Maven - java.lang.ClassNotFoundException: com.mysql.jdbc.Driver

Question

I have a Java app based on Maven, and want to connect to MySQL server.

My pom has:

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.17</version>
    <type>jar</type>
    <scope>runtime</scope>
</dependency>

With runtime , as I want to connect to MySQL server at runtime - have also tried compile and provided, but does not work.

The SQL code is standard:

String dbClass = "com.mysql.jdbc.Driver";

Class.forName(dbClass);
Connection connection = DriverManager.getConnection(dbUrl,
    username, password);
Statement statement = connection.createStatement();
ResultSet resultSet = statement.executeQuery(query);
while (resultSet.next()) {
    String tableName = resultSet.getString(1);
    System.out.println("Table name : " + tableName);
}

When I run this from Eclipse , it works fine and prints table names.

However, from maven, the generated SNAPSHOT always gives an error when executed via > java -jar target\File.jar after running mvn clean install .

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver

What am I missing here to get the maven build to work? Running mvn clean install gives no error and builds fine. It is only when executing the SNAPSHOT exe the error happens.

The MySQL jar is in my .m2 repo, and I tried adding it explicitly via mvn command line, but says it already exists.

Answer 1

Change the scope to compile :

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.17</version>
    <type>jar</type>
    <scope>compile</scope>
</dependency>

Which - since it is the default scope corresponds to leaving away scope definition at all - same counts for the type:

<dependency>
   <groupId>mysql</groupId>
   <artifactId>mysql-connector-java</artifactId>
   <version>5.1.17</version>
</dependency>

Have a look at this: https://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html for detailed information on scoping.

Here is a quick info for your background:

You specified the JDBC driver to have a scope runtime . Most IDEs will anyways ignore the scopes and add all of your dependencies to their classpath (eg the classpath used when you run something outside of eclipse. By the scope runtime you are telling maven that it must not pack that dependeny into your final jar since the execution environment will "provide that dependency at runtime . Eg you would either have to manually add it to the classpath when calling your jar or change the scope to compile which will lead to the driver-jar beeing packed inside your jar and available at runtime.

Answer 2

Since you are running the project by "java -jar" and also you have dependencies, so, you have to use two maven plugins. The first one to copy dependencies into a folder inside target folder (eg lib/) while packaging and the second one for specifying the classpath which should be same as the first one(lib/). I had the same problem and here is what I did:

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-dependency-plugin</artifactId>
            <executions>
                <execution>
                    <id>copy</id>
                    <phase>package</phase>
                    <goals>
                        <goal>copy-dependencies</goal>
                    </goals>
                    <configuration>
                        <outputDirectory>
                            ${project.build.directory}/lib
                        </outputDirectory>
                    </configuration>
                </execution>
            </executions>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <configuration>
                <archive>
                    <manifest>
                        <addClasspath>true</addClasspath>
                        <classpathPrefix>lib/</classpathPrefix>

                  <mainClass>com.tihoo.crawler.Application</mainClass>
                    </manifest>
                </archive>
            </configuration>
        </plugin>
    </plugins>
</build>

Answer 3

The answer is here - How can I create an executable JAR with dependencies using Maven?

I needed to build an uber pom, using the answer in the link above - this builds in the dependencies (in this case the mysql jar file) into a single SNAPSHOT jar file.

Just make sure you run it with mvn clean compile assembly:single (not the usual mvn clean package or whatever.

Answer 4

I had this problem as well. I tried using plugins to set the connector to classpath but it didn't work. I tried to change versions, it didn't work. I've spent two nights to find out that i needed to specify in pom.xml that i need my package to be a "war".

Maybe it's because your project doesn't know what type it is, so try to put this:

<packaging>war</packaging>

right next to your project version. Something like this:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>com.example</groupId>
<artifactId>example-app</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>war</packaging> <!-- Here -->

<properties>
    <!-- Some properties here -->
</properties>

<dependencies>
    <!-- Some dependencies here -->
</dependencies>

Maybe it doesn't suit your problem, but maybe somebody else will need it.

Answer 5

Add this code

    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.6</version>
    </dependency>

to porm.xml file in your maven project