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Can't connect to hsqldb using jdbc java

I've got problem with connection to hsqldb using jdbc in java app. After parsing in main class from json to java I get 3 objects in list which i am trying to save to database.
Here is Dao class
public class EventDao {
private static final String URL = "jdbc:hsql:file:C:/Applications/appName//APPFOLDER";
private static final String USER = "sa";
private static final String PASS = "";
private Connection connection;
public EventDao() {
try {
Class.forName("org.hsqldb.jdbcDrive");
connection = DriverManager.getConnection(URL, USER, PASS);
} catch (ClassNotFoundException e) {
System.out.println("Couldnot establish connection");
} catch (SQLException e) {
e.printStackTrace();
}
}
public void save(Event event) {
final String sql = "insert into event(id,state,timestamp,type,host,alert) values (?,?,?,?,?,?)";
try {
PreparedStatement preparedStatement = connection.prepareStatement(sql);
preparedStatement.setString(1, event.getId());
preparedStatement.setString(2, event.getState());
preparedStatement.setString(3, event.getTimestamp().toString());
preparedStatement.setString(4, event.getType());
preparedStatement.setString(5, event.getHost());
preparedStatement.setString(6, event.getAlert().toString());
preparedStatement.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
}
public void close() {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
And here is main when i am trying to save object Event to db (the list have 3 objects)
public static void main(String[] args) {
EventParser eventParser = new EventParser();
eventParser.mainLoop();
}
public void mainLoop() {
try {
EventDao eventDao = new EventDao();
Map<String, EventWrapper> eventsFromFile = readEventsFromFile();
List<Event> eventsToSave = calculateEventTime(eventsFromFile);
for (Event event : eventsToSave) {
eventDao.save(event);
}
eventDao.close();
System.out.println(eventsFromFile);
} catch (IOException e) {
e.printStackTrace();
}
}
After debuging i found out that connection is null. Any ideas why?

The correct form of the URL is:
URL = "jdbc:hsqldb:file:C:/Applications/appName/APPFOLDER";
The Class.forName("org.hsqldb.jdbcDrive") ensures the HSQLDB jar is on your classpath and loads the JDBC driver class form the jar. This was done without error. The error message indicates there is no driver available for the incorrect jdbc:hsql:file url.

What is the best way Loading XML data to mySql using Java?

I am already working on a project to optimize interactions with dataBases using JAVA.
First Step , I began with loading XML data to mysql.
I found many articles working on this issue , and they parse Data before inserting it , like this article :
https://dzone.com/articles/load-xml-into-mysql-using-java
But I tried to do things simpler : so
I write this code that load data using LOAD local XML infile .. ( an sql Query ) and it works well .
package my.project;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class App {
static final String dbUrl = "jdbc:mysql://localhost/dbOptimization";
static final String password = "azerty";
static final String user = "root";
public Connection conn;
/*
* Load jdbc Driver
*/
static {
try {
Class.forName("com.mysql.jdbc.Driver");
System.out.println("Dirver loaded");
} catch (ClassNotFoundException ex) {
System.err.println("Cannot load driver " + ex);
}
}
/*
* Connect to DB
*/
public void connect() {
try {
conn = DriverManager.getConnection(dbUrl, user, password);
System.out.println("Database connected!");
} catch (SQLException e) {
System.err.println("Cannot connect the database!");
}
}
/*
* Create Table and Load Data
*/
public void createTable() {
try {
conn.createStatement().execute("create Table badges(Id INTEGER,UserId VARCHAR(20),Name varchar(20),Date DATE ,Class INTEGER ,TagBased VARCHAR(20))");
System.out.println("table created");
conn.createStatement().execute("Load xml local infile '/home/lenovo/Bureau/Project/3dprinting/Badges.xml'into Table badges(Id,UserId,Name,Date,Class,TagBased)");
System.out.println("data parsed");
} catch (SQLException e) {
// TODO Auto-generated catch block
System.out.println("connot create Table" + e);
}
}
public static void main(String[] args) {
System.out.println("Hello World!");
App app =new App();
app.connect();
app.createTable();
}
}
So please , Is there any problem with my code .?!
What are the pros and cons of each method ?
which one has a better performence ?
Thanks

The answer depends on whether or not you're going to use the XML as a whole document or not.
If you use XPath to search inside the document parsing and loading might make sense.

Oracle JDBC UCP and Java

I'm wondering if anyone can shed some light on this topic, as I have been racking my brain for days and can't quite understand why this does not work. I have three classes
main, RetrieveDBVersion,GetOracleConnection I've been doing some testing with oracle JDBC, UCP and Java 1.7.
According to the Oracle documentation, If I use connection pooling the connection will be returned to the pool as soon as I close the connection, Invalidate it and set it to null See Here. So I decided to give it a whirl and see if it would perform just like the documentation says it should. In my Main application I have a simple loop which makes a connection 200 times by calling RetrieveDBVersion. RetrieveDBVersion is simply performing a query and returning the driver version. My loop works fine until I hit the magic number of 68 and then I receive an error which states
java.sql.SQLException: Exception occurred while getting connection:
oracle.ucp.UniversalConnectionPoolException:
Cannot get Connection from Datasource: java.sql.SQLException:
Listener refused the connection with the following error:
ORA-12516, TNS:listener could not find available handler with matching protocol stack
These are the detail of the 3 methods. These methods are not in a server environment. They are simply calling a local oracle express database and I'm running them from my desktop. Why would I keep getting this error? If I'm returning the connections back to the pool?
Main
import com.jam.DB.JDBCVersion;
import static java.lang.System.out;
public class MainApp {
public static void main(String[] args) {
String myMainJDBCVar;
try{
for(int i=1; i<200; i++ )
{
myMainJDBCVar= JDBCVersion.RetrieveDBVersion();
out.println(myMainJDBCVar + " " + i);
}
out.println("this is Done!");
}
catch (Exception e) {
System.out.println(e.getMessage());
}
}
}
RetrieveDBVersion
import java.sql.*;
import oracle.ucp.jdbc.ValidConnection;
public class JDBCVersion {
public static String DBVersion;
public static String RetrieveDBVersion()throws SQLException {
Connection conn = JDBCConnection.GetOracleConnection("test");
try {
DatabaseMetaData meta = conn.getMetaData();
//get driver info
System.out.println("JDBC driver version is " + meta.getDriverMajorVersion());
DBVersion = meta.getDriverVersion();
} catch (SQLException e) {
e.printStackTrace();
DBVersion = e.getMessage();
}
finally {
System.out.println("hit the finally clause");
((ValidConnection) conn).setInvalid();
conn.close();
conn=null;
}
return DBVersion;
}
GetOracleConnection
import oracle.ucp.jdbc.PoolDataSource;
import oracle.ucp.jdbc.PoolDataSourceFactory;
import java.sql.*;
public class JDBCConnection {
public static Connection GetOracleConnection(String Enviroment) throws SQLException{
PoolDataSource pds = PoolDataSourceFactory.getPoolDataSource();
Connection conn = null; //ora.defaultConnection();
try {
pds.setConnectionFactoryClassName("oracle.jdbc.pool.OracleDataSource");
pds.setURL("jdbc:oracle:thin:#//localhost:1521/xe");
pds.setUser("system");
//pds.setInitialPoolSize(5);
pds.setPassword("xxx");
pds.setMaxStatements(10);
conn = pds.getConnection();
return conn;
}
catch(Exception e){
e.printStackTrace();
}
return conn;
}

So after careful though and getting a little extra help from the Oracle forum. I finally understand why the above referenced code is giving the error message that I'm receiving. See Here For Response
Because I'm setting the data source everytime the loop goes around, I'm essentially creating more than one pool. The way to do this, is create one pool and than pull connections from that pool.
New code to replace the GetOracleConnection I created a singleton class for datasource and in code I simply retrieve the connection from the data source like such
Connection conn = Database.getInstance().GetPoolSource().getConnection();
package com.jam.DB;
import oracle.ucp.jdbc.PoolDataSource;
import oracle.ucp.jdbc.PoolDataSourceFactory;
public class Database {
private static Database dbIsntance;
private static PoolDataSource pds;
private Database() {
// private constructor //
}
public static Database getInstance() {
if (dbIsntance == null) {
dbIsntance = new Database();
}
return dbIsntance;
}
public PoolDataSource GetPoolSource() {
if (pds == null) {
pds = PoolDataSourceFactory.getPoolDataSource();
try {
pds.setConnectionFactoryClassName("oracle.jdbc.pool.OracleDataSource");
pds.setURL("jdbc:oracle:thin:#//localhost:1521/xe");
pds.setUser("system");
pds.setPassword("xxxx");
pds.setMaxStatements(15);
return pds;
} catch (Exception e) {
}
return pds;
}
return pds;
}
}

Unexpected output in concurrent file writing in java web

I wrote a very simple Java web application ,just included some basic function like register , sign in , changing the password and some others.
I don't use database. I just create a file in the app to record the users' information and do the database stuff.
I used JMeter to stressing the web application, especially the register interface.
The JMeter shows that the result of the 1000 thread is right
but when I look into the information.txt , which stores the users' information, it's wrong because it stores 700+ record :
but it should include 1000 record, it must be somewhere wrong
I use the singleton class to do the write/read stuff, and i add a synchronized word to the class, the insert() function which is used by register to record the register information is shown as below: (a part of it)
public class Database {
private static Database database = null;
private static File file = null;
public synchronized static Database getInstance() {
if (database == null) {
database = new Database();
}
return database;
}
private Database() {
String path = this.getClass().getClassLoader().getResource("/")
.getPath() + "information.txt";
file = new File(path);
if (!file.exists()) {
try {
file.createNewFile();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
public void insert(String account, String password, String username) {
RandomAccessFile infoFile = null;
try {
infoFile = new RandomAccessFile(file, "rw");
String record;
long offset = 0;
while ((record = infoFile.readLine()) != null ) {
offset += record.getBytes().length+2;
}
infoFile.seek(offset);
record = account+"|"+password+"|"+username+"\r\n";
infoFile.write(record.getBytes());
infoFile.close();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (infoFile != null) {
try {
infoFile.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
}
}
the question is why would this happened , the synchronized is thread safe, why i lost so many data and some blank line was inserted into it, what could I do the correct it !

You are synchronizing the getInstance() method, but not the insert() method. This makes the retrieval of the instance of Database thread-safe, but not the write operation.

Java and SQL Server

I am new to java, and I am trying to create a method that will retrieve information from the database based on the query that will pass to it.
I thought that I could create by method by creating an object of type:
private Connection controlTableConnection = null;
and then
Statement statement = controlTableConnection.createStatement();
but when I do that piece of code, I get a highlight error:
Unhandled exception
Any help, would be appreciated.
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;
public class ConnectMSSQLServer {
private static final String db_connect_string = "jdbc:sqlserver://Cdsx\\SQxxs";
private static final String db_userid = "aa";
private static final String db_password = "bb";
private Connection controlTableConnection = null;
public void dbConnect() {
try {
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
Connection controlTableConnection = DriverManager.getConnection(db_connect_string, db_userid, db_password);
} catch (Exception e) {
e.printStackTrace();
}
}
public void dbDisconnect() {
try {
if (controlTableConnection != null && !controlTableConnection.isClosed()) {
controlTableConnection.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
public void createstatement() {
Statement statement = controlTableConnection.createStatement();
}
}

You have to wrap the createStatement line like below, as you have to handle the SQLException.
try {
Statement statement = controlTableConnection.createStatement();
} catch (SQLException e) {
e.printStackTrace();
}

isn't the Connection null? Do you have a driver on the classpath? is the default port correct? Is the sql server live? What kind of exception do you get exactly?
You need to post at least the stack trace or logs