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Vaadin: How do I display data from a MySQL database?

I'm developing a Vaadin Flow (version 14.1) app and I have this issue, I don't get it to connect directly with MySQL database.
I have set up the JDBC connection with maven, I've also created a singleton class I call Datasource where I store my values and methods. However right now it only has one as I'm testing this, this is what I want to do:
Click on a button on the app and update a label
Here's the button click listener:
button.addClickListener(click -> {
label.setText(Datasource.getInstance().getUsername());
});
Here's the Datasource class method:
public String getUsername() {
String username = "QUERY-FAILED";
try {
start();
statement = conn.createStatement();
ResultSet rs = statement.executeQuery("select * from names");
rs.next();
username = rs.getString(1);
} catch (SQLException e) {
e.printStackTrace();
} finally {
close();
}
return username;
}
But the label doesn't update, if I comment the try block it updates to QUERY-FAILED which is the string I put to test if it failed, but if it isn't commented the label just stays the same.
I also tried to add a main method to the Datasource class and run it as a Java application, and the method works fine, it does return a string with the username. So I'm guessing I'm stuck somewhere in between the connection with the vaadin app. Also, If I try to get the username String in my vaadin app when I'm starting the app (and not with a click listener) I got an long stack of errors with the Datasource indicating a nullpointerexception here:
statement = conn.createStatement();
Thanks in advance!

I cannot spot any problem with your code. But I can provide an entire working example app for you to compare
My example app goes along the lines laid out in your Question's code. A Vaadin Button performs a database query using a DataSource object from a table of user names. The value from the first row found is displayed in a Vaadin Label widget on the web page.
This app was built and run with Vaadin 14.1.5 using a "Plain Java Servlet" flavor of a starter project provided by the Vaadin.com site. Running on macOS Mojave with the bundled Jetty web container.
My only changes to their Maven POM file was to change to Java version 13, and to add a dependency for H2 Database Engine to make this a self-contained example using an in-memory database.
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<version>1.4.200</version>
</dependency>
I used the hook for Vaadin starting, to establish my DataSource object and initialize the database. Following the manual, nested in the resources folder, I created folders META-INF > services. Per the Java SPI facility, there I created a file named com.vaadin.flow.server.VaadinServiceInitListener containing a single line to specify the name of my class that implements the interface named in the name of this file:
work.basil.example.ApplicationServiceInitListener
That is, my ApplicationServiceInitListener class implement the Vaadin interface VaadinServiceInitListener. My class will be automatically instantiated and its method invoked via that Java SPI facility when my Vaadin web app launches.
My ApplicationServiceInitListener class:
package work.basil.example;
import com.vaadin.flow.server.ServiceInitEvent;
import com.vaadin.flow.server.VaadinServiceInitListener;
import org.h2.jdbcx.JdbcDataSource;
public class ApplicationServiceInitListener implements VaadinServiceInitListener
{
#Override
public void serviceInit ( ServiceInitEvent serviceInitEvent )
{
System.out.println( "DEBUG Running `serviceInit` of " + this.getClass().getCanonicalName() );
// Database work.
prepareDataSource();
App.INSTANCE.provideDatabase().initializeDatabase();
}
private void prepareDataSource ( )
{
JdbcDataSource ds = new JdbcDataSource();
ds.setURL( "jdbc:h2:mem:demo;DB_CLOSE_DELAY=-1" );
ds.setUser( "scott" );
ds.setPassword( "tiger" );
App.INSTANCE.rememberDataSource( ds );
}
}
That class calls my App class which acts as a sort of service locator. Designed as a singleton via enum.
package work.basil.example;
import javax.sql.DataSource;
import java.util.Objects;
public enum App
{
INSTANCE;
// -------| DataSource |---------------------------------
private DataSource dataSource;
public DataSource provideDataSource ( )
{
return this.dataSource;
}
public void rememberDataSource ( DataSource dataSource )
{
this.dataSource = Objects.requireNonNull( dataSource );
}
// -------| Database |---------------------------------
private Database database;
public Database provideDatabase ( )
{
return new Database();
}
}
That class calls my Database class. In real work, Database would be an interface with various concrete implementations for testing versus deployment. I ignored that here for demonstration purposes.
package work.basil.example;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class Database
{
public String getFirstUserName ( )
{
String userName = "QUERY-FAILED";
String newline = "\n";
StringBuilder sql = new StringBuilder();
sql.append( "SELECT name_ from user_ ; " ).append( newline );
System.out.println( "sql = " + sql );
try (
Connection conn = App.INSTANCE.provideDataSource().getConnection() ;
Statement statement = conn.createStatement() ;
ResultSet resultSet = statement.executeQuery( sql.toString() ) ;
)
{
while ( resultSet.next() )
{
userName = resultSet.getString( "name_" );
break; // Go no further. We need only the first row found.
}
}
catch ( SQLException e )
{
e.printStackTrace();
}
return userName;
}
public void initializeDatabase ( )
{
System.out.println( "DEBUG Running `initializeDatabase` of " + this.getClass().getCanonicalName() );
String newline = "\n";
// Create table.
StringBuilder sql = new StringBuilder();
sql.append( "CREATE TABLE user_ ( " ).append( newline );
sql.append( "pkey_ IDENTITY NOT NULL PRIMARY KEY , " ).append( newline ); // `identity` = auto-incrementing long integer.
sql.append( "name_ VARCHAR NOT NULL " ).append( newline );
sql.append( ") " ).append( newline );
sql.append( ";" ).append( newline );
System.out.println( "sql = " + sql );
try (
Connection conn = App.INSTANCE.provideDataSource().getConnection() ;
Statement statement = conn.createStatement() ;
)
{
statement.executeUpdate( sql.toString() );
}
catch ( SQLException e )
{
e.printStackTrace();
}
System.out.println("DEBUG Finished `CREATE TABLE` statement.");
// Populate table.
sql = new StringBuilder();
sql.append( "INSERT INTO user_ ( name_ ) " ).append( newline );
sql.append( "VALUES " ).append( newline );
sql.append( "( 'Alice' ) , " ).append( newline );
sql.append( "( 'Bob' ) , " ).append( newline );
sql.append( "( 'Carol' ) " ).append( newline );
sql.append( ";" ).append( newline );
System.out.println( "sql = " + sql );
try (
Connection conn = App.INSTANCE.provideDataSource().getConnection() ;
Statement statement = conn.createStatement() ;
)
{
int rowsAffected = statement.executeUpdate( sql.toString() );
System.out.println( "DEBUG Inserted rows into name_ table: " + rowsAffected );
}
catch ( SQLException e )
{
e.printStackTrace();
}
System.out.println("DEBUG Finished `INSERT` statement.");
}
}
And lastly, the MainView class. I disable the #PWA annotation as we are not using that feature for progressive web apps.
package work.basil.example;
import com.vaadin.flow.component.button.Button;
import com.vaadin.flow.component.html.Label;
import com.vaadin.flow.component.notification.Notification;
import com.vaadin.flow.component.orderedlayout.VerticalLayout;
import com.vaadin.flow.router.Route;
/**
* The main view contains a button and a click listener.
*/
#Route ( "" )
//#PWA ( name = "Project Base for Vaadin", shortName = "Project Base" )
public class MainView extends VerticalLayout
{
private Label label;
private Button button;
public MainView ( )
{
// Widgets
this.label = new Label( "User: ?" );
this.button = new Button(
"Get user" ,
event -> {
Notification.show( "Getting user." );
String userName = App.INSTANCE.provideDatabase().getFirstUserName();
this.label.setText( "User: " + userName );
}
);
add( button );
// Arrange
this.add( label , button );
}
}

You should check if the ResultSet rs actually has results. When calling rs.next(), look if it returns false. How to check if ResultSet is empty
public String getUsername() {
String username = "QUERY-FAILED";
try {
start();
statement = conn.createStatement();
ResultSet rs = statement.executeQuery("select userName from names");
if(rs.next() != false){
username = rs.getString(1);
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
close();
}
return username;
}
Another thing I noticed is that from the query select * from names, one cannot be sure that the userName attribute is the first column, which you are reading with rs.getString(1). Make sure to write your query more precise to avoid hard-to-find bugs: select userName from names; Do this even if the table only has one column, because what if somebody prepended another column? it could break your application.

How to compress and email test reports generated in cucumber with selenium webdriver

In my project I am using cucumber with junit, maven and selenium webdriver inclusive with java and extent report.
My extent report is generated in an folder 'output' and within the same folder screenshot of failed test-cases are also saved.
After execution of test and generation of report I want to compress the folder 'output' into zip file and mail it.
Issue : At the instance when my code converts the file into zip format, the test-report is not yet generated (as it generates after completion of all test cases) so when 'output' folder is compressed it only contains the failed screenshot and same is being mailed..
Please suggest
this is my runner file
this is my hooks class
This is my runner class...............
#CucumberOptions(
features = {"featurefiles/DefineStaffType.feature"}
, glue = {"stepdefinitions"}
, monochrome = true
, plugin = {"pretty:STDOUT",
"json:target/cucumber.json",
"junit:target/cucumber.xml",
"com.cucumber.listener.ExtentCucumberFormatter:output/report.html"}
, tags = {"#Scenario1, #Scenario2, #Scenario3"}
)
public class DefineStaffTypeRunner {
#AfterClass
public static void reportSetup ( ) throws IOException, EmailException {
Reporter.loadXMLConfig ( new File ( "configuration\\extentconfig.xml" ) );
Reporter.setSystemInfo ( "User Name", System.getProperty ( "user.name" ) );
Reporter.setSystemInfo ( "Time Zone", System.getProperty ( "user.timezone" ) );
Reporter.setSystemInfo ( "64 Bit", "Windows 10" );
Reporter.setSystemInfo ( "3.1.0", "Selenium" );
Reporter.setSystemInfo ( "1.9", "Maven" );
Reporter.setSystemInfo ( "1.9", "Java Version" );
Reporter.setTestRunnerOutput ( "Define Staff Type " );
FileConversion.convertToZip ( "output" );
new MailHandlingUtility ( ).sendMailWithAttachment ( );
}
}
This is my hooks class
public class CucumberHooks extends GenericBaseClass {
DriverMethods dm = new DriverMethods ( );
CaptureScreenshot cs = new CaptureScreenshot ( );
static MailHandlingUtility mhu = new MailHandlingUtility ( );
#Before
public void launchBrowser (Scenario currentscenario) throws IOException {
this.scenario = currentscenario;
driver = getCurrentDriver ( );
dm.maximizeWindow ( );
}
#After
public void tearDownScenario (Scenario currentscenario) throws IOException, EmailException {
scenario.write ( "Scenario is finished" + currentscenario );
cs.catureScreenshot ( (Scenario) scenario );
driver.close ( );
driver.quit ( );
driver = null;
}
}

Equinox P2 IStatus returns code 10001 in Eclipse RAP application "Your original request has been modified. null children=[]"

I have to work with an already existing Eclipse RAP application which contains of two features and around 40 dependencies.
Since the Eclipse RAP doesn't have a preStartup() method I call the update procedure in the RAP's start() method:
public class MyApplication implements IApplication
{
#Override
public Object start( IApplicationContext context ) throws Exception
{
P2Util.update();
...
}
}
The IProvisioningAgent is not null, the IMetadataRepositoryManager and IArtifactRepositoryManager are correctly initialized.
public static boolean configureRepository( IProvisioningAgent agent )
{
String repo = "file:///c:/export/repository/"; // TODO HERE!
log.debug( "Initiliazing Repository Managers" );
IMetadataRepositoryManager metadataManager = ( IMetadataRepositoryManager ) agent.getService( IMetadataRepositoryManager.SERVICE_NAME );
IArtifactRepositoryManager artifactManager = ( IArtifactRepositoryManager ) agent.getService( IArtifactRepositoryManager.SERVICE_NAME );
URI uri;
try
{
uri = new URI( repo );
}
catch ( URISyntaxException e1 )
{
log.error( "Unexpected URISyntaxException, the specified path is not a valid URI", e1 ); //$NON-NLS-1$
return false;
}
if ( metadataManager == null )
{
log.error( "IMetadataRepositoryManager instance is null!" );
return false;
}
metadataManager.addRepository( uri );
log.debug( "Added repository to MetadataManager: " + repo );
if ( artifactManager == null )
{
log.error( "IArtifactRepositoryManager instance is null!" );
return false;
}
artifactManager.addRepository( uri );
log.debug( "Added repository to ArtifactManager: " + repo );
return true;
}
Still one problem occurs all the time after I call checkForUpdates().
public static IStatus checkForUpdates( IProvisioningAgent agent ) throws OperationCanceledException
{
log.info( "Checking for new updates in repository" );
ProvisioningSession session = new ProvisioningSession( agent );
UpdateOperation operation = new UpdateOperation( session );
IStatus status = operation.resolveModal( new NullProgressMonitor() );
return status;
}
It returns the following status:
Status OK: org.eclipse.equinox.p2.operations code=10001 Your original request has been modified. null children=[]
I have already checked the flag "Support software installation in the launched application" in my run configuration, the problem persists.

Neo4j embedded only stores inside one runtime

I'm experimenting with Neo4J via Embedded Java API.
My Build path seems ok (no Exceptions during runtime).
When I create some nodes and relations, I can query it directly after it with success.
But after shutting down and re-run my programm, i'm only getting the data I created in the new runtime and none of them before.
But if I look at my directory, I see, that the size has grown with each runtime, I perform a creating of data.
Here's my code:
public static void main(String[] args)
{
GraphDatabaseService gdb = new GraphDatabaseFactory().newEmbeddedDatabase( "/mytestdb/" );
create( gdb );
query( gdb );
gdb.shutdown();
}
private static void query( GraphDatabaseService gdb )
{
StringLogger sl = StringLogger.wrap( new Writer()
{
#Override
public void write( char[] arg0, int arg1, int arg2 ) throws IOException
{
for( int i=arg1; i<=arg2; i++ ) System.out.print( arg0[i] );
}
#Override
public void flush() throws IOException
{}
#Override
public void close() throws IOException
{}
} );
ExecutionEngine ee = new ExecutionEngine( gdb, sl );
ExecutionResult result = ee.execute( "MATCH (p:Privilleg) RETURN p" );
System.out.println( result.dumpToString() );
}
private static void create( GraphDatabaseService gdb )
{
Transaction tx = gdb.beginTx();
Node project = gdb.createNode( MyLabels.Project );
Node user = gdb.createNode( MyLabels.User );
Node priv1 = gdb.createNode( MyLabels.Privilleg );
Node priv2 = gdb.createNode( MyLabels.Privilleg );
user.setProperty( "name", "Heinz" );
user.setProperty( "email", "heinz#gmx.net" );
priv1.setProperty( "name", "Allowed to read all" );
priv1.setProperty( "targets", Short.MAX_VALUE );
priv1.setProperty( "read", true );
priv1.setProperty( "write", false );
priv2.setProperty( "name", "Allowed to write all" );
priv2.setProperty( "targets", Short.MAX_VALUE );
priv2.setProperty( "read", false );
priv2.setProperty( "write", true );
project.setProperty( "name", "My first project" );
project.setProperty( "sname", "STARTUP" );
user.createRelationshipTo( priv1, MyRelationships.UserPrivilleg );
user.createRelationshipTo( priv2, MyRelationships.UserPrivilleg );
priv1.createRelationshipTo( project, MyRelationships.ProjectPrivilleg );
priv2.createRelationshipTo( project, MyRelationships.ProjectPrivilleg );
tx.success();
}

Your code doesn't close the transaction. Typically you use a try-with-resources block:
try (Transaction tx=gdb.beginTx()) {
// do stuff in the graph
tx.success();
}
Since Transaction is AutoClosable its close() method will be called implicitly upon leaving the code block. If (for whatever) reason you decide not to use try-with-resources, be sure to explicitly call close().
On a different notice: your code uses ExecutionEngine. Since Neo4j 2.2 you directly call gdb.execute(myCypherString) instead.

Thank you! This works.
Also, before I closed the transaction, it takes about 20 seconds to shuting down the db. This also is now less than a second.

How to multithread in Grizzly

I'm implementing a Java RESTful webservice on Heroku. Currently my entry point looks like
public class Main
{
public static final String BASE_URI = getBaseURI();
public static void main( String[] args ) throws Exception
{
final Map<String, String> initParams = new HashMap<String, String>();
initParams.put( "com.sun.jersey.config.property.packages", "services.contracts" );
initParams.put( "com.sun.jersey.api.json.POJOMappingFeature", "true" );
System.out.println( "Starting grizzly..." );
SelectorThread threadSelector =
GrizzlyWebContainerFactory.create( BASE_URI, initParams );
System.out.println( String.format( "Jersey started with WADL available at %sapplication.wadl.", BASE_URI,
BASE_URI ) );
}
private static String getBaseURI()
{
return "http://localhost:" + ( System.getenv( "PORT" ) != null ? System.getenv( "PORT" ) : "9998" ) + "/";
}
}
where the initParms contains RESTful services being hosted. I understand that GrizzlyWebContainerFactory.create() returns an instance of ServletContainer (SelectorThread), but how would I multithread the returned threadSelector such that multiple SelectorThread's can handle the incoming requests under one process (aka web dyno)? The reason is to increase performance of a single dyno in handling requests.
Any suggestions appreciated! Thanks!

You can call:
SelectorThread.setSelectorReadThreadsCount(int)