I need to use .properties file in Java to store database information.
Here is my database connector class. It's giving NullPointerException. What is the issue with my code ?
Note, that I haven't' assign those property file values. DB connection values are still hard coded.
import java.io.IOException;
import java.io.InputStream;
import java.sql.Statement;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;
import java.util.logging.Level;
import java.util.logging.Logger;
public final class Database {
public Connection connection;
private Statement statement;
private Properties property;
public static Database database;
private Database() {
String url = "jdbc:mysql://localhost:3306/";
String dbName = "edus";
String driver = "com.mysql.jdbc.Driver";
String userName = "root";
String password = "";
try {
InputStream is = Database.class.getClassLoader().getResourceAsStream(
"config.properties");
property.load(is);
System.out.println(property.getProperty("db_user"));
System.out.println(property.getProperty("db_password"));
System.out.println(property.getProperty("db_name"));
Class.forName(driver).newInstance();
this.connection = (Connection) DriverManager.getConnection(url + dbName,
userName, password);
}catch (IOException ex) {
Logger.getLogger(Database.class.getName()).log(Level.SEVERE, null, ex);
} catch (ClassNotFoundException e) {
System.out.println("JDBC driver is missing");
} catch (InstantiationException | IllegalAccessException | SQLException e) {
e.printStackTrace();
}
}
public static synchronized Database getDatabaseConnection() {
if (database == null) {
database = new Database();
}
return database;
}
}
config.properties is not lying under classpath. It should be under classes folder.
you can also try
Database.class.getClassLoader().getResourceAsStream(
"com/lk/apiit/eduservice/config.properties");
As Roman C pointed out you also need to initialize Properties Object first
Properties property = new Properties();
You forgot to initialize
Properties property = new Properties();
This is an issue of NullPointerException in your code, because you referenced not initialized variable.
If you open a stream you should close it after it's not used. Do it by adding finally block.
The code where you getting a connection to the database you can move to the corresponding method. If the connection is closed you will not reinitialize the database again just reopen a connection or get a new one.
Dont keep config properties file in a package. Keep it directly inside the source folder, so that the config properties file comes directly in the build/classes folder after the build is done.
The issue is that your config properties in in the folder com/ik/apiit/eduservice folder but your code is expecting it to be directly in the classes folder (the root folder of classpath).
try this
FileInputStream in = new FileInputStream(System.getProperty("WEB-INF/dbConnection.properties"));
prop.load(in);
Related
I'm coding for hours to insert data into my SQL database, but nothing happens.
I even can't debug Java, because I don't get any output of my console.
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.sql.PreparedStatement;
import java.text.DecimalFormat;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
*
* #author xxx
*/
public class MyServlet extends HttpServlet {
private static final String URL = "jdbc:mysql://localhost:3306/userdata";
private static final String USER = "root";
private static final String PASSWORD = "root";
private static final DecimalFormat DF2 = new DecimalFormat("#.##");
private static Connection con;
private static Statement stmt;
private static ResultSet rs;
protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
try (PrintWriter out = response.getWriter()) {
try {
String myDriver = "com.mysql.jdbc.Driver";
try {
Class.forName(myDriver);
// opening database connection to MySQL server
con = DriverManager.getConnection(URL, USER, PASSWORD);
// getting Statement object to execute query
// the mysql insert statement
String query = "INSERT INTO customers (customer, currency, amount) values ('Name', 'Currency', 100);";
stmt.executeUpdate(query);
// execute the preparedstatement
// executing SELECT query
rs = stmt.executeQuery(query);
con.close();
stmt.close();
rs.close();
} catch (SQLException sqlEx) {
sqlEx.printStackTrace();
}
}
}
}
What did I wrong, that nothing happens? Even if I use this code for Java-Classes (not Servlets), I only receive an compile error, but without message.
I'm using the IDE Netbeans and mysql DB is the MySQL Workbench. The Java Class is using the main method.
Update:
I've tested following Code with IntelliJ:
import java.sql.*;
import java.util.logging.Level;
import java.util.logging.Logger;
public class Main {
public static void main(String[] args) {
String url = "jdbc:mysql://localhost:3306/userdata";
String user = "root";
String password = "root";
String query = "Insert into customers (customer, currency, amount) values('Michael Ballack', 'Euro', 500)";
try (Connection con = DriverManager.getConnection(url, user, password);
PreparedStatement pst = con.prepareStatement(query)) {
pst.executeUpdate();
} catch (SQLException ex) {
Logger lgr = Logger.getLogger(JdbcMySQLVersion.class.getName());
lgr.log(Level.SEVERE, ex.getMessage(), ex);
}
}
private static class JdbcMySQLVersion {
public JdbcMySQLVersion() {
}
}
I can insert data into the MySQL database.
In Netbeans this code won't work, although I've implemented the MySQLConnector. I don't know why, but Netbeans seems hard to handle.
In the servlet code, I don't see you ever write anything to out. So nothing is being sent back to the browser, even if it compiled. You could write your SQL exception to the out writer you created. To be more precise add this in your exception: out.println(sqlEx.printStackTrace()); That should at least show what exception you are getting back to the browser.
What is the compile error you get outside of a servlet?
This maybe obvious, but to get JDBC stuff to work on your server, you need to have the MySQL server installed, started and configured. The table referenced has to be defined, etc. You could check this outside of the Java servlet environment with the tools provided with MySQL.
your code can not compile, you miss catch exception for second 'try'.
Where do you use this class to run, if you run a java class, this class must contain main() function?
you should use some IDEs like eclipse or IntelliJ to code, it help you detect the error easier.
I found the solution. If you are using Netbeans with the Glassfish-Server and you want your servlet to save data into the database, you have to make sure that Netbeans has installed the Driver of your Database Connector (e.g. MySQL Connector). But you also have to configurate your server (e.g. Glassfish) which will support the DB Connector drivers.
In my case my Server didn't load the DB Connector Driver so the JDBC Code couldn't be executed.
Here's a useful link to configurate the Glassfish Server: https://dzone.com/articles/nb-class-glassfish-mysql-jdbc
Using UCanAccess for the first time for a project and I am having a lot of trouble inserting a row into one of my database tables (in Microsoft Access).
My code makes sense but once I execute I end up getting the same error every time, even though NetBeans is able to connect to my database.
package Vegan;
import java.sql.Connection;
import java.sql.DriverManager;
public class connectionString {
static Connection connection = null;
public static Connection getConnection()
{
try
{
connection = DriverManager.getConnection("jdbc:ucanaccess://C://MyDatabase1.accdb");
System.out.println("---connection succesful---");
}
catch (Exception ex)
{
System.out.println("Connection Unsuccesful");
}
return connection;
}
package Vegan;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
public class DB {
private static ResultSet rs = null;
private static PreparedStatement ps = null;
private static Connection connection = null;
public DB() {
connection = connectionString.getConnection();
}
public void AddTest() {
try {
String sql = "INSERT INTO CategoryTbl(CategoryName) VALUES (?)";
ps = connection.prepareStatement(sql);
ps.setString(1, "Flours");
ps.executeUpdate();
System.out.println("Inserted");
} catch (Exception ex) {
System.out.println(ex.getLocalizedMessage().toString());
}
}
After that, when I execute the the AddTest() method, I get this system output:
run:
---connection succesful---
java.nio.channels.NonWritableChannelException
at sun.nio.ch.FileChannelImpl.write(FileChannelImpl.java:724)
at com.healthmarketscience.jackcess.impl.PageChannel.writePage(PageChannel.java:297)
UCAExc:::3.0.6 null
at com.healthmarketscience.jackcess.impl.PageChannel.writePage(PageChannel.java:234)
at com.healthmarketscience.jackcess.impl.TableImpl.writeDataPage(TableImpl.java:1375)
at com.healthmarketscience.jackcess.impl.TableImpl.addRows(TableImpl.java:1624)
at com.healthmarketscience.jackcess.impl.TableImpl.addRow(TableImpl.java:1462)
at net.ucanaccess.converters.UcanaccessTable.addRow(UcanaccessTable.java:44)
at net.ucanaccess.commands.InsertCommand.insertRow(InsertCommand.java:101)
at net.ucanaccess.commands.InsertCommand.persist(InsertCommand.java:148)
at net.ucanaccess.jdbc.UcanaccessConnection.flushIO(UcanaccessConnection.java:315)
at net.ucanaccess.jdbc.UcanaccessConnection.commit(UcanaccessConnection.java:205)
at net.ucanaccess.jdbc.AbstractExecute.executeBase(AbstractExecute.java:161)
at net.ucanaccess.jdbc.ExecuteUpdate.execute(ExecuteUpdate.java:50)
at net.ucanaccess.jdbc.UcanaccessPreparedStatement.executeUpdate(UcanaccessPreparedStatement.java:253)
at Vegan.DB.AddTest(DB.java:91)
at Vegan.TestDB.main(TestDB.java:17)
BUILD SUCCESSFUL (total time: 1 second)
With no changes being made to the database when I check on it again Access.
What could be causing this, and what does the error message mean? Thank you
"java.nio.channels.NonWritableChannelException" means that the database file cannot be updated. In your case that was because the database file was in the root folder of the Windows system drive (C:\) and mere mortals have restricted permissions on that folder.
Solution: Move the database file to a folder where you have full write access.
How do I mock the DriverManager.getConnection() method?
I want to test my method setUpConnectiontoDB()
I tried it with PowerMock, easyMock and Mokito itself. I didn't find anything usefull.
My Code:
import java.io.FileInputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;
public class MysqlDAO implements DAO {
private final Properties properties = new Properties();
public MysqlDAO(String configPath) {
loadProperties(configPath);
}
private Properties loadProperties(String configPath) {
try {
properties.load(new FileInputStream(configPath));
} catch (IOException e) {
e.printStackTrace();
}
return this.properties;
}
#Override
public Connection setUpConnectionToDB() {
try {
Class.forName("com.mysql.jdbc.Driver");
return DriverManager.getConnection(
properties.getProperty("url"),
properties.getProperty("user"),
properties.getProperty("passwd"));
} catch (ClassNotFoundException | SQLException e) {
e.printStackTrace();
}
return null;
}
}
Some notes on that:
Class.forName("com.mysql.jdbc.Driver");
This line is obsolete since JDBC 4.0. You should be able to run the code without. Or if you think you need it at least abstract it as well to do
Class.forName(properties.getProperty("dbdriver", "com.mysql.jdbc.Driver");
Once that's been taken care of, who says you have to mock it? It's much easier to actually run it.
You could just as well use an in memory database (like h2) for testing and check your code for that. All you'd change would be your url, user and passwd properties.
This would be some example properties for use with h2:
dbdriver = org.h2.Driver
url = jdbc:h2:mem:test
user = sa
passwd = sa
That way, you not only take care of your unit-test for setUpConnectionToDB() but could later use that connection for methods that expect some data in that database.
I am new to programming and i am trying to make a connection from my program to database but when i make the code,error occurred on line 34 (package con.msql.jdbc does not exit).Can u tell me why??help me
code :
package Absensi_PEgawai;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import javax.swing.JOptionPane;
public class koneksi {
private static Connection koneksi;
public static Connection getKoneksi()
{
//cek koneksi
if(koneksi == null)
{
try
{
String url;
url = "jdbc:mysql://localhost:3306/dbabsensipegawai";
String user = "root";
String password = "pk12basketboy";
line34 --> **DriverManager.registerDriver(new con.mysql.jdbc.Driver());**
koneksi = DriverManager.getConnection(url,user,password);
}catch(SQLException t)
{
JOptionPane.showMessageDialog(null, "Error Membuat Koneksi");
}
}
return koneksi;
}
static Object getConnection()
{
throw new UnsupportedOperationException("Not Yet Implemented");
}
}
You must have forgotten to add the database driver to the CLASSPATH. If you are under Eclipse, go to the Build path menu and add your driver, otherwise refer to the billion posts on the internet that explain how to add a class to the CLASSPATH for any system.
So I have a MySQL database, and I have a datasource on a local instance of WebLogic which is connected to that database. I am trying to write some client code which will simply connect and query. I am having issues with obtaining a connection from the datasource. Here's my code thus far. I am running WebLogic 12c.
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Hashtable;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;
public class ConnectionTest {
public static void main(String... args) {
ConnectionTest tCon = new ConnectionTest();
tCon.TestConnection();
}
public void TestConnection() {
Context ctx = null;
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
Hashtable<String, String> props = new Hashtable<String, String>();
props.put("java.naming.factory.initial",
"weblogic.jndi.WLInitialContextFactory");
props.put("java.naming.provider.url", "t3://localhost:7001");
props.put("java.naming.security.principal", "weblogic");
props.put("java.naming.security.credentials", "welcome1");
ctx = new InitialContext(props);
DataSource ds = (DataSource) ctx.lookup("RegexDB");
System.out.println(ds);
DAO dao = new DAO();
conn = ds.getConnection();
stmt = conn.createStatement();
stmt.execute("select * from regular_ex");
rs = stmt.getResultSet();
ArrayList<HashMap<String, Object>> results = dao
.resultSetToArrayList(rs);
dao.printArrayList(results);
stmt.close();
conn.close();
} catch (NamingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (stmt != null)
stmt.close();
if (conn != null)
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
This fails at ds.getConnection() with the following exception:
java.lang.ClassCastException: weblogic.jdbc.common.internal.ConnectionEnv cannot be cast to java.io.Serializable
at weblogic.iiop.IIOPOutputStream.writeObject(IIOPOutputStream.java:2285)
at weblogic.utils.io.ObjectStreamClass.writeFields(ObjectStreamClass.java:414)
at weblogic.corba.utils.ValueHandlerImpl.writeValueData(ValueHandlerImpl.java:235)
at weblogic.corba.utils.ValueHandlerImpl.writeValueData(ValueHandlerImpl.java:225)
at weblogic.corba.utils.ValueHandlerImpl.writeValue(ValueHandlerImpl.java:182)
at weblogic.iiop.IIOPOutputStream.write_value(IIOPOutputStream.java:1983)
at weblogic.iiop.IIOPOutputStream.write_value(IIOPOutputStream.java:2021)
at weblogic.iiop.IIOPOutputStream.writeObject(IIOPOutputStream.java:2285)
at weblogic.jdbc.common.internal.RmiDataSource_WLSkel.invoke(Unknown Source)
at weblogic.rmi.internal.BasicServerRef.invoke(BasicServerRef.java:695)
at weblogic.rmi.cluster.ClusterableServerRef.invoke(ClusterableServerRef.java:230)
at weblogic.rmi.internal.BasicServerRef$1.run(BasicServerRef.java:520)
at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:363)
at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:146)
at weblogic.rmi.internal.BasicServerRef.handleRequest(BasicServerRef.java:516)
at weblogic.rmi.internal.wls.WLSExecuteRequest.run(WLSExecuteRequest.java:118)
at weblogic.work.ExecuteThread.execute(ExecuteThread.java:256)
at weblogic.work.ExecuteThread.run(ExecuteThread.java:221)
I have wlclient.jar, wlsafclient.jar, and weblogic.jar in my buildpath. I have tried all sorts of combinations of adding/removing these jars, but I still get the same error regardless of what I do. Any help would be greatly appreciated.
After doing some research, I am deleting my old answer and starting over.
There is a large table of client types in the Oracle Doc for WebLogic Standalone Clients. For each type of client, listed, the table shows the required jar files. For certain types of clients, you need to build an additional jar (wlfullclient.jar) and include that.
Hope this helps.
I have also face this problem and I tried to add "wlfullclient.jar" to my directory to fix it out but I didn't find this jar file in weblogic installation folder.
But at the last I have set all required jar files form weblogic by using setDomainEnv.cmd and it works fine. Here we don't have to care about which jar files required or not it'll simply set classpath for all required jar file for your program.
I am using Weblogic 11g.
In Weblogic 12c, copy the weblogic.jar file to some other directory. Rename the file to weblogic-classes.jar and then build the jar file using wljarbuilder.
Add the newly created wlfullclient.jar file to your Class Path in eclipse.
Build wlfullclient.jar and add just this jar to the build path.
It solved the problem for me.
By the way weblogic.jar from Weblogic 12 is missing some classes as compared to weblogic.jar from Weblogic 10.3