DBA-010

Simple java code to test connection to Oracle database

Assuming that client computer does not have Oracle client installed.

1. Download necessary version of ojdbc jar file from Oracle. The latest version for now is ojdbc8.jar

2. Install java development tools:

# yum install java-devel * -y

3. Create a sample java code, which:
– connects to the database
– selects 1 from dual
– disconnects

# cat JDBCTest.java

import java.sql.*;
 class JDBCTest{
     public static void main(String args[]) throws SQLException {
         Connection con = null;
         try{
             Class.forName("oracle.jdbc.driver.OracleDriver");
             String dbURL = "jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=" + args[0] + ")(PORT=1521))(CONNECT_DATA=(SERVER = DEDICATED)(SERVICE_NAME=orclgg)))";
             System.out.println("jdbcurl=" + dbURL);
             String strUserID = "system";
             String strPassword = "Oracle123";
             con=DriverManager.getConnection(dbURL,strUserID,strPassword);
             System.out.println("Connected to the database.");
             Statement stmt=con.createStatement();
             System.out.println("Executing query");
             ResultSet rs=stmt.executeQuery("SELECT 1 FROM DUAL");
             while(rs.next())
                 System.out.println(rs.getInt("1"));
             con.close();
         }catch(Exception e){ System.out.println(e);}
         finally {
             con.close();
         }
 }
 }

4. Compile java code and check that *.class file was generated:

# javac JDBCTest.java

# ll  JDBCTest.*
 -rw-r--r-- 1 root root 1836 Sep 27 11:45 JDBCTest.class
 -rw-r--r-- 1 root root  925 Sep 27 11:45 JDBCTest.java

5. Run code:

# java -Djava.security.egd=file:/dev/../dev/urandom -cp ojdbc8.jar:. JDBCTest "stbyrac-scan.example.com"

jdbcurl=jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=stbyrac-scan.example.com)(PORT=1521))(CONNECT_DATA=(SERVER = DEDICATED)(SERVICE_NAME=orclgg)))

Connected to the database.
Executing query…
1

Please note that -Djava.security.egd=file:/dev/../dev/urandom parameter is required to have a stable connection. I will discuss the importance of this parameter in the next post.