WSO2 ESB: Configuring db connection in dblookup mediator is failing - wso2

Question

Using IntegrationStudio I have created an ESB project.Then I created a proxy service and added a dblookup mediator. I have configured it to use postgresql DB. I configured as mentioned below.
connection_type as DB_CONNECTION
In database configuration window, I choose connection type as postgresql.
I chose "get from server" radio button and selected "42.2.5" from the combo list and entered the connection parameters.
Connection DB Driver: com.postgres.jdbc.Driver (tried with org.postgresql.Driver)
jdbc url connection: jdbc:postgresql://localhost:5432/EDH_DATABASE
connection username: postgres
password: entered
The test connection works fine. But when running the proxy through IntegrationStudio it gives the following error.
NOTE: I COPIED postgresql-42.2.5.jar to IntegrationStudio.app/Contents/Eclipse/runtime/microesb/lib
[2020-01-08 17:39:25,612] ERROR {org.apache.synapse.mediators.db.DBLookupMediator} - SQL Exception occurred while executing statement : select * from teacher; against DataSource : jdbc:postgresql://localhost:5432/EDH_DATABASE org.apache.commons.dbcp.SQLNestedException: Cannot load JDBC driver class 'com.postgres.jdbc.Driver'
at org.apache.commons.dbcp.BasicDataSource.createConnectionFactory(BasicDataSource.java:1429)
at org.apache.commons.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1371)
at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044)
at org.apache.synapse.mediators.db.DBLookupMediator.processStatement(DBLookupMediator.java:58)
at org.apache.synapse.mediators.db.AbstractDBMediator.mediate(AbstractDBMediator.java:243)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:109)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:71)
at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:158)
at org.apache.synapse.core.axis2.ProxyServiceMessageReceiver.receive(ProxyServiceMessageReceiver.java:224)
at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:180)
at org.apache.synapse.transport.passthru.ServerWorker.processNonEntityEnclosingRESTHandler(ServerWorker.java:367)
at org.apache.synapse.transport.passthru.ServerWorker.processEntityEnclosingRequest(ServerWorker.java:412)
at org.apache.synapse.transport.passthru.ServerWorker.run(ServerWorker.java:181)
at org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.ClassNotFoundException: com.postgres.jdbc.Driver
at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at org.eclipse.osgi.internal.framework.ContextFinder.loadClass(ContextFinder.java:139)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at org.apache.commons.dbcp.BasicDataSource.createConnectionFactory(BasicDataSource.java:1420)
... 16 more
The postgresql-42.2.5.jar does not have the path "com.postgresql.jdbc.Driver".
So tried "org.postgresql.Driver" as the Connection DB Driver field value. But still it gives the same error. INSPITE OF USING"org.postgresql.Driver", using the configurable field, it still gives the same error.
[2020-01-08 17:39:25,612] ERROR {org.apache.synapse.mediators.db.DBLookupMediator} - SQL Exception occurred while executing statement : select * from teacher; against DataSource : jdbc:postgresql://localhost:5432/EDH_DATABASE org.apache.commons.dbcp.SQLNestedException:
Cannot load JDBC driver class 'com.postgres.jdbc.Driver'
at
org.apache.commons.dbcp.BasicDataSource.createConnectionFactory(BasicDataSource.java:1429)
at org.apache.commons.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1371)
at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044)
at
org.apache.synapse.mediators.db.DBLookupMediator.processStatement(DBLookupMediator.java:58)
at org.apache.synapse.mediators.db.AbstractDBMediator.mediate(AbstractDBMediator.java:243)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:109)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:71)
at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:158)
at Org.apache.synapse.core.axis2.ProxyServiceMessageReceiver.receive(ProxyServiceMessageReceiver.java:224)
at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:180)
at org.apache.synapse.transport.passthru.ServerWorker.processNonEntityEnclosingRESTHandler(ServerWorker.java:367)
at
org.apache.synapse.transport.passthru.ServerWorker.processEntityEnclosingRequest(ServerWorker.java:412)
at org.apache.synapse.transport.passthru.ServerWorker.run(ServerWorker.java:181)
at
org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.ClassNotFoundException: com.postgres.jdbc.Driver
at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at org.eclipse.osgi.internal.framework.ContextFinder.loadClass(ContextFinder.java:139)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at
org.apache.commons.dbcp.BasicDataSource.createConnectionFactory(BasicDataSource.java:1420)
... 16 more
Any help would be greatly appreciated.

Answer 1

It seems the correct Driver name is "org.postgresql.Driver". In your error logs, even though you have changed the Driver name from "com.postgres.jdbc.Driver" to "org.postgresql.Driver", it seems to be looking for the former one. Please make sure that, you have stopped the running Micro Integrator by clicking the stop button and run the proxy again by clicking on "Run As -> Run on Micro Integrator".