Checking DB Connection Using Java
For the sake of completeness, here is a Java version of the Groovy post to test your Oracle Database connection.
package atest;
import java.sql.*;
/**
* Run arguments sample:
* jdbc:oracle:thin:@localhost:1521:XE system mypassword123 oracle.jdbc.driver.OracleDriver
*/
public class DbConn {
public static void main(String[] args) throws Exception {
String url = args[0];
String username = args[1];
String password = args[2];
String driver = args[3];
Class.forName(driver);
Connection conn = DriverManager.getConnection(url, username, password);
try {
Statement statement = conn.createStatement();
ResultSet rs = statement.executeQuery("SELECT SYSDATE FROM DUAL");
while(rs.next()) {
System.out.println(rs.getObject(1));
}
} finally {
conn.close();
}
}
}
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Comments
Tomasz O. replied on Fri, 2012/12/14 - 4:23am
I do not have any experience with databases and handling them from java, but I am curious why are you doing this:
I mean why do you create object and don't store a reference to it?
Xavier Dury replied on Fri, 2012/12/14 - 4:40am
in response to:
Tomasz O.
Loading a Driver class triggers a static initialization block inside that class which registers the Driver into the DriverManager (so DriverManager knows which driver to use when it encounters URLs like jdbc:oracle:...). Hence, loading that class with Class.forName(xxx) is sufficient. Since JDBC 4.0, this is not needed anymore as driver jars must include a file META-INF/services/java.sql.Driver which contains the driver class name. DriverManager can then autodiscover the drivers classes by reading all META-INF/services/java.sql.Driver accessible via the current ClassLoader.
Tomasz O. replied on Fri, 2012/12/14 - 5:04am
in response to:
Xavier Dury
Ok, thanks :)
Strange solution.. Anyway, if DriverManager needs to know, then I would prefer to pass the driver to it directly, so that anyone that reads the code would also know.
Xavier Dury replied on Fri, 2012/12/14 - 5:39am
in response to:
Tomasz O.
But then you would have a compile-time dependency on that particular Driver. Changing from one DBMS to another (say from Oracle to MySQL) would be less easy.
Mozart Brocchini replied on Fri, 2012/12/14 - 11:08am
in response to:
Xavier Dury
Xavier, I don't see the compile-time dependency on a particular driver.
The drive variable is being assigned to the value of 4th element of args parameter.
This could also have a little more flexibility if the assignment of driver variable was changed to take an optional java property override.
Something like this:
Would use java property "my.jdbc.driver" to configure the driver.
David Cutter replied on Fri, 2012/12/14 - 1:26pm
"SELECT SYSDATE FROM DUAL" won't work from most databases so passing in driver via properties file or command-line doesn't really buy you much if the SQL itself is database-specific.
Could put the test SQL in a properties file with the driver name and have properties files for each database to test.
Xavier Dury replied on Fri, 2012/12/14 - 1:13pm
in response to:
Mozart Brocchini
I thought Thomasz wanted to pass the Driver instance somehow to the DriverManager, not the Driver class name (which would of course not imply a compile-time dependency).