Is there already a way in groovy to collect objects following a property while not null ?
Object.metaClass {
collectWhileNotNull = { Closure follow ->
def result = []
def previous = null
for (def current = delegate; !current.is(previous) && (current != null); current = follow(current)){
result << current
previous = current
}
return result
}
}
It is useful for recursive data structure.
An example of usage for a groovy.util.Node :
Closure getAncestors = { Node n -> n.collectWhileNotNull{ it.parent() }.tail().reverse() }
You can use a Generator class (this is also the name of the necessary pattern) from cookbook.
Related
From the following code snippet I tried, This runs into an infinite loop regardless of the fact that I mark the initial ds as immutable, and looping it with an each. What am I missing? -
domObject.Whatever.'**'.findAll { it.name() == 'Node' }.asImmutable().each { node -> //Bazinga
nodes.split(/(;|,|\n|&)/).eachWithIndex { nodeName, index ->
def newNode = new Node(null, node.name(), node.attributes(), node.value())
newNode.#name = nodeName
//I'm simply adding new nodes here
node.parent().children().add(0, newNode) //bazinga
}
}
Ive used an xmlparser for the domObject.
I understand that we cannot access Map properties the same way we access them in other classes, because of the ability to get map keys with dot notations in groovy.
Now, Is there a way, for a class that implements java.util.Map, to still benefit from the expando metaclass for using propertyMissing ?
Here is what I'm trying :
LinkedHashMap.metaClass.methodMissing = { method, args ->
println "Invoking ${method}"
"Invoking ${method}"
}
LinkedHashMap.metaClass.propertyMissing = { method, args ->
println "Accessing ${method}"
"Accessing ${method}"
}
def foo = [:]
assert "Invoking bar" == foo.bar() // this works fine
assert "Accessing bar" == foo.bar // this doesn't work, for obvious reasons, but I'd like to be able to do that...
I've been trying through custom DelegatingMetaClasses but didn't succeed...
Not sure it fits your use-case, but you could use Guava and the withDefault method on Maps...
#Grab( 'com.google.guava:guava:16.0.1' )
import static com.google.common.base.CaseFormat.*
def map
map = [:].withDefault { key ->
LOWER_UNDERSCORE.to(LOWER_CAMEL, key).with { alternate ->
map.containsKey(alternate) ? map[alternate] : null
}
}
map.possibleSolution = 'maybe'
assert map.possible_solution == 'maybe'
One side-effect of this is that after the assert, the map contains two key:value pairs:
assert map == [possibleSolution:'maybe', possible_solution:'maybe']
If I understood well you can provide a custom map:
class CustomMap extends LinkedHashMap {
def getAt(name) {
println "getAt($name)"
def r = super.getAt(name)
r ? r : this.propertyMissing(name)
}
def get(name) {
println "get($name)"
super.get(name)
def r = super.get(name)
r ? r : this.propertyMissing(name)
}
def methodMissing(method, args) {
println "methodMissing($method, $args)"
"Invoking ${method}"
}
def propertyMissing(method) {
println "propertyMissing($method)"
"Accessing ${method}"
}
}
def foo = [bar:1] as CustomMap
assert foo.bar == 1
assert foo['bar'] == 1
assert foo.lol == 'Accessing lol'
assert foo['lol'] == 'Accessing lol'
assert foo.bar() == 'Invoking bar'
I reread the groovy Maps javadocs, and I noticed there are 2 versions of the get method. One that takes a single argument, and one that takes 2.
The version that takes 2 does almost what I describe here : it returns a default value if it doesn't find your key.
I get the desired effect, but not in dot notation, therefore I just post this as an alternative solution in case anyone comes across this post :
Map.metaClass.customGet = { key ->
def alternate = key.replaceAll(/_\w/){ it[1].toUpperCase() }
return delegate.get(key, delegate.get(alternate, 'Sorry...'))
}
def m = [myKey : 'Found your key']
assert 'Found your key' == m.customGet('myKey')
assert 'Found your key' == m.customGet('my_key')
assert 'Sorry...' == m.customGet('another_key')
println m
-Result-
m = [myKey:Found your key, my_key:Found your key, anotherKey:Sorry..., another_key:Sorry...]
As in Tim's solution, this leads to m containing both keys after the second assert + 2 keys with the default value (Sorry...) everytime we ask for a new value not present in the initial map... which could be solved by removing the keys with default values. e.g. :
Map.metaClass.customGet = { key ->
def alternate = key.replaceAll(/_\w/){ it[1].toUpperCase() }
def ret = delegate.get(key, delegate.get(alternate, 'Sorry...'))
if (ret == 'Sorry...') {
delegate.remove(key)
delegate.remove(alternate)
}
ret
}
Feel free to comment/correct any mistakes this could lead to... just thinking out loud here...
I want to store objects in a map (called result). The objects are created or updated from SQL rows.
For each row I read I access the map as follows:
def result = [:]
sql.eachRow('SELECT something') { row->
{
// check if the Entry is already existing
def theEntry = result[row.KEY]
if (theEntry == null) {
// create the entry
theEntry = new Entry(row.VALUE1, row.VALUE2)
// put the entry in the result map
result[row.KEY] = theEntry
}
// use the Entry (create or update the next hierarchie elements)
}
I want to minimize the code for checking and updating the map. How can this be done?
I know the function map.get(key, defaultValue), but I will not use it, because it is to expensive to create an instance on each iteration even if I don't need it.
What I would like to have is a get function with a closure for providing the default value. In this case I would have lazy evaluation.
Update
The solution dmahapatro provided is exactly what I want. Following an example of the usage.
// simulate the result from the select
def select = [[a:1, b:2, c:3], [a:1, b:5, c:6], [a:2, b:2, c:4], [a:2, b:3, c:5]]
// a sample class for building an object hierarchie
class Master {
int a
List<Detail> subs = []
String toString() { "Master(a:$a, subs:$subs)" }
}
// a sample class for building an object hierarchie
class Detail {
int b
int c
String toString() { "Detail(b:$b, c:$c)" }
}
// the goal is to build a tree from the SQL result with Master and Detail entries
// and store it in this map
def result = [:]
// iterate over the select, row is visible inside the closure
select.each { row ->
// provide a wrapper with a default value in a closure and get the key
// if it is not available then the closure is executed to create the object
// and put it in the result map -> much compacter than in my question
def theResult = result.withDefault {
new Master(a: row.a)
}.get(row.a)
// process the further columns
theResult.subs.add new Detail(b: row.b, c: row.c )
}
// result should be [
// 1:Master(a:1, subs:[Detail(b:2, c:3), Detail(b:5, c:6)]),
// 2:Master(a:2, subs:[Detail(b:2, c:4), Detail(b:3, c:5)])]
println result
What I learned from this sample:
withDefault returns a wrapper, so for manipulating the map use the wrapper and not the original map
row variable is visible in the closure!
create the wrapper for the map in each iteration again, since row var changed
You asked for it, Groovy has it for you. :)
def map = [:]
def decoratedMap = map.withDefault{
new Entry()
}
It works the same way you would expect it to work lazily. Have a look at withDefault API for a detailed explanation.
I ran into a rather odd closure issue related to spock unit testing and wondered if anyone could explain this.
If we imagine a dao, model, and service as follows:
interface CustomDao {
List<Integer> getIds();
Model getModelById(int id);
}
class CustomModel {
int id;
}
class CustomService {
CustomDao customDao
public List<Object> createOutputSet() {
List<Model> models = new ArrayList<Model>();
List<Integer> ids = customDao.getIds();
for (Integer id in ids) {
models.add(customDao.getModelById(id));
}
return models;
}
}
I would like to unit test the CustomService.createOutputSet. I have created the following specification:
class TestSpec extends Specification {
def 'crazy closures'() {
def mockDao = Mock(CustomDao)
def idSet = [9,10]
given: 'An initialized object'
def customService = new CustomService
customService.customDao = mockDao
when: 'createOutput is called'
def outputSet = customService.createOutputSet()
then: 'the following methods should be called'
1*mockDao.getIds() >> {
return idSet
}
for (int i=0; i<idSet.size(); i++) {
int id = idSet.get(i)
1*mockDao.getModelById(idSet.get(i)) >> {
def tmp = new Model()
int tmpId = id // idSet.get(i)
return tmp
}
}
and: 'each compute package is accurate'
2 == outputSet.size()
9 == outputSet.get(0).getId()
10 == outputSet.get(1).getId()
}
}
Notice that in here I test two things. First, I initialize the dao with my mock, verify that the daos are correctly called and return the proper data, and then I verify that I get the proper output (i.e. "and:").
The tricky part is the for loop, in which I wanted to return models from the mock dao that are related to the method parameter. In the above example, if I use a simple for (__ in idSet), the models only return with id 10: outputSet.get(0).getId() == outputSet.get(1).getId() == 10. If I use the traditional for loop, and set the model with idSet.get(i), I get an IndexOutOfBoundsException . The only way to make this work is by retrieving the value in a local variable (id) and setting with variable, as above.
I know this is related to groovy closures and I suspect that spock captures the mock calls into a set of closures before executing them, which means that the model creation depends on the outer state of the closure. I understand why I would get the IndexOutOfBoundsException, but I don't understand why int id = idSet.get(i) is captured by the closure whereas i is not.
What is the difference?
Note: this is not the live code but rather simplified to demonstrate the crux of my challenge. I would not and do not make two subsequent dao calls on getIds() and getModelById().
While stubbing getModelById by a closure, the arguments to the closure has to match with that of the method. If you try something like below, you would not need the local variable id inside for anymore.
for (int i=0; i<idSet.size(); i++) {
//int id = idSet.get(i)
mockDao.getModelById(idSet.get(i)) >> {int id ->
def tmp = new Model()
tmp.id = id // id is closure param which represents idSet.get(i)
return tmp
}
}
Simplified version would be to use each
idSet.each {
mockDao.getModelById(it) >> {int id ->
def tmp = new Model()
tmp.id = id // id is closure param which represents idSet.get(i)
tmp
}
}
Do we need to worry about how many times method is called if it is being stubbed?
Accessing mutable local variables from a closure whose execution is deferred is a common source of errors not specific to Spock.
I don't understand why int id = idSet.get(i) is captured by the closure whereas i is not.
The former gives rise to a separate hoisted variable per iteration whose value is constant. The latter gives rise to a single hoisted variable whose value changes over time (and before the result generator executes).
Instead of solving the problem by introducing a temporary variable, a better solution (already given by #dmahapatro) is to declare an int id -> closure parameter. If it's deemed good enough to stub the calls without enforcing them, the loop can be omitted altogether. Yet another potential solution is to construct the return values eagerly:
idSet.each { id ->
def model = new Model()
model.id = id
1 * mockDao.getModelById(id) >> model
}
How can I deep copy a map of maps in Groovy? The map keys are Strings or Ints. The values are Strings, Primitive Objects or other maps, in a recursive way.
An easy way is this:
// standard deep copy implementation
def deepcopy(orig) {
bos = new ByteArrayOutputStream()
oos = new ObjectOutputStream(bos)
oos.writeObject(orig); oos.flush()
bin = new ByteArrayInputStream(bos.toByteArray())
ois = new ObjectInputStream(bin)
return ois.readObject()
}
To go about deep copying each member in a class, the newInstance() exists for Class objects. For example,
foo = ["foo": 1, "bar": 2]
bar = foo.getClass().newInstance(foo)
foo["foo"] = 3
assert(bar["foo"] == 1)
assert(foo["foo"] == 3)
See http://groovy-lang.org/gdk.html and navigate to java.lang, Class, and finally the newInstance method overloads.
UPDATE:
The example I have above is ultimately an example of a shallow copy, but what I really meant was that in general, you almost always have to define your own reliable deep copy logic, with perhaps using the newInstance() method, if the clone() method is not enough. Here's several ways how to go about that:
import groovy.transform.Canonical
import groovy.transform.AutoClone
import static groovy.transform.AutoCloneStyle.*
// in #AutoClone, generally the semantics are
// 1. clone() is called if property implements Cloneable else,
// 2. initialize property with assignment, IOW copy by reference
//
// #AutoClone default is to call super.clone() then clone() on each property.
//
// #AutoClone(style=COPY_CONSTRUCTOR) which will call the copy ctor in a
// clone() method. Use if you have final members.
//
// #AutoClone(style=SIMPLE) will call no arg ctor then set the properties
//
// #AutoClone(style=SERIALIZATION) class must implement Serializable or
// Externalizable. Fields cannot be final. Immutable classes are cloned.
// Generally slower.
//
// if you need reliable deep copying, define your own clone() method
def assert_diffs(a, b) {
assert a == b // equal objects
assert ! a.is(b) // not the same reference/identity
assert ! a.s.is(b.s) // String deep copy
assert ! a.i.is(b.i) // Integer deep copy
assert ! a.l.is(b.l) // non-identical list member
assert ! a.l[0].is(b.l[0]) // list element deep copy
assert ! a.m.is(b.m) // non-identical map member
assert ! a.m['mu'].is(b.m['mu']) // map element deep copy
}
// deep copy using serialization with #AutoClone
#Canonical
#AutoClone(style=SERIALIZATION)
class Bar implements Serializable {
String s
Integer i
def l = []
def m = [:]
// if you need special serialization/deserialization logic override
// writeObject() and/or readObject() in class implementing Serializable:
//
// private void writeObject(ObjectOutputStream oos) throws IOException {
// oos.writeObject(s)
// oos.writeObject(i)
// oos.writeObject(l)
// oos.writeObject(m)
// }
//
// private void readObject(ObjectInputStream ois)
// throws IOException, ClassNotFoundException {
// s = ois.readObject()
// i = ois.readObject()
// l = ois.readObject()
// m = ois.readObject()
// }
}
// deep copy by using default #AutoClone semantics and overriding
// clone() method
#Canonical
#AutoClone
class Baz {
String s
Integer i
def l = []
def m = [:]
def clone() {
def cp = super.clone()
cp.s = s.class.newInstance(s)
cp.i = i.class.newInstance(i)
cp.l = cp.l.collect { it.getClass().newInstance(it) }
cp.m = cp.m.collectEntries { k, v ->
[k.getClass().newInstance(k), v.getClass().newInstance(v)]
}
cp
}
}
// assert differences
def a = new Bar("foo", 10, ['bar', 'baz'], [mu: 1, qux: 2])
def b = a.clone()
assert_diffs(a, b)
a = new Baz("foo", 10, ['bar', 'baz'], [mu: 1, qux: 2])
b = a.clone()
assert_diffs(a, b)
I used #Canonical for the equals() method and tuple ctor. See groovy doc Chapter 3.4.2, Code Generation Transformations.
Another way to go about deep copying is using mixins. Let's say you wanted an existing class to have deep copy functionality:
class LinkedHashMapDeepCopy {
def deep_copy() {
collectEntries { k, v ->
[k.getClass().newInstance(k), v.getClass().newInstance(v)]
}
}
}
class ArrayListDeepCopy {
def deep_copy() {
collect { it.getClass().newInstance(it) }
}
}
LinkedHashMap.mixin(LinkedHashMapDeepCopy)
ArrayList.mixin(ArrayListDeepCopy)
def foo = [foo: 1, bar: 2]
def bar = foo.deep_copy()
assert foo == bar
assert ! foo.is(bar)
assert ! foo['foo'].is(bar['foo'])
foo = ['foo', 'bar']
bar = foo.deep_copy()
assert foo == bar
assert ! foo.is(bar)
assert ! foo[0].is(bar[0])
Or categories (again see the groovy doc) if you wanted deep copying semantics based on some sort of runtime context:
import groovy.lang.Category
#Category(ArrayList)
class ArrayListDeepCopy {
def clone() {
collect { it.getClass().newInstance(it) }
}
}
use(ArrayListDeepCopy) {
def foo = ['foo', 'bar']
def bar = foo.clone()
assert foo == bar
assert ! foo.is(bar)
assert ! foo[0].is(bar[0]) // deep copying semantics
}
def foo = ['foo', 'bar']
def bar = foo.clone()
assert foo == bar
assert ! foo.is(bar)
assert foo[0].is(bar[0]) // back to shallow clone
For Json (LazyMap) this wokred for me
copyOfMap = new HashMap<>()
originalMap.each { k, v -> copyOfMap.put(k, v) }
copyOfMap = new JsonSlurper().parseText(JsonOutput.toJson(copyOfMap))
EDIT: Simplification by: Ed Randall
copyOfMap = new JsonSlurper().parseText(JsonOutput.toJson(originalMap))
I've just hit this issue as well, and I just found:
deepCopy = evaluate(original.inspect())
Although I've been coding in Groovy for less than 12 hours, I wonder if there might be some trust issues with using evaluate. Also, the above doesn't handle backslashes. This:
deepCopy = evaluate(original.inspect().replace('\\','\\\\'))
does.
I am afraid you have to do it the clone way. You could give Apache Commons Lang SerializationUtils a try