SpringBoot loader.path Unable to load external Jar

Question

I am using springboot for a webapp and I am attempting to setup an external directory that will hold various JDBC drivers that an end user may select to use. To do this I am adding:

loader.path=/opt/myapp/lib/

to my application.properties file, and this is picked up by the PropertySourcesPropertyResolver

2016-04-28 17:27:38.739 DEBUG 22539 --- [restartedMain] o.s.c.e.PropertySourcesPropertyResolver  : Found key 'loader.path' in [applicationConfigurationProperties] with type [String] and value '/opt/myapp/lib/'

My problem is I can't seem to load any JDBC drivers from any jars that I drop into this directory, what am I missing? I am using the default embedded tomcat server. When I attempt to load the driver using Class.forName, I get the following, like the jars aren't present in that directory.

 public Connection buildConnection(DataSource dataSource) throws ClassNotFoundException, SQLException {

    if (dataSource == null) {
        throw new NullPointerException("Data Source is null!");
    }

    if (!dataSource.isReady()) {
        throw new IllegalArgumentException("Data Source is reporting that it is not ready!");
    }

    logger.debug("Loading JDBC Driver: {}", dataSource.getDriverClass());
    Class.forName(dataSource.getDriverClass());
    logger.debug("Loaded Driver: {}", dataSource.getDriverClass());

    logger.debug("Attempting to build connection using: {}", dataSource.getConnectionString());

    DriverManager.setLoginTimeout(10);
    Connection c = DriverManager.getConnection(dataSource.getConnectionString(), dataSource.getUserName(), dataSource.getPassword());
    if (c != null) {
        c.setAutoCommit(true);
        c.setReadOnly(true);
        return c;
    }
    throw new NullPointerException("Unable to create connection!");
} 

This is the exception that is thrown

2016-04-28 17:38:53.525 DEBUG 22539 --- [nio-8081-exec-5] c.c.reportout.processor.JobProcessor     : Loading JDBC Driver: com.mysql.jdbc.Driver
2016-04-28 17:38:53.526  WARN 22539 --- [nio-8081-exec-5] c.c.reportout.processor.JobProcessor     : Unable to successfully test connection: com.mysql.jdbc.Driver

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[na:1.8.0_91]
at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_91]
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331) ~[na:1.8.0_91]
at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_91]
at org.springframework.boot.devtools.restart.classloader.RestartClassLoader.loadClass(RestartClassLoader.java:151) ~[spring-boot-devtools-1.3.3.RELEASE.jar:1.3.3.RELEASE]
at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_91]
at java.lang.Class.forName0(Native Method) ~[na:1.8.0_91]
at java.lang.Class.forName(Class.java:264) ~[na:1.8.0_91]

Any pointers as to how I can debug this or what I am doing wrong?

Thanks

Answer 1

So after much googling, it turns out I was able to resolve it by adding:

<configuration>
    <layout>ZIP</layout>
</configuration>

to the spring-boot-maven-plugin plugin in my pom file. So the working version looks like this now:

<plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <version>${spring-boot.version}</version>
            <configuration>
                <layout>ZIP</layout>
            </configuration>
            <executions>
                <execution>
                    <goals>
                        <goal>repackage</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>