Committing some experimenting before I mess it all up again.

Current thinking is that I need to implement a CuratorClient object pool which
will make it easier to pluck objects for Ratpack handlers

build.gradle

@@ -34,6 +34,7 @@ dependencies {
      * Zookeeeper
      */
     compile 'org.apache.curator:curator-framework:2.7.0+'
+    compile 'org.apache.commons:commons-pool2:2.2+'
 
     testCompile 'org.spockframework:spock-core:0.7-groovy-2.0'
 }

src/main/groovy/offtopic/CuratorClient.groovy

@@ -0,0 +1,14 @@
+package offtopic
+
+import org.apache.curator.retry.ExponentialBackoffRetry
+import org.apache.curator.framework.CuratorFrameworkFactory
+
+class CuratorClient {
+    private def client = null
+
+    public CuratorClient(String zookeepers) {
+        if (zookeepers?.length() <= 0) {
+            throw new offtopic.errors.ConfigurationError("Cannot pass an empty string to CuratorClient()")
+        }
+    }
+}

src/main/groovy/offtopic/errors/ConfigurationError.groovy

@@ -0,0 +1,53 @@
+package offtopic.errors
+
+import groovy.transform.InheritConstructors
+import groovy.transform.CompileStatic
+
+@CompileStatic /* See note below */
+@InheritConstructors
+class ConfigurationError extends Exception {
+}
+
+/*
+https://jira.codehaus.org/browse/GROOVY-6951
+
+Expected exception offtopic.errors.ConfigurationError, but got java.lang.VerifyError
+    at org.spockframework.lang.SpecInternals.thrownImpl(SpecInternals.java:79)
+    at offtopic.CuratorClientInitializationSpec.with an empty String(CuratorClientSpec.groovy:21)
+Caused by: java.lang.VerifyError: Bad <init> method call from inside of a branch
+Exception Details:
+  Location:
+    offtopic/errors/ConfigurationError.<init>(Ljava/lang/String;)V @87: invokespecial
+  Reason:
+    Error exists in the bytecode
+  Bytecode:
+    0000000: b800 164d 04bd 0029 5903 2b53 5910 ff12
+    0000010: 04b8 002f 2a5f ab00 0000 00af 0000 0005
+    0000020: 8794 83a0 0000 0032 aad3 b1ff 0000 0047
+    0000030: c783 a456 0000 005a f0c1 c756 0000 0087
+    0000040: 0000 9b75 0000 00a6 5f5a 5903 3212 31b8
+    0000050: 0035 c000 315f 57b7 0037 a700 755f 5a59
+    0000060: 0332 b800 3dc0 003f 5f57 b700 42a7 0062
+    0000070: 5f5a 5903 32b8 003d c000 3f5f 5904 3212
+    0000080: 31b8 0035 c000 315f 5905 32b8 0048 5f59
+    0000090: 0632 b800 485f 57b7 0018 a700 355f 5a59
+    00000a0: 0332 b800 3dc0 003f 5f59 0432 1231 b800
+    00000b0: 35c0 0031 5f57 b700 4ba7 0016 5f5a 57b7
+    00000c0: 004e a700 0dbb 0050 5912 52b7 0053 bf57
+    00000d0: 2ab6 001c 4e2d 2a5f b500 1e2d 57b1     
+  Stackmap Table:
+    full_frame(@72,{UninitializedThis,Object[#63],Object[#85]},{Object[#87],UninitializedThis})
+    full_frame(@93,{UninitializedThis,Object[#63],Object[#85]},{Object[#87],UninitializedThis})
+    full_frame(@112,{UninitializedThis,Object[#63],Object[#85]},{Object[#87],UninitializedThis})
+    full_frame(@157,{UninitializedThis,Object[#63],Object[#85]},{Object[#87],UninitializedThis})
+    full_frame(@188,{UninitializedThis,Object[#63],Object[#85]},{Object[#87],UninitializedThis})
+    full_frame(@197,{UninitializedThis,Object[#63],Object[#85]},{Object[#87],UninitializedThis})
+    full_frame(@207,{Object[#2],Object[#63],Object[#85]},{Object[#87]})
+
+    at java.lang.Class.privateGetDeclaredConstructors(Class.java:2658)
+    at java.lang.Class.getDeclaredConstructors(Class.java:2007)
+    at org.codehaus.groovy.util.LazyReference.getLocked(LazyReference.java:46)
+    at org.codehaus.groovy.util.LazyReference.get(LazyReference.java:33)
+    at offtopic.CuratorClient.<init>(CuratorClient.groovy:10)
+    at offtopic.CuratorClientInitializationSpec.with an empty String(CuratorClientSpec.groovy:18)
+*/

src/ratpack/ratpack.groovy

@@ -6,6 +6,8 @@ import static ratpack.jackson.Jackson.json
 import static ratpack.groovy.Groovy.*
 import static ratpack.websocket.WebSockets.websocket
 
+import offtopic
+
 ratpack {
     bindings {
         add new HandlebarsModule()

src/test/groovy/offtopic/CuratorClientSpec.groovy

@@ -0,0 +1,28 @@
+package offtopic
+
+import spock.lang.Specification
+
+class CuratorClientInitializationSpec extends Specification {
+    def "with null"() {
+        when:
+        def client = new CuratorClient()
+
+        then:
+        thrown(offtopic.errors.ConfigurationError)
+    }
+    def "with an empty String"() {
+        when:
+        def client = new CuratorClient('')
+
+        then:
+        thrown(offtopic.errors.ConfigurationError)
+    }
+
+    def "with a valid String"() {
+        when:
+        def client = new CuratorClient('localhost:2181')
+
+        then:
+        client instanceof CuratorClient
+    }
+}