DB-init on Tomcat startup if db does not exist

.classpath

@@ -21,9 +21,11 @@
 	</classpathentry>
 	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8">
 		<attributes>
+			<attribute name="module" value="true"/>
 			<attribute name="maven.pomderived" value="true"/>
 		</attributes>
 	</classpathentry>
 	<classpathentry kind="lib" path="src/main/webapp/WEB-INF/lib/h2-1.4.197.jar"/>
+	<classpathentry kind="lib" path="C:/Program Files/Apache Software Foundation/Tomcat 8.0/lib/servlet-api.jar"/>
 	<classpathentry kind="output" path="target/classes"/>
 </classpath>

src/main/java/university/at/jku/ce/dao/DBInitializerDao.java

@@ -3,4 +3,6 @@ package university.at.jku.ce.dao;
 public interface DBInitializerDao {
 
 	public void initDatabase();
+	
+	public boolean isValidDatabase();
 }

src/main/java/university/at/jku/ce/dao/h2dao/H2DBInitializerDao.java

@@ -211,4 +211,56 @@ public class H2DBInitializerDao implements DBInitializerDao {
         return p2.toAbsolutePath().toString();
       }
 
+	@Override
+	public boolean isValidDatabase() {
+		try {
+			// STEP 1: Register JDBC driver
+			Class.forName(DaoParam.DRIVER);
+
+			// STEP 2: Open a connection
+			con = DriverManager.getConnection(DaoParam.JDBC_URL, DaoParam.USER, DaoParam.PASSWORD);
+			
+			try {
+				String sql="SELECT * from student where rownum<2";	
+				stmt = con.createStatement();
+				stmt.executeQuery(sql);
+				sql="SELECT * from study where rownum<2";	
+				stmt = con.createStatement();
+				stmt.executeQuery(sql);
+				sql="SELECT * from subject where rownum<2";	
+				stmt = con.createStatement();
+				stmt.executeQuery(sql);
+				sql="SELECT * from inscription where rownum<2";	
+				stmt = con.createStatement();
+				stmt.executeQuery(sql);
+			} catch (SQLException e) {return false;}
+			 
+			// STEP 4: Clean-up environment
+			stmt.close();
+			con.close();
+			return true;
+		} catch (SQLException se) {
+			// Handle errors for JDBC
+			se.printStackTrace();
+			return false;
+		} catch (Exception e) {
+			// Handle errors for Class.forName
+			return false;
+		} finally {
+			// finally block used to close resources
+			try {
+				if (stmt != null)
+					stmt.close();
+			} catch (SQLException se2) {
+			} // nothing we can do
+			try {
+				if (con != null)
+					con.close();
+			} catch (SQLException se) {
+				se.printStackTrace();
+			} // end finally try
+			rs = null;
+		} // end try
+	}
+
 }

src/main/java/university/at/jku/ce/init/MyAppServletContextListener.java

+package university.at.jku.ce.init;
+import javax.servlet.ServletContextEvent;
+import javax.servlet.ServletContextListener;
+
+import university.at.jku.ce.dao.DBInitializerDao;
+import university.at.jku.ce.dao.h2dao.H2DBInitializerDao;
+
+public class MyAppServletContextListener implements ServletContextListener{
+
+	DBInitializerDao dao=new H2DBInitializerDao();
+	
+@Override
+public void contextDestroyed(ServletContextEvent arg0) {
+	// Do Nothing
+	
+}
+
+@Override
+public void contextInitialized(ServletContextEvent arg0) {
+	if (!dao.isValidDatabase()) {dao.initDatabase();
+		System.out.println("Initializing Database");
+	}
+	else {System.out.println("No Database initialization required");}
+}
+
+}

src/main/webapp/WEB-INF/web.xml

@@ -15,4 +15,9 @@
         <servlet-name>Jersey Web Application</servlet-name>
         <url-pattern>/webapi/*</url-pattern>
     </servlet-mapping>
+    <listener>
+	<listener-class>
+             university.at.jku.ce.init.MyAppServletContextListener 
+        </listener-class>
+   </listener>
 </web-app>