- Converging Software
- JPA Shopping List
- What Is an Entity?
- Main Program
- Populating the Database
- Conclusion
Like this article? We recommend
Like this article? We recommend
Like this article? We recommend
Populating the Database
To populate the database, we need to execute the main program, as illustrated in Listing 9.
Listing 9 Running the database—populating the data.
C:\java\jpwh-gettingstarted-070401\helloworld-jpa>ant run Buildfile: build.xml compile: copymetafiles: run: [java] 1 message(s) found: [java] Hello World with JPA BUILD SUCCESSFUL
If you compare the program output in Listing 9 with the Java code in Listing 3, you'll see that the following Java code instantiates Message by executing the non-default constructor:
Message message = new Message("Hello World with JPA");
em.persist(message);
The object message is then written (persisted) to the database.
What does the database look like after running the code? Figure 2 illustrates the database contents.
)
Figure 2 The populated database.
Notice in Figure 2 that the row has been populated with the instance of Message. More of that JPA magic! Notice also that the column NEXT_MESSAGE_ID is blank, because no code was executed to populate the column. However, this is easily fixed by a call to the method setNextMessage().
You now have a great framework with which to explore JPA and persistence.