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Archive for April, 2020

SQL Developer Error

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It’s been a couple releases trying to fix the following error thrown by SQL Developer on Fedora 30 and shown as the following dialog:

When you click the Detail button it shows the following error stack:

java.lang.NoClassDefFoundError: javafx/embed/swing/JFXPanel
	at oracle.dbtools.raptor.javafx.ui.JFXPanelFactory.createJFXPanelImpl(JFXPanelFactory.java:58)
	at oracle.dbtools.raptor.javafx.ui.JFXPanelFactory.createJFXPanel(JFXPanelFactory.java:34)
	at oracle.dbtools.raptor.startpage.StartPageViewer.createGUIComponent(StartPageViewer.java:179)
	at oracle.dbtools.raptor.startpage.StartPageViewer.getEditorContent(StartPageViewer.java:136)
	at oracle.ide.editor.AsynchronousEditor$2.run(AsynchronousEditor.java:345)
	at oracle.ide.editor.AsynchronousEditor$5.run(AsynchronousEditor.java:555)
	at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1443)
	at org.netbeans.modules.openide.util.GlobalLookup.execute(GlobalLookup.java:68)
	at org.openide.util.lookup.Lookups.executeWith(Lookups.java:303)
	at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2058)
Caused by: java.lang.ClassNotFoundException: javafx.embed.swing.JFXPanel cannot be found by oracle.sqldeveloper_19.2.0
	at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:501)
	at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:421)
	at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:412)
	at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:107)
	at org.netbeans.modules.netbinox.NetbinoxLoader.loadClass(NetbinoxLoader.java:81)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:352)
	... 10 more

I thought applying the Open Java FX package might fix the problem. I installed the package like the following:

yum install -y openjfx

The installation log:

Last metadata expiration check: 4:03:29 ago on Tue 21 Apr 2020 06:42:26 PM MDT.
Dependencies resolved.
=============================================================================================
 Package            Architecture      Version                       Repository          Size
=============================================================================================
Installing:
 openjfx            x86_64            8.0.202-8.b07.fc30            updates            8.8 M
 
Transaction Summary
=============================================================================================
Install  1 Package
 
Total download size: 8.8 M
Installed size: 11 M
 
Downloading Packages:
openjfx-8.0.202-8.b07.fc30.x86_64.rpm                        2.5 MB/s | 8.8 MB     00:03    
---------------------------------------------------------------------------------------------
Total                                                        2.1 MB/s | 8.8 MB     00:04     
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                                     1/1 
  Installing       : openjfx-8.0.202-8.b07.fc30.x86_64                                   1/1 
  Running scriptlet: openjfx-8.0.202-8.b07.fc30.x86_64                                   1/1 
  Verifying        : openjfx-8.0.202-8.b07.fc30.x86_64                                   1/1 
 
Installed:
  openjfx-8.0.202-8.b07.fc30.x86_64                                                          
 
Complete!

After installing the software, I determined the new JAR files. Then, I added them to my $CLASSPATH environment variable, like:

export CLASSPATH=/usr/share/java/mysql-connector-java.jar:/usr/lib/jvm/openjfx/rt/lib/ext/fxrt.jar:/usr/lib/jvm/openjfx/rt/lib/jfxswt.jar:.

While it appears to load faster with these JAR files, it still raises the same Dialog error. I simply have to continue to look for a complete fix.

Written by maclochlainn

April 21st, 2020 at 11:49 pm

Fedora 30 pgAdmin4 Install

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Last September, the pgAdmin4 installation stymied me. I wasn’t sure what was I had done wrong in the installation but I was on a deadline to release my Fedora 30 Linux virtualization. That meant I had to move on and leave it for later. Today, I’m building the new image and returned to the task.

I installed pgadmin4 with the following command:

dnf -y install pgadmin4

The pgadmin4 configuration instructions can be found for several Linux versions at Josphat Mutai’s Computing for Geeks web page. On Fedora 30, you need to do the following:

  • Install, start, and enable Apache as the httpd service unless you already have done that.
  • Copy the /etc/httpd/conf.d/pgadmin4.conf.sample file to /etc/httpd/conf.d/pgadmin4.conf, which is a new file.
  • Restart the httpd service to incorporate the pgadmin4 configuration file.

After that, my instructions vary from the original web page because they didn’t work. You actually need to create four directories as the sudo or root user:

  • /var/lib/pgadmin4
  • /var/lib/pgadmin4/sessions
  • /var/lib/pgadmin4/storage
  • /var/log/pgadmin4

You can make both directories with a single mkdir command, like:

mkdir -p /var/lib/pgadmin4 /var/lib/pgadmin4/sessions /var/lib/pgadmin4/storage /var/log/pgadmin4

As the root or sudo user, change the ownership of these two directories to the apache user with the following syntax:

chown -R apache:apache /var/lib/pgadmin4 /var/lib/pgadmin4/sessions /var/lib/pgadmin4/storage /var/log/pgadmin4

You add the following four statements to the config_distro.py file in the /usr/lib/python3.7/site-packages/pgadmin4-web directory as the root or sudo user:

LOG_FILE = '/var/log/pgadmin4/pgadmin4.log'
SQLITE_PATH = '/var/lib/pgadmin4/pgadmin4.db'
SESSION_DB_PATH = '/var/lib/pgadmin4/sessions'
STORAGE_DIR = '/var/lib/pgadmin4/storage'

You need to setup the pgadmin user with the following python3 command:

python3 /usr/lib/python3.7/site-packages/pgadmin4-web/setup.py

Enter the following values, a real email address and a password twice:

NOTE: Configuring authentication for SERVER mode.
 
Enter the email address and password to use for the initial pgAdmin user account:
 
Email address: admin@example.com   
Password: your_password
Retype password: your_password
pgAdmin 4 - Application Initialisation
======================================

Before you move on, you should check ownership of the pgadmin4 directories in the /var/lib and /var/log directories and their files by long listing them as follows:

  • Check the /var/lib directory:

    ll /var/lib/pgadmin4

    It should display:

    total 148
    -rw-r--r--. 1 root   root     1296 Apr 11 12:12 my-httpd.pp
    -rw-r--r--. 1 root   root      332 Apr 11 12:12 my-httpd.te
    -rw-------. 1 apache apache 131072 Apr 11 12:16 pgadmin4.db
    drwx------. 2 apache apache   4096 Apr 11 12:15 sessions
    drwxr-xr-x. 2 apache apache   4096 Apr 10 17:33 storage
  • Check the /var/log directory:

    ll /var/log/pgadmin4

    It should display:

    total 4
    -rw-r--r--. 1 apache apache 1174 Apr 11 12:15 pgadmin4.log

Assuming you have an enabled firewall, you need to issue the following two commands as the root or sudo user:

firewall-cmd --permanent --add-service=http
firewall-cmd --reload

You invoke pgAdmin4 from within a browser window with the following URL for a stand alone workstation (for a workstation on a DNS network you would enter pgadmin.domain.domain_type in lieu of localhost):

pgadmin/localhost/pgadmin4

You most likely will encounter an Internal Server Error, the recommended fix is reputed to be:

ausearch -c 'httpd' --raw | audit2allow -M my-httpd
semodule -i my-httpd.pp

After completing the installation, you should be able to run pgadmin4, by typing in the following URL into a web browser:

http://localhost/pgadmin4

You should see the pgAmin4 web page if everything works. If it fails to launch, you should check the Apache error log. The error_log file is found in the /var/log/httpd directory. This is a type of error you may get if the ownership privileges aren’t assigned to the apache user and apache group.

As always, I hope my notes are helpful to those who want to work with pgadmin4 and the PostgreSQL database.

Written by maclochlainn

April 11th, 2020 at 2:45 pm

Java & MySQL 8.0.19

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It’s the in-between term time and we’re all stuck at home. I decided to update the image for my Fedora 30 virtual machine. I had a work around to the update issue that I had encountered last October in Bug #96969 but it was not required with the current version. However, after updating from MySQL 8.0.17 to MySQL 8.0.19, I found that my Java connection example failed.

The $CLASSPATH value was correct:

/usr/share/java/mysql-connector-java.jar:.

The first error that I got was the my reference to MySQL JDBC driver was incorrect. The error message is quite clear:

Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.
Cannot connect to database server:
The server time zone value 'MDT' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the 'serverTimezone' configuration property) to use a more specifc time zone value if you want to utilize time zone support.

I changed the MySQL Driver reference as instructed by the error message:

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      // Create instance of MySQLDriver.
      Class.forName ("com.mysql.cj.jdbc.Driver").newInstance();
      conn = DriverManager.getConnection (url, username, password);

After the change, I got the following error while retesting my little MySQL Java driver connection test program. Initially, I thought this required a change in the Java environment but that wasn’t it.

Cannot connect to database server:
The server time zone value 'MDT' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the 'serverTimezone' configuration property) to use a more specifc time zone value if you want to utilize time zone support.

It required me to add the following line to my /etc/my.cnf configuration file, which synchronizes the database’s timezone with the operating system.

# Synchronize the MySQL clock with the computer system clock.
default-time-zone='+00:00'

Then, running my MySQL Driver connection test program worked like a charm. It returns the following:

Database connection established
MySQLDriver Version [8.0.19]
Database connection terminated

Here’s the MySQL Connector Java code if you’d like to use the MySQLDriver.java file:

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// Import classes.
import java.sql.*;
 
/* You can't include the following on Linux without raising an exception. */
// import com.mysql.jdbc.Driver;
 
public class MySQLDriver {
  public MySQLDriver() {
    /* Declare variables that require explicit assignments because
       they're addressed in the finally block. */
    Connection conn = null;
    Statement stmt = null;
    ResultSet rset = null;
 
    /* Declare other variables. */
    String url;
    String username = "student";
    String password = "student";
    String database = "studentdb";
    String hostname = "localhost";
    String port = "3306";
    String sql;
 
    /* Attempt a connection. */
    try {
      // Set URL.
      url = "jdbc:mysql://" + hostname + ":" + port + "/" + database;
 
      // Create instance of MySQLDriver.
      Class.forName ("com.mysql.cj.jdbc.Driver").newInstance();
      conn = DriverManager.getConnection (url, username, password);
 
      // Query the version of the database.
      sql = "SELECT version()";
      stmt = conn.createStatement();
      rset = stmt.executeQuery(sql);
 
      System.out.println ("Database connection established");
 
      // Read row returns for one column.
      while (rset.next()) {
        System.out.println("MySQLDriver Version [" + rset.getString(1) + "]"); }
 
    }
    catch (SQLException e) {
      System.err.println ("Cannot connect to database server:");
      System.out.println(e.getMessage());
    }
    catch (ClassNotFoundException e) {
      System.err.println ("Cannot find MySQL driver class:");
      System.out.println(e.getMessage());
    }
    catch (InstantiationException e) {
      System.err.println ("Cannot instantiate class:");
      System.out.println(e.getMessage());
    }
    catch (IllegalAccessException e) {
      System.err.println ("Illegal access exception:");
      System.out.println(e.getMessage());
    }
    finally {
      if (conn != null) {
        try {
          rset.close();
          stmt.close();
          conn.close();
          System.out.println ("Database connection terminated");
        }
        catch (Exception e) { /* ignore close errors */ }
      }
    }
  }
  /* Unit test. */
  public static void main(String args[]) {
    new MySQLDriver();
  }
}

As always, I hope this helps those who encounter similar problems.

Written by maclochlainn

April 10th, 2020 at 12:42 pm