Beginning Apache Struts - From Novice To Professional (2006)

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public String getPassword(){ return _password;

}

public String setPassword(String password){ _password = password;

}

}

For each bean you want to persist using Hibernate, you have to create an XML description of it, which essentially maps the bean’s properties to tables and columns in your database. The XML mapping for User appears in Listing A-8.

Listing A-8. Hibernate XML Description of the User Bean

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping

PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">

<hibernate-mapping>

<class name="net.thinksquared.registration.data.User" table="user">

<id name="userId" type="string" unsaved-value="null">

<column name="user-id" sql-type="char(32)" not-null="true"/>

<generator class="assigned"/> </id>

<property name="password">

<column name="password" sql-type="char(32)" not-null="true"/>

</property>

</class> </hibernate-mapping>

The XML is fairly self-explanatory, and I won’t describe it further in any detail. The essential idea is that you have an XML file that maps your bean to an existing table in the database.

Saving a bean from scratch is a simple three-step process, very similar to saving data with JDBC:

1.Initialize Hibernate.

2.Obtain a Session object.

3.Save the bean using the Session and close the Session.

Step 1 is usually performed once, when the application starts up. Listing A-9 illustrates steps 1 to 3.

Listing A-9. Saving a User Bean with Hibernate

User u = new User(); u.setUserId("kolmogorov"); u.setPassword("turbulence23");

//Step 0: Start Hibernate

Configuration config = new Configuration().addClass(User.class); SessionFactory factory = config.buildSessionFactory();

//Step 1: Get a Session

Session s = factory.openSession();

//Step 2: Save and close

Transaction t = s.beginTransaction(); s.save(u);

t.commit();

s.close();

Remember that the User class is not autogenerated by Hibernate—it’s assumed to be an existing class in your app. Hibernate’s job is to allow you to save instances of User to a database without you having to worry about SQL and databases.

Doing a search for an object is easy, too. Listing A-10 shows how to implement the exists() function to check whether a given user ID exists.

•CONTACT, which stores contact information (see Lab 6)

•COLLECTION, which stores a collection’s name and notes

•COLLECTION_MAP, which stores the actual contacts that go into a collection

To use Lisptorq to generate these classes, you first create a LISP file describing the three tables, as in Listing A-11.

Listing A-11. models.lisp, the Lisptorq LISP File to Autogenerate LILLDEP Model Classes

(import lisptorq.lisp)

define database

(

(contact

(contact_id (PRIMARY REQUIRED INTEGER AUTO)) (name ((VARCHAR 1024)))

(designation ((VARCHAR 1024))) (department ((VARCHAR 1024))) (email ((VARCHAR 255)))

(tel ((VARCHAR 255))) (fax ((VARCHAR 255)))

(company ((VARCHAR 1024))) (address ((VARCHAR 1024))) (postcode ((VARCHAR 16)))

(website ((VARCHAR 255))) (activity ((VARCHAR 2048))) (classification ((VARCHAR 16))) (memo ((VARCHAR 2048)))

)

(collection

(collection_id (PRIMARY REQUIRED INTEGER AUTO)) (name ((VARCHAR 1024)))

(memo ((VARCHAR 2048)))

)

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(lisptorq:generate database)

To autogenerate the Model classes from this definition, simply put the JAR files jlisp.jar and lisptorq.jar in your classpath, and call the Loader class, like so:

java -classpath jlisp.jar;lisptorq.jar net.thinksquared.jlisp.Loader models.lisp

This will generate all your Model and helper classes, including a DatabaseSetup class, which you can call to create the tables on the database. For a tutorial on using Lisptorq, see www.thinksquared.net/dev/lisptorq/.

Unfortunately, as for LILLDEP, we’ll have to use two different derby-homes: one when the database is initialized for the first time, and the other when it is deployed on Tomcat. This means that you’ve got to create the class twice, or manually change the static section that sets up derby-home in Database.java to that listed in Listing A-12.

Listing A-12. A Tweak to Database.java

//set path to database

String catalinaHome = System.getProperty("catalina.home"); if(catalinaHome == null){

//we are called from an pre-install program System.setProperty("derby.system.home","./dbase");

}else{

//we are on a Tomcat servlet System.setProperty("derby.system.home",

catalinaHome + "/webapps/lilldep/dbase");

}

Useful Links

•The Derby project: http://incubator.apache.org/derby/

•For more on ACID: http://en.wikipedia.org/wiki/ACID

•Hibernate: www.hibernate.org/

•Torque: http://db.apache.org/torque/

•Lisptorq: www.thinksquared.net/dev/lisptorq/