Persistent Objects using JDO

Aim: Design Persistent Objects using JDO and implement min 10 queries on objects using JDOQL in ObjectDB NOSQL DATABASE

Procedure:

First install and configure Cassandra from http://www.professionalcipher.com/2018/03/installation-of-nosql-database-cassandra.html

#Start Cassandra Daemons

~/cassandra/bin/cassandra -f

# The cassandra daemon should start in the foreground
#(don’t press ctrl + c; as it’ll terminate the daemon)

#Now open a new terminal

~/cassandra/bin/cqlsh

#Create a keyspace
cqlsh> CREATE KEYSPACE keyspace1 WITH REPLICATION = { 'class' : 'SimpleStrategy', 'replication_factor' : 1 };
cqlsh> USE keyspace1

#Now open Eclipse

# Install DataNucleus plugin In Eclipse

Go to Help
Install new software
Add
Set name as DataNucleus
Set Location as http://www.datanucleus.org/downloads/eclipse-update/
ok

#After searching the plugin on internet, it will display one checkbox “DataNucleus Eclipse plugin”

Check the checkbox
Next
Next
I accept
Finish
Ignore the warning (if any)
Restart eclipse
yes

# Download DataNucleus AccessPlatform from http://sourceforge.net/projects/datanucleus/files/datanucleus-accessplatform/4.2.3/datanucleus-accessplatform-cassandra-4.2.3.zip/download

# Extract the downloaded zip file
When you open the zip you will find DataNucleus jars files in the lib directory, and dependency jars in the deps directory.

# From the lib directory copy all jar files except following
datanucleus-jodatime-4.1.1.jar
datanucleus-java8-4.2.1.jar
datanucleus-guava-4.1.3.jar

# In eclipse -> right click on project exp6 -> Paste
# One by one, right click on pasted jar file -> Build path -> add to build path
# Add all pasted jar files to build path

# Similarly from the deps folder copy all jar files
# Once again In eclipse -> right click on project exp6 -> Paste
# One by one, right click on pasted jar file -> Build path -> add to build path
# Add all pasted jar files to build path

# In eclipse -> Create a new class - > Product -> add following code in it


package exp6;

import javax.jdo.annotations.IdGeneratorStrategy;
import javax.jdo.annotations.PersistenceCapable;
import javax.jdo.annotations.Persistent;
import javax.jdo.annotations.PrimaryKey;

@PersistenceCapable
public class Product
{
 @PrimaryKey
 @Persistent (valueStrategy=IdGeneratorStrategy.INCREMENT)
 long id;
    String name = null;
    String description = null;
    double price = 0.0;
    public Product(String name, String desc,double price)
    {
     this.name = name;
     this.description = desc;
     this.price = price;
    }
}

# save the file

# In eclipse -> Create a new class - > Book -> add following code in it


package exp6;
import javax.jdo.annotations.PersistenceCapable;

@PersistenceCapable
public class Book extends Product
{   
 String author=null;
 String isbn=null;
 String publisher=null;
 public Book(String name, String desc,double price, String author,String isbn, String publisher)
 {
  super(name,desc,price);
  this.author=author;
  this.isbn=isbn;
  this.publisher=publisher;
 }
}

# In eclipse -> Create a new class - > Inventory -> add following code in it


package exp6;
import java.util.HashSet;
import java.util.Set;
import javax.jdo.annotations.PersistenceCapable;
import javax.jdo.annotations.PrimaryKey;

@PersistenceCapable 
public class Inventory
{
 @PrimaryKey
 String name=null;
 @SuppressWarnings({"rawtypes","unchecked"})Set<Product>products=new HashSet();
 
 public Inventory(String name)
 {
  this.name=name;
 }
 public Set<Product> getProducts() 
 {
  return products;
 }
}

# In eclipse -> Create a new class - > MyApp -> add following code in it


package exp6;
import java.util.Iterator;
import java.util.List;
import javax.jdo.JDOHelper;
import javax.jdo.PersistenceManager;
import javax.jdo.PersistenceManagerFactory;
import javax.jdo.Query;
import javax.jdo.Transaction;
public class MyApp {
public static void main(String[] args)
{//TEST is the persistent unit name
PersistenceManagerFactory pmf = 
JDOHelper.getPersistenceManagerFactory("TEST");
PersistenceManager pm = pmf.getPersistenceManager();
Transaction tx=pm.currentTransaction();
try
{
    tx.begin();
    Inventory inv = new Inventory("My Inventory");
    Product product = new Product("Sony Discman", "A standard discman from Sony", 49.99);
    Product product1 = new Product("Sony xperia z1", "A smart phone", 149.99);
    inv.getProducts().add(product);
    inv.getProducts().add(product1);
    pm.makePersistent(inv);
    Query q = pm.newQuery("SELECT FROM " + Product.class.getName() + " WHERE price < 150.00 ORDER BY price ASC");
// add some more JDOQL queries here
    List<Product> products = (List<Product>)q.execute();
    Iterator<Product> iter = products.iterator();
    while (iter.hasNext())
{
Product p = iter.next();
System.out.println("Name: "+p.name+"\t Description: "+p.description+"\tPrice: "+p.price);
}
    tx.commit();
}
finally
{
    if (tx.isActive())
    {
        tx.rollback();
    }
    pm.close();
}
}
}

# save the file

# Plugin configuration

Right click on exp6 project
Properties
DataNucleus
check “ Enable project specific settings ”
Add JARS
add all 18 jar files ( 10 from lib folder, 8 from deps folder)
apply
ok

# Plugin configuration – Enhancer

Right click on exp6 project
Properties
double click on DataNucleus
Enhancer
check “ Enable project specific settings ”
check verbose mode
check Capture Output
Give persistence-unit name -> TEST

# Plugin configuration – SchemaTool

Right click on exp6 project
Properties
Under DataNucleus
SchemaTool
check “ Enable project specific settings ”
check verbose mode
Give persistence-unit name -> TEST

# Right-click project exp6 -> select DataNucleus ->" Add DataNucleus Support "

# Right-click on package exp6 -> DataNucleus -> select " Create JDO XML Metadata File " -> Give Filename-> package.jdo -> finish

# Right-click on package exp6 -> DataNucleus -> select " Create persistence.xml file ”

# Edit persistence.xml file


<?xml version="1.0" encoding="UTF-8" ?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd" version="1.0">

    <persistence-unit name="TEST">
        <mapping-file>/home/huzaif/eclipse-workspace/exp6/src/exp6/package.jdo</mapping-file>
        
        <properties>
   <property name = "javax.jdo.option.ConnectionURL" value = "cassandra:" />
   <property name = "javax.jdo.mapping.Schema" value = "keyspace1" />
   <property name = "datanucleus.schema.autoCreateAll" value = "true" />
 </properties>
  
    </persistence-unit>
</persistence>

# Save the file

# Download the cassandra-java driver from http://downloads.datastax.com/java-driver/cassandra-java-driver-2.0.2.tar.gz

# Extract the downloaded file.
# Paste all jar files (total 12) from the extracted folder into your eclipse project (Note :: 10 jar files are present under lib folder)

# In eclipse -> One by one, right click on pasted jar file -> Build path -> add to build path
# Add all pasted jar files to the build path

# DONE!!! Right-click on project exp6 -> DataNucleus-> select " Run Enhancer tool "

OUTPUT:

ENHANCED (Persistable) : exp6.Inventory
ENHANCED (Persistable) : exp6.Book
ENHANCED (Persistable) : exp6.Product
DataNucleus Enhancer completed with success for 3 classes. Timings : input=101 ms, enhance=74 ms, total=175 ms. Consult the log for full details

# Make sure that cassandra is running before doing next step

# Right-click on project exp6 -> DataNucleus-> select " Run Schema tool " -> Set Connection URL -> cassandra: -> next -> finish
OUTPUT:

DataNucleus SchemaTool : Input Files
>>  /home/huzaif/eclipse-workspace/exp6/bin/exp6/Book.class
>>  /home/huzaif/eclipse-workspace/exp6/bin/exp6/Inventory.class
>>  /home/huzaif/eclipse-workspace/exp6/bin/exp6/MyApp.class
>>  /home/huzaif/eclipse-workspace/exp6/bin/exp6/Product.class
>>  /home/huzaif/eclipse-workspace/exp6/bin/exp6/package.jdo
>>  /home/huzaif/eclipse-workspace/exp6/src/exp6/package.jdo

# Right click on MyApp.java -> Run as -> Java Application
OUTPUT:

log4j:WARN No appenders could be found for logger (DataNucleus.General).
log4j:WARN Please initialize the log4j system properly.
Name: Sony Discman  Description: A standard discman from Sony Price: 49.99
Name: Sony xperia z1  Description: A smart phone Price: 149.99

# In cqlsh prompt, verify the output
cqlsh>SELECT * FROM Product;
OUTPUT:

cqlsh:keyspace1> select * from product;

 id | description                  | name           | price
----+------------------------------+----------------+--------
  0 | A standard discman from Sony |   Sony Discman |  49.99
  1 |                A smart phone | Sony xperia z1 | 149.99

(2 rows)
cqlsh:keyspace1>

# Now edit MyApp.java to add some more JDOQL queries one by one ( minimum 10 are expected)

# Then, Run MyApp.java

# Verify the output in cqlsh prompt by using SELECT query.

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