java.lang.ClassNotFoundException: org.postgresql.Driver - Cause and Solution

java.lang.ClassNotFoundException: org.postgresql.Driver error comes when you are trying to connect to a PostgreSQL database from Java program but Java ClassLoader is not able to find the Driver class "org.postgresql.Driver" required to make the connection. Usually this class is find in PostgreSQL JDBC driver JAR e.g. postgresql-9.4-1201.jdbc41.jar, which is required to connect PostgreSQL server version greater than 9.3 from JDK 1.7 or JDK 1.8, the exact JAR depends upon your PostgreSQL server version, the Java version you are running and JDBC version your are using. Now your problem could be either you don't have that PostgreSQL JDBC driver JAR in your machine or the JAR is not in your classpath, or you might be battling with some classpath intricacies. If you don't have this JAR, then solution of "java.lang.ClassNotFoundException: org.postgresql.Driver" is simple, just download it from PostgreSQL site. Make sure you download the correct version of JDBC driver based upon the PostgreSQL server you are connecting and JVM version of your machine. Once you download that, just put in the lib directory of your Java application e.g. WEB-INF/lib if you are connecting to PostgreSQL from Java Web Application. If you are running in Tomcat, then you can alternatively also put this in tomcat/lib directory, but beware of the difference in the application dependency in WEB-INF/lib or in tomcat/lib. You can also take a look at Practical database programming with Java book by Ying Bai. This books is a comprehensive guide of how to use JDBC in Java to connect to different databases. You will learn right ways of doing things with respect to Java and database.

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