Connecting to as400 JDBC on Play Framework

I'm having issues making a connection to an AS400 database inside of Play!.

My application.conf looks like:

db.default.driver="com.ibm.as400.access.AS400JDBCDriver"
db.default.url="jdbc:as400://SERVER;libraries=A,B,C;toolbox trace=all;trace=true"
db.default.username="user"
db.default.password="password"

I've set up jt400 in the classpath, and I can see under "external libraries" that it shows up and is available. But essentially I get an error message about failing to connect (on user/password I know works) and failure to execute isValid(), which is a function that can not be found inside of AS400JDBCConnection class.

[error] c.z.h.p.PoolBase - HikariPool-1 - Failed to execute isValid() for connection, configure connection test query. (com.ibm.as400.access.AS400JDBCConnection.isValid(I)Z)
[error] application - 

! @72265nf0a - Internal server error, for (GET) [/] ->

play.api.Configuration$$anon$1: Configuration error[Cannot connect to database [default]]
    at play.api.Configuration$.configError(Configuration.scala:154)
    at play.api.Configuration.reportError(Configuration.scala:806)
    at play.api.db.DefaultDBApi$$anonfun$connect$1.apply(DefaultDBApi.scala:48)
    at play.api.db.DefaultDBApi$$anonfun$connect$1.apply(DefaultDBApi.scala:42)
    at scala.collection.immutable.List.foreach(List.scala:381)
    at play.api.db.DefaultDBApi.connect(DefaultDBApi.scala:42)
    at play.api.db.DBApiProvider.get$lzycompute(DBModule.scala:72)
    at play.api.db.DBApiProvider.get(DBModule.scala:62)
    at play.api.db.DBApiProvider.get(DBModule.scala:58)
    at com.google.inject.internal.ProviderInternalFactory.provision(ProviderInternalFactory.java:81)
Caused by: play.api.Configuration$$anon$1: Configuration error[Failed to initialize pool: com.ibm.as400.access.AS400JDBCConnection.isValid(I)Z]
    at play.api.Configuration$.configError(Configuration.scala:154)
    at play.api.PlayConfig.reportError(Configuration.scala:996)
    at play.api.db.HikariCPConnectionPool.create(HikariCPModule.scala:70)
    at play.api.db.PooledDatabase.createDataSource(Databases.scala:199)
    at play.api.db.DefaultDatabase.dataSource$lzycompute(Databases.scala:123)
    at play.api.db.DefaultDatabase.dataSource(Databases.scala:121)
    at play.api.db.DefaultDatabase.getConnection(Databases.scala:142)
    at play.api.db.DefaultDatabase.getConnection(Databases.scala:138)
    at play.api.db.DefaultDBApi$$anonfun$connect$1.apply(DefaultDBApi.scala:44)
    at play.api.db.DefaultDBApi$$anonfun$connect$1.apply(DefaultDBApi.scala:42)
Caused by: com.zaxxer.hikari.pool.HikariPool$PoolInitializationException: Failed to initialize pool: com.ibm.as400.access.AS400JDBCConnection.isValid(I)Z
    at com.zaxxer.hikari.pool.HikariPool.checkFailFast(HikariPool.java:512)
    at com.zaxxer.hikari.pool.HikariPool.<init>(HikariPool.java:105)
    at com.zaxxer.hikari.HikariDataSource.<init>(HikariDataSource.java:71)
    at play.api.db.HikariCPConnectionPool$$anonfun$1.apply(HikariCPModule.scala:58)
    at play.api.db.HikariCPConnectionPool$$anonfun$1.apply(HikariCPModule.scala:54)
    at scala.util.Try$.apply(Try.scala:192)
    at play.api.db.HikariCPConnectionPool.create(HikariCPModule.scala:54)
    at play.api.db.PooledDatabase.createDataSource(Databases.scala:199)
    at play.api.db.DefaultDatabase.dataSource$lzycompute(Databases.scala:123)
    at play.api.db.DefaultDatabase.dataSource(Databases.scala:121)
Caused by: java.lang.AbstractMethodError: com.ibm.as400.access.AS400JDBCConnection.isValid(I)Z
    at com.zaxxer.hikari.pool.PoolBase.checkDriverSupport(PoolBase.java:400)
    at com.zaxxer.hikari.pool.PoolBase.setupConnection(PoolBase.java:375)
    at com.zaxxer.hikari.pool.PoolBase.newConnection(PoolBase.java:346)
    at com.zaxxer.hikari.pool.HikariPool.checkFailFast(HikariPool.java:506)
    at com.zaxxer.hikari.pool.HikariPool.<init>(HikariPool.java:105)
    at com.zaxxer.hikari.HikariDataSource.<init>(HikariDataSource.java:71)
    at play.api.db.HikariCPConnectionPool$$anonfun$1.apply(HikariCPModule.scala:58)
    at play.api.db.HikariCPConnectionPool$$anonfun$1.apply(HikariCPModule.scala:54)
    at scala.util.Try$.apply(Try.scala:192)
    at play.api.db.HikariCPConnectionPool.create(HikariCPModule.scala:54)

I'm able to connect in other java-based projects using something like:

try {
                Class.forName("com.ibm.as400.access.AS400JDBCDriver");
                Connection con = DriverManager.getConnection("jdbc:as400://" + 
                    ApplicationAuthentication.server + "/" + 
                    ApplicationAuthentication.library, 
                    ApplicationAuthentication.user, 
                    ApplicationAuthentication.password
                );
            } catch (Exception e) {
                System.err.println(e);
                throw new WebApplicationException(genericError, Response.Status.UNAUTHORIZED);
            }

Guessing from the stacktrace, it appears that the connection returned from your driver is not playing well with the connection Hikari Connection Pool. Hikari is default connection pool in playframework.

Specifically, your exception trace shows that the Hikari CP is attempting to call isValid method on the connection object returned by your JDBC driver and then failing with java.lang.AbstractMethodError.

You can try switching to BoneCP connection pool and see if it helps. You can also check comments on this issue on hikari github issue list