 @@
+const Repository = require('../repository/repository');
+const router = require('express').Router();
+
+// Develop routes here
+
+module.exports = router;
\ No newline at end of file
diff --git a/src/js/repository/mongoClient.js b/src/js/repository/mongoClient.js
index cb20689..dddbb54 100644
--- a/src/js/repository/mongoClient.js
+++ b/src/js/repository/mongoClient.js
@@ -1,13 +1,15 @@
 const mongodb = require('mongodb');
-const assert = require('assert');
-
 const configuration = require('../configuration');
 const mongoConfig = configuration.database;
 
 class MongoClient {
     constructor() {
         mongodb.MongoClient.connect(mongoConfig.url, (error, client) => {
-            assert.equal(null, error, `Unable to connect to mongodb: ${error}.`);
+            console.log(error);
+            if (error !== null) {
+                throw new Error(`Unable de connect to Mongo database: ${error}`);
+            }
+
             console.log('Connected successfuly to mongodb');
             this.db = client.db(mongoConfig.database);
         });
@@ -19,12 +21,17 @@ class MongoClient {
                 console.log(`Entities ${collectionName} founded.`);
                 callback(results);
             })
-            .catch(error => console.error(error));
+            .catch(error => {
+                throw new Error(`Unable to find entities in collection ${collectionName}: ${error}`);
+            });
     }
 
     insert(collectionName, entity, callback) {
-        this.db.collection(collectionName).insert(entity, (error, result) => {
-            assert.equal(null, error, `Unable to insert ${collectionName} entity: ${error}.`);
+        this.db.collection(collectionName).insertOne(entity, (error, result) => {
+            if (error !== null) {
+                throw new Error(`Unable to insert ${collectionName} entity: ${error}`);
+            }
+            
             console.log(`Entity ${collectionName} inserted.`);
             // Return only the inserted document.
             callback(result.ops[0]);
@@ -32,8 +39,11 @@ class MongoClient {
     }
 
     update(collectionName, entity, callback) {
-        this.db.collection(collectionName).save(entity, (error) => {
-            assert.equal(null, error, `Unable to update ${collectionName} entity: ${error}.`);
+        this.db.collection(collectionName).updateOne({_id: mongodb.ObjectId(entity._id)}, {$set: entity}, {upsert: true}, (error) => {
+            if (error !== null) {
+                throw new Error(`Unable to update ${collectionName} entity: ${error}`);
+            }
+
             console.log(`Entity ${collectionName} updated.`);
             callback();
         });
@@ -41,12 +51,16 @@ class MongoClient {
 
     delete(collectionName, entityId, callback) {
         this.db.collection(collectionName).deleteOne({_id: mongodb.ObjectId(entityId)}, (error) => {
-            assert.equal(null, error, `Unable to delete ${collectionName} entity with id ${entityId}: ${error}.`);
+            if (error !== null) {
+                throw new Error(`Unable to delete ${collectionName} entity with id ${entityId}: ${error}`);
+            }
+
             console.log(`Entity ${collectionName} with id ${entityId} deleted.`);
             callback();
         });
     }
 }
 
+// Define a singleton of class "MongoClient".
 const mongoClient = new MongoClient();
 module.exports = mongoClient;
\ No newline at end of file
diff --git a/src/js/repository/repository.js b/src/js/repository/repository.js
index 06e7320..f17bf90 100644
--- a/src/js/repository/repository.js
+++ b/src/js/repository/repository.js
@@ -1,26 +1,63 @@
 const mongoClient = require('./mongoClient');
+const ObjectId = require('mongodb').ObjectId;
 
-class Repository {
+/**
+ * If entity in parameters has an attribute named "_id", this function converts it into a MongoDB {@code ObjectId}.
+ */
+function convertIdToMongodbFormat(entity) {
+    if (!!entity._id && !(entity._id instanceof ObjectId)) {
+        entity._id = ObjectId(entity._id);
+    }
+}
+
+module.exports = class Repository {
+    /**
+     * Creates a new repository which read and write into the {@code collectionName} collection in database.
+     * @param {*} collectionName 
+     */
     constructor(collectionName) {
         this.collectionName = collectionName;
         this.mongoClient = mongoClient;
     }
 
+    /**
+     * Returns the entities that matches criteria in {@code query}.
+     * @param {*} query The query which contains criteria to find some entities.
+     * @param {*} callback The function to execute after getting entities.
+     */
     find(query, callback) {
+        convertIdToMongodbFormat(query);
         this.mongoClient.find(this.collectionName, query, callback);
     }
 
+    /**
+     * Insert entity in database.
+     * @param {*} entity The entity to insert into database.
+     * @param {*} callback The function to execute after inserting entity.
+     */
     insert(entity, callback) {
         this.mongoClient.insert(this.collectionName, entity, callback);
     }
 
+    /**
+     * Update the whole entity in database.
+     * @param {*} entity The entity to update into database.
+     * @param {*} callback The function to execute after updating entity.
+     */
     update(entity, callback) {
+        convertIdToMongodbFormat(entity);
         this.mongoClient.update(this.collectionName, entity, callback);
     }
 
+    /**
+     * Delete entity in database.
+     * @param {*} entityId Entity to delete id.
+     * @param {*} callback The function to execute after deleting entity.
+     */
     delete(entityId, callback) {
+        if (!(entityId instanceof ObjectId)) {
+            entityId = ObjectId(entityId);
+        }
         this.mongoClient.delete(this.collectionName, entityId, callback);
     }
-}
-
-module.exports = Repository;
\ No newline at end of file
+};
\ No newline at end of file