воскресенье, 22 июля 2012 г.

OrientDB - Java sample 1

1. The first step it is need to create a simple POJO. An empty constructor is mandatory.


public class Organization {
    String  name;
    String  description;


    public Organization() {
    }

    public Organization(String name, String description) {
        this.name = name;
        this.description = description;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

}

2. Next step, we open  a database and save POJO

    public void createNewOrg() {

//Open the database in a thread-safe way i.e. in every thread we must create new db object this way
//A database mydb must exist.
        OObjectDatabaseTx db = OObjectDatabasePool.global().acquire("remote:localhost/mydb", "admin", "admin");
        try {

            //Register our class in OrientDB Entity manager to work with POJO's
            db.getEntityManager().registerEntityClass(Organization.class);

            // create a new proxied object and fill its properties
            Organization org = db.newInstance(Organization.class);
            org.setName("MyOrg");
            org.setDescription("This is my good org.");
            db.save(org);
        } finally {

    //ALWAYS CLOSE TO RELEASE CONNECTION POOL RESOURCES
            db.close();
        }

    }

3. Next step we demonstrate a simple query


   public void browseAllOrgs() {
        // Open a database
        OObjectDatabaseTx db = OObjectDatabasePool.global().acquire("remote:localhost/mydb", "admin", "admin");
        try {
            //Register the class to work with it with Entity Manager
            db.getEntityManager().registerEntityClass(Organization.class);

            //Select all objects of class Organization and print their properties
            for (Organization orgItem : db.browseClass(Organization.class)) {
                System.out.print(orgItem.getName() + ' ');
                System.out.println(orgItem.getDescription());
            }

            System.out.println("-------------------");

            //Select all objects of class Organization were description contains word good
            // and print their properties
            List result = db.query(
                    new OSQLSynchQuery("select * from Organization where description like '%good%'"));

            for (Organization org : result) {
                System.out.print(org.getName() + ' ');
                System.out.println(org.getDescription());
            }
        } finally {
            //ALWAYS CLOSE
            db.close();
        }

    }

That's all.

PS. OObjectDatabasePool.global().acquire reuses the database connection to avoid to create it every time. db.close() doesn't close the database but release it to the owner pool. It could be reused in the future.

PPS. It is not necessary to create table (class) type of Organization before run this sample. New table (class) with name Organization  will be created during the first run.

PPPS. If you add a new property (field) to class Organization then at next run a new object  will appear in database with this new field. Older objects will remain unchanged.

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