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What is it?

Buttle is a proxying JDBC driver with hooks.


Buttle ships a java.sql.Driver which delegates connect calls to a backing (or real) driver (like org.postgresql.Driver). The Buttle driver wraps a Buttle proxy around the returned java.sql.Connection. The Buttle proxy then (recursivly) does the same to the wrapped instance -- i.e. it wraps a Buttle proxy around the return value of delegated method calls.

The effect of this is that the application which is using the Buttle java.sql.Driver will ever only call JDBC API methods through a Buttle proxy (e.g. for java.sql.Statement and java.sql.ResultSet).

Buttle proxies are only constructed for methods (i.e. their returned values) that have interface-typed declared return types.


Buttle proxies delegate calls to the backing JDBC driver's instances through buttle.proxy/handle multi method. Via buttle.proxy/def-handle users can inject/hook their own multi-method implemenations (per interface/method) into the delegation mechanism. See example in examples/buttle/examples/open_tracing.clj and examples/buttle/examples/handle.clj.


Buttle proxies also create events for every method invocation and completion incl. when an Exception is thrown (see buttle.proxy/handle-default).

These events include info about

  • timestamp of the event
  • duration (for completion/Exception)
  • stacktrace (for exceptions)
  • invoked class/method
  • arguments
  • returned value/Exception

Events (see event.clj) are communicated through a clojure.core.async/mult that users can tap onto to receive the events. See usage example in examples/buttle/examples/event_channel.clj.


Similar things have been done before:

What to use it for?

Use it for

  • testing

  • troubleshooting

  • debugging

  • performance measurements

  • application monitoring

Note: I haven't done any measurements on how much Buttle hurts the performance.

How to extend?

There are two ways to hook into Buttle:

events: receive events from Buttle through buttle.event/event-mult like this:

(let [ch (clojure.core.async/chan)]
  (clojure.core.async/tap buttle.event/event-mult ch)
   (loop []
	 (when-let [e (clojure.core.async/<! ch)]
	   (println e) ;; do something with the event

multi method: inject your own proxy for target interfaces/methods. This acts like an AOP advice/proxy. Note that in this case you have to take care to send events if you need that (see buttle.proxy/handle-default).

So you can (re-) register the buttle.proxy/handle :default.

(defmethod buttle.proxy/handle :default [the-method target-obj the-args]
  (do-some-thing-with-call the-method target-obj the-args))

And you can register multi method implementation for just specific interfaces, methods or a combination of these (see test/buttle/proxy_test.clj, examples/buttle/examples/open_tracing.clj and examples/buttle/examples/handle.clj for more examples):

(buttle.proxy/def-handle [java.sql.Connection :buttle/getCatalog] [the-method target-obj the-args]
  (do-some-thing-with-call the-method target-obj the-args))

do-some-thing-with-call could look like this:

(defn invoke-with-logging [the-method target-obj the-args]
  (println (format "buttle.examples.handle: INVOKE %s"
                   (pr-str [the-method target-obj (into [] the-args)])))
  (let [r (try
            (proxy/handle-default the-method target-obj the-args)
            (catch Throwable t
                (println (format "buttle.examples.handle: THROW %s : %s"
                                 (pr-str [the-method target-obj (into [] the-args)]) (pr-str t)))
                (throw t))))]
    (println (format "buttle.examples.handle: RETURN %s --> %s"
                     (pr-str [the-method target-obj (into [] the-args)]) (pr-str r)))



(1) In squirrel-sql.bat add system property buttle.user-file to java call:

set BUTTLE="-Dbuttle.user-file=<path-to>/buttle/examples/handle.clj"
java [...] %BUTTLE% [...]

(2) In the GUI add a Driver with extra classpath <path-to>/buttle-standalone.jar and class buttle.jdbc.Driver.

(3) In the GUI add an Alias with URL (replace <user> and <password>). Text following jdbc:buttle: will be read/eval'ed as Clojure map form.

jdbc:buttle:{:user "<user>" :password "<password>" :target-url "jdbc:postgresql://"}


When using Buttle in Wildfly (either domain mode oder standalone) you can either include it in your application (but usually JDBC drivers are not included in the main app) or you can deploy it as a module (tested with Wildfly 12.0.0.Final).

For this you have to:

  • define a <module>
  • define a <driver>
  • define a <datasource> (or <xa-datasource>; see below)

(1) Define <module>: put this into <wildfly-root>/modules/buttle/main/module.xml. You may have to adjust path to Buttle's JAR filename. Note that you have to include <dependencies> for the javax.api base module and the JDBC driver you want to wrap (Postgres in this case). Otherwise Buttle won't be able to see the JDBC driver's classes.

<?xml version="1.0" encoding="UTF-8"?>
<module xmlns="urn:jboss:module:1.1" name="buttle">

	<resource-root path="buttle-standalone.jar"/>

	<module name="postgres"/>
	<module name="javax.api"/> 


(2) Define <driver>: Note that Wildfly does not need to know Buttle's driver class (buttle.jdbc.Driver). It relies on Buttle being loaded via SPI (META-INF/services/java.sql.Driver). Wildfly then finds the Buttle driver via DriverManager/getConnection.

  <driver name="buttle-driver" module="buttle"/>

(3) Define <datasource>: in this example there is no extra Postgres <datasource>/<driver> entry so Wildfly will not load the Postgres JDBC driver for us. Therefore we put :class-for-name "org.postgresql.Driver" into the Buttle URL. Now Buttle loads the JDBC driver's class and usually these will register themselves with the DriverManager. After that Buttle can connect to Postgres through the DriverManager (see section A note on authentication below for details on how authentication works with Buttle).

<datasource jndi-name="java:/jdbc/buttle-ds" pool-name="buttle-ds">
	        :user "<user>"
	        :password "<password>"
	        :class-for-name "org.postgresql.Driver"
	        :target-url "jdbc:postgresql://<host>:<port>/<db-id>"}

Note: if you define a <datasource> with <connection-url> then Wildfly will create a javax.sql.DataSource datasource proxy that uses the java.sql.DriverManager API to lookup the JDBC driver and open connections. So in the example above it will effectively use buttle.jdbc.Driver and not buttle.jdbc.DataSource. Below you find an example which involves buttle.jdbc.DataSource.

Instead of loading the class explicitly you can just use a class literal with some arbitrary key in the map -- like this:

	        :user "<user>"
	        :password "<password>"
	        :_ org.postgresql.Driver
	        :target-url "jdbc:postgresql://<host>:<port>/<db-id>"}

If you rather have Wildfly load the Postgres driver you just add a <driver> entry for Postgres. In this case you do not need the :class-for-name/class-literal entry.

  <driver name="buttle-driver" module="buttle"/>
  <driver name="postgresql" module="postgres"/>

There is yet another way to make Wildfly load Postgres JDBC driver. Instead of adding the <driver> you can add services="import" to the module/dependencies:

<module name="postgres" services="import"/>

Since Buttle itself doesn't give you much functionality beyond delegation logic you probably want to define buttle.user-file system property to have Buttle load your hook code:

  <property name="buttle.user-file" value="<path-to>/buttle-user-file.clj" boot-time="true"/>

Using buttle.jdbc.DataSource

Depending on how you define the <datasource> Wildfly will use the java.sql.DriverManager/java.sql.Driver (see above) or javax.sql.DataSource API. The following example shows how to make Wildfly use the javax.sql.DataSource API:

<datasource jndi-name="java:jboss/datasources/buttle-ds" pool-name="buttle-ds">
      <connection-property name="DelegateSpec">
          {:delegate-class org.postgresql.ds.PGSimpleDataSource :url "jdbc:postgresql://"}

Note that for connection-property there must be no linebreak in the element value!

A note on authentication

Usually JEE containers let you define a datasource and with it supply authentication credentials (e.g. username and password). For Wildfly this is done through the security element:

    <xa-datasource jndi-name="java:/jdbc/postgres-xa" pool-name="postgres-xa">
      <xa-datasource-property name="Url">jdbc:postgresql://</xa-datasource-property>

For IBM WAS you enter security aliases (see below).

Then when your application needs a JDBC connection it calls javax.sql.DataSource.getConnection() on the datasource which it usually retrieves from JNDI. Your app rarely calls javax.sql.DataSource.getConnection(String username, String password) since no-one wants to give authentication credentials to your app. That's why it is given to the JEE container only.

When calling getConnection() your app will be talking to a javax.sql.DataSource datasource proxy that the JEE container puts between your code and the real datasource (which may even be an XA-datasource really; like in the example shown above). If you have given authentication credentials explicitly to the container (like shown above) then the container's datasource proxy will call javax.sql.DataSource.getConnection(String username, String password) on the real datasource when delegating your call and thus supplying the configured authentication credentials for connecting to the database.

Instead of giving authentication credentials explicitly to the container (like shown above) you can usually set some of the real datasource's Java-Beans property values to give it username and password.

Note that in this case the container has no explicit knowledge about the details on how and what authentication credentials you give to the datasource. And it depends on the JDBC datasource class which Java-Beans properties you have to set (e.g. it's User and Password for Postgres, but it may be UserName and Passphrase for some other driver).

For Wildfly and Postgres this looks like this:

    <xa-datasource jndi-name="java:/jdbc/postgres-xa" pool-name="postgres-xa">
      <xa-datasource-property name="Url">jdbc:postgresql://</xa-datasource-property>
      <xa-datasource-property name="User">postgres-user</xa-datasource-property>
      <xa-datasource-property name="Password">postgres-password</xa-datasource-property>

For IBM WAS you set the datasource's custom properties (see below).

Now when your app calls javax.sql.DataSource.getConnection() on the datasource proxy this time the proxy will call getConnection() (instead of getConnection(String, String)) on the underlying real datasource. In this case the real datasource must, should and usually will use the Java-Beans property values for User and Password (or whatever property it uses) to authenticate against the database. Note though that JDBC drives may support even more ways to supply authentication credentials (like Postgres which can take these from the JDBC URL).

When using a Buttle datasource (to proxy the real datasource) all this is working just the same way. Only now the Buttle datasource (proxy) introduces an additional indirection/delegation step.

You configure authentication for the Buttle datasource just like you do it for the real datasource.

With the following configuration the container will call getConnection(String, String) on the Buttle datasource which in turn calls getConnection(String, String) on the real datasource:

    <xa-datasource jndi-name="java:/jdbc/buttle-xa" pool-name="buttle-xa">
      <xa-datasource-property name="DelegateSpec">
		 :delegate-class org.postgresql.xa.PGXADataSource
		 :url "jdbc:postgresql://"

The Buttle datasource classes support the map-typed Java-Bean property DelegateSpec. Keys (other than :delegate-class) are used to set the corresponding Java-Bean property of the real datasource (see below for more details). So in the following example we're setting Url, User and Password Java-Beans property values.

    <xa-datasource jndi-name="java:/jdbc/buttle-xa" pool-name="buttle-xa">
      <xa-datasource-property name="DelegateSpec">
          :delegate-class org.postgresql.xa.PGXADataSource
          :url "jdbc:postgresql://"
          :user "postgres-user"
          :password "postgres-password"

In this case the container will call getConnection() on the Buttle datasource which in turn calls getConnection() on the real datasource which again must/will use the Java-Beans property values that Buttle has set before.

So when configuring authentication for your datasource keep in mind that the whole story starts with a call from the JEE container and this call will be determined by how you configure the datasource that your app retrieves from JNDI. From there the rest follows as described above.


In Wildfly you define an <xa-datasource> like this (for Postgres):

<xa-datasource jndi-name="java:/jdbc/postgres-xa" pool-name="postgres-xa">
  <xa-datasource-property name="Url">jdbc:postgresql://</xa-datasource-property>

Note that security configuration is included here only for you to be able to test this datasource through the Wildfly admin console GUI in isolation. When proxying this datasource with Buttle these security settings will never be used (as explaied in A note on authentication).

You can retrieve this from JNDI like this (done via nREPL into running Wildfly; build UBERJAR with lein with-profile +swank,+wildfly uberjar to include nrepl and Swank):

user=> (buttle.util/jndi-lookup "java:/jdbc/postgres-xa")
#object[ ,,,]

Note though that Wildfly does not give us a javax.sql.XADataSource but a javax.sql.DataSource:

user=> (->> (buttle.util/jndi-lookup "java:/jdbc/postgres-xa") .getClass .getInterfaces (into []))

Since there is no (easy) way to implement javax.sql.XADataSource based on a javax.sql.DataSource Buttle cannot proxy XA-datasources retrieved from JNDI for Wildfly.

Others got bitten by this [1, 2] and it probably won't get fixed [3]. So Buttle only supports (a) wrapping real javax.sql.XADataSource implemenations retrieved from JNDI and (b) creating a JDBC driver's XA-datasource directly.


Creating a JDBC driver's XA-datasource directly

So for Wildfly you define a Buttle XA-datasource and specify the real XA-datasource by setting the DelegateSpec property to a Clojure map form (to be exact I should say 'a form that evaluates to a map'; line-breaks are removed so DO NOT use ; comments other than at the very end). This map must have :delegate-class giving the real XA-datasource's class (note that it IS a class-literal!). Any other map key/value will be used to set the real XA-datasource's Java-Bean properties. You have to supply the correct property type through the map. Overloaded setter-methods are not supported.

<xa-datasource jndi-name="java:/jdbc/buttle-xa" pool-name="buttle-xa">
  <xa-datasource-property name="DelegateSpec">
    {:delegate-class org.postgresql.xa.PGXADataSource
     :url "jdbc:postgresql://"}

IBM Websphere

IBM Websphere (WAS) supports datasources of type javax.sql.XADataSource and javax.sql.ConnectionPoolDataSource (tested with WAS ND).

For XA-datasource WAS (like Wildfly; see above) does not put a javax.sql.XADataSource into JNDI so Buttle cannot proxy XA-datasources from JNDI for WAS.

For WAS you have the following options:

  • proxy a JNDI javax.sql.ConnectionPoolDataSource
    Define the Buttle datasource with buttle.jdbc.ConnectionPoolDataSource and target the real datasource by setting delegateSpec to its JNDI name.

  • define a javax.sql.ConnectionPoolDataSource
    Define the Buttle datasource with buttle.jdbc.ConnectionPoolDataSource and (create) target the real CP-datasource by setting delegateSpec to the map with :delegate-class <real-jdbc-driver-cp-ds-class> and the CP-datasource's Java-Beans property values.

  • define a javax.sql.XADataSource
    Define the Buttle datasource with buttle.jdbc.XADataSource and (create) target the real XA-datasource by setting delegateSpec to the map with :delegate-class <real-jdbc-driver-xa-ds-class> and the XA-datasource's Java-Beans property values.

Define Buttle JDBC provider

For all options you need to define the Buttle JDBC provider first. You can repeat the following steps to define more than one provider (e.g. to define one provider for XA-datasources and one for CP-datasources).

In the WAS admin console navigate to Resources/JDBC/JDBC providers, select scope (i.e. your Cell/Node/Server), hit New....

Step 1: Create new JDBC provider

  • select Database type: User-defined
  • enter Implementation class name: buttle.jdbc.ConnectionPoolDataSource or buttle.jdbc.XADataSource (see above)
  • enter Name (e.g. Buttle CP-DS) and Description
  • hit Next

Step 2: Enter database class path information

  • enter Class path: <path-to-buttle-standalone.jar>
  • hit Next

Step 3: Summary

  • just hit Finish

Define Buttle datasource

Now you need to define one or more datasources. In the WAS admin console navigate to Resources/JDBC/Data sources, select scope (i.e. your Cell/Node/Server), hit New....

Step 1: Enter basic data source information

  • enter Data source name (e.g. buttle_cp_ds) and JNDI name (e.g. jdbc/buttle_cp_ds)
  • hit Next

Step 2: Select JDBC provider

  • select Select an existing JDBC provider: e.g. Buttle CP-DS (see above)
  • hit Next

Step 3: Enter database specific properties for the data source

  • Data store helper class name: do not change default
  • Use this data source in container managed persistence (CMP): do not change default checked
  • just hit Next

Step 4: Setup security aliases

  • set all selections in Select the authentication values for this resource to (none). In this case authentication must come from Buttle datasource configuration which is described below (see also section A note on authentication above).
  • hit Next

Step 5: Summary

  • just hit Finish

Configure Buttle datasource

Before you can use/test the Buttle datasource you need to configure it. Navigate to Resources/JDBC/Data sources, select scope (i.e. your Cell/Node/Server) and click on the Buttle datasource you want to configure. Click on Additional Properties/Custom properties.

If you have not added delegateSpec yet hit New... to add a new entry. Otherwise click on delegateSpec entry in the table.

When adding a new entry enter Name delegateSpec.

Enter/change the entry Value.

Example: Postgres

{:delegate-class org.postgresql.ds.PGConnectionPoolDataSource
 :databaseName "<postgres-db-name>"
 :password "<postgres-password>"
 :portNumber (int <postgres-port-number>)
 :serverName "<postgres-hostname>"
 :user "<postgres-user>"}

Then hit OK.

Test Buttle datasource

Finally we can test/use the Buttle datasource. Navigate to Resources/JDBC/datasources, select scope (e.g. your cell/node/server). Select (checkbox) the datasource. Hit Test connection. If you have just changed the datasource you may get an error stating that you have to synchronize the datasource settings first. Go ahead and click Synchronize and then repeat the test.


C:>java -cp buttle-0.1.0-SNAPSHOT-standalone.jar;postgresql-9.4.1212.jar clojure.main -r
Clojure 1.8.0
user=> (use 'buttle.driver-manager)
;;--> nil
(-> (get-connection "jdbc:buttle:{:user \"<user>\" :password \"<password>\" :target-url \"jdbc:postgresql://\"}" nil nil)
	(.executeQuery "select * from pg_catalog.pg_tables where schemaname = 'pg_catalog'")


import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class ButtleTest {

	public static void processEvent(Object e) {
		System.out.println("event : " + e);

	public static void main(String[] args) throws Exception {

		System.setProperty("buttle.user-file", "examples/buttle/examples/java_events.clj");

		String user = System.getProperty("buttle_user");
		String password = System.getProperty("buttle_password");

		String jdbcUrl = "jdbc:postgresql://";
		String buttleUrl = String.format("jdbc:buttle:{:user \"%s\" :password \"%s\" :target-url \"%s\"}", user,
				password, jdbcUrl);

		Connection conn = DriverManager.getConnection(buttleUrl, user, password);

		Statement stmt = conn.createStatement();
		ResultSet rs = stmt.executeQuery("select * from pg_catalog.pg_tables where schemaname = 'pg_catalog'");

		for (int cc = rs.getMetaData().getColumnCount();;) {
			for (int i = 1; i <= cc; i++) {
				System.out.print(i == 1 ? "" : ",");

Build to target/ dir:

C:\>javac -d target java\

And run (adjust paths as needed):

C:\>java -cp buttle-standalone.jar;postgresql-9.4.1212.jar;target -Dbuttle_user=<user> -Dbuttle_password=<password> ButtleTest


You'll need a Postgres at (but see jdbc-url in test/buttle/core_test.clj).


> set buttle_user=<user>
> set buttle_password=<password>
> lein test


$ buttle_user=<user> buttle_password=<password> lein test


Building buttle-standalone.jar

Use lein make-doc to build documenation to resources/public/generated-doc.

Use lein uberjar to build the minimum Buttle UBERJAR (target/uberjar/buttle-standalone.jar). It'll contain Buttle, Clojure and core.async. It won't contain the Open Tracing API and no Jaeger.

Use lein with-profile +jaeger,+wildfly uberjar to build an UBERJAR incl. Open Tracing and Jaeger and suitable for usage in Wildfly.

Deploying a SNAPSHOT

Deploy the current target/uberjar/buttle-standalone.jar to your own artefact repo:

lein with-profile +my-private-repos deploy-uberjar snapshots

For this to work you have to put your repository info into <user-home>/.lein/profiles.clj:

:my-private-repos {:repositories [["snapshots" {:url "http://<host>:<path>/nexus/content/repositories/snapshots/"
                                                :username "<username>" :password "<password>"}]
                                  ["releases" {:url "http://<host>:<path>/nexus/content/repositories/releases/"
                                               :username "<username>" :password "<password>"}]]}

Releasing Buttle

For releasing to my internal Nexus I do:

lein with-profile +my-private-repos release

For releasing to Clojars I do: (in ~/.lein/profiles.clj I define :clojars {:repositories [,,,):

lein with-profile +clojars release

Building Buttle library

You can build and use Buttle as a library via lein install. You could probably use buttle.proxy for proxying other APIs like LDAP und JMS but I usually use it like you would use a self-contained JDBC driver.


  • review uses of butte.proxy/make-proxy and buttle.util/with-tccl -- which classloader is picked? And why.

  • add optional loading of buttle-user-file.clj via classloader to driver. With that you don't even need to set the system property buttle.user-file to load your own code. You just need a dir that the classpath/classloader of your app points to.

  • add :driver-class option to Buttle JDBC-URL so that Buttle directly instanciates and uses that driver to delegate to (and not indirectly delegate to the driver by calling DriverManager/connect).

  • add :datasource-jndi-name option to Buttle JDBC-URL so that Buttle fetches a DataSource (not a Driver) from JNDI and delegates to that.

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