Crash Introduction to Modern Java Data Access: Understanding JPA, Hibernate, MyBatis, and pureQuery

Dr. Vladimir Bacvanski

Session Code: E13Session Code: E13May 6, 2011 * 8:00 May 6, 2011 * 8:00 –– 9:00am | Platform: Cross Platform9:00am | Platform: Cross Platform

Outline

• Database/Programming Languages ChasmP i t O ti• Persistence Options

• JDBCObj t R l ti l M i• Object Relational Mapping

• JPA & Hibernate• MyBatis• pureQuery• Conclusions

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Database/Programming Languages Chasmg g g g

• Relational Database • JavaCustomer

pid  name phone  email1      Joe        123‐…      

c1: Customername="Joe"phone=123 456 7890joe@...

Add

email="joe@xyz.com"phone=123‐ 456‐7890email="joe@xyz.com"

AddressycustId street city

1               1 Nice …            San

a1: Addressstreet="1 Nice Way"

• The world consists of • The world consists of

San…city="San Francisco"

tables objects, which are instances of classes 3

Accessing Databases: Many Choices!g yJDBCpureQuery

SQLJSQLJMyBatisMyBatis(iBatis)

Hibernate

Hibernate

)(iBatis)

JPA EJB

There are more choices, but we'll discuss just the more popular ones4

JDBC

• JDBC (Java Database Connectivity) provides an API allowing for explicit creation of SQL queries from Javaallowing for explicit creation of SQL queries from Java

• The API allows for issuing of SQL commands• Prepared queries• Prepared queries• Ad-hoc queries• Callable statements

• The result comes back as a cursored table

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Code Example: JDBCpTable Column TypeEMP NAME CHAR(64)

java.sql.PreparedStatement ps = con.prepareStatement(

EMP ADDRESS CHAR(128)

EMP PHONE_NUM CHAR(10)

"SELECT NAME, ADDRESS,PHONE_NUM FROM EMP WHERE NAME=?");

ps.setString(1, name);java.sql.ResultSet rs = ps.executeQuery();rs.next();

class Employee {public String name;

();Employee myEmp = new Employee();myEmp.setName(rs.getString(1));myEmp setHomeAddress(rs getString(2)); public String name;

public String homeAddress;public String homePhone;…

myEmp.setHomeAddress(rs.getString(2));myEmp.setHomePhone(rs.getString(3));rs.close();

}

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Issues with Plain JDBC• Benefits

• Performance• It is possible to write optimized queries for a particular task• It is possible to take advantage of underlying DB capabilities

• Ease of debugging• Ease of debugging• The connection between the DB and application code is clear

• Drawbacks• Cumbersome programming

• The mapping from the application world (Java objects) to the DB world may be cumbersome and complexworld may be cumbersome and complex

• Much code may have to be written and debugged• It is easy to introduce mechanical bugs

• E.g., closing of connections

• JDBC API lags behind modern database features 7

Object-Relational Mappingj pp g

• Issues with JDBC led to development of O/R mapping, most notably Hibernate as the leading implementationmost notably Hibernate as the leading implementation

• One popular approach to connect applications to the database is the use of an object-relational mapping tooldatabase is the use of an object-relational mapping tool (ORM)

• Many ORM technologies and implementations available:Many ORM technologies and implementations available:• JPA: The dominant specification• Hibernate, OpenJPA, EclipseLink: JPA implementations

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Mapping Between the Worldspp g

RACINGMOUNTAIN

<<enumeration>>BikeType

name: String

Vehicle

name: String

Person

1*

vehiclePark owner

**

availableCars legalUsers

STREETUNICYCLE

name: Stringdescription: String

MotorizedVehicleType

fuelCapacity: Integer

MotorizedVehicle

bikeType: BikeType

Bikeinstances

type1

*street: Stringcity: Stringstate: Stringcountry: String

Address

*

VEHICLE_2_PERSON_MAP

PK,FK2 legal_driver_id char (10)PK,FK1 available _car_id char (10)

PERSON_TBL

PK id char (10)

name varchar (50)

MOTORIZED_VEHICLE_TYPE

PK id char(10)

name varchar (50)description varchar(255)

VEHICLE_TBL

PK id char(10)

FK1 owner_id char(10)name varchar (50)type smallint

ADDRESS_TBL

PK id varchar (16)MOTORIZED_VEHICLE_TBL

PK,FK1,FK2 id char(10)

fuel_consumption realtype_id char(10)

BIKE_TBL

PK,FK1 id char(10)

bike_type smallint

PK id varchar (16)

FK1 occupant_id char(10)street varchar (250)city varchar (50)state varchar (50)country varchar (40)

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JPA Example: Annotationsp@Entitypublic class Employee {

@Idprivate Long id;

@ManyToOneprivate Department department;...

}

@ i@Entitypublic class Department {

@OneToMany(mappedBy="department") private Collection<Employee> employees = new HashSet();

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JPA Inheritance Examplep@Entity

@Inheritance@

@DiscriminatorColumn(name="DISC", discriminatorType=STRING,length=20)

@DiscriminatorValue(“PERSON")@DiscriminatorValue( PERSON )

public class Person { ... }

@Entity

@DiscriminatorValue("CUSTOMER") public class Customer extends Person { ... }p { }

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Hibernate: More than JPA

• JPA was heavily inspired by HibernateT d Hib t i l t th JPA t d d• Today, Hibernate implements the JPA standard

• Provides more features in areas:P i k t• Primary key generators

• Control over cascade behaviors• Criteria for query buildingCriteria for query building• Query language HQL• Caching• …

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Issues with ORM Tools• Benefits

• Ease of use for the application programmer• Ease of use for the application programmer• The programmer writes code assuming an object model• The tool maps the object model to SQL

• Continuity• The domain model (from analysis) is preserved in implementation

Drawbacks• Drawbacks• Performance

• It is hard for the general purpose mapping tool to take advantage of g p p pp g gthe underlying database capabilities

• Complex to debug• The mapping can make finding errors very hard• The mapping can make finding errors very hard

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MyBatis (iBatis)y ( )• MyBatis was earlier known as iBatis• SQL is fully exposed: MyBatis is not a full ORM! y p y• Persistence access is explicit through SQL• Reduced Java boilerplate code in comparison with JDBC

MappingXML or Annotations

Input

Hashtable

Output

HashtableMapped

POJO POJO

Mapped Statement

Primitive Primitive

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SQL Mapping and Call in MyBatisQ pp g yMapping:<?xml version="1.0" encoding="UTF‐8" ?><?xml version 1.0  encoding UTF 8  ?><!DOCTYPE mapper PUBLIC "‐//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis‐3‐mapper.dtd"><mapper namespace="com.scispike.CustomerMapper"><mapper namespace com.scispike.CustomerMapper >

<select id="selectCustomer" parameterType="int"resultType="Customer">

select * from Customer where id = #{id}select   from Customer where id = #{id}</select>

</mapper>

Call:Customer cust = (Customer) session.selectOne("com.scispike.CustomerMapper.selectCustomer", 1001);

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Issues with MyBatisy• Benefits

• Full control over SQL and improved productivity in comparison• Full control over SQL and improved productivity in comparison with JDBC

• Suitable for dealing with legacy databases• Troubleshooting easier in comparison with JPA

D b k• Drawbacks• Tooling support is lacking• Productivity initially reduced in comparison with JPA but catches• Productivity initially reduced in comparison with JPA, but catches

up later through easier troubleshooting

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pureQueryp Q y

• A high-performance, data access platform to simplify developing managing securing and optimizing datadeveloping, managing, securing, and optimizing data access

pureQuery Components:• Simple and intuitive API

• Enables SQL access to databases or in-memory Java objectsy j• Facilitates best practices

• Optim Development Studio (integrates with RAD/RSA)• Integrated development environment with Java and SQL supportIntegrated development environment with Java and SQL support • Improve problem isolation and impact analysis• Optimize existing code: JDBC/JPA/Hibernate/MyBatis

• Optim pureQuery Runtime• Optim pureQuery Runtime• Flexible static SQL deployment for DB2

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Code Example: pureQueryp p Q y

• "Inline" query:

Employee myEmp = db.queryFirst("SELECT NAME, ADDRESS, PHONE_NUM FROM EMP

?" l l )WHERE NAME=?", Employee.class, name);

• Even simpler if we have a method getEmployee with aEven simpler, if we have a method getEmployee with a Java annotation or XML file with SQL for the query:

Employee myEmp = db.getEmployee(name);

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Optim Development Studio: pureQuery IDEp p p Q y

R l SQL

Visualize application SQL

Visualize execution metrics

Replace SQL without changing

the application

P iti i

Execute, tune, share, trace, explore

SQL

Position in Database Explorer

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SQL Integration with JavaQ g• SQL content assist

SQL lid ti• SQL validation

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Data Access Objects – pureQuery supportj p Q y pp

Quickly create JEE Data Access ObjectsA i t f ith l th d• An interface with only your methods

• Methods for each database accessE h th d h l t• Each method has only your parameters

• SQL can be in XML file or annotations• Implementation automatically generated with best practice

database access and optimizations.T l t b d ti ith t l t t i ti• Template-based generation with template customization

• Mix hand-written and generated code. C dif t d d d f l t• Can modify generated code and safely regenerate.

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pureQuery: Optimal Productivity and Controlp Q y p y

Managed Objects Object-Relational MappingFull SQL Control

Code all your SQL

JDBC / SQLJJDBC / SQLJ

MyBatis

Complex O/R mapping and persistence management, but loss of control

Add basic OR mapping and annotated-method stylepureQuery

p pp g p g

Adds container management option

JPA/Hibernate

EJB 3

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Conclusion

• Each approach has its strengths and weaknessesJDBC l• JDBC alone• To low level for most applications

• JPA and Hibernate• JPA and Hibernate• Good choice when you own the database, performance not critical

• MyBatis• MyBatis• Full control over SQL, reduced boilerplate

• pureQuerypureQuery• Full control over SQL , mixing productivity, static SQL, and

integrated tooling

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Getting in Touchg

• Email: vladimir.bacvanski@scispike.comBl htt // O B ildi S ft /• Blog: http://www.OnBuildingSoftware.com/

• Twitter: http://twitter.com/OnSoftwareLi k dI htt // li k di /i /Vl di i B ki• LinkedIn: http://www.linkedin.com/in/VladimirBacvanski

• Parts of the presentation are from SciSpike courses:• Developing Database Applications with Optim Development Studio and pureQuery• Developing Database Applications with Optim Development Studio and pureQuery• Hibernate

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