GamerForSale
15.07.2007, 12:53
Wer mit Java zu tun hat, kommt irgendwann natürlich auch mit Datenbanken in Berührung. Apache stellt mit Derby eine leichtgewichtige und leistungsfähige (aber manchmal auch etwas ... *eigensinnige*) Datenbank zur Verfügung. Zudem sind seit dem JDK 6 nativ Treiber für die Derby-Datenbank integriert, weshalb das Aufsetzen einer Derby-Datenbank wirklich recht unkompliziert ist. Ich hab in meinem (sich noch im Aufbau befindlichen) Wiki nun ein komplettes Tutorial zu dem Thema Derby & Java (mit Eclipse) erstellt, was ich der Einfachheit halber einfach hier noch einmal Abdrucke.
Den Original Artikel findet ihr unter : http://wiki.gamerforsale.com/index.php/Java_Database
Bei Fragen oder Anregungen meldet euch einfach hier im Thread oder schreibt mich per PN/Email an.
Viel Spaß,
Nico
__________________________________________________ ______________
Those of you, who are working in Java, will sooner or later need databases as well. Apache offers a very powerful, and flexible Java-Database called "Derby". The reason why Derby would be a good Database to start with is, that as of JDK 6, DerbyDrivers are natively integrated, which eases the overall setup of the Database especially for Java-newcomers. In the following I'll provide a brief but comprehensible Tutorial on how to setup up and use a Derby-Database in Eclipse.
The article is also posted on my wikipage, which can be reached by following this link : http://wiki.gamerforsale.com/index.php/Java_Database
In case you have any questions or suggestions, please don't hesitate to voice them either right here or by sending me a PN/Email.
Enjoy,
Nicolai
__________________________________________________ ______________
Und nun zum Tutorial :
Derby and Java
Useful Links
Derby Homepage (http://db.apache.org/derby/manuals/index.html)
Derby Documentation (http://db.apache.org/derby/manuals/index.html)
Download Derby (http://db.apache.org/derby/derby_downloads.html)
Getting Started
While writing this article, the current Version of Derby is Version 10.2.2.0. Simply head over to the download-Section on the official Derby-Website (link given above) and download the current Release - mind, that actually all you need as of JDK 6.0 is the derby.jar (no drivers needed if you go for the embedded ones shipped with JDK 6), hence the "lib-Distribution-Package" will do the Job. After downloading the package, unpack it into a temporary folder and safely delete everything from it, except the derby.jar.
Derby meets Eclipse
Now its about time to integrate your Derby-Database into an Eclipse-Project. I'll assume, that you are already more or less familiar with the Eclipse-IDE. If that isn't the case, best check out the Eclipse Documentation (http://www.eclipse.org/documentation/). Open your Eclipse-IDE and create a New Project. Now open your Eclipse-Workspace (the Location where your newly created Projects are kept) either in a Terminal or a Window. Switch to the folder of your current Project (Top-Level) and create a Folder called "lib" - here we're going to store all ".jar"-Files that are used in our Project. Copy the derby.jar into this lib-Folder.
Now switch back to Eclipse and refresh it by right-clicking on your Project and hitting the "Refresh-Button"). The lib-folder should now pop up and list display the derby.jar as well. Now we're going to add our derby.jar to the build-path of our Project. To accomplish this, simply right-click on the derby.jar and chose "Build->Add to Build-Path".
As for the configuration we're pretty much done. Now comes the fun-part : Coding :-) ...
Derby meets Java
First of all I recommend you to create a class called something like "DatabaseManager", which offers some basic functionality for administrating and accessing the Database. Since only one instance of this DatabaseManager is needed, I would setup the class as a Singleton (http://wiki.gamerforsale.com/index.php/Design_Patterns#Singleton) in order to provide instant access without creating thousands of instances. The DatabaseManager will provide Connections to the Database on request and contain some basic Database-Operations according to the CRUD-Pattern (Create, Read, Update, Delete). In the following I'll provide a class-template which will give you an idea of how to structure your DatabaseManager.
public class DatabaseManager
{
private static String dbURL : "jdbc:derby:softcondb;create=true";
private static String dbDriver : "org.apache.derby.jdbc.EmbeddedDriver";
//Self-Reference
private static DatabaseManager self;
//Private Constructor which Sets up the Database-Driver
private DatabaseManager()
{
Class.forName(dbDriver).newInstance();
}
//Method to acquire an instance of the DatabaseManager
public static DatabaseManager getInstance()
{
if (self == null)
self = new DatabaseManager();
return self;
}
//This method returns a Connection to the Database
public Connection getconnection() throws SQLException
{
Connection con = DriverManager.getConnection(dbURL);
con.setAutoCommit(true);
return con;
}
//Add some Methods for handling DB-Requests such as Inserts,Updates or Selects
//Consider using static (String) class-variables for the DB-Commands in order
//to make future-adjustments easier and maintainance overall
}
You may now call the above Manager from pretty much any class which needs access to the Database, in the following I'll demonstrate how to make a request and cleanup afterwards (Closing the Database-Connection and freeing the ResultSets).
public void getAllOrders() trows SQLException
{
//We set these variables to null, so that we can check for null in the finally-block
//which will save us from running into a nullpointer-exception in the finally-block
Connection con = null;
Statement getOrders = null;
try
{
//Get a Connection to the Database by using the DatabaseManager
con = DatabaseManager.getInstance().getConnection();
//Create a Statement
getOrders = con.createStatement();
//Execute a Statement
ResultSet resultGetOrders = getOrders.executeQuery("SELECT * FROM Orders");
//Do somemthing with the Result Set
//Free the ResultSet
resultGetOrders.close();
}
finally
{
try
{
if (con != null)
con.close();
if(getOrders != null)
getOrders.close();
}
catch (SQLException e)
{
//Consider throwing a self-made exception here which specifies the error
}
}
}
Den Original Artikel findet ihr unter : http://wiki.gamerforsale.com/index.php/Java_Database
Bei Fragen oder Anregungen meldet euch einfach hier im Thread oder schreibt mich per PN/Email an.
Viel Spaß,
Nico
__________________________________________________ ______________
Those of you, who are working in Java, will sooner or later need databases as well. Apache offers a very powerful, and flexible Java-Database called "Derby". The reason why Derby would be a good Database to start with is, that as of JDK 6, DerbyDrivers are natively integrated, which eases the overall setup of the Database especially for Java-newcomers. In the following I'll provide a brief but comprehensible Tutorial on how to setup up and use a Derby-Database in Eclipse.
The article is also posted on my wikipage, which can be reached by following this link : http://wiki.gamerforsale.com/index.php/Java_Database
In case you have any questions or suggestions, please don't hesitate to voice them either right here or by sending me a PN/Email.
Enjoy,
Nicolai
__________________________________________________ ______________
Und nun zum Tutorial :
Derby and Java
Useful Links
Derby Homepage (http://db.apache.org/derby/manuals/index.html)
Derby Documentation (http://db.apache.org/derby/manuals/index.html)
Download Derby (http://db.apache.org/derby/derby_downloads.html)
Getting Started
While writing this article, the current Version of Derby is Version 10.2.2.0. Simply head over to the download-Section on the official Derby-Website (link given above) and download the current Release - mind, that actually all you need as of JDK 6.0 is the derby.jar (no drivers needed if you go for the embedded ones shipped with JDK 6), hence the "lib-Distribution-Package" will do the Job. After downloading the package, unpack it into a temporary folder and safely delete everything from it, except the derby.jar.
Derby meets Eclipse
Now its about time to integrate your Derby-Database into an Eclipse-Project. I'll assume, that you are already more or less familiar with the Eclipse-IDE. If that isn't the case, best check out the Eclipse Documentation (http://www.eclipse.org/documentation/). Open your Eclipse-IDE and create a New Project. Now open your Eclipse-Workspace (the Location where your newly created Projects are kept) either in a Terminal or a Window. Switch to the folder of your current Project (Top-Level) and create a Folder called "lib" - here we're going to store all ".jar"-Files that are used in our Project. Copy the derby.jar into this lib-Folder.
Now switch back to Eclipse and refresh it by right-clicking on your Project and hitting the "Refresh-Button"). The lib-folder should now pop up and list display the derby.jar as well. Now we're going to add our derby.jar to the build-path of our Project. To accomplish this, simply right-click on the derby.jar and chose "Build->Add to Build-Path".
As for the configuration we're pretty much done. Now comes the fun-part : Coding :-) ...
Derby meets Java
First of all I recommend you to create a class called something like "DatabaseManager", which offers some basic functionality for administrating and accessing the Database. Since only one instance of this DatabaseManager is needed, I would setup the class as a Singleton (http://wiki.gamerforsale.com/index.php/Design_Patterns#Singleton) in order to provide instant access without creating thousands of instances. The DatabaseManager will provide Connections to the Database on request and contain some basic Database-Operations according to the CRUD-Pattern (Create, Read, Update, Delete). In the following I'll provide a class-template which will give you an idea of how to structure your DatabaseManager.
public class DatabaseManager
{
private static String dbURL : "jdbc:derby:softcondb;create=true";
private static String dbDriver : "org.apache.derby.jdbc.EmbeddedDriver";
//Self-Reference
private static DatabaseManager self;
//Private Constructor which Sets up the Database-Driver
private DatabaseManager()
{
Class.forName(dbDriver).newInstance();
}
//Method to acquire an instance of the DatabaseManager
public static DatabaseManager getInstance()
{
if (self == null)
self = new DatabaseManager();
return self;
}
//This method returns a Connection to the Database
public Connection getconnection() throws SQLException
{
Connection con = DriverManager.getConnection(dbURL);
con.setAutoCommit(true);
return con;
}
//Add some Methods for handling DB-Requests such as Inserts,Updates or Selects
//Consider using static (String) class-variables for the DB-Commands in order
//to make future-adjustments easier and maintainance overall
}
You may now call the above Manager from pretty much any class which needs access to the Database, in the following I'll demonstrate how to make a request and cleanup afterwards (Closing the Database-Connection and freeing the ResultSets).
public void getAllOrders() trows SQLException
{
//We set these variables to null, so that we can check for null in the finally-block
//which will save us from running into a nullpointer-exception in the finally-block
Connection con = null;
Statement getOrders = null;
try
{
//Get a Connection to the Database by using the DatabaseManager
con = DatabaseManager.getInstance().getConnection();
//Create a Statement
getOrders = con.createStatement();
//Execute a Statement
ResultSet resultGetOrders = getOrders.executeQuery("SELECT * FROM Orders");
//Do somemthing with the Result Set
//Free the ResultSet
resultGetOrders.close();
}
finally
{
try
{
if (con != null)
con.close();
if(getOrders != null)
getOrders.close();
}
catch (SQLException e)
{
//Consider throwing a self-made exception here which specifies the error
}
}
}