Implementing ObjectivityDB aggregation queries using Java
To implement various aggregation queries in ObjectivityDB using Java, the following steps need to be followed:
1. Add Maven dependency for ObjectivityDB:
<dependency>
<groupId>com.objectivity</groupId>
<artifactId>objectivitydb</artifactId>
<version>xx. x.x</version><-- Version number -->
</dependency>
2. Import necessary dependencies into Java code:
import com.objy.db.app.oo;
import com.objy.db.app.ooHandle;
import com.objy.db.app.ooId;
import com.objy.db.app.ooObj;
import com.objy.db.util.ooCollection;
3. Create a database connection for ObjectivityDB:
oo.connect("db_path", "user", "password");
Among them, 'db_path' is the path to the database, and 'user' and 'password' are the login credentials for the database.
4. Define aggregation query methods, including selecting aggregation functions, query conditions, and sorting methods. Here is an example method:
public static double aggregateQuery() {
OoId classId=ooObjId (Object. class)// Replace with the Class Id of the class to be queried
ooCollection collection = ooObj.inlineAll(classId);
//Defining Aggregate Functions
ooScalar sum = new ooScalar();
//Create query criteria
OoObj attr=(ooObj) collection. resolve ("[attrname]")// Replace with the property name to be queried
OoBitmask queryMask=collection. mask()// Masks that can add other query criteria
//Implement aggregated queries
collection.scan(queryMask, sum);
return (double) sum.get();
}
In the above code, you need to replace the placeholders in the example according to the actual situation.
5. Close database connection:
oo.close();
Complete Java code example:
import com.objy.db.app.oo;
import com.objy.db.app.ooHandle;
import com.objy.db.app.ooId;
import com.objy.db.app.ooObj;
import com.objy.db.util.ooCollection;
public class ObjectivityDBAggregationQueryExample {
public static void main(String[] args) {
try {
oo.connect("db_path", "user", "password");
double result = aggregateQuery();
System.out.println("Aggregation result: " + result);
} catch (Exception e) {
e.printStackTrace();
} finally {
oo.close();
}
}
public static double aggregateQuery() {
OoId classId=ooObjId (Object. class)// Replace with the Class Id of the class to be queried
ooCollection collection = ooObj.inlineAll(classId);
//Defining Aggregate Functions
ooScalar sum = new ooScalar();
//Create query criteria
OoObj attr=(ooObj) collection. resolve ("[attrname]")// Replace with the property name to be queried
OoBitmask queryMask=collection. mask()// Masks that can add other query criteria
//Implement aggregated queries
collection.scan(queryMask, sum);
return (double) sum.get();
}
}
Please note that the above example has omitted some specific implementation details for simplicity, and you need to make appropriate modifications and adjustments according to your business needs.
