FlywayDB is unable to find Postgresql Driver

Question

I am trying to get Flyway setup within a Spigot/Bukkit MC plugin. Currently everytime I execute our SQL code, I get the error `

[10:37:14 WARN]: org.flywaydb.core.api.FlywayException: Unable to instantiate JDBC driver: org.postgresql.Driver => Check whether the jar file is present
[10:37:14 WARN]:        at org.flywaydb.core.internal.jdbc.DriverDataSource.<init>(DriverDataSource.java:180)
[10:37:14 WARN]:        at org.flywaydb.core.internal.jdbc.DriverDataSource.<init>(DriverDataSource.java:144)
[10:37:14 WARN]:        at org.flywaydb.core.api.configuration.ClassicConfiguration.setDataSource(ClassicConfiguration.java:1341)
[10:37:14 WARN]:        at org.flywaydb.core.api.configuration.FluentConfiguration.dataSource(FluentConfiguration.java:803)
[10:37:14 WARN]:        at com.mclockup.core.database.SqlWrapper.<init>(SqlWrapper.java:42)
[10:37:14 WARN]:        at com.mclockup.core.database.SqlWrapper.initialize(SqlWrapper.java:78)
[10:37:14 WARN]:        at com.mclockup.core.LockupCore.onEnable(LockupCore.java:22)
[10:37:14 WARN]:        at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:263)
[10:37:14 WARN]:        at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:337)
[10:37:14 WARN]:        at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:435)
[10:37:14 WARN]:        at org.bukkit.craftbukkit.v1_15_R1.CraftServer.enablePlugin(CraftServer.java:470)
[10:37:14 WARN]:        at org.bukkit.craftbukkit.v1_15_R1.CraftServer.enablePlugins(CraftServer.java:384)
[10:37:14 WARN]:        at org.bukkit.craftbukkit.v1_15_R1.CraftServer.reload(CraftServer.java:884)
[10:37:14 WARN]:        at org.bukkit.Bukkit.reload(Bukkit.java:654)
[10:37:14 WARN]:        at org.bukkit.command.defaults.ReloadCommand.execute(ReloadCommand.java:54)
[10:37:14 WARN]:        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:159)
[10:37:14 WARN]:        at org.bukkit.craftbukkit.v1_15_R1.CraftServer.dispatchCommand(CraftServer.java:752)
[10:37:14 WARN]:        at org.bukkit.craftbukkit.v1_15_R1.CraftServer.dispatchServerCommand(CraftServer.java:714)
[10:37:14 WARN]:        at net.minecraft.server.v1_15_R1.DedicatedServer.handleCommandQueue(DedicatedServer.java:469)
[10:37:14 WARN]:        at net.minecraft.server.v1_15_R1.DedicatedServer.b(DedicatedServer.java:431)
[10:37:14 WARN]:        at net.minecraft.server.v1_15_R1.MinecraftServer.a(MinecraftServer.java:1112)
[10:37:14 WARN]:        at net.minecraft.server.v1_15_R1.MinecraftServer.run(MinecraftServer.java:934)
[10:37:14 WARN]:        at java.lang.Thread.run(Thread.java:748)
[10:37:14 WARN]: Caused by: org.flywaydb.core.api.FlywayException: Unable to instantiate class org.postgresql.Driver : org.postgresql.Driver
[10:37:14 WARN]:        at org.flywaydb.core.internal.util.ClassUtils.instantiate(ClassUtils.java:59)
[10:37:14 WARN]:        at org.flywaydb.core.internal.jdbc.DriverDataSource.<init>(DriverDataSource.java:176)
[10:37:14 WARN]:        ... 22 more
[10:37:14 WARN]: Caused by: java.lang.ClassNotFoundException: org.postgresql.Driver
[10:37:14 WARN]:        at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
[10:37:14 WARN]:        at java.lang.ClassLoader.loadClass(ClassLoader.java:419)
[10:37:14 WARN]:        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:352)
[10:37:14 WARN]:        at java.lang.ClassLoader.loadClass(ClassLoader.java:352)
[10:37:14 WARN]:        at java.lang.Class.forName0(Native Method)
[10:37:14 WARN]:        at java.lang.Class.forName(Class.java:348)
[10:37:14 WARN]:        at org.flywaydb.core.internal.util.ClassUtils.instantiate(ClassUtils.java:57)
[10:37:14 WARN]:        ... 23 more

` I don't think this is a dependency issue since I've included Flyway & postgresql in my build.gradle

    plugins {
        id 'java'
        id 'maven-publish'
        id 'signing'
    }

    group = 'com.mclockup'
    version = '1.0.0-SNAPSHOT'
    description = 'Core functionality used everywhere in Lockup'

    archivesBaseName = 'core'
    sourceCompatibility = '1.8'

    repositories {
        mavenLocal()
        mavenCentral()
    }

    dependencies {
        // Spigot
        implementation group: 'org.spigotmc', name: 'spigot-api', version: '1.15.2-R0.1-SNAPSHOT'

        // Postgres
        compile group: 'org.postgresql', name: 'postgresql', version: '42.2.12'

        // Flyway
        compile group: 'org.flywaydb', name: 'flyway-core', version: '6.4.1'

        // MyBatis
        compile group: 'org.mybatis', name: 'mybatis', version: '3.5.4'

        // Log4J
        compile group: 'org.apache.logging.log4j', name: 'log4j-api', version: '2.13.2'
        compile group: 'org.apache.logging.log4j', name: 'log4j-core', version: '2.13.2'
    }

    jar {
        from {
            configurations.compile.collect { it.isDirectory() ? it : zipTree(it) }
        }
    }

    javadoc {
        options.links += "https://hub.spigotmc.org/javadocs/spigot/"
    }

    task sourcesJar(type: Jar) {
        from sourceSets.main.allJava
        archiveClassifier.set("sources")
    }

    task javadocJar(type: Jar, dependsOn: javadoc) {
        classifier 'javadoc'
        from javadoc.destinationDir
    }

And it errors here on our 2nd line

    Flyway flyway = Flyway.configure()
            .dataSource(getJdbcString(), DATABASE_USERNAME, DATABASE_PASSWORD)
            .load();
    flyway.migrate();

I can confirm the jdbcstring & username/password are correct as I was able to make a connection via DriverManager, but Flyway just can't seem to find the driver. Plus I can see the driver in my output jar, where its located in blah.jar\org\postgresql\Driver.class

I appreciate any help!! Thank you

Answer 1

figured it out! turns out the spigot server software we use uses a different class loader than the main java thread, so it was causing issues when loading the jdbc driver. We fixed this by passing in the correct class loader.

Flyway flyway = Flyway.configure(LockupCore.getInstance().getPublicClassLoader())