GWT Database

In this tutorial, we will setup database connectivity using GWT. We can use Eclipse to configure database.

Eclipse consists of HSQLDB plugin which can be installed. Plugin makes installation easy to set up. Plugin provides many features such as start/stop db, invokes database manager GUI. Here, the following steps are of configuration.

Select Help → Eclipse MarketPlace search keyword HSQLDB and click install button.

Now, choose Window → Show View → Others and in Show View dialog expand HSQL Database server and select HSQLDB Server to open the HSQLDB view.
Click on View Menu and select Preferences from the drop down menu. Enter values shown in the Figure.

Start the database and open database manager by selecting Show database Client from drop down menu.

Load Database

We use RStore to load data it has following features:

It enhances java classes for persistence.
It creates database schema.
It deletes database schema.
It persists and retrieves objects from database.

Dependencies

RStore requires HSQLDB, Data Nucleus JDO, MyBatis and Hibernate libraries. Following table lists the dependencies.

Common	JDO	Hibernate	MyBatis
hsqldb-2.2.9.jar	jdo-api-3.0.1.jar	hibernate-commons-annotations-4.0.1.Final.jar	mybatis-3.2.0.jar
commons-lang-2.6.jar	datanucleus-api-jdo-3.1.3.jar	hibernate-core-4.1.10.Final.jar
log4j-1.2.16.jar	datanucleus-core-3.1.4.jar	hibernate-jpa-2.0-api-1.0.1.Final.jar
	datanucleus-rdbms-3.1.4.jar	jboss-logging-3.1.0.GA.jar
	datanucleus-enhancer-3.1.1.jar	jboss-transaction-api_1.1_spec-1.0.0.Final.jar
	asm-4.0.jar	antlr-2.7.7.jar
		dom4j-1.6.1.jar
		javassist-3.15.0-GA.jar

Download: To download above files here are the links:

Common: hsqldb , Common-lang , log4j .

JDO: datanucleus , showfiles , jdo .

Hibernate: hibernate .

MyBatis: mybatis .

Implementation

Adding Mysql configuration to GWT

LoginScreen.gwt.xml

<module>
 <!-- Inherit the core Web Toolkit stuff. -->
 <inherits name='com.google.gwt.user.User'/>
 <!-- Specify the app entry point class. -->
 <entry-point class='com.yourdomain.projectname.client.LoginScreen'/>
 <!-- servlet context - path is arbritray, but must match up with the rpc init
inside java class -->
 <!-- Tomcat will listen for this from the server and waits for rpc request in
this context -->
 <servlet class="com.yourdomain.projectname.server.MySQLConnection"path="/MySQLConnection" />
 <inherits name="com.google.gwt.user.theme.standard.Standard"/>
 <inherits name="com.google.gwt.user.theme.chrome.Chrome"/>
 <inherits name="com.google.gwt.user.theme.dark.Dark"/>
</module>

Database Connection

DBConnection.java

public interface DBConnection extends RemoteService
 {
 public User authenticateUser(String user, String pass);
 }

DBConnectionAsync.java

public interface DBConnectionAsync {
 public void authenticateUser(String user, String pass, AsyncCallback<User>
callback);
}

User.java (Frontend designing)

import com.google.gwt.user.client.rpc.IsSerializable;
public class User implements IsSerializable {
 private String username;
 private String password;
 @SuppressWarnings("unused")
 private User() {
 //just here because GWT wants it.
 }
 public User(String username, String password) {
 this.username = username;
 this.password = password;
 }
}

MySQLConnection.java (Creating Servlet)

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Vector;
import com.google.gwt.user.server.rpc.RemoteServiceServlet;
import com.yourdomain.projectname.client.User;
public class MySQLConnection extends RemoteServiceServlet implements DBConnection {
 private Connection conn = null;
 private String status;
 private String url = "jdbc:mysql://yourDBserver/yourDBname";
 private String user = "DBuser";
 private String pass = "DBpass";
 public MySQLConnection() {
 try {
 Class.forName("com.mysql.jdbc.Driver").newInstance();
 conn = DriverManager.getConnection(url, user, pass);
 } catch (Exception e) {
 //NEVER catch exceptions like this
 }

 }
 public int authenticateUser(String user, String pass) {
 User user;
 try {
 PreparedStatement ps = conn.prepareStatement(
 "select readonly * from users where
username = \"" + user + "\" AND " +
 "password = \"" + pass + "\""
 );
 ResultSet result = ps.executeQuery();
 while (result.next()) {
 user = new User(result.getString(1),
result.getString(2));
 }
 result.close();
 ps.close();
 } catch (SQLException sqle) {
 //do stuff on fail
 }
 return user;
 }
}

Output