Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Thinking Beyond ORM in JPA
Patrycja Wegrzynowicz
CTO
Yonita, Inc.
March 15, 2016
Please Stand By. This session will begin promptly at the time
indicated on the agenda. Thank You.

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Safe Harbor Statement
The following is intended to outline our general product direction. It is intended for
information purposes only, and may not be incorporated into any contract. It is not a
commitment to deliver any material, code, or functionality, and should not be relied upon
in making purchasing decisions. The development, release, and timing of any features or
functionality described for Oracle’s products remains at the sole discretion of Oracle.
2

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About Me
• 15+ professional experience
– Still an active developer!
• Author and speaker
– JavaOne, Devoxx, JavaZone, others
• Finalizing PhD in Computer Science
• Founder and CTO of Yonita
– Consulting plus automated tools for
detection of bugs in software
– Security, performance, databases
• Twitter @yonlabs
Oracle Confidential – Internal/Restricted/Highly Restricted
3

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Outline
• Why?
– App-centric vs. data-centric
• What?
– Use cases and performance
• How?
– JPA (2.1)

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Database

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Database – The Mordor of Java Developers

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Why? Different paradigms!
• One size doesn’t fit all!
• App-centric
– Java code drives database design
– One app accesses data
– CRUD more often than complex
queries
• Data-centric
– Database design drives Java code
– Several apps access data
– CRUD as often as complex queries

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What? Use Cases

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What? Performance

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Legacy Systems

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Legacy systems and Database-Level Abstraction
• Legacy systems
– It’s always worked that way!
– Database was all we had!
– We need to feed all those apps!
• Abstraction
– Views
– Stored procedures
– Triggers

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Stored Procedures in JPA
• 2.0 and before
– Native queries to call stored procedures
– No OUT/INOUT parameters
– Database dependent CALL syntax
• 2.1
– EntityManager.createStoredProcedureQuery
– @NamedStoredProcedureQuery

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Example: Stored Procedure
Result Set
-- MySQL
CREATE PROCEDURE GET_EMPLOYEES()
BEGIN
SELECT * FROM EMPLOYEES;
END

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Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
// gather the results
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
// gather the results
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
// gather the results
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
// gather the results, an implicit call to an execute method!
List<Employee> list = (List<Employee>) q.getResultList();

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Example: Stored Procedure
OUT Parameter
-- MySQL
CREATE PROCEDURE SUM_SALARIES(OUT TOTAL INT)
BEGIN
SELECT SUM(SALARY) INTO TOTAL
FROM EMPLOYEES;
END

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Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("SUM_SALARIES");
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// execute the query...
q.execute();
// ...to obtain the output value
Integer total = (Integer) q.getOutputParameterValue("TOTAL");

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("SUM_SALARIES");
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// execute the query...
q.execute();
// ...to obtain the output value
Integer total = (Integer) q.getOutputParameterValue("TOTAL");

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("SUM_SALARIES");
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// execute the query...
q.execute();
// ...to obtain the output value
Integer total = (Integer) q.getOutputParameterValue("TOTAL");

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("SUM_SALARIES");
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// execute the query...
q.execute();
// ...to obtain the output value
Integer total = (Integer) q.getOutputParameterValue("TOTAL");

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
All in One
-- MySQL
CREATE PROCEDURE GET_EMPLOYEES(
IN GIVEN_COUNTRY VARCHAR(255),
OUT TOTAL INT
)
BEGIN
SELECT SUM(SALARY) INTO TOTAL
FROM EMPLOYEES
WHERE COUNTRY = GIVEN_COUNTRY;
SELECT *
FROM EMPLOYEES
WHERE COUNTRY = GIVEN_COUNTRY;
END

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
q.registerStoredProcedureParameter("COUNTRY", String.class, ParameterMode.IN);
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// obtain the employees...
List<Employee> list = (List<Employee>) q.getResultList();
// ...and the output value
Integer total = (Integer) q.getOutputParameterValue("TOTAL");

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
q.registerStoredProcedureParameter("COUNTRY", String.class, ParameterMode.IN);
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// obtain the employees...
List<Employee> list = (List<Employee>) q.getResultList();
// ...and the output value
Integer total = (Integer) q.getOutputParameterValue("TOTAL");

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
q.registerStoredProcedureParameter("COUNTRY", String.class, ParameterMode.IN);
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// obtain the employees...
List<Employee> list = (List<Employee>) q.getResultList();
// ...and the output value
Integer total = (Integer) q.getOutputParameterValue("TOTAL");

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
q.registerStoredProcedureParameter("COUNTRY", String.class, ParameterMode.IN);
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// obtain the employees...
List<Employee> list = (List<Employee>) q.getResultList();
// ...and the output value
Integer total = (Integer) q.getOutputParameterValue("TOTAL");

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
q.registerStoredProcedureParameter("COUNTRY", String.class, ParameterMode.IN);
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// obtain the employees...
List<Employee> list = (List<Employee>) q.getResultList();
// ...and the output value
Integer total = (Integer) q.getOutputParameterValue("TOTAL");

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("GET_EMPLOYEES",Employee.class);
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// obtain the employees
List<Employee> list = (List<Employee>) q.getResultList();
// do we need the execute call here?
Integer total = (Integer) q.getOutputParameterValue("TOTAL");

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
q.registerStoredProcedureParameter("COUNTRY", String.class, ParameterMode.IN);
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// first, an implicit call to execute
List<Employee> list = (List<Employee>) q.getResultList();
// ...then, we can safely obtain the output value 
Integer total = (Integer) q.getOutputParameterValue("TOTAL");

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
q.registerStoredProcedureParameter("COUNTRY", String.class, ParameterMode.IN);
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// what if we reorder the lines?
Integer total = (Integer) q.getOutputParameterValue("TOTAL");
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
q.registerStoredProcedureParameter("COUNTRY", String.class, ParameterMode.IN);
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// what if we reorder the lines?
Integer total = (Integer) q.getOutputParameterValue("TOTAL");
// an implicit call to execute
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
q.registerStoredProcedureParameter("COUNTRY", String.class, ParameterMode.IN);
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// execute must be called before getOutputParameterValue
q.execute();
Integer total = (Integer) q.getOutputParameterValue("TOTAL");
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
q.registerStoredProcedureParameter("COUNTRY", String.class, ParameterMode.IN);
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// execute must be called before getOutputParameterValue
q.execute();
Integer total = (Integer) q.getOutputParameterValue("TOTAL");
// does it call execute once more?
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
q.registerStoredProcedureParameter("COUNTRY", String.class, ParameterMode.IN);
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// execute must be called before getOutputParameterValue
q.execute();
Integer total = (Integer) q.getOutputParameterValue("TOTAL");
// an implicit call to execute only if not executed yet!
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
// what about the order here?
q.registerStoredProcedureParameter("COUNTRY", String.class, ParameterMode.IN);
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// execute and retrieve the results
q.execute();
Integer total = (Integer) q.getOutputParameterValue("TOTAL");
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
// what if we switch the lines?
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
q.registerStoredProcedureParameter("COUNTRY", String.class, ParameterMode.IN);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// execute and retrieve the results
q.execute();
Integer total = (Integer) q.getOutputParameterValue("TOTAL");
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
// what about the order here?
q.registerStoredProcedureParameter("COUNTRY", String.class, ParameterMode.IN);
q.registerStoredProcedureParameter("TOTAL", Integer.class, ParameterMode.OUT);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// execute and retrieve the results
q.execute();
Integer total = (Integer) q.getOutputParameterValue("TOTAL");
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
// what about the order of the positional parameters?
q.registerStoredProcedureParameter(2, Integer.class, ParameterMode.OUT);
q.registerStoredProcedureParameter(1, String.class, ParameterMode.IN);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// execute and retrieve the results
q.execute();
Integer total = (Integer) q.getOutputParameterValue("TOTAL");
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
// what about the order of the positional parameters?
q.registerStoredProcedureParameter(2, Integer.class, ParameterMode.OUT);
q.registerStoredProcedureParameter(1, String.class, ParameterMode.IN);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// execute and retrieve the results
q.execute();
Integer total = (Integer) q.getOutputParameterValue("TOTAL");
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
Annotation
@NamedStoredProcedureQuery {
name = "getEmployees",
procedureName = "GET_EMPLOYEES",
resultClasses = Employee.class,
parameters = {
@StoredProcedureParameter(name="COUNTRY", mode=ParameterMode.IN, type=String.class),
@StoredProcedureParameter(name="TOTAL", mode=ParameterMode.OUT, type=Integer.class)
}
}
@Entity
public class Employee {
// …
}

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createNamedStoredProcedureQuery("getEmployees");
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// first, an implicit call to execute
List<Employee> list = (List<Employee>) q.getResultList();
// ...then, we can safely obtain the output value 
Integer total = (Integer) q.getOutputParameterValue("TOTAL");

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createNamedStoredProcedureQuery("getEmployees");
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// first, an implicit call to execute
List<Employee> list = (List<Employee>) q.getResultList();
// ...then, we can safely obtain the output value 
Integer total = (Integer) q.getOutputParameterValue("TOTAL");

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createNamedStoredProcedureQuery("getEmployees");
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// first, an implicit call to execute
List<Employee> list = (List<Employee>) q.getResultList();
// ...then, we can safely obtain the output value 
Integer total = (Integer) q.getOutputParameterValue("TOTAL");

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createNamedStoredProcedureQuery("getEmployees");
// no calls to registerStoredProcedureParameter
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// first, an implicit call to execute
List<Employee> list = (List<Employee>) q.getResultList();
// ...then, we can safely obtain the output value 
Integer total = (Integer) q.getOutputParameterValue("TOTAL");

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
-- PostgreSQL
CREATE OR REPLACE FUNCTION GET_EMPLOYEES(
IN GIVEN_COUNTRY VARCHAR(255),
OUT TOTAL INT)
RETURNS REFCURSOR AS
$BODY$
DECLARE
EMPS REFCURSOR;
BEGIN
OPEN EMPS FOR SELECT * FROM EMPLOYEE WHERE COUNTRY = GIVEN_COUNTRY;
RETURN EMPS;
END;
$BODY$
LANGUAGE plpgsql

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
-- PostgreSQL
CREATE OR REPLACE FUNCTION GET_EMPLOYEES(
IN GIVEN_COUNTRY VARCHAR(255),
OUT TOTAL INT)
RETURNS REFCURSOR AS
$BODY$
DECLARE
EMPS REFCURSOR;
BEGIN
OPEN EMPS FOR SELECT * FROM EMPLOYEE WHERE COUNTRY = GIVEN_COUNTRY;
RETURN EMPS;
END;
$BODY$
LANGUAGE plpgsql

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createStoredProcedureQuery("GET_EMPLOYEES", Employee.class);
q.registerStoredProcedureParameter(1, void.class, ParameterMode.REF_CURSOR);
q.registerStoredProcedureParameter("COUNTRY", String.class, ParameterMode.IN);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// an implicit call to execute
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
Annotation
@NamedStoredProcedureQuery(
name = "getEmployees",
procedureName = "GET_EMPLOYEES",
resultClasses = Employee.class,
parameters = {
@StoredProcedureParameter(mode=ParameterMode.REF_CURSOR, type=void.class),
@StoredProcedureParameter(name="COUNTRY", mode=ParameterMode.IN, type=String.class)
}
)
@Entity
public class Employee {
// …
}

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createNamedStoredProcedureQuery(”getEmployees”);
// setup the parameters
q.setParameter("COUNTRY", "Poland");
// an implicit call to execute
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
Annotation
@NamedStoredProcedureQuery(
name = "getEmployees",
procedureName = "GET_EMPLOYEES",
resultClasses = Employee.class,
parameters = {
@StoredProcedureParameter(mode=ParameterMode.REF_CURSOR, type=void.class),
@StoredProcedureParameter(name="COUNTRY", mode=ParameterMode.IN, type=String.class)
}
)
@Entity
public class Employee {
// …
}

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createNamedStoredProcedureQuery("getEmployees");
// setup the parameters
q.setParameter(2, "Poland");
// obtain the result
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Example: Stored Procedure
EntityManager API
// create and setup a stored procedure query
StoredProcedureQuery q = em.createNamedStoredProcedureQuery("getEmployees");
// setup the parameters
q.setParameter(2, "Poland");
// obtain the result
List<Employee> list = (List<Employee>) q.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Stored Procedures in JPA 2.1
Wrap-up
• Annotation
– @NamedStoredProcedureQuery
• EntityManager API
– createStoredProcedureQuery
– registerStoredProcedureParameter
• Use cases
– Existing database
– Abstraction on database level (e.g., for several applications)
• Still differences between databases!
– Much smaller though

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Reporting

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Reporting Anti-Patterns
• Direct usage of an object-oriented domain model
• Too much data loaded
• Heavy processing on the Java side

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Reporting Anti-Patterns
Example

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Reporting Anti-Patterns
Employee Entity
@Entity public class Employee {
@Id @GeneratedValue
private Long id;
private String firstName;
private String lastName;
private BigDecimal salary;
@OneToOne @JoinColumn(name = "address_id")
private Address address;
@Temporal(TemporalType.DATE)
private Date startDate;
@Temporal(TemporalType.DATE)
private Date endDate;
@ManyToOne @JoinColumn(name = "manager_id")
private Employee manager;
// …
}

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Sum of Salaries By Country
Select All (1)
TypedQuery<Employee> query = em.createQuery(
"SELECT e FROM Employee e", Employee.class);
List<Employee> list = query.getResultList();
// calculate sum of salaries by country
// map: country->sum
Map<String, BigDecimal> results = new HashMap<>();
for (Employee e : list) {
String country = e.getAddress().getCountry();
BigDecimal total = results.get(country);
if (total == null) total = BigDecimal.ZERO;
total = total.add(e.getSalary());
results.put(country, total);
}

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Sum of Salaries by Country
Select Join Fetch (2)
TypedQuery<Employee> query = em.createQuery(
"SELECT e FROM Employee e
JOIN FETCH e.address", Employee.class);
List<Employee> list = query.getResultList();
// calculate sum of salaries by country
// map: country->sum
Map<String, BigDecimal> results = new HashMap<>();
for (Employee e : list) {
String country = e.getAddress().getCountry();
BigDecimal total = results.get(country);
if (total == null) total = BigDecimal.ZERO;
total = total.add(e.getSalary());
results.put(country, total);
}

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Reporting Anti-Patterns
Projection (3)
Query query = em.createQuery(
"SELECT e.salary, e.address.country
FROM Employee e");
List<Object[]> list = (List<Object[]>) query.getResultList();
// calculate sum of salaries by country
// map: country->sum
Map<String, BigDecimal> results = new HashMap<>();
for (Object[] e : list) {
String country = (String) e[1];
BigDecimal total = results.get(country);
if (total == null) total = BigDecimal.ZERO;
total = total.add((BigDecimal) e[0]);
results.put(country, total);
}

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Reporting Anti-Patterns
Aggregation JPQL (4)
Query query = em.createQuery(
"SELECT SUM(e.salary), e.address.country
FROM Employee e
GROUP BY e.address.country");
List<Object[]> list = (List<Object[]>) query.getResultList();
// already calculated!

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Reporting Anti-Patterns
Aggregation SQL (5)
Query query = em.createNativeQuery(
"SELECT SUM(e.salary), a.country
FROM employee e JOIN address a ON e.address_id = a.id
GROUP BY a.country");
List<Object[]> list = (List<Object[]>) query.getResultList();
// already calculated!

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Comparison 1-5
100 000 employees, EclipseLink
MySQL PostgreSQL
Select all (1+N) (1) 25704ms 18120ms
Select join fetch (2)
Projection (3)
Aggregation JPQL (4)
Aggregation SQL (5)

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Comparison 1-5
100 000 employees, EclipseLink
MySQL PostgreSQL
Select all (1+N) (1) 25704ms 18120ms
Select join fetch (2) 6211ms 3954ms
Projection (3)
Aggregation JPQL (4)
Aggregation SQL (5)

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Comparison 1-5
100 000 employees, EclipseLink
MySQL PostgreSQL
Select all (1+N) (1) 25704ms 18120ms
Select join fetch (2) 6211ms 3954ms
Projection (3) 533ms 569ms
Aggregation JPQL (4)
Aggregation SQL (5)

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Comparison 1-5
100 000 employees, EclipseLink
MySQL PostgreSQL
Select all (1+N) (1) 25704ms 18120ms
Select join fetch (2) 6211ms 3954ms
Projection (3) 533ms 569ms
Aggregation JPQL (4) 410ms 380ms
Aggregation SQL (5) 380ms 409ms

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
MySQL vs. PostgreSQL
68
25704
6211
533 410 380
18120
3954
569 380 4090
5000
10000
15000
20000
25000
30000
Select all
(1+N) (1)
Select join
fetch (2)
Projection
(3)
Aggregation
JPQL (4)
Aggregation
SQL (5)
MySQL
PostgreSQL

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Projection
JPQL -> Value Object
Query query = em.createQuery(
"SELECT new com.yonita.jpa.vo.EmployeeVO(e.salary, e.address.country)
FROM Employee e");
// The list of value objects
List<EmployeeVO> list = (List<EmployeeVO>) query.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Projection
JPQL -> Value Object
Query query = em.createQuery(
"SELECT new com.yonita.jpa.CountryStatVO(
sum(e.salary), e.address.country)
FROM Employee e
GROUP BY e.address.country");
// The list of value objects
List<CountryStatVO> list = (List<CountryStatVO>) query.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Projection
SQL -> Value Object
@SqlResultSetMapping(
name = "countryStatVO",
classes = {
@ConstructorResult(
targetClass = CountryStatVO.class,
columns = {
@ColumnResult(name = "ssum", type = BigDecimal.class),
@ColumnResult(name = "country", type = String.class)
})
}
)

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Projection
SQL -> Value Object
Query query = em.createNativeQuery("countryStatVO");
// The list of value objects
List<CountryStatVO> list = (List<CountryStatVO>) query.getResultList();

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Projection
Wrap-up
• JPA 2.0
– Only JPQL query to directly produce a value object!
• JPA 2.1
– JPQL and native queries to directly produce a value object!
• Managed entities
– Sync with database
– L1/L2 cache
• Use cases for Direct Value Object
– Reporting, statistics, history
– Read-only data, GUI data
• Performance
– No need for managed objects
– Rich (or fat) managed objects
– Subset of attributes required
– Gain speed
– Offload an app server

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Aggregation
Wrap-up
• JPA 2.0
– Selected aggregation functions: COUNT, SUM, AVG, MIN, MAX
• JPA 2.1
– All function as supported by a database
– Call any database function with new FUNCTION keyword
• Database-specific aggregate functions
– MS SQL: STDEV, STDEVP, VAR, VARP,…
– MySQL: BIT_AND, BIT_OR, BIT_XOR,…
– Oracle: MEDIAN, PERCENTILE,…
– More…
• Use cases
– Reporting, statistics
– Performance
• Gain speed
• Offload an app server to a database!

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Complex Queries

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
JPQL vs. SQL
• Column/table visibility
– JPA 2.0/2.1: Only mapped columns and tables
• Operations on sets
– UNION, INTERSECT, EXCEPT
– JPA 2.0/2.1: No support
• Nested fetch joins
– JPA 2.0: No support
– JPA 2.1: entity graphs for different fetching strategies
• ON
– JPA 2.0: No support
– JPA 2.1: Only on “connected entities”

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
JPQL vs. SQL
• Database functions
– Aggregate functions
– Conversion functions
– Extraction functions
– Manipulation functions
– Functions, functions, functions…
– JPA 2.0: Selected functions
– JPA 2.1: All functions

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Helper Functions JPA 2.1
• String functions:
– CONCAT, SUBSTRING, TRIM, LOWER, UPPER, LENGTH, LOCATE
• Arithmetic functions:
– ABS, SQRT, MOD, SIZE, INDEX
• Date/time functions:
– CURRENT_DATE, CURRENT_TIME, CURRENT_TIMESTAMP
• Aggregate functions:
– COUNT, SUM, MIN, MAX, AVG
• Invocation of predefined or user-defined functions:
– FUNCTION(function_name {, function_args}*)

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Helper Functions JPA 2.1
• Invocation of predefined or user-defined functions:
– FUNCTION(function_name {, function_args}*)
– SELECT c
FROM Customer c
WHERE FUNCTION(‘hasGoodCredit’, c.balance, c.creditLimit)

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
JPA 2.1

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Wrap-up
• JPA 2.1
– Stored procedures support
– Projections
• Direct value object for native queries
– Richer JPQL

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Wrap-up
• JPA 2.1
– Stored procedures support
– Projections
• Direct value object for native queries
– Richer JPQL
• Performance

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Wrap-up
• JPA 2.1
– Stored procedures support
– Projections
• Direct value object for native queries
– Richer JPQL
• Performance
– Don’t load if you don’t need

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Wrap-up
• JPA 2.1
– Stored procedures support
– Projections
• Direct value object for native queries
– Richer JPQL
• Performance
– Don’t load if you don’t need
– Don’t execute many small queries if you can execute one big query

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Wrap-up
• JPA 2.1
– Stored procedures support
– Projections
• Direct value object for native queries
– Richer JPQL
• Performance
– Don’t load if you don’t need
– Don’t execute many small queries if you can execute one big query
– Don’t calculate if a database can

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
A fool with a tool is still a fool!

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Continuous Learning Paradigm
87

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Q+A

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Keep Learning with Training from Oracle University
89
• Hands-on training delivered in-class or online by
tenured instructors around the world
• New subscription-based learning services to give you
any-time access to training
• Certification programs to validate your skills
education.oracle.com

Copyright © 2014 Oracle and/or its affiliates. All rights reserved. | 90

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Copyright © 2014 Oracle and/or its affiliates. All rights reserved. | 92