javadevelopmentwithmongodb1-100430175419-phpapp02

7/29/2019 javadevelopmentwithmongodb1-100430175419-phpapp02

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Java Development withMongoDBJames Williams

Software Engineer, BT/Ribbit


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Agenda

Java Driver basicsMaking ConnectionsManaging CollectionsBasicDBObjectBuilder

Document QueriesGridFS

MorphiaBeyond the Java language

Groovy utilitiesGrails plugin


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Making a Connection

import com.mongodb.Mongo;

import com.mongodb.DB;

Mongo m = new Mongo();

Mongo m = new Mongo( "localhost" );Mongo m = new Mongo( "localhost" , 27017 );

DB db = m.getDB( "mydb" );


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Working with Collections

Getting all collections in the databaseSet colls = db.getCollectionNames();

for (String s : colls) {

System.out.println(s);

}Getting a single collection

DBCollection coll = db.getCollection("testCollection")


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Inserting Documents

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);


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BasicDBObjectBuilder

Utility for building objectsCan coerce Maps (and possibly JSON*) to DBObjectsExample:

BasicDBObjectBuilder.start()

.add( "name" , "eliot" )

.add( "number" , 17 )

.get();


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Document Queries

DBObject myDoc = coll.findOne();

// can also use

BasicDBObject query = new BasicDBObject(); query.put("i", 71);

DBCursor cur = coll.find(query);


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GridFS

mechanism for storing files larger than 4MBfiles are chunked allowing fetching of a portion or out oforderchunking is mostly transparent to underlying operating

systemcan store files in buckets, a MongoDB metaphor for foldersdefault is the fs bucket


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Saving a file to GridFS

def mongo = new Mongo(host)

def gridfs = new GridFS(mongo.getDB("db"))

def save(inputStream, contentType, filename) {def inputFile = gridfs.createFile(inputStream)inputFile.setContentType(contentType)inputFile.setFilename(filename)inputFile.save()

}


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Retrieving/Deleting a file

def retrieveFile(String filename) {

return gridfs.findOne(filename)

}

def deleteFile(String filename) {

gridfs.remove(filename)

}


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Morphia

Apache 2 Licensedbrings Hibernate/JPA paradigms to MongoDBallows annotating of POJOs to make converting thembetween MongoDB and Java very easy

supports DAO abstractionsoffers type-safe query supportcompatible with GWT, Guice, Spring, and DI frameworks


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Morphia Annotations

@Id@Entity@Embedded@Reference

@Indexed@Serialized@Property


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Creating a Morphia POJO

import com.google.code.morphia.annotations.*;

@Entity("collectionName")

public class Contact {

@Id

private String id; //generated by MongoDB

private String firstName;

private String lastName;

@Embedded

private List phoneNumbers;

// getters and setters

}


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Mapping a POJO to a Mongo doc

Morphia morphia = ...;

Mongo mongo = ...;

DB db = mongo.getDB("contacts");

Contact contact = ...;

// map the contact to a DBObject

DBObject contactObj = morphia.toDBObject(contact);

db.getCollection("personal").save(contactObj);


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Getting a POJO from a Mongo doc

Morphia morphia = ...;

Mongo mongo = ...;

DB db = mongo.getDB("contacts");

String contactId = ...;

//load the object from the collection

BasicDBObject idObj = new BasicDBObject(

"_id", new ObjectId(contactId)

);

BasicDBObject obj = (BasicDBObject)

db.getCollection("personal").findOne(idObj);

Contact contact = morphia.fromDBObject(Contact.class, obj);


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DAOs

Encapsulate saving and retrieving objectsAuto-converts to and from POJOsCan provide constraints on searchesKey functions:

get()find() or find(constraints)findOne(constraints)deleteById()


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DAO Example

import com.mongodb.Mongo

import com.google.code.morphia.*

class EntryDAO extends DAO {

public EntryDAO(Morphia morphia, Mongo mongo) {

super(mongo, morphia, "entries")

}

}


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Constraints Examples

dao.find(new Constraints() .

orderByDesc("dateCreated")

).asList()

dao.find(new Constraints()

.field("dateCreated").greaterThanOrEqualTo(date).field("title").

equalTo(params.title)

).asList()


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Beyond the Java Language


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MongoDB with Groovy

Metaprogramming with MongoDB can reduce LOCDynamic findersFluent interface mirroring Ruby and Python


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Groovy + MongoDB

JavaBasicDBObject doc = new BasicDBObject();

doc.put("name", "MongoDB");

doc.put("type", "database");

doc.put("count", 1);

coll.insert(doc);

Groovierdef doc = [name:"MongoDB",type:"database", count:1, info:

[x:203, y:102] ] as BasicDBObject

coll.insert(doc)

Grooviest (using groovy-mongo)coll.insert([name:"MongoDB", type:"database", info: [x:203, y:102]])


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Dynamic Finders

can build complex queries at runtimecan even reach into objects for addition query parameters

Ex. collection.findByAuthorAndPostCreatedGreaterThan(...)

collection.findByComments_CreatedOn(...)


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How dynamic finders work

Groovy receives the request for the methodThe method is not found (invoking methodMissing)The method name used to construct a query templateThe method is cached

The method is invoked with the parametersFuture invocations use the cached method


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MongoDB Grails Plugin

Replaces JDBC layer in Grails applicationsCan use dynamic findersRequires only slight modifications to domain classeshttp://github.com/mpriatel/mongodb-grails
http://github.com/mpriatel/mongodb-grails


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Links

Personal Blog: http://jameswilliams.be/blogTwitter: http://twitter.com/ecspike

Morphia: http://code.google.com/p/morphia

Utilities for Groovy: http://github.com/jwill/groovy-mongoMongoDB Grails plugin: http://github.com/mpriatel/mongodb-grails
http://github.com/mpriatel/mongodb-grailshttp://github.com/mpriatel/mongodb-grailshttp://github.com/mpriatel/mongodb-grailshttp://github.com/jwill/groovy-mongohttp://github.com/jwill/groovy-mongohttp://code.google.com/p/morphiahttp://github.com/mpriatel/mongodb-grailshttp://github.com/mpriatel/mongodb-grailshttp://github.com/jwill/groovy-mongohttp://code.google.com/p/morphiahttp://twitter.com/ecspikehttp://jameswilliams.be/blog