From Snipplr
Ok here is the script code, in the comments is the question and the exception thrown
class Class1 {
def closure = {
println this.class.name
println delegate.class.name
def nestedClos = {
println owner.class.name
}
nestedClos()
}
}
def clos = new Class1().closure
clos.delegate = this
clos()
//Now I want to add a new closure to Class1
def newClosure = {
println "new Closure"
println this.class.name
println delegate.class.name
def nestedClos = {
println owner.class.name
}
nestedClos()
}
//getAbc to create a property, not a method
Class1.metaClass.getAbc = newClosure
//What happens here is that the property abc is not used as a closure per se, it's used
//as a property and when I execute it just run the closure and when I want to change
//the delegate, a null pointer is thrown
clos = new Class1().abc //abc executed instead of passing the reference closure
clos.delegate = this //Exception!!!!
clos()
Ok, It's done it's not a fancy way, but I have the solution....yeah!
Create the property as object and later assign the closure
class Class1 {
def closure = {
println this.class.name
println delegate.class.name
def nestedClos = {
println owner.class.name
}
nestedClos()
}
}
def clos = new Class1().closure
clos.delegate = this
clos()
//Now I want to add a new closure to Class1
def newClosure = {
println "new Closure"
println this.class.name
println delegate.class.name
def nestedClos = {
println owner.class.name
}
nestedClos()
}
//before edit
//Class1.metaClass.abc = new Object()
Class1.metaClass.abc = newClosure
def cl = new Class1()
//Before edit
//For the sake of simplicity we are going to use & for the method
//clos = cl.abc
closs = cl.&abc
clos.delegate = this
clos()
Related
I am puzzling over Groovy delegation strategy in nested closures. Here is a simplified example:
class Clazz {
String name
String whoAmI() {
return name
}
void doit(Clazz clazz) {
def cl = {
println "Outer closure: resolveStrategy=${resolveStrategy}, " +
"implicit=${whoAmI()}, delegated=${delegate.whoAmI()}"
{->
println "Inner closure: resolveStrategy=${resolveStrategy}, " +
"implicit=${whoAmI()}, delegated=${delegate.whoAmI()}"
}.call()
}
cl.resolveStrategy = Closure.DELEGATE_FIRST
cl.delegate = clazz
cl()
}
}
def a = new Clazz(name: 'A')
def b = new Clazz(name: 'B')
a.doit(b)
Output:
Outer closure: resolveStrategy=1, implicit=B, delegated=B
Inner closure: resolveStrategy=0, implicit=A, delegated=B
Why doesn't resolveStrategy propagate to the inner closure? The point of setting resolution strategy is to change the way implicit this is resolved. But if it doesn't propagate inside closures, then the mechanism seems to be as good as useless. Closures are so ubiquitous in Groovy that you can hardly write a couple of lines without them.
Found a similar question from almost five years ago: Nested closure resolution different between methods and properties? Apparently it's a bug, and it has been open without any movement since then: https://issues.apache.org/jira/browse/GROOVY-7232
The linked post notes something I also noticed: properties are correctly resolved to the delegate, but not method calls. Here is a reworked example to demonstrate this:
class Clazz {
String name
void doit(Clazz clazz) {
def cl = {
println "Outer closure: property=${name}, method=${getName()}"
{->
println "Inner closure: property=${name}, method=${getName()}"
}.call()
}
cl.resolveStrategy = Closure.DELEGATE_FIRST
cl.delegate = clazz
cl()
}
}
def a = new Clazz(name: 'A')
def b = new Clazz(name: 'B')
a.doit(b)
Result:
Outer closure: property=B, method=B
Inner closure: property=B, method=A
Someone in the linked post posted a workaround using rehydrate. In my case though it works (sort of) only if all references are replaced, including this!
class Clazz {
String name
void doit(Clazz clazz) {
def cl = {
println "Outer closure: property=${name}, method=${getName()}"
{->
println "Inner closure: property=${name}, method=${getName()}"
}.call()
}
cl.rehydrate(clazz, clazz, clazz)()
}
}
def a = new Clazz(name: 'A')
def b = new Clazz(name: 'B')
a.doit(b)
Result:
Outer closure: property=B, method=B
Inner closure: property=B, method=B
I have JSON looking like:
{
"days": [
{
"mintemp": "21.8"
}
]
}
With Groovy, I parse it like this:
class WeatherRow {
String mintemp
}
def file = new File("data.json")
def slurper = new JsonSlurper().parse(file)
def days = slurper.days
def firstRow = days[0] as WeatherRow
println firstRow.mintemp
But actually, I would like to name my instance variable something like minTemp (or even something completely random, like numberOfPonies). Is there a way in Groovy to map a member of a map passed to a constructor to something else?
To clarify, I was looking for something along the lines of #XmlElement(name="mintemp"), but could not easily find it:
class WeatherRow {
#Element(name="mintemp")
String minTemp
}
Create a constructor that takes a map.
Runnable example:
import groovy.json.JsonSlurper
def testJsonStr = '''
{"days": [
{ "mintemp": "21.8" }
]}'''
class WeatherRow {
String minTemp
WeatherRow(map) {
println "Got called with constructor that takes a map: $map"
minTemp = map.mintemp
}
}
def slurper = new JsonSlurper().parseText(testJsonStr)
def days = slurper.days
def firstRow = days[0] as WeatherRow
println firstRow.minTemp
Result:
Got called with constructor that takes a map: [mintemp:21.8]
21.8
(of course you'd remove the println line, it's just there for the demo)
You can achieve this using annotation and simple custom annotation processor like this:
1. Create a Custom Annotation Class
#Retention(RetentionPolicy.RUNTIME)
#interface JsonDeserializer {
String[] names() default []
}
2. Annotate your instance fields with the custom annotation
class WeatherRow{
#JsonDeserializer(names = ["mintemp"])
String mintemp;
#JsonDeserializer(names = ["mintemp"])
String minTemp;
#JsonDeserializer(names = ["mintemp"])
String numberOfPonies;
}
3. Add custom json deserializer method using annotation processing:
static WeatherRow fromJson(def jsonObject){
WeatherRow weatherRow = new WeatherRow();
try{
weatherRow = new WeatherRow(jsonObject);
}catch(MissingPropertyException ex){
//swallow missing property exception.
}
WeatherRow.class.getDeclaredFields().each{
def jsonDeserializer = it.getDeclaredAnnotations()?.find{it.annotationType() == JsonDeserializer}
def fieldNames = [];
fieldNames << it.name;
if(jsonDeserializer){
fieldNames.addAll(jsonDeserializer.names());
fieldNames.each{i ->
if(jsonObject."$i")//TODO: if field type is not String type custom parsing here.
weatherRow."${it.name}" = jsonObject."$i";
}
}
};
return weatherRow;
}
Example:
def testJsonStr = '''
{
"days": [
{
"mintemp": "21.8"
}
]
}'''
def parsedWeatherRows = new JsonSlurper().parseText(testJsonStr);
assert WeatherRow.fromJson(parsedWeatherRows.days[0]).mintemp == "21.8"
assert WeatherRow.fromJson(parsedWeatherRows.days[0]).minTemp == "21.8"
assert WeatherRow.fromJson(parsedWeatherRows.days[0]).numberOfPonies == "21.8"
Check the full working code at groovyConsole.
how do I print available environments from a config file? What is the form of the ojbect ConfigSlurper creates?
I tried
def config2 = new ConfigSlurper().parse(new File('obieeadmincfg.groovy').toURL())
config2.config.environments.each { println ${it} }
and
println prettyPrint(toJson(config2))
and
for ( i in 0 ..config2.config.environments.size()-1)
println config2.config.environments[i]
groovy.config
//Config3.groovy
obieadmin {
//default values
serverurl = "http://default.mycompany.com"
}
environments {
pldev01 {
obieeadmin {
serverurl = 'devgdwobi03.x.com'
}
}
plsbx02 {
obieeadmin {
serverurl = 'devgdwobi03.x.com'
}
}
}
I'm afraid you can't do this out-of box.
But using a bit of Groovy Metaprogramming it's achievable.
Groovy config slurper parses proper Groovy file, and you can do the same with GroovyShell. You can catch call to environment method providing closure in binding. In that closure you have to collect all top-level method calls(with same methodMissing).
Providing base script with property and method missing handlers, you can suppress runtime errors, and execute script without much care to other properties.
Not the nicest path, but it works.
package test
import org.codehaus.groovy.control.CompilerConfiguration
class A extends Script {
def propertyMissing(String name) { null }
def propertyMissing(String name, def arg) {}
def methodMissing(String name, def args) {}
#Override Object run() { null }
}
class NameCollector {
def envs = []
def methodMissing(String name, def args) { envs << name }
}
// configure interceptors.
def configuration = new CompilerConfiguration()
configuration.scriptBaseClass = 'test.A'
def nc = new NameCollector()
def environments = { Closure it ->
it.delegate = nc;
it.resolveStrategy = Closure.DELEGATE_ONLY
it()
}
// execute config script
new GroovyShell([environments: environments] as Binding, configuration).evaluate(new File("config.groovy"))
nc.envs // Return, print them.
Not sure if this is going to work forever but currently you can do it by overriding the setting for the 'environments' conditional block, like this:
def config = """environments {
dev {
foo = "bar"
}
prod {
foo = "baz"
}
}"""
def configSlurper = new ConfigSlurper()
configSlurper.registerConditionalBlock('environments', null)
assert configSlurper.parse(config).environments.keySet() == ['dev', 'prod'].toSet()
Let's say I have a DSL like this
setup {name = "aDSLScript"}
println "this is common groovy code"
doStuff {println "I'm doing dsl stuff"}
One would have a delegating class implementing the methods 'setup' and 'doStuff' usually. Beside, one could write common Groovy code to be executed (println...).
What I am searching for, is a way to execute this in two steps. In the first step only the setup method should be processed (neither println). The second step handles the other parts.
At the moment, I have two delegating classes. One implements 'setup' the other one implements 'doStuff'. But both execute the println statement, of course.
You can create a single class to intercept the method calls from the script and let it coordinate the following method invoke. I did it through reflection, but you can go declarative if you want. These are the model and script classes:
class FirstDelegate {
def setup(closure) { "firstDelegate.setup" }
}
class SecondDelegate {
def doStuff(closure) { "secondDelegate.doStuff" }
}
class MethodInterceptor {
def invokedMethods = []
def methodMissing(String method, args) {
invokedMethods << [method: method, args: args]
}
def delegate() {
def lookupCalls = { instance ->
def invokes = instance.metaClass.methods.findResults { method ->
invokedMethods.findResult { invocation ->
invocation.method == method.name ?
[method: method, invocation: invocation] : null
}
}
invokes.collect { invoked ->
invoked.method.invoke(instance, invoked.invocation.args)
}
}
return lookupCalls(new FirstDelegate()) + lookupCalls(new SecondDelegate())
}
}
Here be scripts and assertions:
import org.codehaus.groovy.control.CompilerConfiguration
def dsl = '''
setup {name = "aDSLScript"}
println "this is common groovy code"
doStuff {println "Ima doing dsl stuff"}
'''
def compiler = new CompilerConfiguration()
compiler.scriptBaseClass = DelegatingScript.class.name
def shell = new GroovyShell(this.class.classLoader, new Binding(), compiler)
script = shell.parse dsl
interceptor = new MethodInterceptor()
script.setDelegate interceptor
script.run()
assert interceptor.invokedMethods*.method == [ 'setup', 'doStuff' ]
assert interceptor.delegate() ==
['firstDelegate.setup', 'secondDelegate.doStuff']
Notice I didn't bothered intercepting println call, which is a DefaultGroovyMethods thus, a little more cumbersome to handle.
Also having the class MethodInterceptor implementing the method delegate() is not a good idea, since this allows the user-defined script to call it.
I found a way to split up execution of the DSL script. I used a CompilationCustomizer to remove every statement from AST except the doFirst{}. So the first run will only execute doFirst. The second run does everything else. Here's some code:
class DoFirstProcessor {
def doFirst(Closure c) {
c()
}
}
class TheRestProcessor {
def doStuff(Closure c) {
c()
}
def methodMissing(String name, args) {
//nothing to do
}
}
def dsl = "
println 'this is text that will not be printed out in first line!'
doFirst { println 'First things first: e.g. setting up environment' }
doStuff { println 'doing some stuff now' }
println 'That is it!'
"
class HighlanderCustomizer extends CompilationCustomizer {
def methodName
HighlanderCustomizer(def methodName) {
super(CompilePhase.SEMANTIC_ANALYSIS)
this.methodName = methodName
}
#Override
void call(SourceUnit sourceUnit, GeneratorContext generatorContext, ClassNode classNode) throws CompilationFailedException {
def methods = classNode.getMethods()
methods.each { MethodNode m ->
m.code.each { Statement st ->
if (!(st instanceof BlockStatement)) {
return
}
def removeStmts = []
st.statements.each { Statement bst ->
if (bst instanceof ExpressionStatement) {
def ex = bst.expression
if (ex instanceof MethodCallExpression) {
if (!ex.methodAsString.equals(methodName)) {
removeStmts << bst
}
} else {
removeStmts << bst
}
} else {
removeStmts << bst
}
}
st.statements.removeAll(removeStmts)
}
}
}
}
def cc = new CompilerConfiguration()
cc.addCompilationCustomizers new HighlanderCustomizer("doFirst")
cc.scriptBaseClass = DelegatingScript.class.name
def doFirstShell = new GroovyShell(new Binding(), cc)
def doFirstScript = doFirstShell.parse dsl
doFirstScript.setDelegate new DoFirstProcessor()
doFirstScript.run()
cc.compilationCustomizers.clear()
def shell = new GroovyShell(new Binding(), cc)
def script = shell.parse dsl
script.setDelegate new TheRestProcessor()
script.run()
I did another variation of this where I execute the DSL in one step. See my blog post about it: http://hackserei.metacode.de/?p=247
A class implements call method so that it's objects can be called as a method. This works for most of the case but not when the call is being made inside a closure on a object which is instance variable of a class.
To demonstrate the problem, in the code below I've commented the interesting lines with numbers. While most variants result in same output, only the line with comment 5 doesn't work. It throws groovy.lang.MissingMethodException: No signature of method: Client2.instanceVar() is applicable for argument types: () values: [])
Can someone help me understand the reason? Is it a bug?
class CallableObject {
def call() { println "hello" }
}
class Client {
def instanceVar = new CallableObject()
def method() {
def localVar = new CallableObject()
def closure1 = { localVar() }
def closure2 = { instanceVar.call() }
def closure3 = { instanceVar() } // doesn't work
localVar() // 1
instanceVar() // 2
closure1() // 3
closure2() // 4
closure3() // 5
}
}
new Client().method()
I guess this will make it clear.
class CallableObject {
def call() { println "hello" }
}
class Client {
def instanceVar = new CallableObject()
def getInstanceVar() {
println "Getter Called"
instanceVar
}
def method() {
def localVar = new CallableObject()
def closure1 = { localVar() }
def closure2 = { instanceVar.call() }
def closure3 = { this.#instanceVar() } //should work now
localVar() // 1
instanceVar() // 2
closure1() // 3
closure2() // 4
closure3() // 5
}
}
new Client().method()
You will see "Getter Called" printed when closure2() invoked. For a global property to be accessed in the closure inside a method, the getter in called instead. To surmount the error you get, the field instanceVar needs to be accessed directly in order to implicitly use call().