Swing Hacks

Create a JDBC Table Model #24

Chapter 3, Tables and Trees

127

HACK

With the queries done, you just convert the ArrayLists to real arrays (which

offer quick lookups for the get methods). The implementations of the

AbstractTableModel

methods mentioned previously, as well as the improved

implementations of

getColumnClass( )

and

getColumnName( )

, are trivial uses

of the

columnNames

columnClasses

, and

contents

arrays built up by this

method.

Testing Things Out

Before you say “I can’t run this hack, I don’t have a database,” relax! The

open source world has you covered. And no, it’s not some big thing like

JBoss. HSQLDB, more commonly known by its old name, Hypersonic, is a

JDBC relational database engine written in Java. It is really small and can be

run as a standalone server or within your JVM. If you are database-less, grab

HSQLDB from http://hsqldb.sourceforge.net/.

Whatever your database, you’ll need a driver classname, URL, username,

and password to make a connection to the database. If you have your own

database, I trust you already know this. If you just downloaded HSQLDB

one paragraph ago, then you’ll be using the following information:

• Driver: org.hsqldb.jdbcDriver

• URL: jdbc:hsqldb:file:testdb

• User: sa

• Password: (none)

This assumes you’ll be running Hypersonic as part of your application,

meaning you’ll need to extend your classpath to pick up the hsqldb.jar file.

Also note that this will create some testdb files in your current directory that

you can clean up when done. You can also provide a full path to some other

directory; see HSQLDB’s docs for more info.

The test runner expects to pick up the connection strings as properties

named

jdbctable.driver, jdbctable.url, jdbctable.user, and jdbctable.pass.

To make things easier, there are two ways to pass these in: either as system

properties (usually specified with

-D arguments to the java command), or in

a file called jdbctable.properties. The book code has a sample of the latter

with HSQLDB values as defaults.

To test the

JDBCTableModel, the TestJDBCTable creates an entirely new table

in the database. The model gets the

Connection and the name of this table

and loads the data from the database. Then the test class simply creates a

new

JTable from the model and puts it in a JFrame. Example 3-13 shows the

source for this demo.

128

Chapter 3, Tables and Trees

#24 Create a JDBC Table Model

HACK

Example 3-13. Testing the JDBC-based table

import javax.swing.*;

import javax.swing.table.*;

import java.sql.*;

import java.util.*;

import java.io.*;

public class TestJDBCTable {

public static void main (String[] args) {

try {

driver, url, user, and pass can be passed in as

system properties "jdbctable.driver",

"jdbctable.url", "jdbctable.user", and

"jdbctable.pass", or specified in a file

called "jdbctable.properties" in current

directory

Properties testProps = new Properties( );

String ddriver = System.getProperty ("jdbctable.driver");

String durl = System.getProperty ("jdbctable.url");

String duser = System.getProperty ("jdbctable.user");

String dpass = System.getProperty ("jdbctable.pass");

if (ddriver != null)

testProps.setProperty ("jdbctable.driver", ddriver);

if (durl != null)

testProps.setProperty ("jdbctable.url", durl);

if (duser != null)

testProps.setProperty ("jdbctable.user", duser);

if (dpass != null)

testProps.setProperty ("jdbctable.pass", dpass);

try {

testProps.load (new FileInputStream (

new File ("jdbctable.properties")));

} catch (Exception e) {} // ignore FNF, etc.

System.out.println ("Test Properties:");

testProps.list (System.out);

// now get a connection

// note care to replace nulls with empty strings

Class.forName(testProps.getProperty

("jdbctable.driver")).newInstance( );

String url = testProps.getProperty ("jdbctable.url");

url = ((url == null) ? "" : url);

String user = testProps.getProperty ("jdbctable.user");

user = ((user == null) ? "" : user);

String pass = testProps.getProperty ("jdbctable.pass");

pass = ((pass == null) ? "" : pass);

Create a JDBC Table Model #24

Chapter 3, Tables and Trees

129

HACK

Connection conn =

DriverManager.getConnection (url, user, pass);

// create db table to use

String tableName = createSampleTable(conn);

// get a model for this db table and add to a JTable

TableModel mod =

new JDBCTableModel (conn, tableName);

JTable jtable = new JTable (mod);

JScrollPane scroller =

new JScrollPane (jtable,

ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,

ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED);

JFrame frame = new JFrame ("JDBCTableModel demo");

frame.getContentPane( ).add (scroller);

frame.pack( );

frame.setVisible (true);

conn.close( );

} catch (Exception e) {

e.printStackTrace( );

}

public static String createSampleTable (Connection conn)

throws SQLException {

Statement statement = conn.createStatement( );

// drop table if it exists

try {

statement.execute ("DROP TABLE EMPLOYEES");

} catch (SQLException sqle) {

sqle.printStackTrace( ); // if table !exists

}

statement.execute ("CREATE TABLE EMPLOYEES " +

"(Name CHAR(20), Title CHAR(30), Salary INT)");