Develop Reference

Unable to locate tables in Derby database

I can't work out why the following program is unable to locate tables in my derby database:
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.Properties;
import java.util.logging.Level;
import java.util.logging.Logger;
public class NdConnect
{
public final static String SETUP_FILE_PATH = "/AppData/Local/NewdawnTest";
private static final String CONNECTION_URL = "jdbc:derby:" + "C:/Users/" + System.getenv("USERNAME") + SETUP_FILE_PATH + "db" + ";create=true";
private static Connection conn = null;
private final static Properties dbProperties = new Properties();
private static PreparedStatement pstmtSelectTxns;
public static void connect() {
try {
conn = DriverManager.getConnection(CONNECTION_URL + ";create=true", dbProperties);
pstmtSelectTxns = conn.prepareStatement("SELECT * from TXNS");
System.out.println("Connected OK to " + CONNECTION_URL);
}
catch (SQLException sqle) {
System.out.println("SQL exception");
System.out.println("Connected NOK:The connection URL is " + CONNECTION_URL);
Logger.getLogger(NdConnect.class.getName()).log(Level.SEVERE, null, sqle);
}
}
public static void disconnect()
{
try {
if (conn != null) {
conn.close();
conn = null;
System.out.println("0048 NDC OK:DB closed ");
}
} catch (SQLException sqle) {
Logger.getLogger(NdConnect.class.getName()).log(Level.SEVERE, null, sqle);
}
}
public static void main(String[] args)
{
// NdConnect nd = new NdConnect();
NdConnect.connect();
NdConnect.disconnect();
// System.out.println("NdConnect finished");
}
}
The program throws a SQLSyntaxErrorException:
run:
SQL exception
Connected NOK:The connection URL is jdbc:derby:C:/Users/Administrator/AppData/Local/NewdawnTestdb;create=true
Nov 25, 2018 6:58:42 AM NdConnect connect
0048 NDC OK:DB closed
SEVERE: null
java.sql.SQLSyntaxErrorException: Table/View 'TXNS' does not exist.
at org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(Unknown Source)
at org.apache.derby.impl.jdbc.Util.generateCsSQLException(Unknown Source)
at org.apache.derby.impl.jdbc.TransactionResourceImpl.wrapInSQLException(Unknown Source)
at org.apache.derby.impl.jdbc.TransactionResourceImpl.handleException(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedConnection.handleException(Unknown Source)
at org.apache.derby.impl.jdbc.ConnectionChild.handleException(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedPreparedStatement.<init>(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedPreparedStatement42.<init>(Unknown Source)
at org.apache.derby.jdbc.Driver42.newEmbedPreparedStatement(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedConnection.prepareStatement(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedConnection.prepareStatement(Unknown Source)
at NdConnect.connect(NdConnect.java:21)
at NdConnect.main(NdConnect.java:47)
Caused by: ERROR 42X05: Table/View 'TXNS' does not exist.
at org.apache.derby.iapi.error.StandardException.newException(Unknown Source)
at org.apache.derby.iapi.error.StandardException.newException(Unknown Source)
at org.apache.derby.impl.sql.compile.FromBaseTable.bindTableDescriptor(Unknown Source)
at org.apache.derby.impl.sql.compile.FromBaseTable.bindNonVTITables(Unknown Source)
at org.apache.derby.impl.sql.compile.FromList.bindTables(Unknown Source)
at org.apache.derby.impl.sql.compile.SelectNode.bindNonVTITables(Unknown Source)
at org.apache.derby.impl.sql.compile.DMLStatementNode.bindTables(Unknown Source)
at org.apache.derby.impl.sql.compile.DMLStatementNode.bind(Unknown Source)
at org.apache.derby.impl.sql.compile.CursorNode.bindStatement(Unknown Source)
at org.apache.derby.impl.sql.GenericStatement.prepMinion(Unknown Source)
at org.apache.derby.impl.sql.GenericStatement.prepare(Unknown Source)
at org.apache.derby.impl.sql.conn.GenericLanguageConnectionContext.prepareInternalStatement(Unknown Source)
... 7 more
However the database and table do exist. I have verified this by creating a connection to the database in Netbeans > Services. When I run this command in Services:
SELECT * from TXNS
the desired table is correctly displayed and the output window returns:
Executed successfully in 0 s.
Fetching resultset took 0.016 s.
Line 1, column 1
Execution finished after 0.254 s, no errors occurred.
Looking at the properties of this connection via Netbeans services shows the following attribute values:
Display name NewDawn – TEST DB
Database URL jdbc:derby:C:\Users\Administrator\AppData\Local\NewdawnTest\db
Driver apache_derby_embedded
Driver class org.apache.derby.jdbc.EmbeddedDriver
This seems to correspond to the setup I have in the java code example so I don't understand why the code doesn't work.

The URL is not the same:
In Netbeans: jdbc:derby:C:\Users\Administrator\AppData\Local\NewdawnTest\db
In Java: jdbc:derby:C:/Users/Administrator/AppData/Local/NewdawnTestdb;create=true
Change the CONNECTION_URL line to:
private static final String CONNECTION_URL = "jdbc:derby:" + "C:/Users/" + System.getenv("USERNAME") + SETUP_FILE_PATH + "/db"

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver exception in linux and text editor [duplicate]

This question already has answers here:
Connect Java to a MySQL database
(14 answers)
Closed 5 years ago.
My code looks like this-(working in normal text editor)
import java.sql.*;
import java.sql.DriverManager;
class JDBCTest {
private static final String url = "jdbc:mysql://localhost/learn";
private static final String user = "root";
private static final String password = "B!SHu12345";
public static void main(String args[]) {
try {
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection(url, user, password);
Statement st=con.createStatement();
ResultSet rs=st.executeQuery("select * from bishu where id =101");
while(rs.next()){
String s=rs.getString("id");
System.out.println(s);
}
System.out.println("Success");
} catch (Exception e) {
e.printStackTrace();
System.out.println(e.getMessage());
}
}
}
At run time it gives an exception as follows-
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:195)
at JDBCTest.main(first.java:14)
Mysql connector was downloaded and saved in the path- Java/jre1.8.0_91/lib/ext/
I have gone through many similar solutions available, but wasn't able to find a valid one.

Add the MYSQL JDBC Driver from the library of your IDE.or place this JDBC driver file inside the lib directory of your project. Your question looks similar to this question

Trying to connect mySQL database with a java app keep getting stuck [duplicate]

This question already has answers here:
Connect Java to a MySQL database
(14 answers)
Closed 5 years ago.
ok so i have a java fx app that will display info from a mysql database runing locally on the same computer. i keep getting driver not found. here is the code:
String databaseURL = "jdbc:mysql://localhost:3307/mysql?zeroDateTimeBehavior=convertToNull";
String user = "user";
String password = "password";
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(databaseURL, user, password);
if (conn != null) {
System.out.println("Connected to the database");
}
} catch (ClassNotFoundException ex) {
System.out.println("Could not find database driver class");
ex.printStackTrace();
} catch (SQLException ex) {
System.out.println("An error occurred. Maybe user/password is invalid");
ex.printStackTrace();
} finally {
if (conn != null) {
try {
conn.close();
} catch (SQLException ex) {
ex.printStackTrace();
}
}
and here is the stack trace:
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at java.net.URLClassLoader$1.run(URLClassLoader.java:372)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:360)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:259)
at got_map.GOT_Map.start(GOT_Map.java:130)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$153(LauncherImpl.java:821)
at com.sun.javafx.application.LauncherImpl$$Lambda$51/1468396900.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$166(PlatformImpl.java:323)
at com.sun.javafx.application.PlatformImpl$$Lambda$44/584634336.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$null$164(PlatformImpl.java:292)
at com.sun.javafx.application.PlatformImpl$$Lambda$47/1960854798.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$165(PlatformImpl.java:291)
at com.sun.javafx.application.PlatformImpl$$Lambda$45/501263526.run(Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$141(WinApplication.java:102)
at com.sun.glass.ui.win.WinApplication$$Lambda$37/96639997.run(Unknown Source)
at java.lang.Thread.run(Thread.java:745)
Apr 21, 2017 6:29:06 PM javafx.fxml.FXMLLoader$ValueElement processValue
WARNING: Loading FXML document with JavaFX API of version 8.0.111 by JavaFX runtime of version 8.0.20
Any help would be much appreciated

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
...
at java.lang.Class.forName(Class.java:259)
at got_map.GOT_Map.start(GOT_Map.java:130)
This : Class.forName("com.mysql.jdbc.Driver"); is not enough.
Indeed, it rises a ClassNotFoundException if the class cannot be retrieved from the runtime classpath.
You need just to add in the runtime classpath the MySQL JDBC driver matching with the installed MySQL version.

The problem is in the line, Class.forName("com.mysql.jdbc.Driver");
The reason for getting java.lang.ClassNotFoundException can be an issue in loading the driver.Add the *.jar driver to your project if you haven't added it.

java.net.UnknownHostException when attempting to connect to database

I am attempting to connect to an Oracle database through Java with the Oracle JDBC driver with the following code (obscuring the host, service, user, and password):
import java.sql.*;
public class Main {
public Main () {
try {
String host = "HOST_NAME";
String port = "1521";
String service = "SERVICE_NAME";
String user = "SCHEMA_USER";
String password = "SCHEMA_PASSWORD";
Class.forName("oracle.jdbc.driver.OracleDriver");
Connection connection = DriverManager.getConnection("jdbc:oracle:thin:#(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=" +
host +
")(PORT=" +
port +
")))(CONNECT_DATA=(SERVICE_NAME=" +
service +
")))",
user,
password);
connection.close ();
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main (String args) {
new Main ();
}
}
However, I receive the following error:
java.sql.SQLException: IO Error: The Network Adapter could not establish the connection
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:458)
at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:546)
at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:236)
at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:32)
at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:521)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at com.acxiom.axle.reporting.database.DatabaseConnection.connect(DatabaseConnection.java:23)
at com.acxiom.axle.reporting.Reporting.establishDatabaseConnection(Reporting.java:53)
at com.acxiom.axle.reporting.Reporting.beginReporting(Reporting.java:20)
at com.acxiom.axle.reporting.Entry.<init>(Entry.java:28)
at com.acxiom.axle.reporting.Entry.main(Entry.java:118)
Caused by: oracle.net.ns.NetException: The Network Adapter could not establish the connection
at oracle.net.nt.ConnStrategy.execute(ConnStrategy.java:392)
at oracle.net.resolver.AddrResolution.resolveAndExecute(AddrResolution.java:434)
at oracle.net.ns.NSProtocol.establishConnection(NSProtocol.java:687)
at oracle.net.ns.NSProtocol.connect(NSProtocol.java:247)
at oracle.jdbc.driver.T4CConnection.connect(T4CConnection.java:1102)
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:320)
... 11 more
Caused by: java.net.UnknownHostException: null
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress$2.lookupAllHostAddr(Unknown Source)
at java.net.InetAddress.getAddressesFromNameService(Unknown Source)
at java.net.InetAddress.getAllByName0(Unknown Source)
at java.net.InetAddress.getAllByName(Unknown Source)
at java.net.InetAddress.getAllByName(Unknown Source)
at oracle.net.nt.TcpNTAdapter.connect(TcpNTAdapter.java:117)
at oracle.net.nt.ConnOption.connect(ConnOption.java:133)
at oracle.net.nt.ConnStrategy.execute(ConnStrategy.java:370)
... 16 more
The strange thing is, I can connect to the database from PL/SQL Developer, I can ping the remote host, and I can telnet to the remote host on port 1521.
Why would only Java appear to give an UnknownHostException, but I can connect and ping the host with other applications?
EDIT: I removed "hr/hr" from the connection string above. I have tried the connection as-is with it removed and still receive the same error. I've also tried changing the connection string to match the version morgano listed in his answer, with the same result. Finally, I tried to change the port number to a port I know it's not listening on, and it still receives the same error.

The connection string is of the correct format. The problem is that the host isn't set. It's null, or perhaps the string "null". There's simply no other way to generate the error message java.net.UnknownHostException: null
In your sample code, you write String host = "HOST_NAME";. This makes it look like in your real code you are assigning a constant string to the variable host. However, I'm going to stick my neck out and say that in your real code you are not doing this. You are looking up the host name from somewhere, this lookup fails for some reason, you don't check this, and hence you pass a null value into the connection string.

Your JDBC url is wrong, according to the documentation it should be something like:
jdbc:oracle:driver_type:[username/password]#//host_name:port_number/service_name
In your case your code would be something like:
import java.sql.*;
public class Main {
public Main () {
try {
String host = "HOST_NAME";
String port = "1521";
String service = "SERVICE_NAME";
String user = "SCHEMA_USER";
String password = "SCHEMA_PASSWORD";
Class.forName("oracle.jdbc.driver.OracleDriver");
Connection connection = DriverManager.getConnection(
"jdbc:oracle:thin:#//" + host
+ ":" + port + "/" + service, user, password);
connection.close ();
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main (String args) {
new Main ();
}
}

java.lang.ClassNotFoundException

I've installed MaxDB in my local machine and I'm trying to make a connection to it using Java.
And I'm getting this error when running :
Exception in thread "main"
java.lang.ClassNotFoundException:
com.sap.dbtech.jdbc.DriverSapDB
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at sap.maxdb.Hello.main(Hello.java:15)
This is the code I'm using :
package sap.maxdb;
import java.sql.*;
public class Hello
{
public static void main(String[] args) throws ClassNotFoundException, SQLException
{
String username = "DBM";
String password = "azerty";
String dbname = "SAPDB";
Class.forName ("com.sap.dbtech.jdbc.DriverSapDB");
String url = "jdbc:sapdb://" + dbname;
Connection connection = DriverManager.getConnection (url, username, password);
Statement stmt = connection.createStatement ();
ResultSet resultSet = stmt.executeQuery ("SELECT * FROM HOTEL.CUSTOMER");
resultSet.next ();
String hello = resultSet.getString (1);
System.out.println (hello);
resultSet.close ();
stmt.close();
connection.close ();
}
}
I did like they said in their website :
set CLASSPATH=%CLASSPATH%;C:\Program
Files\sdb\programs\runtime\jar\sapdbc.jar
But I get always the same error.
I know that I'm missing something but can't find it °!°
Waiting for your help.
Thanks.

What does "install" mean? Basically, the db server must be installed and running.
Step two is to add the driver (which you can find under C:\Program Files\sdb\programs\runtime\jar\sapdbc.jar, assuming this applies to your installation too) to the build path of your project. If the driver class cannot be found, it'll raise a ClassNotFoundException as you experienced.
You don't mention which IDE you are using, but try to set your project buildpath from the context menu.

Try adding the following code to make sure that your application picks up the CLASSPATH that you specified:
Map<String, String> env = System.getenv();
for (String envName : env.keySet()) {
System.out.format("%s=%s%n", envName, env.get(envName));
}

Copy the driver's jar file to the 'lib' folder of the server. Then restart the server.