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6.3.3.2   JDBC Uniform Resource Locators (URLs) A JDBC url provides all information for applications to access a special resource, such as a data-base. Generally, a url contains three parts: protocol name, sub-protocol and subname for the data-base to be connected. Each of these three segments has a different function when they work together to provide unique information for the target database. The syntax for a JDBC url can be presented as: protocol:sub-protocol:subname The protocol name works as an identifier to show what kind of protocol should be adopted when connecting to the desired database. For a JDBC driver, the name of the protocol should beRead More →

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6.3.3.3   Create and Manage the Statement and PreparedStatement Objects The Statement class contains three important query methods with different functions: execute-Query(), executeUpdate() and execute(). For each method, different operations can be performed and different results can be returned. Generally, the execute methods can be divided into two categories: 1) execute methods that need to perform a data query, such as executeQuery(), which returns an instance of ResultSet that contains the queried results, and 2) execute methods that do not perform a data query and only return an integer, such as executeUpdate(). An inter-esting method is execute(), which can be used either way. method and theRead More →

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6.3.3.4   Use ResultSet Object The ResultSet class contains 25 methods, and the most popular methods used are: The ResultSet object can be created by either executing the executeQuery() or getRe-sultSet() method, which means that the ResultSet instance cannot be created or used without executing a query operation first. Similarly to a Statement object, a Connection object must be first created, and then the Statement component can be created and implemented based on the Connection object to perform a query. The queried result or data is stored in the ResultSet with a certain format, generally in a 2D tabular form with columns and rows. Each columnRead More →

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6.3.3.4.2   Fetching by Column: When a valid data row has been retrieved, we need to get each column from that row. To do that, a different getXXX() method should be used based on the different data type of the returned data. One can use either the name of the column or the index of that column to get the data value. For example, in our LogIn Table, both the user _ name and the pass _ word are Strings; therefore, a getString() method should be used with the index of each column. A point to be noted is that the first column has an indexRead More →

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6.3.4   Develop Code for the LogIn Table to Connect to Our Sample Database Now let’s develop the code to load and register the Oracle JDBC Driver in our LogInFrame class. Open the Code Window of the LogInFrame by clicking on the Source tab at the top of the win-dow, and enter the code shown in Figure 6.14 into this window. Let’s have a closer look at this piece of code to see how it works. A. Since all JDBC-related classes and interfaces are located in the java.sql package, we first need to import this package.B. A class instance, con, is declared here since we needRead More →

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6.3.5   Use the PreparedStatement Object to Perform Dynamic Query for the LogIn Table In the Design View of the LogInFrame Form window, double-click on the LogIn button to open its event handler, and enter the code shown in Figure 6.15 into this event handler. Let’s have a closer look at this piece of code to see how it works. A. Two local string variables, username and password, are declared first, since we need to use them to hold the returned query results later.B. An instance of the next Java Frame Form, selFrame, is generated, and this frame form will be displayed if the login processRead More →

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FIGURE 6.19   Code for the getter() method and the Exit button Click event handler. A. The function of the getter() method is: as it is called, the current SelectionFrame object is obtained by returning the this component that is a pointer to the current Frame object. A point to be noted is that the access mode of this method must be public, since we want this method to be called by other objects to get the SelectionFrame object as the project runs.B. In the Exit button Click event handler, a try-catch block is used to check whether the database connection we created in the LogInFrameRead More →

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6.3.6   Develop the Code for the SelectionFrame Form The function of this frame form is to enable users to select a desired query form to perform the related query to the selected Table in our sample database if the login process is successful. Select the SelectionFrame class by clicking on it in the Projects window and open its code window, enter the codes shown in Figure 6.17 into this window. Let’s have a closer look at this piece of code to see how it works. A. The Java JDBC Driver package is imported first, since we need to use some classes located in that packageRead More →