根据 MongoDB 的 Web APP(建为 Heroku)-PART 1

最前言

眼看是自及学期写的章,算是教程,最初发在我自己之网站齐,其实还该算是学习笔记吧,因为小代码我啊得回看一样肉眼才能够想起来。从太基础之
MongoDB 的 Shell 端开始学习,然后上 Web 开发,然后做了只非常简单的
Demo, 基于 MongoDB, Java, Heroku, SparkAngularJS
Web
App
。因为都是因此英文学的,学校里同人交流为是故英文,所以就就此英文写了,但自我最近勾勒的
Swift 学习之几乎片文章都是华语的,我理解你们都非爱看英文 🙂
但这有限首实在是无心再翻成汉语了。。。所以本着 MongoDB
有趣味之童鞋就用就看吧。

Foreword

Sometimes you spend tons and tons of time just looking for one method or
function or even one simple syntax, but with no result.

Suddenly, you get the answer, and it is on a very common webpage.

“WTF, this is a fking waste of time! Why can’t I find it earlier,
instead of suffering so much pain?!”

I don’t know. Maybe this is exactly the difficulty that stops most
people becoming a good engineer. You know, I am still struggling on this
way. However, when I write the post, I am happy.

Now, let’s get started with our project.)

Add a MongoDB to your Heroku application

First, we need to add a MongoDB database to your Heroku application.
There are two choices, Compose MongoDB and mLab MongoDB. Compose MongoDB
has no free plan, whereas mLab has a free plan – sandbox. Here I use
Compose MongoDB.

To add a Compose database to your Heroku application (using your
console):

$ heroku addons:create mongohq:ssd_1g_elastic 

To add a mLab MongoDB (free plan):

$ heroku addons:create mongolab

Use the heroku config command to view your app’s config variables. The
URL contains all the MongoDB connection information you will need to
connect to your database.

$ heroku config | grep MONGOHQ_URL

Now, you can use the MONGOHQ_URL variable in code and configurations
for your driver, depending on the language you app is created in,
connecting and authenticating to your MongoDB database hosted with
Compose.

Use with Java

==NOTE==: The syntaxes between 2.x and 3.x are very different. If you
don’t want to waste a lot of time like me, please make it clear what
version of mongo-java-driver you are using.

Add the Mongo Java driver to your pom.xml

<dependency>
    <groupId>org.mongodb</groupId>
    <artifactId>mongo-java-driver</artifactId>
    <version>3.2.2</version>
</dependency>

And this is apache.maven.plugin:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.5.1</version>
    <configuration>
        <source>1.8</source>
        <target>1.8</target>
    </configuration>
</plugin>

Use MongoDB in your application

    MongoURI mongoURI = new MongoURI(System.getenv("MONGOHQ_URL"));
    //get connected
    DB db = mongoURI.connectDB();
    // authenticate
    // (version 2.7.2) db.authenticate(mongoURI.getUsername(), mongoURI.getPassword());
    MongoCredential credential = MongoCredential.createCredential(mongoURI.getUsername(), mongoURI.getDatabase(), mongoURI.getPassword());
    MongoClient mongoClient = new MongoClient(new ServerAddress(), Arrays.asList(credential));

Setting Write Concern

mongoClient.setWriteConcern(WriteConcern.JOURNALED);

As of version 2.10.0, the default write concern is
WriteConcern.ACKNOWLEDGED, but it can be easily changed.

Use MongoDB with
Spring.

And here is a sample
code.
(==Note==: this sample is under 2.7.2 version, now the newest is 3.2.2
which I am using)

==Note:== Java MongoDB driver provides its own connection pooling by
default, and it’s thread safe. See the details in the
docs.

CRUD

Get collection names. (like show databases):

Set<String> colls = db.getCollectionNames();
System.out.println("Collections found in DB: " + colls.toString());

Get a collection (for CRUD):

DBCollection coll = db.getCollection("testCollection");

Let’s assume a json dataset like this:

{
“name” : “MongoDB”,
“type” : “database”,
“count” : 1,
“info” : {x : 203, y : 102}
}

To insert this dataset into MongoDB, there are two ways shown bellow. I
prefer using .append.

BasicDBObject doc = new BasicDBObject("name", "MongoDB")
    .append("type", "database")
    .append("count", 1)
    .append("info", new BasicDBObject("x", 204).append("y", 103));
    coll.insert(doc);

Another way to insert data.

     BasicDBObject doc = new BasicDBObject();

     doc.put(“name”, “MongoDB”);
     doc.put(“type”, “database”);
     doc.put(“count”, 1);

     BasicDBObject info = new BasicDBObject();

     info.put(“x”, 203);
     info.put(“y”, 102);

     doc.put(“info”, info);

     coll.insert(doc);

Get the first document:

DBObject myDoc = coll.findOne();
System.out.println(myDoc);

Get the total amount of documents:

System.out.println(coll.getCount());

Using a Cursor to Get All the Documents:

DBCursor cursor = coll.find();
try {
while(cursor.hasNext()) {
System.out.println(cursor.next());
}
} finally {
cursor.close();
}

Getting A Single Document with A Query:

BasicDBObject query = new BasicDBObject("name", "MongoDB");

DBCursor cursor = coll.find(query);

try {
    while(cursor.hasNext()) {
        System.out.println(cursor.next());
    }
} finally {
    cursor.close();
}

You may know this kind of statement, which is in shell:

$ db.things.find({j: {$ne: 3}, k: {$gt: 10} });

You can implement in the java driver, using embedded DBObjects:

query = new BasicDBObject("j", new BasicDBObject("$ne", 3))
    .append("k", new BasicDBObject("$gt", 10));

cursor = coll.find(query);

try {
while(cursor.hasNext()) {
    System.out.println(cursor.next());
}
} finally {
cursor.close();
}

Create index list:

//create index,1 for ascending,-1 for descending
coll.createIndex("name"); //Forces creation of an ascending index on a field with the default options.
//get the index list
List<DBObject> list = coll.getIndexInfo();
for (DBObject o : list) {
System.out.println(o);
}

See more methods of DBCollection please refer to this
docs.
You can also find other index types there.


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