We Keep Coding

H2 in-memory creating a server to access via Shell

I'm using the DataSourceFactory of dropwizard and H2 to create an in-memory db for testing. Here is what I have
private static final String DBNAME = String.format("JDBITest-%d", System.currentTimeMillis());
protected final DataSourceFactory config = new DataSourceFactory();
{
final String url = String.format("jdbc:h2:mem:%s;", DBNAME) +
"MODE=MySQL;" +
"TRACE_LEVEL_FILE=3;" +
"DB_CLOSE_DELAY=-1;" +
"IGNORECASE=TRUE";
System.out.println("Creating in memory H2 using " + url);
BootstrapLogging.bootstrap();
config.setUrl(url);
config.setUser("sa");
config.setDriverClass("org.h2.Driver");
config.setValidationQuery("SELECT 1");
}
#Before
public void setUp() throws Exception {
Server server = Server.createTcpServer().start(); // (4)
System.out.println("Server started and connection is open.");
System.out.println("URL: jdbc:h2:" + server.getURL() + "/mem:" + DBNAME);
}
When this runs I see
Creating in memory H2 using jdbc:h2:mem:JDBITest-1541641621470;MODE=MySQL;TRACE_LEVEL_FILE=3;DB_CLOSE_DELAY=-1;IGNORECASE=TRUE
Server started and connection is open.
URL: jdbc:h2:tcp://0.0.17.56:9092/mem:JDBITest-1541641621470
Why is the TCP 0.0.17.56? I cannot access this nor can I use the H2.jar to access the shell.

There are several wrong things here.
H2 has different connections modes. In your example you configure DataSourceFactory for in memory connection, but then in #Before method you create new instance of H2 with tcp based connection. More about connection modes here.
So now you have basically 2 instances of H2, in memory and tcp and they are completely unrelated. So you probably need to have only 1 connection type configured for you tests.
If you want to connect to your H2 db outside of JVM (from browser for example) - then you need to have tcp-based connection.
To be able to connect to db from browser you also need to run console application. Which should be inside h2.jar with command like that java -jar h2*.jar. More about this here.
And finally, this peace of code should suitable for you (with in-memory connection):
private static final String DBNAME = String.format("JDBITest-%d", System.currentTimeMillis());
private ManagedDataSource dataSource;
#Before
public void setUp() {
System.out.println("Server started and connection is open.");
final String url = String.format("jdbc:h2:mem:%s;", DBNAME) +
"MODE=MySQL;" +
"TRACE_LEVEL_FILE=3;" +
"DB_CLOSE_DELAY=-1;" +
"IGNORECASE=TRUE";
System.out.println("Creating in memory H2 using " + url);
DataSourceFactory config = new DataSourceFactory();
BootstrapLogging.bootstrap();
config.setUrl(url);
config.setUser("sa");
config.setDriverClass("org.h2.Driver");
config.setValidationQuery("SELECT 1");
dataSource = config.build(null, "test");
}
#Test
public void test() throws SQLException {
Connection connection = dataSource.getConnection();
connection.createStatement().executeUpdate("CREATE TABLE TEST (`id` INT)");
connection.createStatement().executeUpdate("INSERT INTO TEST (`id`) VALUES (1)");
ResultSet resultSet1 = connection.createStatement().executeQuery("SELECT * FROM TEST WHERE `id` = 1");
resultSet1.next();
resultSet1.getInt(1);
System.out.println("Found ID: " + resultSet1.getInt(1));
}
Out:
Server started and connection is open.
Creating in memory H2 using jdbc:h2:mem:JDBITest-1541649996267;MODE=MySQL;TRACE_LEVEL_FILE=3;DB_CLOSE_DELAY=-1;IGNORECASE=TRUE
Found ID: 1

Run java method to start database before Tomcat deploy

I am developing a web project with HSQLDB persistence. My database instance is on server mode, therefore, I need to run a cmd script/ Java method to access my schema.
Tomcat is the container I use to drop my war on port 8080. Gradle is my build system.
Currently I am using the following main method before I deploy my app to properly access my database on runtime:
public static void main(String[] args) throws IOException, ServerAcl.AclFormatException {
final String URL = "file:~/db/cursago";
String user = "user";
String password = "password";
HsqlProperties p = new HsqlProperties();
p.setProperty("server.database.0",URL+";user="+user+";password="+password);
p.setProperty("server.dbname.0","cursago");
Server server = new Server();
server.setProperties(p);
server.setLogWriter(null);
server.setErrWriter(null);
server.start();
System.out.println("Database is running with path: " + URL);
System.out.println("Username: " + user+", Password: " + password);
}
I would like to know if there's a way of making Tomcat/Gradle/IntelliJ IDEA run this main method before a project deploy, instead of running this script by hand.

from here:
you could run the content of your main in the onApplicationEvent like:
public class ApplicationListenerBean implements ApplicationListener<ContextRefreshedEvent> {
#Override
public void onApplicationEvent(ContextRefreshedEvent event) {
final String URL = "file:~/db/cursago";
String user = "user";
String password = "password";
HsqlProperties p = new HsqlProperties();
p.setProperty("server.database.0",URL+";user="+user+";password="+password);
p.setProperty("server.dbname.0","cursago");
Server server = new Server();
server.setProperties(p);
server.setLogWriter(null);
server.setErrWriter(null);
server.start();
System.out.println("Database is running with path: " + URL);
System.out.println("Username: " + user+", Password: " + password);
}
}
This will trigger on every event, that could be application started or redeployed and happens before your application handles requests.
You also can wire in your properties.
There are some difficulties if the server is already running and it can't run in this scope only.

JDBC not connecting

While the build paths are not correct I obtain “com.microsoft.sqlserver.jdbc.SQLServerDriver” from the stack trace. As they are built correctly, I obtain my printed statement “Successfully connected”. The JDBC is living within the getter/setters of the webservice as a method.
When I place the JDBC content in its own file with no builds and run as a java application I receive: “com.microsoft.sqlserver.jdbc.SQLServerDriver”
When I place the JDBC content in its own file with builds and run as a java application I receive: “Successfully connected”
When the method is called from a test file as a java application I receive: “Successfully connected”
Ex:
public static void main(String[] args) {
insert.main(args);
When the method is run as a java application on PO I receive: “Successfully connected”
When I place the method to be called under a setter (which will be invoked by the client, which will cause the jdbc to be invoked) I receive: “com.microsoft.sqlserver.jdbc.SQLServerDriver”
Would you happen to have any tips for me? I’m clueless why it will work under being invoked as an application but not via client?
public class insert{
public static void main(String[] args) {
Connection con = null;
Statement st = null;
final String DB_URL = "jdbc:jtds:sqlserver://00.00.00.00:0000/DB";
// Database credentials
final String USER = "usrname";
final String PASS = "pw";
try {
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
con = DriverManager.getConnection(DB_URL, USER, PASS);
st = con.createStatement();
System.out.println("successfully connected!");
} catch (Exception err) {
System.out.println(" " + err.getMessage ());
}
finally {
try {
con.close();
} catch (Exception e) { /* ignored */ }
try {
st.close();
} catch (Exception e) {
/* ignored */
}
}
}
}
Any tips at this point would be greatly appreciated.

The problem is that your jar misses the necessary libraries that provides com.microsoft.sqlserver.jdbc.SQLServerDriver class and others to communicate with your SQL server. You have to make sure the library is loaded and available when is being executed from tomcat. Just copy your library and drop it inside %TOMCAT_INSTALL%/lib folder, where %TOMCAT_INSTALL% is the folder where your tomcat is installed, so the library will be available for every project (war, jar, etc) that runs in your tomcat installation.

java database connection confusion

I was some practice code from Big Java 4th on connecting my program to a derby database. I get the following every time though.
Usage: java -classpath driver_class_path;. TestDB database.properties as the output and I can't figure out why it won't connect.
This is my test database:
public class TestDB
{
public static void main(String[] args) throws Exception
{
if (args.length == 0)
{
System.out.println(
"Usage: java -classpath driver_class_path"
+ File.pathSeparator
+ ". TestDB database.properties");
return;
}
else
SimpleDataSource.init(args[0]); `
Connection conn = SimpleDataSource.getConnection();
try
{
Statement stat = conn.createStatement();
stat.execute("CREATE TABLE Test (Name CHAR(20))");
stat.execute("INSERT INTO Test VALUES ('Romeo')");
ResultSet result = stat.executeQuery("SELECT * FROM Test");
result.next();
System.out.println(result.getString("Name"));
stat.execute("DROP TABLE Test");
}
finally
{
conn.close();
}
}
}
This is the connection program supplied:
public class SimpleDataSource
{
private static String url;
private static String username;
private static String password;
/**
Initializes the data source.
#param fileName the name of the property file that
contains the database driver, URL, username, and password
*/
public static void init(String fileName)
throws IOException, ClassNotFoundException
{
Properties props = new Properties();
FileInputStream in = new FileInputStream(fileName);
props.load(in);
String driver = props.getProperty("jdbc.driver");
url = props.getProperty("jdbc:url");
username = props.getProperty("jdbc.username");
if (username == null) username = "";
password = props.getProperty("jdbc.password");
if (password == null) password = "";
if (driver != null)
Class.forName(driver);
}
/**
Gets a connection to the database.
#return the database connection
*/
public static Connection getConnection() throws SQLException
{
return DriverManager.getConnection(url, username, password);
}
}

The usage method is telling you how to run the program correctly. Let me translate that into English, in case for some reason the place where you got this code from doesn't explain it.
Usage:
Here we are going to show how to use the program from a command prompt. If running the program from an IDE it would be similar but you would omit "java" and the classpath and program name would be configured separately.
java
The command to run Java programs
-classpath driver_class_path;.
specifying your classpath as the location of the Derby driver, and then the current directory (where your program lives)
TestDB
The name of your program - which is TestDB, so don't change this
database.properties
The filename of the properties file to use. The properties file contains the database connection parameters. This is a software development good practice! The database password, if any, must match the password you have set up.

Connecting to Derby using JDBC

I am trying to connect to Derby database on my locahost using JDBC.
I have started the database using the command: java -jar lib;derbyrun.jar server start, which starts successfully on port 1527.
On another command terminal, I use the command: java -classpath .;lib;derbyclient.jar testsqldatabase.TestSQLDatabase but I get the error below:
java.sql.SQLException: No suitable driver found for jdbc:postgresql:COREJAVA
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at testsqldatabase.TestSQLDatabase.getConnection(TestSQLDatabase.jav
)
at testsqldatabase.TestSQLDatabase.runTest(TestSQLDatabase.java:39)
at testsqldatabase.TestSQLDatabase.main(TestSQLDatabase.java:26)
My datatbase.properties file contains the following lines:
jdbc.drivers=org.postgresql.Driver
jdbc.url=jdbc:postgresql:COREJAVA
jdbc.username=dbuser
jdbc.password=secret
The java program is is listed below:
public class TestSQLDatabase
{
/**
* #param args the command line arguments
*/
public static void main(String[] args) throws IOException
{
try
{
runTest();
}
catch(SQLException ex)
{
for(Throwable t: ex)
t.printStackTrace();
}
}
/*Runs a test by creating a table, adding a value,
showing the table contents, removing the table*/
public static void runTest() throws SQLException, IOException
{
try(Connection conn = getConnection())
{
Statement stat = conn.createStatement();
stat.executeUpdate("CTEATE TABLE Greetings (Message CHAR(20))");
stat.executeUpdate("INSERT INTO Greetings VALUES ('Hello, World!')");
try(ResultSet result = stat.executeQuery("SELECT * FROM Greetings"))
{
if(result.next())
System.out.println(result.getString(1));
}
stat.executeUpdate("DROP TABLE Greetings");
}
}
/*
* Gets a connection from the properties specified in the
* file database.properties. #return the database connection
*/
public static Connection getConnection() throws SQLException, IOException
{
Properties props = new Properties();
try(InputStream in = Files.newInputStream(Paths.get("database.properties")))
{
props.load(in);
}
String drivers = props.getProperty("jdbc.drivers");
if(drivers != null) System.setProperty("jdbc.drivers", drivers);
String url = props.getProperty("jdbc.url");
String username = props.getProperty("jdbc.username");
String password = props.getProperty("jdbc.password");
return DriverManager.getConnection(url, username, password);
}
}
Can anyone figure out why I am getting that error from the second command terminal?
Thanks, much appreciated

Derby is a database. PostgreSQL is a different database. You're running a Derby database and you need the corresponding Derby JDBC driver to talk to it - not the PostgreSQL one.

You want to connect to Derby by using the PostgreSQL driver (in the properties file); also the URL of the database is no written well; it should be: jdbc:${dataBaseVendor}:${server}:${port}/${databaseName} where in your case databaseVendor=derby.
And also make sure you have the Derby JDBC driver jar on your classpath.