Why can't I wrap withRest() with my own method and run a closure within it? - groovy

Question

The HTTPBuilder plugin for Griffon is great and it simplifies my server calls quite well. The only problem, however, is that I don't want to have to keep repeating the same setup code all over the place.
What I want to do is wrap a set of server calls and other code with the same connection setup so that I only have it in one place.
As an example, this is what I have:
def persistCurrentSession() {
withRest(uri: serverBaseURL) {
headers = requestHeaders
post(path: "${sessionBaseURL}${currentSession.id}",
body: currentSession,
requestContentType: groovyx.net.http.ContentType.JSON)
}
}
def refreshCurrentSession() {
withRest(uri: serverBaseURL) {
headers = requestHeaders
currentSession = get(path: "${sessionBaseURL}${currentSession.id}").responseData.sessionInstance
}
}
And this is what I want to do:
def persistCurrentSession() {
withMyRest {
post(path: "${sessionBaseURL}${currentSession.id}",
body: currentSession,
requestContentType: groovyx.net.http.ContentType.JSON)
}
}
def refreshCurrentSession() {
withMyRest {
currentSession = get(path: "${sessionBaseURL}${currentSession.id}").responseData.sessionInstance
}
}
def withMyRest(Closure stmts) {
withRest(uri: serverBaseURL) {
headers = requestHeaders
stmts()
}
}
From what I know about Groovy and closures, this should be a great use for closures, since it removes the common "set up / tear down resources" code to a single place and allows the focus to be on the meat of the server calls.
The problem is that it doesn't seem like the dynamic methods are being properly added because when I run the code set up the way I want to have it, MissingMethodExceptions get thrown when stmts() gets called:
2011-12-20 11:12:40,097 [pool-2-thread-1] ERROR griffon.util.GriffonExceptionHandler - Uncaught Exception
org.codehaus.groovy.runtime.InvokerInvocationException: groovy.lang.MissingMethodException: No signature of method: client.MyAppServerService.post() is applicable for argument types: (java.util.LinkedHashMap) values: [[path:http://localhost:8080/Server/session/4, ...]]
Possible solutions: wait(), wait(long), print(java.lang.Object), use([Ljava.lang.Object;), is(java.lang.Object), split(groovy.lang.Closure)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:97)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1053)
at groovy.lang.ExpandoMetaClass.invokeMethod(ExpandoMetaClass.java:1071)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:883)
at groovy.lang.Closure.call(Closure.java:410)
at groovy.lang.Closure.call(Closure.java:404)
at groovy.lang.Closure.run(Closure.java:488)
at org.codehaus.griffon.runtime.util.AbstractUIThreadHandler$1.run(AbstractUIThreadHandler.java:41)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)
Caused by: groovy.lang.MissingMethodException: No signature of method: client.MyAppServerService.post() is applicable for argument types: (java.util.LinkedHashMap) values: [[path:http://localhost:8080/Server/session/4, ...]]
Possible solutions: wait(), wait(long), print(java.lang.Object), use([Ljava.lang.Object;), is(java.lang.Object), split(groovy.lang.Closure)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:55)
at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.callCurrent(PogoMetaClassSite.java:78)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:46)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:133)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:141)
at client.MyAppServerService$_persistCurrentSession_closure2.doCall(MyAppServerService.groovy:49)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite$PogoCachedMethodSite.invoke(PogoMetaMethodSite.java:226)
at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite.callCurrent(PogoMetaMethodSite.java:52)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:46)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:133)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:141)
at client.MyAppServerService$_persistCurrentSession_closure2.doCall(MyAppServerService.groovy)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1053)
at groovy.lang.ExpandoMetaClass.invokeMethod(ExpandoMetaClass.java:1071)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:883)
at groovy.lang.Closure.call(Closure.java:410)
at groovy.lang.Closure.call(Closure.java:404)
at java_util_concurrent_Callable$call.call(Unknown Source)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:42)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:112)
at client.MyAppServerService$_withMyRest_closure4.doCall(MyAppServerService.groovy:71)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite$PogoCachedMethodSite.invoke(PogoMetaMethodSite.java:226)
at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite.callCurrent(PogoMetaMethodSite.java:52)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:46)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:133)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:141)
at client.MyAppServerService$_withMyRest_closure4.doCall(MyAppServerService.groovy)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1053)
at groovy.lang.ExpandoMetaClass.invokeMethod(ExpandoMetaClass.java:1071)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:883)
at groovy.lang.Closure.call(Closure.java:410)
at groovy.lang.Closure.call(Closure.java:404)
at java_util_concurrent_Callable$call.call(Unknown Source)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:42)
at java_util_concurrent_Callable$call.call(Unknown Source)
at griffon.plugins.rest.RestConnector.doWithBuilder(RestConnector.groovy:90)
at griffon.plugins.rest.RestConnector.this$2$doWithBuilder(RestConnector.groovy)
at griffon.plugins.rest.RestConnector$this$2$doWithBuilder.callCurrent(Unknown Source)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:46)
at griffon.plugins.rest.RestConnector$this$2$doWithBuilder.callCurrent(Unknown Source)
at griffon.plugins.rest.RestConnector.withRest(RestConnector.groovy:67)
at griffon.plugins.rest.RestConnector$withRest.call(Unknown Source)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:42)
at griffon.plugins.rest.RestConnector$withRest.call(Unknown Source)
at griffon.plugins.rest.RestConnector$_enhance_closure5.doCall(RestConnector.groovy:49)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaMethod.invoke(ClosureMetaMethod.java:80)
at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite$PogoMetaMethodSiteNoUnwrapNoCoerce.invoke(PogoMetaMethodSite.java:308)
at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite.callCurrent(PogoMetaMethodSite.java:52)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:46)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:133)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:145)
at client.MyAppServerService.withMyRest(MyAppServerService.groovy:68)
at client.MyAppServerService$withMyRest.callCurrent(Unknown Source)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:46)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:133)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:141)
at client.MyAppServerService.persistCurrentSession(MyAppServerService.groovy:48)
at client.MyAppServerService$persistCurrentSession.callCurrent(Unknown Source)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:46)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:133)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:137)
at client.MyAppServerService.closeSession(MyAppServerService.groovy:41)
at client.MyAppServerService$closeSession.call(Unknown Source)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:42)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:112)
at client.StartController$_closure1_closure2.doCall(StartController.groovy:20)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite$PogoCachedMethodSite.invoke(PogoMetaMethodSite.java:226)
at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite.callCurrent(PogoMetaMethodSite.java:52)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:46)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:133)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:141)
at client.StartController$_closure1_closure2.doCall(StartController.groovy)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
... 14 more
I'm sure there are better ways to do what I'm trying for, but even so, what I'm trying to do should work, I think. I'm still quite new to Groovy, but I've gone over the scope rules a bunch of times and all I can think of is that the dynamic methods for the HTTPBuilder are not being properly attached through the passed closures, or something like that

Answer 1

It looks like what's happening is the closure delegate is getting lost. Delegates are an important part of how groovy closures work. Each closure has a delegate object associated with it, and any methods called within the closure can be invoked on the delegate. The exact order is customizable with Closure.setResolveStrategy, but the default is to try the method on the owner (where the closure is declared) first, then the delegate. You can always reference the delegate explicitly inside a closure with delegate.
Delegates are the main mechanism for providing those magic dynamic methods like setHeaders(). When HttpBuilder calls the closure you pass in, it sets the explicit closure's delegate, but stmts() gets skipped. All you need to do is pass on the delegate to stmts(). Try something like this:
def withMyRest(Closure stmts) {
withRest(uri: serverBaseURL) {
headers = requestHeaders
stmts.delegate = delegate
stmts()
}
}