7.4 PERFORM DATA DELETE TO ORACLE DATABASE USING THE JAVA RUNTIME OBJECT
We still want to work with the Faculty Table in our sample database via the FacultyFrame Form, sowe do not need to create a brand new project to perform this data update action, and instead we can use an existing project, OracleUpdateFaculty, and make it our new project to do the data delete action.
Perform the following operations to make our new project based on that project:
1) Open Windows Explorer and create a new folder, such as Class DB Project\ Chapter 7, on your root drive if you did not already do this.
2) Open Apache NetBeans 12.4, and one can find the project OracleUpdateFaculty we built in the last section in the Projects window. The other way to find this project is to go to the CRC Press ftp site, where it is located inthe Class DB Projects\Chapter 7 folder in the Students folder (refer to Figure 1.2 in Chapter 1). You can copy and paste that project to any folder, such as Class DB Projects\Chapter 7, on your computer.
3) Right-click on that project and select the Copy item from the popup menu to open the Copy Project wizard.
4) Change the project name to OracleDeleteFaculty in the Project Name box.
5) Browse to the folder, Class DB Projects\Chapter 7, which was created in step 1, and click on the OK button to select this location as your project location.
6) Click on the Copy button to complete this copy process.
Basically, there is no significant difference between data update and deletion using the Java run-time object method. In this section, we try to use the Delete button we built in the FacultyFrame Form window to perform this data deletion operation.
7.4.1 Develop the Code for the Delete Button Event Handler
Open our new project, OracleDeleteFaculty, and the Delete button click event handler, and enter the code shown in Figure 7.14 into this event handler. Let’s have a closer look at this piece of code to see how it works.
A. Two local variables, numDeleted and cFacultyName, are created first, and these two variables are used to hold the run result of the data delete action and the current faculty name.
B. The delete query string is created with one positional parameter. The query criterion is the faculty name that is placed after the WHERE clause.
C. A try-catch block is used to assist this data delete action. First, a PreparedStatement instance is created using the Connection object that is located in the LogInFrame class with the delete query string as the argument.
FIGURE 7.14 The developed code for the Delete button click event handler.
D. The setString() method is used to initialize the positional parameter, which is the faculty name to be deleted from the Faculty Name combo box.
E. After this faculty record has been deleted, we need to remove the faculty name from the Faculty Name combo box. In order to remember the current faculty name, we need to tem-porarily store it in our local string variable, cFacultyName.
F. The data delete action is performed by calling the executeUpdate() method. The delete result, which is an integer that is equal to the number of rows that have been deleted by the data delete action, is returned and assigned to the local integer variable numDeleted.
G. The catch block is used to track and collect any possible exception encountered when the data delete is executed.
H. The run result is printed out for debugging purposes.
I. The CurrentFaculty() method is executed to update the Faculty Name combo box.
Now we are ready to build and run the project to test the data deletion function.
