CS 157B: Database Management Systems II February 6 Class Meeting Department of Computer Science San...

CS 157B: Database Management Systems IIFebruary 6 Class Meeting

Department of Computer ScienceSan Jose State University

Spring 2013Instructor: Ron Mak

www.cs.sjsu.edu/~mak

Department of Computer ScienceSpring 2013: February 6

CS 157B: Database Management Systems II© R. Mak

2

Hibernate Oral Presentations

Next Monday, February 11. Four teams volunteer to each give a quick

15-minute presentation and demoof its project. What data did you use. Logical design of your database. How you used Hibernate. Demo of your application. Q & A



3

Hibernate Oral Presentations

Monday, February 11

Section 1 Team Cosmos Team VoidStarStar

Section 2 Team Xeon



4

Internet Connection Required

Recall the configuration file hibernate.cfg.xml:

The URL is for the Document Type Definition (DTD). Hibernate can’t parse the configuration file without it. Therefore, you need a working Internet connection

to execute a Hibernate program!

<?xml version='1.0' encoding='utf-8'?><!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration> <session-factory> ... </session-factory></hibernate-configuration>



5

No Internet Connection Required

Solution: Download that DTD and put it somewhere local,

such as in your source folder. Modify your hibernate.cfg.xml accordingly:

<?xml version='1.0' encoding='utf-8'?><!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "file:///G:/NetBeansProjects/SchoolDemo5/src/hibernate-configuration-3.0.dtd">

<hibernate-configuration> <session-factory> ... </session-factory></hibernate-configuration>



6

Queries Without SQL

... or anything that resembles SQL.

Hibernate offers an object-oriented way to formulate and execute database queries.

Criteria API Build nested, structured query expressions in Java. Compile-time syntax checking.

Unlike embedded SQL.

Like Hibernate itself, it isn’t perfect.



7

Get a List of Objects of a Class

Sort them:

Session session = HibernateContext.getSession();Criteria criteria = session.createCriteria(Student.class);

List<Student> students = (List<Student>) criteria.list();

criteria.addOrder(Order.asc("lastName"));List<Student> students = criteria.list();

Paginate:

Get only the first 5 objects.

criteria.setFirstResult(0);criteria.setMaxResults(5);List<Student> students = (List<Student>) criteria.list();

Also:Order.desc()



8

Query by Example

Query by Example (QBE) is a simple query technique. Create a prototype object. Set one or more of the prototype object’s field values. Use the prototype object to make an example object. Use the example object in a query to fetch all the objects

whose field values match those of the example.

Student prototype = new Student();prototype.setLastName("Smith");Example example = Example.create(prototype); Session session = HibernateContext.getSession();Criteria criteria = session.createCriteria(Student.class);criteria.add(example);

Student student = (Student) criteria.uniqueResult();

QBE doesn’t seem to workwith the primary key field.



9

Query by Example

Ignore zero-valued fields when matching:

Example example = Example.create( ... );example.excludeZeroes();

Don’t ignore null fields. The default is to ignore null fields when matching. Also enables matching on zero-valued fields.

Example example = Example.create( ... );example.excludeNone();

Ignore a particular field:

Example example = Example.create( ... );example.excludeProperty("firstName");



10

Query by Example

Fuzzy matches:

Get all students whose email addresses end in .com

MatchMode ANYWHERE START END EXACT

Student prototype = new Student();prototype.setEmailAddress(".com");Example example = Example.create(prototype);example.enableLike(MatchMode.END); Session session = HibernateContext.getSession();Criteria criteria = session.createCriteria(Student.class);criteria.add(example);

List<Student> students = (Student) criteria.list();



11

Restrictions

Query by example has some obvious limitations. What about the query “fetch all students with GPA > 3.0”?

Use the Criteria API’s Restrictions class. This class has many static methods.

See:

Session session = HibernateContext.getSession();Criteria criteria = session.createCriteria(Student.class);criteria.add(Restrictions.gt("gpa", 3.0f));

List<Student> smarties = (List<Student>) criteria.list();

http://docs.jboss.org/hibernate/orm/3.3/api/org/hibernate/criterion/Restrictions.html



12

Restrictions

You can “and” together multiple restrictions:Criterion crit1 = Restrictions.gt("gpa", 3.0f);Criterion crit2 = Restrictions.le("gpa", 3.5f);Criterion crit3 = Restrictions.isNotNull("emailAddress");

Student prototype = new Student();prototype.setEmailAddress(".com");

Example example = Example.create(prototype);example.enableLike(MatchMode.END);example.ignoreCase();

Session session = HibernateContext.getSession();Criteria criteria = session.createCriteria(Student.class);criteria.add(crit1);criteria.add(crit3);criteria.add(crit3);criteria.add(example);




13

Restrictions

You can also “or” together multiple restrictions. Fetch all students whose GPA is less that 3.0

or greater than 3.5

Criterion crit1 = Restrictions.lt("gpa", 3.0f);Criterion crit2 = Restrictions.gt("gpa", 3.5f);Disjunction disjunction = Restrictions.disjunction();disjunction.add(crit1);disjunction.add(crit2);

Session session = HibernateContext.getSession();Criteria criteria = session.createCriteria(Student.class);criteria.add(disjunction);




14

Criteria and Associations

What classes are taught by John Lane? Sorted by subject.

“Chain” criteria across associated objects. Use the reference fields.

Id Last First

7003 Rogers Tom

7008 Thompson Art

7012 Lane John

7051 Flynn Mabel

Code Teacher_id Subject

908 7008 Data structures

926 7003 Java programming

931 7051 Compilers

951 7012 Software engineering

974 7012 Operating systems

Teacher Class



15

Klass.java

@Entity@Table(name="Class")public class Klass{ ... private Teacher teacher; ... @ManyToOne @JoinColumn(name="teacher_id") public Teacher getTeacher() { return teacher; } public void setTeacher(Teacher teacher) { this.teacher = teacher; } ...}

What classes are taught by John Lane?



16


Id Last First

7003 Rogers Tom

7008 Thompson Art

7012 Lane John

7051 Flynn Mabel

Code Teacher_id Subject

908 7008 Data structures

926 7003 Java programming

931 7051 Compilers

951 7012 Software engineering

974 7012 Operating systems

Teacher Class

Session session = HibernateContext.getSession();Criteria classCriteria = session.createCriteria(Klass.class);Criteria teacherCriteria = classCriteria.createCriteria("teacher");

teacherCriteria.add(Restrictions.eq("firstName", "John")) .add(Restrictions.eq("lastName", "Lane"));

classCriteria.setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY);classCriteria.addOrder(Order.asc("subject"));

List<Klass> klasses = (List<Klass>) classCriteria.list();



17

Student.java

@Entitypublic class Student { ... private List<Klass> klasses = new ArrayList<Klass>(); ... @ManyToMany @JoinTable(name="Student_Class", joinColumns={@JoinColumn(name="student_id")}, inverseJoinColumns={@JoinColumn(name="class_code")}) public List<Klass> getKlasses() { return klasses; } public void setKlasses(List<Klass> klasses) { this.klasses = klasses; } ...}

Who are the students taught by John Lane?



18


Who are the students taught by John Lane?

Session session = HibernateContext.getSession();Criteria studentCriteria = session.createCriteria(Student.class);Criteria classCriteria = studentCriteria.createCriteria("klasses");Criteria teacherCriteria = classCriteria.createCriteria("teacher");

teacherCriteria.add(Restrictions.eq("firstName", "John")) .add(Restrictions.eq("lastName", "Lane"));

studentCriteria.setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY);studentCriteria.addOrder(Order.asc("lastName")); List<Student> students = (List<Student>) studentCriteria.list();

SchoolDemo6

Why is this line necessary?



19

Project #1

Now you should be able to use Hibernate to: Map Java classes to relational database tables. Specify one-to-one, one-to-many, and many-to-

many associations, and handle class hierarchies. Create and populate your database tables.

Use sample datasets downloaded from the Internet, or make up your own data.

Do queries using the Criteria API._



20

Hibernate Query Language (HQL)

Looks like SQL. However, queries are based on Java classes

and their fields, not database tables. Insulate your Java code from the database.

Value injection with named parameters. Example:public static Teacher find(String lastName){ Session session = HibernateContext.getSession(); Query query = session.createQuery("from Teacher where lastName = :name"); query.setString("name", lastName); Teacher teacher = (Teacher) query.uniqueResult(); session.close(); return teacher;}



21

Native SQL

As a last resort, Hibernate allows native SQL. Example:

The result will be an array of field values. Similar to a JDBC result set.

Session session = HibernateContext.getSession();SQLQuery query = session.createSQLQuery( "SELECT * FROM Teacher WHERE last_name = '" + lastName + "'"); Object result = query.uniqueResult();

Date post:	31-Dec-2015
Category:	Documents
Upload:	randell-smith
View:	214 times
Download:	0 times

CS 157B: Database Management Systems II February 6 Class Meeting Department of Computer Science San...

Documents