import com.mongodb.*;

import java.sql.Date;

import java.util.ArrayList;

public class ArticleMongoDao<T extends Article> implements ArticleDbService<T> {

// A collection in Mongo can be thought of as a table in a relational DB

private DBCollection collection;

public ArticleMongoDao() {

try {

// Connect to MongoDB using the default port on your local machine

MongoClient mongoClient = new MongoClient("localhost");

// Note that the sparkledb will not actually be created until we save a document

DB db = mongoClient.getDB("sparkledb");

collection = db.getCollection("Articles");

System.out.println("Connecting to MongoDB@" + mongoClient.getAllAddress());

} catch(Exception e) {

System.out.println(e.getMessage());

}

}

@Override

public Boolean create(T entity) {

// MongoDB is a document store which by default has no concept of a schema so its

// entirely up to the developer to decide which attributes a document will use

BasicDBObject doc = new BasicDBObject("title", entity.getTitle()).

append("id", entity.getId()).

append("content", entity.getContent()).

append("summary", entity.getSummary()).

append("deleted", false).

append("createdAt", new Date(new java.util.Date().getTime()));

// As soon as we insert a doucment into our collection MongoDB will craete our sparkle database and

// Article collection within it.

collection.insert(doc);

return true;

}

@Override

@SuppressWarnings("unchecked")

public T readOne(int id) {

// MongoDB queries are not queries in the sense that you have a separate language such as SQL

// With MongoDB you can think of it as Document pattern matching

// Thus we construct a document with a specific id value and ask Mongo to search our Article

// collection for all documents which match

BasicDBObject query = new BasicDBObject("id", id);

// Cursors are the default representation of Mongo query result

// Think of cursors as a pointer to a array of documents

// It can traverse the array of documents and when requested can dereference and pull out the contents

// But at any given time it only takes up enough memory needed to maintain the reference of the data type it points to

// MongoDB was written in C++ so an analogy to the C language is probably how Cursors were implemented

// A technical presentation by Dwight Merriman co-founder of 10gen the company that makes MongoDB

// @see http://www.mongodb.com/presentations/mongodb-internals-tour-source-code

// Watch that shit... best technical deep-dive of MongoDB ever!

DBCursor cursor = collection.find(query);

try {

if(cursor.hasNext()) {

BasicDBObject doc = (BasicDBObject) cursor.next();

Article entity = new Article(

doc.getString("title"),

doc.getString("summary"),

doc.getString("content"),

doc.getInt("id"),

doc.getDate("createdAt"),

doc.getBoolean("deleted")

);

return (T) entity;

} else {

return null;

}

} finally {

cursor.close();

}

}

@Override

@SuppressWarnings("unchecked")

public ArrayList<T> readAll() {

// When you use DBCollection::find() without an argument it defaults to find all

DBCursor cursor = collection.find();

ArrayList<Article> results = (ArrayList<Article>) new ArrayList<T>();

try {

while(cursor.hasNext()) {

BasicDBObject doc = (BasicDBObject) cursor.next();

Article entity = new Article(

doc.getString("title"),

doc.getString("summary"),

doc.getString("content"),

doc.getInt("id"),

doc.getDate("createdAt"),

doc.getBoolean("deleted")

);

results.add(entity);

}

return (ArrayList<T>) results;

} finally {

cursor.close();

}

}

@Override

public Boolean update(int id, String title, String summary, String content) {

// NOTE: MongoDB also allow us to do SQL style updates by specifying update conditions

// within our query document. It requires a much deeper knowledge of MongoDB but for now

// we can stick with the less performant(two operations versus one) find() and put() style of updating

BasicDBObject query = new BasicDBObject("id", id);

DBCursor cursor = collection.find(query);

try {

if(cursor.hasNext()) {

BasicDBObject doc = (BasicDBObject) cursor.next();

// BasicDBObject::put() allows us to update a document in-place

doc.put("title", title);

doc.put("summary", summary);

doc.put("content", content);

collection.save(doc);

return true;

} else {

return false;

}

} finally {

cursor.close();

}

}

@Override

public Boolean delete(int id) {

BasicDBObject query = new BasicDBObject("id", id);

DBCursor cursor = collection.find(query);

try {

if(cursor.hasNext()) {

// Deleting works by telling the cursor to free the document currently being pointed at

collection.remove(cursor.next());

return true;

} else {

return false;

}

} finally {

cursor.close();

}

}

}