Java: connecting to psql database throws an error (ClassNotFoundException)

Question

I am new to Java and I am trying to connect to my local PSql database without success, below the code and the details of the error.

I have 2 files: DbContract.java and TestConnection.java and I am using Eclipse.

DbContract.java

package dbcontract.db;

public interface DbContract {

    public static final String HOST = "jdbc:postgresql://localhost:5432/";
    public static final String DB_NAME = "db_notespesa";
    public static final String USERNAME = "postgres";
    public static final String PASSWORD = "";
}

TestConnection.java

package dbcontract;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

import dbcontract.db.DbContract;

public class TestConnection {

    public static void main(String[] args) {
        try {
            Class.forName("org.postgresql.Driver");
            Connection conn = DriverManager.getConnection(
                    DbContract.HOST+DbContract.DB_NAME,
                    DbContract.USERNAME,
                    DbContract.PASSWORD);
            System.out.println("DB connected");

        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }
    }
}

Error:

java.lang.ClassNotFoundException: org.postgresql.Driver
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:583)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
    at java.base/java.lang.Class.forName0(Native Method)
    at java.base/java.lang.Class.forName(Class.java:315)
    at TestConnection.main(TestConnection.java:13)

That is not really relevant: that question may be tagged netbeans, nothing in it is related to netbeans at all. This is something any Java developer should be able to deal with unless you have never before used any libraries at all and have always only used classes included in Java SE. — Mark Rotteveel, Dec 14 '18 at 19:20
This is my situation: I used Java today for the very first time :) — Marco Giuseppe de Pinto, Dec 14 '18 at 19:45
Unfortunately, stack overflow is not really the right place to get up to speed on a language or an IDE. Try to google for some introductory tutorials or documentation on Eclipse — Mark Rotteveel, Dec 14 '18 at 19:49

Mohammad Karmi · Accepted Answer · 2018-12-14T16:30:49.733

2

You need to add the dependency for the driver of Postgress as the error explains , if you are using maven just add this to pom.xml :

    <`<!-- https://mvnrepository.com/artifact/org.postgresql/postgresql -->
<dependency>
    <groupId>org.postgresql</groupId>
    <artifactId>postgresql</artifactId>
    <version>42.2.5</version>
</dependency>

Updated the version as Mark mentioned in the comment , here is the link for all the versions on maven repo : https://mvnrepository.com/artifact/org.postgresql/postgresql

edited Dec 14 '18 at 16:30

answered Dec 14 '18 at 16:26

Mohammad Karmi

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I am not using Maven, I have installed psql from the following link: https://www.postgresql.org/download/macosx/ . Inserting the file as you described unfortunately does not work.. – Marco Giuseppe de Pinto Dec 14 '18 at 16:29
1

Version `postgresql:postgresql:9.1-901-1.jdbc4` is extremely old. The latest version is `org.postgresql:postgresql:42.2.5`, see https://search.maven.org/search?q=g:org.postgresql%20AND%20a:postgresql – Mark Rotteveel Dec 14 '18 at 16:29
1

@MarcoG.dePinto Just downloading a JDBC driver is not enough, you'll need to add it to the runtime classpath of your application. – Mark Rotteveel Dec 14 '18 at 16:29
@MarkRotteveel: How can I add it using Eclipse? – Marco Giuseppe de Pinto Dec 14 '18 at 16:41
1

@MarcoG.dePinto create maven project and then add to pom.xml http://www.vogella.com/tutorials/EclipseMaven/article.html – Mohammad Karmi Dec 14 '18 at 16:42
1

@MarcoG.dePinto I strongly suggest to start using Maven or Gradle (Eclipse supports them), but otherwise look at [How to import a jar in Eclipse](https://stackoverflow.com/questions/3280353/how-to-import-a-jar-in-eclipse) – Mark Rotteveel Dec 14 '18 at 16:43
Thank you, marked the question as solved! – Marco Giuseppe de Pinto Dec 14 '18 at 16:44

Java: connecting to psql database throws an error (ClassNotFoundException)

1 Answers1