Database for Objects -DB4O

db4o (database for objects) is an embeddable open source object database for Java and .NET developers.

db4o represents an object-oriented database model.

db4o does not require a separate data model creation, the application’s class model defines the structure of the data in db4o database.

Features:

• One-line-of-code database
• Embeddable
• Client-server mode
• Dynamic schema evolution
• Native Queries 

Advantages:

• 40% faster to market with your application.

• Full ACID transactional capabilities.

• Slashes 40% of cost to develop persistence.

• Deployable in large volumes without local administration.

• Build asynchronously-distributed, fully synchronized data architectures.

• Fewer errors, better maintainability and software longevity.

Drawbacks:

• Lack of full-text indexing, poor performance on full-text search.
• Lack of Indexing for string types, text based searches can potentially be very slow
• Replication cannot be done administratively—i.e. one needs to program an application to achieve replication.
• Deleted fields are never removed but just hidden until the next Defrag.
• There is no built-in support to import/export data to/from text, XML or JSON files.
• Support of Unique constraints and cascaded operation is partially incomplete and highly immature

Eliminate Mapping Complexity

• Using relational DB, the difficulty comes from the fact that the schema in the database does not match your application schema and you're forced to bridge that gap.

• With an object database like db4o your application schema IS your data schema, no mapping required, no extra work - which translates into ease of use and higher performance!

Java Sample Code:

Model Class:

public class Pilot {
   private String name;
   private int points;
   private List<String> address ;
   private Map<String,String> addressMap ;
   

public Pilot(String name, int points,List<String> address,Map<String,String> addressMap) {

       this.name = name;

       this.points = points;

       this.address = address;

       this.addressMap = addressMap;

       }
   
      //Getter and Setter Methods
}

Access DB4O database:

public static void accessDb4o() {

ObjectContainer db = Db4oEmbedded.openFile(Db4oEmbedded.newConfiguration(), DB4OFILENAME);

       try {
           // do something with db4o
       } finally {
           db.close();
       }
   }

Store Object:

Pilot pilot1 = new Pilot("Michael Schumacher", 100,address,addressMap);
db.store(pilot1);

Display List:

public static void listResult(List<?> result){

System.out.println("Total Records: " + result.size());

for (Object o : result) {

           System.out.println("Object: " + o);

       }
}


Retrieve Object:

Pilot proto = new Pilot(null, 0,null,null);
ObjectSet result = db.queryByExample(proto);

OR

ObjectSet result = db.queryByExample(Pilot.class);

OR

Pilot proto = new Pilot("Michael Schumacher", 0,null,null);
ObjectSet result = db.queryByExample(proto);

OR

Pilot proto = new Pilot(null, 100,null,null);
ObjectSet result = db.queryByExample(proto);

Update Object:

Pilot proto = new Pilot("Michael Schumacher", 0,null,null);
ObjectSet result = db.queryByExample(proto);
Pilot found = (Pilot) result.next();
found.addPoints(11);
db.store(found);

Delete Object:

Pilot proto = new Pilot("Michael Schumacher", 0,null,null);
ObjectSet result = db.queryByExample(proto);
Pilot found = (Pilot) result.next();
db.delete(found);

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