Transcript Apache Cayenne.

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Apache Cayenne
Object Relational Mapping
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What is ORM?
• ORM stands for Object Relational Mapping.
• It is a technique that creates an object oriented data model on top
of a Relational Database.
Grupo
PK
Alumno
id_grupo
1
programa
semestre
PK
id_alumno
FK
id_grupo
*
nombre_completo
Grupo
Alumno
id
programa
semestre
id
grupo
nombreCompleto
getId()
setId()
getPrograma()
setPrograma()
getSemestre()
setSemestre()
getId()
setId()
getGrupo()
setGrupo()
getNombreCompleto()
setNombreCompleto()
Persistence
• Persistence means that the data used in a software application
survives the application process.
• In other words, once you stop using or close the application the
data will remain stored in a (relational) database.
• In Java terms, we would like the state of some of our objects to live
beyond the JVM so that the same state is available later.
Object-Relational Impedance Mismatch
• Impedance mismatch refers to the structural differences between a
Relational Database and an Object Oriented Database.
• In order to do the mapping between both, we must overcome the
following problems:
– Granularity.
– Subtypes (Inheritance).
– Identities.
– Associations.
– Access to the information.
Frameworks for ORM
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Hibernate.
EclipseLink.
Data Knowledge Objects.
jOOQ.
Enterprise Java Beans EJB3.
Apache Cayenne.
Prerequisites
• Have already installed:
– Java 7.
– Eclipse EE with Maven plugin.
– Install any *AMP server or MySQL from scratch.
– Apache Cayenne Modeler 3.0 version.
– MySQL JDBC driver.
• It is important to have the required versions because there are
syntax changes from version to version.
Getting Started
• The next step is to follow the Getting Started tutorial from the
Cayenne website:
• https://cayenne.apache.org/docs/3.0/tutorial-starting-project.html
• We are going to build a simple web application that has this
database design:
Hands On
1. Create a Maven Project in Eclipse.
– File > New > Project > Other > Maven > Maven Project > Simple project
– Group Id: org.example.cayenne
– Artifact Id: tutorial
2. Create a Cayenne Modeler Project.
– New Project > Project
– DataDomain Name > datadomain
3. Create a MySQL database in PHPMyAdmin
– Start the Apache and MySQL servers
– Open PHPMyAdmin
– Databases > testdb > Create
Cayenne Modeler
New Project > Project
Create Data Node > datanode
– Datanode Name: datanode
– JDBC Driver: com.mysql.jdbc.Driver
– DB URL: jdbc:mysql://localhost:3306/testdb (port might change)
– User: root
– Password:
Create DataMap
– DataMap Name: datamap
– DataNode: datanode
– Java Package: org.example.cayenne.persistent
– Save the project in: tutorial/src/main/resources
Cayenne Modeler
Create the database tables:
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datamap > Create DB Entity
Name: ARTIST
Create Attribute: ID, INTEGER, PK
Repeat the steps for the Painting and Gallery tables.
Create relations between tables:
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Select DB Entity ARTIST.
Select Relationships and Create Relationship.
Target: Painting.
Select Database Mapping. Relationship: PAINTING; Reverse: ARTIST; Source: ID;
Target: ARTIST_ID
– In the paintings relation from ARTIST select To Many.
– In the artist relation from PAINTING unselect To Many.
– Repeat the same process for the GALLERY to PAINTING relation.
Cayenne Modeler
Create entities for class generation:
– Right click on ARTIST and click CREATE OBJECT ENTITY.
– Select the generated object and click synchronize relationships.
Generate Java Classes:
– Tools > Generate Classes
– Output Directory: tutorial/src/main/java
– Classes > Check All Classes
– Generate
Eclipse
Refresh the workspace and solve the dependencies:
– Refresh (F5).
– Edit the file pom.xml to look like in the following link:
– http://cayenne.apache.org/docs/3.0/tutorial-java-classes.html
Cayenne Modeler
Generate the Database Schema:
– Tools > Preferences > ClassPath > Add Jar and select the JAR file for MySQL
Connector J
– Tools > Generate Database Schema.
– Username: root
– Password:
Eclipse
Create Main class in the org.example.cayenne package.
– http://cayenne.apache.org/docs/3.0/tutorial-objectcontext.html
– Add the MySQL J Connector dependency to the pom.xml file.
– http://mvnrepository.com/artifact/mysql/mysql-connector-java/5.1.27
Refer to the following page in the tutorial:
– http://cayenne.apache.org/docs/3.0/tutorial-persistent-objects.html
– Add the setDateOfBirth method to Artist.java
– In the Main class, write the code to add one painter, two paintings and
one gallery.
– Run the code and check the results in phpMyAdmin.
– Then try the delete rules proposed in the tutorial:
– http://cayenne.apache.org/docs/3.0/tutorial-delete.html
Eclipse
Go to http://cayenne.apache.org/docs/3.0/tutorial-webapp.html in order
to convert our Applcation it into a Web Application:
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Create the folder src/main/webapp/WEB-INF
Create the file web.xml into src/main/webapp/WEB-INF
Create the file webapp/index.jsp
Create the file webapp/detail.jsp
Add the dependencies of maven-jetty-plugin to the pom.xml
Create an execution configuration for Maven:
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Run > Run Configurations > Maven Build > New
Name: cayenne-tutorial
Base directory: ${workspace_loc:/tutorial}
Goals: jetty:run
Apply > Run
Go to http://localhost:8080/tutorial/
Enhance your web application so it can add paintings to an artist.