Netbean Creating a Simple Web Application Using a MySQL Database


หน้าแรก Netbeans Netbean Creating a Simple Web Application Using a MySQL Database

This document describes how to create a simple web application that connects to a MySQL database server. It also covers some basic ideas and technologies in web development, such as JavaServer Pages (JSP), JavaServer Pages Standard Tag Library (JSTL), the Java Database Connectivity (JDBC) API, and two-tier, client-server architecture. This tutorial is designed for beginners who have a basic understanding of web development and are looking to apply their knowledge using a MySQL database.

MySQL is a popular open source database management system commonly used in web applications due to its speed, flexibility and reliability. MySQL employs SQL, or Structured Query Language, for accessing and processing data contained in databases.

This tutorial is a continuation from the Connecting to a MySQL Database tutorial and assumes that you have already created a MySQL database named MyNewDatabase, which you have registered a connection for in the NetBeans IDE. The table data used in that tutorial is contained in ifpwafcad.sql and is also required for this tutorial. This SQL file creates two tables, Subject and Counselor, then populates them with sample data. If needed, save this file to your computer, then open it in the NetBeans IDE and run it on the MySQL database named MyNewDatabase.

Contents

Content on this page applies to NetBeans IDE 6.8, 6.9 and 7.0

To follow this tutorial, you need the following software and resources.

Software or Resource Version Required
NetBeans IDE 6.8, 6.9 and 7.0, Java
Java Development Kit (JDK) 6
MySQL database server 5.x
MySQL Connector/J JDBC Driver version 5.x
GlassFish Server Open Source Edition 3.x

Notes:

  • The Java download bundle of the NetBeans IDE enables you to install the GlassFish server. You require the GlassFish server to work through this tutorial.
  • The MySQL Connector/J JDBC Driver, necessary for communication between Java platforms and the MySQL database protocol, is included in the NetBeans IDE.
  • If you need to compare your project with a working solution, you can download the sample application.

Planning the Structure

Simple web applications can be designed using a two-tier architecture, in which a client communicates directly with a server. In this tutorial, a Java web application communicates directly with a MySQL database using the Java Database Connectivity API. Essentially, it is the MySQL Connector/J JDBC Driver that enables communication between the Java code understood by the application server (the GlassFish server), and any content in SQL, the language understood by the database server (MySQL).

The application you build in this tutorial involves the creation of two JSP pages. In each of these pages you use HTML and CSS to implement a simple interface, and apply JSTL technology to perform the logic that directly queries the database and inserts the retrieved data into the two pages. The two database tables, Subject and Counselor, are contained in the MySQL database, MyNewDatabase, which you create by completing the Connecting to a MySQL Database tutorial. Consider the following two-tier scenario.

Diagram depicting the structure of a two-tier web application

The welcome page (index.jsp) presents the user with a simple HTML form. When a browser requests index.jsp, the JSTL code within the page initiates a query on MyNewDatabase. It retrieves data from the Subject database table, and inserts it into to the page before it is sent to the browser. When the user submits his or her selection in the welcome page's HTML form, the submit initiates a request for the response page (response.jsp). Again, the JSTL code within the page initiates a query on MyNewDatabase. This time, it retrieves data from both the Subject and Counselor tables and inserts it into to the page, allowing the user to view data based upon his or her selection when the page is returned to the browser.

In order to implement the scenario described above, you develop a simple application for a fictitious organization named IFPWAFCAD, The International Former Professional Wrestlers' Association for Counseling and Development.

index.jsp

index.jsp displayed in a browser

response.jsp

response.jsp displayed in a browser

Creating a New Project

Begin by creating a new Java web project in the IDE:

  1. Choose File > New Project (Ctrl-Shift-N; ⌘-Shift-N on Mac) from the main menu. Select the Java Web category, then select Web Application. Click Next.
    New Project wizard

    The New Project wizard allows you to create an empty web application in a standard IDE project. The standard project uses an IDE-generated Ant build script to compile, deploy, and run the application.

  2. In Project Name, enter IFPWAFCAD. Also, specify the location for the project on your computer. (By default, the IDE places projects in a NetBeansProjects folder located in your home directory.) Click Next.
  3. In the Server and Settings panel, specify the GlassFish server as server which will be used to run the application.

    Note. The GlassFish server displays in the Server drop-down field if you installed the Java version of the NetBeans IDE. Because the GlassFish server is included in the download, it is automatically registered with the IDE. If you want to use a different server for this project, click the Add button located next to the Server drop-down field, and register a different server with the IDE. However, working with servers other than the GlassFish server is beyond the scope of this tutorial.

  4. In the Java EE Version field, select Java EE 5.
    New Web Application wizard - Server and Settings

    Java EE 6 web projects do not require the use of the web.xml deployment descriptor, and the NetBeans project template does not include the web.xml file in Java EE 6 projects. However, this tutorial demonstrates how to declare a data source in the deployment descriptor, and it does not rely on any features specific to Java EE 6, so you can set the project version to Java EE 5.

    Note. You could equally set the project version to Java EE 6, then create a web.xml deployment descriptor. (From the New File wizard, select the Web category, then Standard Deployment Descriptor.)

  5. Click Finish. The IDE creates a project template for the entire application, and opens an empty JSP page (index.jsp) in the editor. The index.jsp file serves as the welcome page for the application. The new project is structured according to Sun Java BluePrints guidelines.

Preparing the Web Interface

Begin by preparing the welcome (index.jsp) and response (response.jsp) pages. The welcome page implements an HTML form that is used to capture user data. Both pages implement an HTML table to display data in a structured fashion. In this section, you also create a stylesheet that enhances the appearance of both pages.

Setting up the welcome page

Make sure index.jsp is opened in the editor. If it is not already open, double-click index.jsp from IFPWAFCAD > Web Pages in the Projects window.

  1. In the editor, change the text between the <title> tags to: IFPWAFCAD Homepage.
  2. Change the text between the <h1> tags to: 'Welcome to IFPWAFCAD, the International Former Professional Wrestlers' Association for Counseling and Development!.
  3. Open the IDE's Palette by choosing Window > Palette (Ctrl-Shift-8; ⌘-Shift-8 on Mac) from the main menu. Hover your pointer over the Table icon from the HTML category and note that the default code snippet for the item displays.
    Palette displaying code snippet when hovering over an item
    You can configure the Palette to your liking - right-click in the Palette and choose Show Big Icons and Hide Item Names to have it display as in the image above.
  4. Place your cursor at a point just after the <h1> tags. (This is where you want to implement the new HTML table.) Then, in the Palette, double-click the Table icon.
  5. In the Insert Table dialog that displays, specify the following values then click OK:

    • Rows: 2
    • Columns: 1
    • Border Size: 0
    The HTML table code is generated and added to your page.
  6. Add the following content to the table heading and the cell of the first table row (new content shown in bold): 
    <table border="0">
    <thead>
        <tr>
            <th>IFPWAFCAD offers expert counseling in a wide range of fields.</th>
        </tr>
    </thead>
    <tbody>
        <tr>
            <td>To view the contact details of an IFPWAFCAD certified former
                professional wrestler in your area, select a subject below:</td>
        </tr>
  7. For the bottom row of the table, insert an HTML form. To do so, place your cursor between the second pair of <td> tags, then double-click the HTML form ( HTML form icon ) icon in the Palette. In the Insert Form dialog, type in response.jsp in the Action text field, then click OK.
    Insert Form dialog
  8. Type in the following content between the <form> tags (new content shown in bold): 
    <tr>
    <td>
        <form action="response.jsp">
            <strong>Select a subject:</strong>
        </form>
    </td>
</tr>
    All of the items listed in the Palette can equally be accessed using the IDE's code completion support. To take advantage of code completion when working in the editor, press Ctrl-Space. The following two steps demonstrate how you add a drop-down list and submit button using code completion.
  9. In the editor, press Enter to add an empty line after the content you just added, then press Ctrl-Space to invoke the IDE's code completion support.
    Code completion pop-up window
    Select Drop-down List.
  10. In the Insert Drop-down dialog that displays, type in subject_id for the Name text field, and click OK. Note that the code snippet for the drop-down list is added to the form.

    The number of options for the drop-down is currently not important. Later in the tutorial you will add JSTL tags that dynamically generate options based on the data gathered from the Subject database table.
  11. Add a submit button item ( Submit button icon ) to a point just after the drop-down list you just added. You can either use the Palette to do this, or invoke the editor's code completion as illustrated in the previous step. In the Insert Button dialog, enter submit for both the Label and Name text fields, then click OK.
  12. To format your code, right-click in the editor and choose Format (Alt-Shift-F; Ctrl-Shift-F on Mac). Your code is automatically formatted, and should now look similar to the following: 
    <body>
    <h2>Welcome to <strong>IFPWAFCAD</strong>, the International Former
        Professional Wrestlers' Association for Counseling and Development!
    </h2>

    <table border="0">
        <thead>
            <tr>
                <th>IFPWAFCAD offers expert counseling in a wide range of fields.</th>
            </tr>
        </thead>
        <tbody>
            <tr>
                <td>To view the contact details of an IFPWAFCAD certified former
                    professional wrestler in your area, select a subject below:</td>
            </tr>
            <tr>
                <td>
                    <form action="response.jsp">
                        <strong>Select a subject:</strong>
                        <select name="subject_id">
                            <option></option>
                        </select>
                        <input type="submit" value="submit" name="submit" />
                    </form>
                </td>
            </tr>
        </tbody>
    </table>
</body>
    To view this page in a browser, right-click in the editor and choose Run File (Shift-F6; Fn-Shift-F6 on Mac). When you do this, the JSP page is automatically compiled and deployed to your server. The IDE opens your default browser to display the page from its deployed location.
    index.jsp displayed in a browser

Creating the response page

In order to prepare the interface for response.jsp you must first create the file in your project. Note that most of the content that displays in this page is generated dynamically using JSP technology. Therefore, in the following steps you add placeholders which you will later substitute for the JSP code.

  1. Right-click the IFPWAFCAD project node in the Projects window and choose New > JSP. The New JSP File dialog opens.
  2. In the JSP File Name field, enter response. Note that Web Pages is currently selected for the Location field, meaning that the file will be created in the project's web directory. This is the same location as where the index.jsp welcome page resides.
  3. Accept any other default settings and click Finish. A template for the new response.jsp page is generated and opens in the editor. A new JSP node also displays under Web Pages in the Projects window.
    response.jsp node appears in the Projects window
  4. In the editor, change the title to: IFPWAFCAD - {placeholder}.
  5. Remove the <h1>Hello World!</h1> line between the <body> tags, then copy and paste the following HTML table into the body of the page: 
    <table border="0">
    <thead>
        <tr>
            <th colspan="2">{placeholder}</th>
        </tr>
    </thead>
    <tbody>
        <tr>
            <td><strong>Description: </strong></td>
            <td><span style="font-size:smaller; font-style:italic;">{placeholder}</span></td>
        </tr>
        <tr>
            <td><strong>Counselor: </strong></td>
            <td>{placeholder}
                <br>
                <span style="font-size:smaller; font-style:italic;">
                member since: {placeholder}</span>
            </td>
        </tr>
        <tr>
            <td><strong>Contact Details: </strong></td>
            <td><strong>email: </strong>
                <a href="mailto:{placeholder}">{placeholder}</a>
                <br><strong>phone: </strong>{placeholder}
            </td>
        </tr>
    </tbody>
</table>
    To view this page in a browser, right-click in the editor and choose Run File (Shift-F6; Fn-Shift-F6 on Mac). The page compiles, is deployed to the GlassFish server, and opens in your default browser.
    response.jsp displayed in a browser

Creating a stylesheet

Create a simple stylesheet that enhances the display of the web interface. This tutorial assumes that you understand how style rules function, and how they affect corresponding HTML elements found in index.jsp and response.jsp.

  1. Open the New File wizard by pressing the New File ( New File button ) button in the IDE's main toolbar. Select the Web category, then select Cascading Style Sheet and click Next.
  2. Type style for CSS File Name and click Finish. The IDE creates an empty CSS file and places it in the same project location as index.jsp and response.jsp. Note that a node for style.css now displays within the project in the Projects window, and the file opens in the editor.
  3. In the editor, add the following content to the style.css file: 
    body {
    font-family: Verdana, Arial, sans-serif;
    font-size: smaller;
    padding: 50px;
    color: #555;
}

h1 {
    text-align: left;
    letter-spacing: 6px;
    font-size: 1.4em;
    color: #be7429;
    font-weight: normal;
    width: 450px;
}

table {
    width: 580px;
    padding: 10px;
    background-color: #c5e7e0;
}

th {
    text-align: left;
    border-bottom: 1px solid;
}

td {
    padding: 10px;
}

a:link {
   color: #be7429;
   font-weight: normal;
   text-decoration: none;
}

a:link:hover {
   color: #be7429;
   font-weight: normal;
   text-decoration: underline;
}
  4. Link the stylesheet to index.jsp and response.jsp. In both pages, add the following line between the <head> tags: 
    <link rel="stylesheet" type="text/css" href="style.css">
    To quickly navigate between files that are open in the editor, press Ctrl-Tab, then select the file you are wanting.


Preparing Communication between the Application and Database

The most efficient way to implement communication between the server and database is to set up a database connection pool. Creating a new connection for each client request can be very time-consuming, especially for applications that continuously receive a large number of requests. To remedy this, numerous connections are created and maintained in a connection pool. Any incoming requests that require access to the application's data layer use an already-created connection from the pool. Likewise, when a request is completed, the connection is not closed down, but returned to the pool.

After preparing the data source and connection pool for the server, you then need to instruct the application to use the data source. This is typically done by creating an entry in the application's web.xml deployment descriptor. Finally, you need to ensure that the database driver (MySQL Connector/J JDBC Driver) is accessible to the server.


  1. Setting up a JDBC data source and connection pool
  2. Referencing the data source from the application
  3. Adding the database driver's JAR file to the server

Setting up a JDBC data source and connection pool

The GlassFish Server Open Source Edition contains Database Connection Pooling (DBCP) libraries that provide connection pooling functionality in a way that is transparent to you as a developer. To take advantage of this, you need to configure a JDBC (Java Database Connectivity) data source for the server which your application can use for connection pooling.

For more information on JDBC technology, see The Java Tutorials: JDBC Basics.

You could configure the data source directly within the GlassFish server Admin Console, or, as described below, you can declare the resources that your application needs in a sun-resources.xml file. When the application is deployed, the server reads in the resource declarations, and creates the necessary resources.

The following steps demonstrate how to declare a connection pool, and a data source that relies on the connection pool. The NetBeans JDBC Resource wizard allows you to perform both actions.

  1. Open the New File wizard by pressing the New File ( New File button ) button in the IDE's main toolbar. Select the GlassFish server category, then select JDBC Resource and click Next.
  2. In step 2, General Attributes, choose the Create New JDBC Connection Pool option, then in the JNDI Name text field, type in jdbc/IFPWAFCAD.
    JDBC Resource wizard, step 2: General Attributes
    The JDBC data source relies on JNDI, the Java Naming and Directory Interface. The JNDI API provides a uniform way for applications to find and access data sources. For more information, see The JNDI Tutorial.
  3. Optionally, add a description for the data source. For example, type in: Accesses the database that provides data for the IFPWAFCAD application.
  4. Click Next, then click Next again to skip step 3, Additional Properties.
  5. In Step 4, type in IfpwafcadPool for JDBC Connection Pool Name. Make sure the Extract from Existing Connection option is selected, and choose jdbc:mysql://localhost:3306/MyNewDatabase from the drop-down list.
    JDBC Resource wizard, step 4: Choose Database Connection

    Note: The wizard detects any database connections that have been set up in the IDE. Therefore, you need to have already created a connection to the MyNewDatabase database at this point. You can verify what connections have been created by opening the Services window (Ctrl-5; ⌘-5 on Mac) and looking for connection nodes ( database connection node icon ) under the Databases category.
  6. Click Next. In Step 5, note that the IDE extracts information from the database connection you specified in the previous step, and sets name-value properties for the new connection pool.
    JDBC Resource wizard, step 5: Add Connection Pool Properties
  7. Click Finish. The wizard generates a glassfish-resources.xml file that contains entries for the data source and connection pool you specified.

In the Projects window, you can open the newly created Server Resources > glassfish-resources.xml file and note that, within the <resources> tags, a data source and connection pool have been declared containing the values you previously specified.

Note. In NetBeans IDE 6.9 and earlier versions of the IDE, the name of the file generated by the IDE is sun-resources.xml.

To confirm that a new data source and connection pool are indeed registered with the GlassFish server, you can deploy the project to the server, then locate the resources in the IDE's Services window:

  1. In the Projects window, right-click the IFPWAFCAD project node and choose Deploy. The server starts up if not already running, and the project is compiled and deployed to it.
  2. Open the Services window (Ctrl-5; ⌘-5 on Mac) and expand the Servers > GlassFish > Resources > JDBC > JDBC Resources and Connection Pools nodes. Note that the new data source and connection pool are now displayed:
    New data source and connection pool displayed in Services window

Referencing the data source from the application

You need to reference the JDBC resource you just configured from the web application. To do so, you can create an entry in the application's web.xml deployment descriptor.

Deployment descriptors are XML-based text files that contain information describing how an application is to be deployed to a specific environment. For example, they are normally used to specify application context parameters and behavioral patterns, security settings, as well as mappings for servlets, filters and listeners.

Note. If you specified Java EE 6 as the Java version when you created the project, you need to create the deployment descriptor file by choosing Web > Standard Deployment Descriptor in the New File wizard.

Perform the following steps to reference the data source in the application's deployment descriptor.

  1. In the Projects window, expand the Configuration Files folder and double-click web.xml. A graphical interface for the file displays in the IDE's main window.
  2. Click the References tab located along the top of the editor.
  3. Expand the Resource References heading and click Add to open the Add Resource Reference dialog.
  4. For Resource Name, enter the resource name that you gave when configuring the data source for the server above (jdbc/IFPWAFCAD). The Description field is optional, but you can enter a human-readable description of the resource, e.g., Database for IFPWAFCAD application. Click OK.
    Add Resource Reference dialog

    Click OK. The new resource is now listed under the Resource References heading.

    New JDBC resource listed in the deployment descriptor
  5. To verify that the resource is now added to the web.xml file, click the XML tab located along the top of the editor. Notice that the following <resource-ref> tags are now included. 
    <resource-ref>
    <description>Database for IFPWAFCAD application</description>
    <res-ref-name>jdbc/IFPWAFCAD</res-ref-name>
    <res-type>javax.sql.dataSource</res-type>
    <res-auth>Container</res-auth>
    <res-sharing-scope>Shareable</res-sharing-scope>
</resource-ref>

Adding the database driver's JAR file to the server

Adding the database driver's JAR file is another step that is vital to enabling the server to communicate with your database. Ordinarily, you would need to locate your database driver's installation directory and copy the mysql-connector-java-5.1.6-bin.jar file from the driver's root directory into the library folder of the server you are using. Fortunately, the IDE's server management is able to detect at deployment whether the JAR file has been added - and if not, it does so automatically.

In order to demonstrate this, open the Servers window (Choose Tools > Servers). The IDE provides a JDBC driver deployment option. If the option is enabled, it initiates a check to determine whether any drivers are required for the server's deployed applications. In the case of MySQL, if the driver is required and it is missing, the IDE's bundled driver is deployed to the appropriate location on the server.

  1. Choose Tools > Servers to open the Servers window. Select the GlassFish server in the left pane.
  2. In the main pane, select the Enable JDBC Driver Deployment option.
    Servers window - the GlassFish server 3.0.1
  3. Before you close the window, make a note of the path indicated in the Domains folder text field. When you connect to the GlassFish server in the IDE, you are actually connecting to an instance of the application server. Each instance runs applications in a unique domain, and the Domain Name field indicates the name of the domain your server is using. As shown in the image above, the driver JAR file should be located within domain1, which is the default domain created upon installing the GlassFish server.
  4. Click Close to exit the Servers window.
  5. On your computer, navigate to the GlassFish server installation directory and drill into the domains > domain1 > lib subfolder. Because you should have already deployed the IFPWAFCAD project to the server, you should see the mysql-connector-java-5.1.6-bin.jar file. If you do not see the driver JAR file, perform the following step.
  6. Deploy your project to the server. In the IDE's Projects window, choose Deploy from the right-click menu of the project node. You can view progress in the IDE's Output window (Ctrl-4; ⌘-4 on Mac). The output indicates that the MySQL driver is deployed to a location in the GlassFish server.
    Output window indicating MySQL driver has been deployed
    Now, if you return to the domain1/lib subfolder on your computer, you can see that the mysql-connector-java-5.1.6-bin.jar file has been automatically added.

Adding Dynamic Logic

Returning to the index.jsp and response.jsp placeholders that you created earlier in the tutorial, you can now implement the JSTL code that enables pages to generate content dynamically, i.e., based on user input. To do so, perform the following three tasks.

  1. Add the JSTL library to the project's classpath
  2. Implement JSTL code

Adding the JSTL library to the project's classpath

You can apply the JavaServer Pages Standard Tag Library (JSTL) to access and display data taken from the database. The GlassFish server includes the JSTL library by default. You can verify this by expanding IFPWAFCAD's Libraries > the GlassFish server node in the Projects window, and searching for the jstl-impl.jar file. Because the GlassFish server libraries are by default added to your project's classpath, you don't have to perform any steps for this task.

JSTL provides four basic areas of functionality. These are:

  • core: common, structural tasks such as iterators and conditionals for handling flow control
  • fmt: internationalization and localization message formatting
  • sql: simple database access
  • xml: handling of XML content

This tutorial focuses on usage of the core and sql tag libraries.

For more information on JSTL, see The Java EE 5 Tutorial, Chapter 7: JavaServer Pages Standard Tag Library.

Implementing JSTL code

Now you can implement the code that dynamically retrieves and displays data for each page. Both pages require that you implement an SQL query that utilizes the data source created earlier in the tutorial.

The IDE provides several database-specific JSTL snippets which you can select from the Palette (Ctrl-Shift-8; ⌘-Shift-8 on Mac).

Database snippets available from the Palette

You can also access Palette items by pressing Ctrl-Space in the editor. You can filter database items by typing 'db', then pressing Ctrl-Space.

Database snippets available from the Palette

index.jsp

In order to dynamically display the contents of the form in index.jsp, you need to access all names from the Subject database table.

  1. Hover your mouse over the DB Report item in the Palette.
    Database snippets available from the Palette
    The DB Report item uses the <sql:query> tag to create an SQL query, then it uses the <c:forEach> tag to loop through the query's resultset and output the retrieved data.
  2. Place your cursor above the <%@page ... %> declaration (line 7), then double-click the DB Report item in the Palette. In the dialog that displays, enter the following details:
    • Variable Name: subjects
    • Scope: page
    • Data Source: jdbc/IFPWAFCAD
    • Query Statement: SELECT subject_id, name FROM Subject
    Insert DB Report dialog
  3. Click OK. The following content is generated in the index.jsp file. (New content shown in bold.) 
    <%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglib prefix="sql" uri="http://java.sun.com/jsp/jstl/sql"%>
<%--
    Document   : index
    Created on : Dec 22, 2009, 7:39:49 PM
    Author     : nbuser
--%>

<sql:query var="subjects" dataSource="jdbc/IFPWAFCAD">
    SELECT subject_id, name FROM Subject
</sql:query>

<table border="1">
    <!-- column headers -->
    <tr>
    <c:forEach var="columnName" items="${subjects.columnNames}">
        <th><c:out value="${columnName}"/></th>
    </c:forEach>
</tr>
<!-- column data -->
<c:forEach var="row" items="${subjects.rowsByIndex}">
    <tr>
    <c:forEach var="column" items="${row}">
        <td><c:out value="${column}"/></td>
    </c:forEach>
    </tr>
</c:forEach>
</table>

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
    "http://www.w3.org/TR/html4/loose.dtd">
    Note that the IDE automatically added taglib directives needed for the JSTL tags used in the generated content (<sql:query> and <c:forEach>). A taglib directive declares that the JSP page uses custom (i.e., JSTL) tags, names the tag library that defines them, and specifies their tag prefix.
  4. Run the project to see how it displays in a browser. Right-click the project node in the Projects window and choose Run.

    When you choose Run, the IDE deploys the project to the GlassFish server, the index page is compiled into a servlet, and the welcome page opens in your default browser. The code generated from the DB Report item creates the following table in the welcome page.

    Browser displaying table containing data from Subject database table

    As you can see, the DB Report item enables you to quickly test your database connection, and enables you to view table data from the database in your browser. This can be particularly useful when prototyping.

    The following steps demonstrate how to integrate the generated code into the HTML drop-down list you created earlier in the tutorial.

  5. Examine the column data in the generated code. Two <c:forEach> tags are used; one is nested inside the other. This causes the JSP container (i.e., the GlassFish server) to perform a loop on all table rows, and for each row, it loops through all columns. In this manner, data for the entire table is displayed.
  6. Integrate the <c:forEach> tags into the HTML form as follows. The value of each item becomes the subject_id, and the output text becomes the name, as recorded in the database. (Changes are displayed in bold). 
    <form action="response.jsp">
    <strong>Select a subject:</strong>
    <select name="subject_id">
        <c:forEach var="row" items="${subjects.rowsByIndex}">
            <c:forEach var="column" items="${row}">
                <option value="<c:out value="${column}"/>"><c:out value="${column}"/></option>
            </c:forEach>
        </c:forEach>
    </select>
    <input type="submit" value="submit" name="submit" />
</form>
    An alternative, simpler way to integrate the <c:forEach> tags into the HTML form would be as follows. 
    <form action="response.jsp">
    <strong>Select a subject:</strong>
    <select name="subject_id">
        <c:forEach var="row" items="${subjects.rows}">
            <option value="${row.subject_id}">${row.name}</option>
        </c:forEach>
    </select>
    <input type="submit" value="submit" name="submit" />
</form>

    In either case, the <c:forEach> tags loop through all subject_id and name values from the SQL query, and insert each pair into the HTML <option> tags. In this manner, the form's drop-down list is populated with data.

  7. Delete the table that was generated from the DB Report item. (Deletion shown below as strike-through text.) 
    <%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglib prefix="sql" uri="http://java.sun.com/jsp/jstl/sql"%>
<%--
    Document   : index
    Created on : Dec 22, 2009, 7:39:49 PM
    Author     : nbuser
--%>

<sql:query var="subjects" dataSource="jdbc/IFPWAFCAD">
    SELECT subject_id, name FROM Subject
</sql:query>

<table border="1">
    <!-- column headers -->
    <tr>
    <c:forEach var="columnName" items="${subjects.columnNames}">
        <th><c:out value="${columnName}"/></th>
    </c:forEach>
</tr>
<!-- column data -->
<c:forEach var="row" items="${subjects.rowsByIndex}">
    <tr>
    <c:forEach var="column" items="${row}">
        <td><c:out value="${column}"/></td>
    </c:forEach>
    </tr>
</c:forEach>
</table>

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
    "http://www.w3.org/TR/html4/loose.dtd">
  8. Save your changes (Ctrl-S; ⌘-S on Mac).
  9. Refresh the welcome page of the project in your browser.

    Note that the drop-down list in the browser now contains subject names that were retrieved from the database.

    subject drop-down list displayed in a browser

    Note that you do not need to redeploy your project. By default, compile-on-save is enabled for your project. This means that when you modify and save a file, the file is automatically compiled and deployed and you do not need to recompile the entire project. You can enable and disable compile-on-save for your project in the Compiling category of the Properties window of the project.

response.jsp

The response page provides details for the counselor who corresponds to the subject chosen in the welcome page. The query you create must select the counselor record whose counselor_id matches the counselor_idfk from the selected subject record.

  1. Place your cursor above the <%@page ... %> declaration (line 7), type 'db' then press Ctrl-Space. Select DB Query. (See the code completion tip displayed above.)
  2. In the dialog that displays, enter the following details:
    • Variable Name: counselorQuery
    • Scope: page
    • Data Source: jdbc/IFPWAFCAD
    • Query Statement: SELECT * FROM Subject, Counselor WHERE Counselor.counselor_id = Subject.counselor_idfk AND Subject.subject_id = ? <sql:param value="${param.subject_id}"/>
    Insert DB Query dialog
  3. Click OK. The following content is generated in the response.jsp file. (New content shown in bold.) 
    <%@taglib prefix="sql" uri="http://java.sun.com/jsp/jstl/sql"%>
<%--
    Document   : response
    Created on : Dec 22, 2009, 8:52:57 PM
    Author     : nbuser
--%>

<sql:query var="counselorQuery" dataSource="jdbc/IFPWAFCAD">
    SELECT * FROM Subject, Counselor
    WHERE Counselor.counselor_id = Subject.counselor_idfk
    AND Subject.subject_id = ? <sql:param value="${param.subject_id}"/>
</sql:query>

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
    "http://www.w3.org/TR/html4/loose.dtd">
    Note that the IDE automatically added the taglib directive needed for the <sql:query> tag. Also, note that you used an <sql:param> tag directly within the query. Because this query relies on the subject_id value that was submitted from index.jsp, you can extract the value using an EL (Expression Language) statement in the form of ${param.subject_id}, and then pass it to the <sql:param> tag so that it can be used in place of the SQL question mark (?) during runtime.
  4. Use a <c:set> tag to set a variable that corresponds to the first record (i.e., row) of the resultset returned from the query. (New content shown in bold.) 
    <sql:query var="counselorQuery" dataSource="jdbc/IFPWAFCAD">
    SELECT * FROM Subject, Counselor
    WHERE Counselor.counselor_id = Subject.counselor_idfk
    AND Subject.subject_id = ? <sql:param value="${param.subject_id}"/>
</sql:query>

<c:set var="counselorDetails" value="${counselorQuery.rows[0]}"/>
    Although the resultset returned from the query should only contain a single record, this is a necessary step because the page needs to access values from the record using EL (Expression Language) statements. Recall that in index.jsp, you were able to access values from the resultset simply by using a <c:forEach> tag. However, the <c:forEach> tag operates by setting a variable for the rows contained in the que

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