Chapter 4. Collections and Associationscontents.kocw.net/KOCW/document/2016/hanbat/kimyoungchan/4.pdf · Prof. Youngchan KIM, Dept of Computer Engineering, 1 / 51 Hanbat National

1 / 51Prof. Youngchan KIM, Dept of Computer Engineering, Hanbat National University

Database Programming

Chapter 4. Collections and Associations

Collections

Associations



Java Variable and Collection

class Person {

Long id;

Address address;

}

class Address {

Long id;

Set<Person> persons = new HashSet<Person>;

}



Java Collections

Java Collections

Implementations

Interfaces

HashTable

ResizableArray Tree Linked

ListHash Table +Linked List

Set HashSet TreeSet LinkedHashSetList ArrayList LinkedList

QueueDeque ArrayDeque LinkedListMap HashMap TreeMap LinkedHashMap



Association and Mapping

Bidirectional Associations




Bidirectional Many-to-One/One-to-Many Associations 1/3

Person

id

Address

id*persons

1address

PersonAddress

class Person {Long id;Address address;

}

class Address {Long id;Set<Person> persons =

new HashSet<Person>;}

create table Address (addressId bigint not null primary key

)

create table Person (personId bigint not null primary key,addressId bigint not null

)





<class name="Person">

<id name="id" column="personId">

<generator class="native"/>

</id>

<many-to-one name="address"class="Address"column="addressId"not-null="true" />

</class>

<class name="Address">

<id name="id" column="addressId">


</id>

<set name="persons" inverse="true"><key column="addressId"/><one-to-many class="Person"/>

</set>

</class>


}




generated by default as identity)

create table Person (personId bigint not null primary key

generated by default as identity,addressId bigint not null

)



Association and Mapping (detail)





</id>

<many-to-one name="address"class="Address"column="addressId"not-null="true" />

</class>




</id>

<set name="persons" inverse="true"><key column="addressId"/><one-to-many class="Person"/>

</set>

</class>


}




generated by default as identity)


generated by default as identity,addressId bigint not null

)




Bidirectional Many-to-Many Associations 1/2

Person

id

Address

id*persons

*addresses

PersonAddress

create table PersonAddress ( personId bigint not null,addressId bigint not null,primary key (personId, addressId)

)

class Person {Long id;Set<Address> addresses =

new HashSet<Address>;}




)

create table Person (personId bigint not null primary key,

)




Bidirectional Many-to-Many Associations 2/2




</id>

<set name="addresses" table="PersonAddress"><key column="personId"/><many-to-many class="Address"

column="addressId"/></set>

</class>




</id>

<set name="persons" table="PersonAddress"inverse="true">

<key column="addressId"/><many-to-many class="Person"

column="personId"/></set>

</class>

create table Person ( personId bigint not null primary key )create table PersonAddress (

personId bigint not null,addressId bigint not null,primary key (personId, addressId)

)create table Address ( addressId bigint not null primary key )








Bidirectional One-to-One Associations on a Foreign Key 1/2

Person

id

Address

id1person

1address

PersonAddress


}

class Address {Long id;Person person;

}


)


)




Bidirectional One-to-One Associations on a Foreign Key 2/2




</id>

<many-to-one name="address"

class="Address"

column="addressId"

unique="true"

not-null="true" />

</class>




</id>

<one-to-one name="person"

property-ref="address"/>

</class>

property-ref (optional):the name of a property of the associated class that

is joined to the primary key of this classIf not specified, the primary key of the associated class is used.


}


}


)


)




Bidirectional One-to-One Associations on a Primary Key 1/2

Person

id

Address

id1person

1address

PersonAddress


}


}

create table Address (personId bigint not null primary key

)


)




Bidirectional One-to-One Associations on a Primary Key 2/2




</id>

<one-to-one name="address" cascade=“all”/>

</class>


}


}


)


)



<generator class="foreign">

<param name="property">person</param>

</generator>

</id>

<one-to-one name="person" constrained="true"/></class>

constrained (optional): specifies that a foreign key constraint on the primary key of the mapped table and references the table of the associated class




Unidirectional Associations




Unidirectional Many-to-One Associations 1/2


}

class Address {Long id;

}


)


)

Person

id

Address

id*persons

1address

PersonAddress




Unidirectional Many-to-One Associations 2/2




</id>

<many-to-one name="address" column="addressId" not-null="true" />

</class>




</id>

</class>


}


}


)


)




Unidirectional One-to-Many Associations (unusual case) 1/2

Person

id

Address

id1person

*addresses

PersonAddress

class Person {Long id;Set<Address> addresses;

}


}

create table Address (addressId bigint not null primary key,personId bigint not null

)


)




Unidirectional One-to-Many Associations (unusual case) 2/2




</id>

<set name="addresses">

<key column="personId" not-null="true"/>

<one-to-many class="Address"/>

</set>

</class>


<id name="id" column=“addressId">

<generator class=“native">

</id>

</class>

class Person {Long id;Set<Address> addresses;

}


}

create table Address (addressId bigint not null primary key,personId bigint not null

)


)




Unidirectional Many-to-Many Associations 1/2

Person

id

Address

id*persons

*addresses

PersonAddress


)




}


)


)




Unidirectional Many-to-Many Associations 2/2




</id>

<set name="addresses" table="PersonAddress">

<key column="personId"/>

<many-to-many class="Address" column="addressId" />

</set>

</class>


<id name="id" column=“addressId">

<generator class=“native">

</id>

</class>


)




}


)


)




Unidirectional One-to-One Associations on a Foreign Key 1/2

Person

id

Address

id1person

1address

PersonAddress


}


}


)


)




Unidirectional One-to-One Associations on a Foreign Key 2/2




</id>

<many-to-one name="address"

class="Address"

column="addressId"

unique="true"

not-null="true" />

</class>




</id>

</class>


}


}


)


)




Unidirectional One-to-One Associations on a Primary Key 1/2

Person

id

Address

id1person

1address

PersonAddress

class Person {Long id;

}


}


)


)




Unidirectional One-to-One Associations on a Primary Key 2/2



<generator class=“native“/>

</id>

</class>

class Person {Long id;

}


}


)


)


<id name="id" column="personId"><generator class=“foreign“>

<param name=“property”>person</param>

</generator>

</id>

<one-to-one name=“person" constrained=“true”/>

</class>



Association and Mapping Exercise

hibernate-369-mkyong-win

– 01-stock-quickstart-xml

– 03-stock-onetomany-xml

– 05-stock-manytomany-xml

– 08-stock-onetoone-xml



Exercise #4: Generate hbm.xml of Employee and Company

ex04/src/main/java/com/oreilly/hh/data/Employee.hbm.xml:

<hibernate-mapping>

<class name="com.oreilly.hh.data.Employee" …>

<id name="id" …>

…

</id>

…

</class>

</hibernate-mapping>

ex04/src/main/java/com/oreilly/hh/data/Company.hbm.xml:

<hibernate-mapping>

<class name="com.oreilly.hh.data.Company" …>

<id name="id" …>

…

</id>

…

</class>




Exercise #4: test

$ gradle test

:ex04:test

…

Results: SUCCESS (3 tests, 3 successes, 0 failures, 0 skipped)

BUILD SUCCESSFUL



Java Collections vs Database Relationships …

Bidirectional Many-to-Many Associations

Artist

idname

Track

idtitlefilePathplayTimeaddedvolume

0..*artists

0..*tracks

track_artists

class Artist {

Integer id;

String name;

Set<Track> tracks;

}

class Track {

Integer id;

String title;

String filePath;

time playTime;

date added;

short volume;

Set<Artist> artists;

}

UML

Java



Java Collections vs Database Relationships …

Unidirectional Many-to-Many Associations

Artist

idname

Track


0..*tracks

track_artists

class Artist {

Integer id;

String name;

Set<Track> tracks;

}

class Track {

Integer id;

String title;

String filePath;

time playTime;

date added;

short volume;

}

UML

Java



Java Collections vs Database Relationships

Many-to-Many Associations and Database Relationships

create table ARTIST (

id integer primary key,

name varchar(62)

)

create table TRACK (

id integer primary key,

title varchar(62),

filePath varchar(62),

playTime time,

added date,

volume smallint

)

UML

Tablecreate table TRACK_ARTISTS (

artist_id integer,

track_id integer,

foreign key (artist_id) references artist(id),

foreign key (track_id) references track(id)

)

Artist

idname

Track


0..*tracks

track_artists0..*

artists



Mapping Collections (for Bidirectional Many-to-Many Association)

Artist

idname

Track


0..*tracks

track_artists0..*

artists

<set name="tracks" table="TRACK_ARTISTS" inverse="true">

<key column="ARTIST_ID“ />

<many-to-many class="com.oreilly.hh.data.Track" column="TRACK_ID"/>

</set>

<set name="artists" table="TRACK_ARTISTS">

<key column="TRACK_ID"/>

<many-to-many class="com.oreilly.hh.data.Artist" column="ARTIST_ID"/>

</set>



Mapping Collections (for Unidirectional Many-to-Many Association)

Artist

idname

Track


0..*tracks

track_artists

<set name="tracks" table="TRACK_ARTISTS">

<key column="ARTIST_ID“ />


</set>



Mapping Collections (Artist.hbm.xml)

<?xml version="1.0“ encoding="UTF-8"?>

<!DOCTYPE hibernate-mapping PUBLIC ...>

<hibernate-mapping>

<class name="com.oreilly.hh.data.Artist" table="ARTIST">

<meta attribute="class-description"> ... </meta>

<id name="id" type="int" column="ARTIST_ID">


</id>

<property name="name" type="string">

<column name="NAME" not-null="true" unique="true" index="ARTIST_NAME"/>

</property>

<set name="tracks" table="TRACK_ARTISTS" inverse="true">

<key column="ARTIST_ID"/>


</set>

</class>




Mapping Collections (Track.hbm.xml)


<!DOCTYPE hibernate-mapping PUBLIC ...>

<hibernate-mapping>

<class name="com.oreilly.hh.data.Track" table="TRACK">

...

<set name="artists" table="TRACK_ARTISTS">


<many-to-many class="com.oreilly.hh.data.Artist" column="ARTIST_ID"/>

</set>

...

</class>




Mapping Collections (hibernate.cfg.xml)

hibernate.cfg.xml :


<!DOCTYPE hibernate-configuration PUBLIC ...>

<hibernate-configuration>

<session-factory>

...

<mapping resource="com/oreilly/hh/data/Track.hbm.xml"/>

<mapping resource="com/oreilly/hh/data/Artist.hbm.xml"/>

</session-factory>

</hibernate-configuration>



Persisting Collections (CreateTest.java)

public class CreateTest {

public static Artist getArtist(String name, boolean create, Session session)

{

Query query = session.getNamedQuery("com.oreilly.hh.artistByName");

query.setString("name", name);

Artist found = (Artist)query.uniqueResult();

if (found == null && create) {

found = new Artist(name, new HashSet<Track>());

session.save(found);

}

return found;

}

/**

* Utility method to associate an artist with a track

*/

private static void addTrackArtist(Track track, Artist artist) {

track.getArtists().add(artist);

}

...



Persisting Collections (Artist.hbm.xml)

Artist.hbm.xml :

...

<query name="com.oreilly.hh.artistByName">

<![CDATA[

from Artist as artist

where upper(artist.name) = upper(:name)

]]>

</query>

...

Track.hbm.xml :

...

<query name="com.oreilly.hh.tracksNoLongerThan">

<![CDATA[

from Track as track

where track.playTime <= :length

]]>

</query>

...



Persisting Collections (CreateTest.java) …...

public static void main(String args[]) throws Exception {

...

try {

// Create some data and persist it

tx = session.beginTransaction();

Track track = new Track("Russian Trance", "vol2/album610/track02.mp3",

Time.valueOf("00:03:30"), new HashSet<Artist>(), new Date(), (short)0);

addTrackArtist(track, getArtist("PPK", true, session));

session.save(track);

track = new Track("Video Killed the Radio Star", "vol2/album611/track12.mp3",


addTrackArtist(track, getArtist("The Buggles", true, session));


track = new Track("Gravity's Angel", "vol2/album175/track03.mp3",


addTrackArtist(track, getArtist("Laurie Anderson", true, session));




Persisting Collections (CreateTest.java)...

track = new Track("Adagio for Strings (Ferry Corsten Remix)", "vol2/album972/track01.mp3",


addTrackArtist(track, getArtist("William Orbit", true, session));

addTrackArtist(track, getArtist("Ferry Corsten", true, session));

addTrackArtist(track, getArtist("Samuel Barber", true, session));


track = new Track("Adagio for Strings (ATB Remix)", "vol2/album972/track02.mp3",


addTrackArtist(track, getArtist("William Orbit", true, session));

addTrackArtist(track, getArtist("ATB", true, session));

addTrackArtist(track, getArtist("Samuel Barber", true, session));


track = new Track("The World '99", "vol2/singles/pvw99.mp3",


addTrackArtist(track, getArtist("Pulp Victim", true, session));

addTrackArtist(track, getArtist("Ferry Corsten", true, session));


track = new Track("Test Tone 1", "vol2/singles/test01.mp3",


session.save(track);...



Persisting Collections : What just happened?

$ gradle ctest

$ gradle db



Retrieving Collections (QueryTest.java) …

package com.oreilly.hh;

...

public class QueryTest {

...

public static String listArtistNames(Set<Artist> artists) {

StringBuilder result = new StringBuilder();

for (Artist artist : artists) {

result.append((result.length() == 0) ? "(" : ", ");

result.append(artist.getName());

}

if (result.length() > 0) {

result.append(") ");

}

return result.toString();

}

...



Retrieving Collections (QueryTest.java)

public class QueryTest {

...

public static String listArtistNames(Set<Artist> artists) { ... }

public static void main(String args[]) throws Exception {

...

try {

// Print the tracks that will fit in seven minutes

List tracks = tracksNoLongerThan(Time.valueOf("00:07:00"),

session);

for ( Track aTrack : tracks ) {

System.out.println("Track: \"" + aTrack.getTitle() + "\" " +

listArtistNames(aTrack.getArtists()) +

aTrack.getPlayTime());

}

}

...

}

}



Retrieving Collections (Hibernate.cfg.xml)

...



<property name="show_sql">false</property>

...



Retrieving Collections : QueryTest Output

$ gradle qtest

:ch04:compileJava UP-TO-DATE

:ch04:processResources UP-TO-DATE

:ch04:classes UP-TO-DATE

:ch04:qtest

Track: "Russian Trance" (PPK) 00:03:30

Track: "Video Killed the Radio Star" (The Buggles) 00:03:49

Track: "Gravity's Angel" (Laurie Anderson) 00:06:06

Track: "Adagio for Strings (Ferry Corsten Remix)" (Ferry Corsten, William Orbit, Samuel Ba

rber) 00:06:35

Track: "Test Tone 1" 00:00:10

Comment: Pink noise to test equalization

BUILD SUCCESSFUL

Total time: 2.299 secs



Using Bidirectional Associations (QueryTest2.java)// Example 4-12. Source for QueryTest2.java

public class QueryTest2 extends JPanel {

...

private void updateTracks(String name) {

model.removeAllElements(); // Clear out previous tracks

if (name.length() < 1) return; // Nothing to do

try {

// Ask for a session using the JDBC information we've configured

Session session = sessionFactory.openSession();

try {

Artist artist = CreateTest.getArtist(name, false, session);

if (artist == null) { // Unknown artist

model.addElement("Artist not found");

return;

}

// List the tracks associated with the artist

for (Track aTrack : artist.getTracks()) {

model.addElement("Track: \"" + aTrack.getTitle() + "\", " + aTrack.getPlayTime());

}

} finally {

session.close();

}

} catch (Exception e) {

System.err.println("Problem updating tracks:" + e);

e.printStackTrace();

}

}



Using Bidirectional Associations (build.gradle)

...

task qtest2(dependsOn: classes, type: JavaExec) {

main = 'com.oreilly.hh.QueryTest2'classpath = sourceSets.main.runtimeClasspath

}

$ gradle qtest2



Working with Simpler Collections …




Collections of associations to other objects

collections of simple values, like strings, numbers, and nonpersistentvalue classes– want to record some number of comments about each track in the database– Track.hbm.xml

– gradle schema

...

<set name="comments" table="TRACK_COMMENTS">


<element column="COMMENT" type="string"/>

</set>

create table TRACK_COMMENTS (TRACK_ID integer not null, COMMENT varchar(255));

alter table TRACK_COMMENTS

add constraint FK105B26882DCBFAB5 foreign key (TRACK_ID) references TRACK;




Add Comment Set at the end of each Constructor of CreateTest.java :

Then assign a comment on the following line :

track = new Track("Test Tone 1", "vol2/singles/test01.mp3",

Time.valueOf("00:00:10"), new HashSet<Artist>(),

new Date(), (short)0, new HashSet<String>());

track.getComments().add("Pink noise to test equalization");




Add another loop after the track println( ) in QueryTest.java to print the comments for the track :

gradle qtest

for (String comment : aTrack.getComments()) {

System.out.println(" Comment: " + comment);

}

...

Track: "Test Tone 1" 00:00:10

Comment: Pink noise to test equalization



Materials for Further Study

Hibernate Home– http://www.hibernate.org/

Hibernate Manual– Hibernate Getting Started Guide 3.6

• http://docs.jboss.org/hibernate/core/3.6/quickstart/en-US/html/

– Hibernate Reference Documentation 3.6• http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html/• http://docs.jboss.org/hibernate/core/3.6/reference/en-US/pdf/hibernate_reference.pdf

– Hibernate Reference Documentation 4.3 and 5.0

Hibernate Tutorial– http://www.mkyong.com/tutorials/hibernate-tutorials/

Documents

Chapter 4. Collections and Associationscontents.kocw.net/KOCW/document/2016/hanbat/kimyoungchan/4.pdf · Prof. Youngchan KIM, Dept of Computer Engineering, 1 / 51 Hanbat National