Posted by
arungupta on June 20, 2007 at 5:54 AM PDT
After
much discussion, I was able to finally create a simple "Hello JPA World"
example that uses
Java
Persistence API (JPA) to store and retrieve data from JavaDB from a Servlet
deployed on
GlassFish V2 b50 using NetBeans IDE 5.5.1.
This blog describes the steps, in detail, on how to create this sample.
- In NetBeans IDE, create a new Web project and name it as "
HelloJPA".
- Create an Entity class. Right-click the project, select '
New', 'Entity
Class ...'. Specify the values as shown below:
- Create a new Persistence Unit by selecting '
Create Persistence Unit ...'
and entering values as shown below:
and click on 'Create'.
and click on 'Finish'.
- Expand '
Configuration Files', open 'persistence.xml', click 'Add Class
...', select 'server.Company' and click on 'OK'. The 'persistence.xml'
will look like:
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0"
xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
<persistence-unit name="HelloJPAPU" transaction-type="RESOURCE_LOCAL">
<provider>oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider</provider>
<non-jta-data-source>jdbc/sample</non-jta-data-source>
<class>server.Company</class>
<properties>
<property name="toplink.ddl-generation" value="drop-and-create-tables"/>
</properties>
</persistence-unit>
</persistence>
- Add the following fields to the newly generated '
Company.java':
private String companyName;
private float price;
private float change;
private float percentChange;
private String lastUpdated;
- Generate getters/setters for each field by selecting the newly added
fields, right-click on the selected text, select '
Refactor',
'Encapsulate Fields ...' and choose the getter/setters for each field as
shown below:
- Add a constructor to '
Company' class as follows:
public Company(String companyName, float price, float change,
float percentChange, String lastUpdated) {
this.companyName = companyName;
this.price = price;
this.change = change;
this.percentChange = percentChange;
this.lastUpdated = lastUpdated;
}
- Change the toString method in Company to:
return "server.Company[id=" + id + ", lastUpdated=" + lastUpdated +
"]";
- Add a new Servlet by right-click on the Project, select New, '
Servlet
...' as shown below:
and click on 'Finish'.
- Update the generated Servlet template code such that it looks like:
protected void processRequest(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
beginHTML(out);
EntityManagerFactory emf =
Persistence.createEntityManagerFactory("HelloJPAPU");
EntityManager em = emf.createEntityManager();
em.getTransaction().begin();
out.println("<h1>Hello JPA World!</h1>");
Company c = new Company("AAA Co", (float)10.0, (float)2.0, (float)10.0,
new Date().toString());
em.persist(c); // persisting to the source
em.getTransaction().commit(); // now committed
List list = em.createQuery(
"select c from Company c where
c.companyName = :companyName")
.setParameter("companyName",
c.getCompanyName()).getResultList();
out.println("<b>Total Companies: " + list.size() + "</b><br>");
for (int i=0; i<list.size(); i++) {
out.println((Company) list.get(i) +
"<br>");
}
endHTML(out);
}
void beginHTML(PrintWriter out) {
out.println("<html>");
out.println("<head>");
out.println("<title>Hello JPA World!</title>");
out.println("</head>");
out.println("<body>");
}
void endHTML(PrintWriter out) {
out.println("</body>");
out.println("</html>");
out.close();
}
Fix the imports by using 'Alt+Shift+F' default keyboard shortcut.
- Right-click on the Project, select '
Properties', 'Run'
Categories, change the Relative URL to '/Hello'.
-
And that's it! Hit the Green button to run the project or the default
keyboard shortcut of '
F6'. After re-loading the page twice, the following output
will be seen in the browser window:
Technorati: jpa
glassfish
netbeans
