Crash Introduction to Modern Java Data Access: Understanding JPA, Hibernate, MyBatis, and pureQuery
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This document summarizes a presentation on modern Java data access options. It introduces JDBC, object-relational mapping with JPA and Hibernate, MyBatis, and the pureQuery framework. The presentation outlines the benefits and drawbacks of each approach and how they map objects to databases. It also demonstrates code examples and the Optim Development Studio IDE for pureQuery.
Crash Introduction to Modern Java Data Access: Understanding JPA, Hibernate, MyBatis, and pureQuery
- 1. Crash Introduction to Modern Java Data Access: Understanding JPA, Hibernate, MyBatis, and pureQuery Dr. Vladimir Bacvanski Session Code: E13 May 6, 2011 * 8:00 – 9:00am | Platform: Cross Platform
- 2. Outline • Database/Programming Languages Chasm • Persistence Options P i t O ti • JDBC • Object R l ti Obj t Relational M l Mapping i • JPA & Hibernate • MyBatis • pureQuery • Conclusions 2
- 3. Database/Programming Languages Chasm g g g g • Relational Database • Java Customer c1: Customer id name p phone email name="Joe" 1 Joe 123‐… joe@... phone=123‐ 456‐7890 phone=123 456 7890 email="[email protected]" Address Add custId street city y a1: Address 1 1 Nice … street="1 Nice Way" San… San city="San Francisco" • The world consists of • The world consists of tables objects, which are instances of classes 3
- 4. Accessing Databases: Many Choices! g y pureQuery JDBC SQLJ MyBatis (iBatis) ) Hibernat e JPA EJB There are more choices, but we'll discuss just the more popular ones 4
- 5. JDBC • JDBC (Java Database Connectivity) provides an API allowing for explicit creation of SQL queries from Java • The API allows for issuing of SQL commands • Prepared queries • Ad-hoc queries • Callable statements • The result comes back as a cursored table 5
- 6. Code Example: JDBC p java.sql.PreparedStatement ps = Table Column Type con.prepareStatement( EMP NAME CHAR(64) "SELECT NAME, ADDRESS, EMP ADDRESS CHAR(128) PHONE_NUM FROM EMP EMP PHONE_NUM CHAR(10) WHERE NAME=?"); ps.setString(1, name); java.sql.ResultSet rs = ps.executeQuery(); rs.next(); (); Employee myEmp = new Employee(); myEmp.setName(rs.getString(1)); class Employee { myEmp.setHomeAddress(rs.getString(2)); myEmp setHomeAddress(rs getString(2)); public String name; public String name; public String homeAddress; myEmp.setHomePhone(rs.getString(3)); public String homePhone; rs.close(); … } 6
- 7. 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 • 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 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
- 8. Object-Relational Mapping j pp g • Issues with JDBC led to development of O/R mapping, most notably Hibernate as the leading implementation • One popular approach to connect applications to the database is the use of an object-relational mapping tool (ORM) • Many ORM technologies and implementations available: • JPA: The dominant specification • Hibernate, OpenJPA, EclipseLink: JPA implementations 8
- 9. Mapping Between the Worlds pp g <<enumeration>> BikeType RACING MOUNTAIN STREET UNICYCLE Vehicle vehiclePark owner Person name: String name: String * 1 MotorizedVehicleType * * name: String availableCars legalUsers description: String 1 type * instances MotorizedVehicle Bike fuelCapacity: Integer bikeType: BikeType Address * street: String city: String state: String country: String MOTORIZED_VEHICLE_TYPE VEHICLE_2_PERSON_MAP PERSON_TBL PK id char(10) PK,FK2 legal_driver_id char (10) PK id char (10) PK,FK1 available _car_id char (10) name varchar (50) 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 BIKE_TBL FK1 occupant _id char(10) PK,FK1,FK2 id char(10) PK,FK1 id char(10) street varchar (250) city varchar (50) fuel_consumption real bike_type smallint state varchar (50) type_id char(10) country varchar (40) 9
- 10. JPA Example: Annotations p @Entity public class Employee { @Id private Long id; @ManyToOne private Department department; ... } @Entity @ i public class Department { @OneToMany(mappedBy="department") private Collection<Employee> employees = new HashSet(); 10
- 11. JPA Inheritance Example p @Entity @ @Inheritance @DiscriminatorColumn( name="DISC", discriminatorType=STRING,length=20) @DiscriminatorValue( PERSON ) @DiscriminatorValue(“PERSON") public class Person { ... } @Entity @DiscriminatorValue("CUSTOMER") p public class Customer extends Person { ... } { } 11
- 12. Hibernate: More than JPA • JPA was heavily inspired by Hibernate • T d Today, Hib Hibernate i l t implements th JPA standard t the t d d • Provides more features in areas: • Primary k generators Pi key t • Control over cascade behaviors • Criteria for query building • Query language HQL • Caching • … 12
- 13. Issues with ORM Tools • Benefits • 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 • Performance • It is hard for the general p p g purpose mapping tool to take advantage of pp g g the underlying database capabilities • Complex to debug • The mapping can make finding errors very hard 13
- 14. 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 Mapping XML or Annotations Input Output Hashtable Hashtable Mapped Mapped POJO Statement POJO Primitive Primitive 14
- 15. SQL Mapping and Call in MyBatis Q pp g y Mapping: <?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"> 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); 15
- 16. Issues with MyBatis y • Benefits • Full control over SQL and improved productivity in comparison with JDBC • Suitable for dealing with legacy databases • Troubleshooting easier in comparison with JPA • D Drawbacks b k • Tooling support is lacking • Productivity initially reduced in comparison with JPA but catches JPA, up later through easier troubleshooting 16
- 17. p pureQuery Q y • A high-performance, data access platform to simplify developing, managing, securing, developing managing securing and optimizing data access pureQuery Components: • Simple and intuitive API • Enables SQL access to databases or in-memory Java objects y j • Facilitates best practices • Optim Development Studio (integrates with RAD/RSA) • Integrated development environment with Java and SQL support • Improve problem isolation and impact analysis • Optimize existing code: JDBC/JPA/Hibernate/MyBatis • Optim pureQuery Runtime • Flexible static SQL deployment for DB2 17
- 18. Code Example: pureQuery p p Q y • "Inline" query: Employee myEmp = db.queryFirst( "SELECT NAME, ADDRESS, PHONE_NUM FROM EMP WHERE NAME=?", Employee.class, name); ?" l l ) • Even simpler, if we have a method getEmployee with a simpler Java annotation or XML file with SQL for the query: Employee myEmp = db.getEmployee(name); 18
- 19. Optim Development Studio: pureQuery IDE p p p Q y Visualize application SQL Replace SQL R l Visualize execution without changing metrics the application Position i P iti in Database Explorer Execute, tune, share, trace, explore 19 SQL
- 20. SQL Integration with Java Q g • SQL content assist • SQL validation lid ti 20
- 21. Data Access Objects – pureQuery support j p Q y pp Quickly create JEE Data Access Objects • A i t f An interface with only your methods ith l th d • Methods for each database access • E h method h only your parameters Each th d has l t • SQL can be in XML file or annotations • Implementation automatically generated with best practice database access and optimizations. • T Template-based generation with t l t b d ti ith template customization l t t i ti • Mix hand-written and generated code. • C modify generated code and safely regenerate. Can dif t d d d f l t 21
- 22. p pureQuery: Optimal Productivity and Control Q y p y Full SQL Control Object-Relational Mapping Managed Objects Code all your SQL JDBC / SQLJ MyBatis Add basic OR mapping and annotated-method style pureQuery Complex O/R mapping and persistence management, but loss of control p pp g p g JPA/Hibernate Adds container management option EJB 3 22
- 23. Conclusion • Each approach has its strengths and weaknesses • JDBC alone l • To low level for most applications • JPA and Hibernate • Good choice when you own the database, performance not critical • MyBatis • Full control over SQL, reduced boilerplate • pureQuery • Full control over SQL , mixing productivity, static SQL, and integrated tooling 23
- 24. Getting in Touch g • Email: [email protected] • Blog: htt // Bl http://www.OnBuildingSoftware.com/ O B ildi S ft / • Twitter: http://twitter.com/OnSoftware • LinkedIn: http://www.linkedin.com/in/VladimirBacvanski Li k dI htt // li k di /i /Vl di i B ki • Parts of the presentation are from SciSpike courses: • Developing Database Applications with Optim Development Studio and pureQuery • Hibernate 24