OrientDB for Java Developers in Five Minutes
In the previous step you established a DB connection from Java, then you created the DB schema (two classes and an index)
Now it's time to insert and query some data
Step 5/5 - Create and Query a Graph
First of all, let's create three vertices: Alice, Bob and Jim
Creating vertices
We are good Java developers, aren't we? Let's encapsulate a single vertex creation in a method:
private static OVertex createPerson(ODatabaseSession db, String name, String surname) {
OVertex result = db.newVertex("Person");
result.setProperty("name", name);
result.setProperty("surname", surname);
result.save();
return result;
}
Wow, we never mentioned that people have a surname!!! In the previous section we just defined the schema for name property...
OrientDB can work schemaful (with all the property names and types defined), schemaless (schema-free, no schema defined) or schema-mixed like in this case, where we define a part of the schema (ie. the name) but we leave the developer the ability to add new properties at run time, without having to deal with further schema definitions.
Now let's create the three vertices:
private static void createPeople(ODatabaseSession db){
OVertex alice = createPerson(db, "Alice", "Foo");
OVertex bob = createPerson(db, "Bob", "Bar");
OVertex jim = createPerson(db, "Jim", "Baz");
}
Creating edges
Suppose that Alice is a friend of Bob and that Bob is a friend of Jim:
Alice --FriendOf--> Bob --FriendOf--> Jim
Let's create the edges in the database:
OEdge edge1 = alice.addEdge(bob, "FriendOf");
edge1.save();
OEdge edge2 = bob.addEdge(jim, "FriendOf");
edge2.save();
Please consider that edges are plain documents, so you can get/set properties on them exactly like for vertices.
Executing queries
Last step of this journey: let's write and execute a simple query that finds friends of friends (FoaF) of a person. We will use a SELECT for this.
private static void executeAQuery(ODatabaseSession db) {
String query = "SELECT expand(out('FriendOf').out('FriendOf')) from Person where name = ?";
OResultSet rs = db.query(query, "Alice");
while (rs.hasNext()) {
OResult item = rs.next();
System.out.println("friend: " + item.getProperty("name"));
}
rs.close(); //REMEMBER TO ALWAYS CLOSE THE RESULT SET!!!
}
or, if you prefer Java Streams API:
private static void executeAQuery(ODatabaseSession db) {
String query = "SELECT expand(out('FriendOf').out('FriendOf')) from Person where name = ?";
OResultSet rs = db.query(query, "Alice");
rs.stream().forEach(x -> System.out.println("friend: " + x.getProperty("name")));
rs.close();
}
Let's try a more complex query, let's find all the people that are friends of both Alice and Jim. We will use a MATCH for this.
private static void executeAnotherQuery(ODatabaseSession db) {
String query =
" MATCH " +
" {class:Person, as:a, where: (name = :name1)}, " +
" {class:Person, as:b, where: (name = :name2)}, " +
" {as:a} -FriendOf-> {as:x} -FriendOf-> {as:b} " +
" RETURN x.name as friend ";
Map<String, Object> params = new HashMap<String, Object>();
params.put("name1", "Alice");
params.put("name2", "Jim");
OResultSet rs = db.query(query, params);
while (rs.hasNext()) {
OResult item = rs.next();
System.out.println("friend: " + item.getProperty("name"));
}
rs.close();
}
Good job!!! This is your first OrientDB Java program!
Here is the full source code of the main class:
import com.orientechnologies.orient.core.db.ODatabaseSession;
import com.orientechnologies.orient.core.db.OrientDB;
import com.orientechnologies.orient.core.db.OrientDBConfig;
import com.orientechnologies.orient.core.metadata.schema.OClass;
import com.orientechnologies.orient.core.metadata.schema.OType;
import com.orientechnologies.orient.core.record.OEdge;
import com.orientechnologies.orient.core.record.OVertex;
import com.orientechnologies.orient.core.sql.executor.OResult;
import com.orientechnologies.orient.core.sql.executor.OResultSet;
import java.util.HashMap;
import java.util.Map;
public class Main {
public static void main(String[] args) {
OrientDB orient = new OrientDB("remote:localhost", OrientDBConfig.defaultConfig());
ODatabaseSession db = orient.open("test", "admin", "admin");
createSchema(db);
createPeople(db);
executeAQuery(db);
executeAnotherQuery(db);
db.close();
orient.close();
}
private static void createSchema(ODatabaseSession db) {
OClass person = db.getClass("Person");
if (person == null) {
person = db.createVertexClass("Person");
}
if (person.getProperty("name") == null) {
person.createProperty("name", OType.STRING);
person.createIndex("Person_name_index", OClass.INDEX_TYPE.NOTUNIQUE, "name");
}
if (db.getClass("FriendOf") == null) {
db.createEdgeClass("FriendOf");
}
}
private static void createPeople(ODatabaseSession db) {
OVertex alice = createPerson(db, "Alice", "Foo");
OVertex bob = createPerson(db, "Bob", "Bar");
OVertex jim = createPerson(db, "Jim", "Baz");
OEdge edge1 = alice.addEdge(bob, "FriendOf");
edge1.save();
OEdge edge2 = bob.addEdge(jim, "FriendOf");
edge2.save();
}
private static OVertex createPerson(ODatabaseSession db, String name, String surname) {
OVertex result = db.newVertex("Person");
result.setProperty("name", name);
result.setProperty("surname", surname);
result.save();
return result;
}
private static void executeAQuery(ODatabaseSession db) {
String query = "SELECT expand(out('FriendOf').out('FriendOf')) from Person where name = ?";
OResultSet rs = db.query(query, "Alice");
while (rs.hasNext()) {
OResult item = rs.next();
System.out.println("friend: " + item.getProperty("name"));
}
rs.close(); //REMEMBER TO ALWAYS CLOSE THE RESULT SET!!!
}
private static void executeAnotherQuery(ODatabaseSession db) {
String query =
" MATCH " +
" {class:Person, as:a, where: (name = :name1)}, " +
" {class:Person, as:b, where: (name = :name2)}, " +
" {as:a} -FriendOf-> {as:x} -FriendOf-> {as:b} " +
" RETURN x.name as friend ";
Map<String, Object> params = new HashMap<String, Object>();
params.put("name1", "Alice");
params.put("name2", "Jim");
OResultSet rs = db.query(query, params);
while (rs.hasNext()) {
OResult item = rs.next();
System.out.println("friend: " + item.getProperty("friend"));
}
rs.close();
}
}
Next steps:
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