I have this code in Groovy:
class Person {
def age
Person () {
println age // null
}
}
def p = new Person ([age: '29'])
println p.age // 29
I need to read age value in constructor, but it isn't setted yet.
How can I do this?
Note: I don't want to use a init() method and call manually every time, like
class Person {
def age
def init() {
println age // now have 29
}
}
def p = new Person ([age: '29'])
p.init()
println p.age // 29
Link to GroovyConsole.
Thanks!
You can write a constructor like this:
class Person {
def age
Person(Map map) {
for (entry in map) {
this."${entry.key}" = entry.value
}
println age
}
}
If you're using groovy 1.8, take a look at the #TupleConstructor annotation, which will automatically build a constructor like the one above, as well as a list based one.
import groovy.transform.TupleConstructor
#TupleConstructor
class Person {
int age
}
p = new Person([age: 99])
assert p.age == 99
Related
ok - tried looking /reading and not sure i have an answer to this.
I have a Utility class which wraps a static ConcurrentLinkedQueue internally.
The utility class itself adds some static methods - i dont expect to call new to create an instance of the Utility.
I want to intercept the getProperty calls the utility class - and implement these internally in the class definition
I can achieve this by adding the following to the utility classes metaclass, before i use it
UnitOfMeasure.metaClass.static.propertyMissing = {name -> println "accessed prop called $name"}
println UnitOfMeasure.'Each'
however what i want to do is declare the interception in the class definition itself. i tried this in the class definition - but it never seems to get called
static def propertyMissing (receiver, String propName) {
println "prop $propName, saught"
}
i also tried
static def getProperty (String prop) { println "accessed $prop"}
but this isnt called either.
So other than adding to metaClass in my code/script before i use, how can declare the in the utility class that want to capture property accesses
the actual class i have looks like this at present
class UnitOfMeasure {
static ConcurrentLinkedQueue UoMList = new ConcurrentLinkedQueue(["Each", "Per Month", "Days", "Months", "Years", "Hours", "Minutes", "Seconds" ])
String uom
UnitOfMeasure () {
if (!UoMList.contains(this) )
UoMList << this
}
static list () {
UoMList.toArray()
}
static getAt (index) {
def value = null
if (index in 0..(UoMList.size() -1))
value = UoMList[index]
else if (index instanceof String) {
Closure matchClosure = {it.toUpperCase().contains(index.toUpperCase())}
def position = UoMList.findIndexOf (matchClosure)
if (position != -1)
value = UoMList[position]
}
value
}
static def propertyMissing (receiver, String propName) {
println "prop $propName, saught"
}
//expects either a String or your own closure, with String will do case insensitive find
static find (match) {
Closure matchClosure
if (match instanceof Closure)
matchClosure = match
if (match instanceof String) {
matchClosure = {it.toUpperCase().contains(match.toUpperCase())}
}
def inlist = UoMList.find (matchClosure)
}
static findWithIndex (match) {
Closure matchClosure
if (match instanceof Closure)
matchClosure = match
else if (match instanceof String) {
matchClosure = {it.toUpperCase().contains(match.toUpperCase())}
}
def position = UoMList.findIndexOf (matchClosure)
position != -1 ? [UoMList[position], position] : ["Not In List", -1]
}
}
i'd appreciate the secret of doing this for a static utility class rather than instance level property interception, and doing it in class declaration - not by adding to metaClass before i make the calls.
just so you can see the actual class, and script that calls - i've attached these below
my script thats calling the class looks like this
println UnitOfMeasure.list()
def (uom, position) = UnitOfMeasure.findWithIndex ("Day")
println "$uom at postition $position"
// works UnitOfMeasure.metaClass.static.propertyMissing = {name -> println "accessed prop called $name"}
println UnitOfMeasure[4]
println UnitOfMeasure.'Per'
which errors like this
[Each, Per Month, Days, Months, Years, Hours, Minutes, Seconds]
Days at postition 2
Years
Caught: groovy.lang.MissingPropertyException: No such property: Per for class: com.softwood.portfolio.UnitOfMeasure
Possible solutions: uom
groovy.lang.MissingPropertyException: No such property: Per for class: com.softwood.portfolio.UnitOfMeasure
Possible solutions: uom
at com.softwood.scripts.UoMTest.run(UoMTest.groovy:12)
Static version of propertyMissing method is called $static_propertyMissing:
static def $static_propertyMissing(String name) {
// do something
}
This method gets invoked by MetaClassImpl at line 1002:
protected static final String STATIC_METHOD_MISSING = "$static_methodMissing";
protected static final String STATIC_PROPERTY_MISSING = "$static_propertyMissing";
// ...
protected Object invokeStaticMissingProperty(Object instance, String propertyName, Object optionalValue, boolean isGetter) {
MetaClass mc = instance instanceof Class ? registry.getMetaClass((Class) instance) : this;
if (isGetter) {
MetaMethod propertyMissing = mc.getMetaMethod(STATIC_PROPERTY_MISSING, GETTER_MISSING_ARGS);
if (propertyMissing != null) {
return propertyMissing.invoke(instance, new Object[]{propertyName});
}
} else {
// .....
}
// ....
}
Example:
class Hello {
static def $static_propertyMissing(String name) {
println "Hello, $name!"
}
}
Hello.World
Output:
Hello, World!
How do I check for deep object equality with spock.
Lets say we have a super simple test that compares to identical person objects
def "A persons test"() {
setup:
def person1 = new Person("Foo", new Address("Bar"))
def person2 = new Person("Foo", new Address("Bar"))
expect:
person1 == person2
}
The test fails
Condition not satisfied:
person1 == person2
| | |
| | Person#6bedbc4d
| false
Person#57af006c
This looks like a very natural way of asserting equality.
One of the main reason to start using spock was to avoid having to write a lot of hamcrest boilerplate matchers code.
Spock has no built-in mechanism for performing deep Object comparison, because defining object equality is out of scope of any testing framework. You can do a various things.
1. Both classes are Groovy classes
If both your classes (Person and Address) are Groovy classes you can generate equals and hashCode methods using #EqualsAndHashCode annotation over both classes, like:
import groovy.transform.EqualsAndHashCode
import groovy.transform.TupleConstructor
import spock.lang.Specification
class PersonSpec extends Specification {
def "a person test"() {
setup:
def person1 = new Person("Foo", new Address("Bar"))
def person2 = new Person("Foo", new Address("Bar"))
expect:
person1 == person2
}
#TupleConstructor
#EqualsAndHashCode
static class Person {
String name
Address address
}
#TupleConstructor
#EqualsAndHashCode
static class Address {
String city
}
}
This is just a convenient alternative for implementing both methods in Groovy.
2. Both classes are Java classes
If you want to compare both objects with == operator then you will have to define equals and hashCode methods in both classes, something like:
public final class Person {
private final String name;
private final Address address;
public Person(String name, Address address) {
this.name = name;
this.address = address;
}
public String getName() {
return name;
}
public Address getAddress() {
return address;
}
#Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Person person = (Person) o;
if (name != null ? !name.equals(person.name) : person.name != null) return false;
return address != null ? address.equals(person.address) : person.address == null;
}
#Override
public int hashCode() {
int result = name != null ? name.hashCode() : 0;
result = 31 * result + (address != null ? address.hashCode() : 0);
return result;
}
static class Address {
private final String city;
public Address(String city) {
this.city = city;
}
public String getCity() {
return city;
}
#Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Address address = (Address) o;
return city != null ? city.equals(address.city) : address.city == null;
}
#Override
public int hashCode() {
return city != null ? city.hashCode() : 0;
}
}
}
In this example both methods were defined using IntelliJ IDEA "Generate equals and hashCode" command.
3. I can use Lombok!
If you don't want to define both methods manually (because e.g. you have to remember to change them anytime you modify your class fields) then you can use Lombok's #EqualsAndHashCode annotation that does something similar to Groovy's annotation, but can be applied to any Java class.
4. I want to keep default equals and hashCode methods
Well, in this case you can try various things:
You can try comparing both objects field-by-field, like:
class PersonSpec extends Specification {
def "a person test"() {
setup:
def person1 = new Person("Foo", new Address("Bar"))
def person2 = new Person("Foo", new Address("Bar"))
expect:
person1.name == person2.name
and:
person1.address.city == person2.address.city
}
#TupleConstructor
static class Person {
String name
Address address
}
#TupleConstructor
static class Address {
String city
}
}
You can try using 3rd party tools like Unitils reflection assertion
That may sound bizarre, but you can compare JSON representation of both objects, something like:
import groovy.json.JsonOutput
import groovy.transform.TupleConstructor
import spock.lang.Specification
class PersonSpec extends Specification {
def "a person test"() {
setup:
def person1 = new Person("Foo", new Address("Bar"))
def person2 = new Person("Foo", new Address("Bar"))
expect:
new JsonOutput().toJson(person1) == new JsonOutput().toJson(person2)
}
#TupleConstructor
static class Person {
String name
Address address
}
#TupleConstructor
static class Address {
String city
}
}
Anyway, I would definitely suggest defining equals and hashCode in one way or another and simply use == operator. Hope it helps.
You can take advantage of Groovy's succinct map comparison syntax:
person1.properties == person2.properties
That only works for simple flat objects, not nested ones. You could adapt it like so:
person1.properties << ['address': person1.address.properties] == person2.properties << ['address': person2.address.properties]
...but JSON solution is more elegant at that point.
It seems, that you need to correct override your equals and hashcode methods.
In Groovy it can be done really easily, you need to use #Canonical annotation. It gives you more than equals and hashcode, buy the way.
I highly recommend you use Assertj for deep assertions. See below an example:
def "labels1 should be deeply equal to labels2"() {
when:
def labels1 = [new Label("labelA"), new Label("labelB")]
def labels2 = [new Label("labelB"), new Label("labelA")]
then:
assertThat(labels1)
.usingRecursiveComparison()
.ignoringCollectionOrder()
.isEqualTo(labels2)
}
Don't forget to add the Gradle dependency:
dependencies {
testImplementation "org.assertj:assertj-core:3.11.1"
}
I want to retrieve the annotation value used from MyAnnot. I am getting 3 annotations in the list even though there are only 2. Also, I have tried obtaining the used field of MyAnnot but with no success. I would like to return a map where MyAnnot's used is the key and type as the map's value.
// Then, define your class with it's annotated Fields
class MyClass {
#MyAnnot(used = "Hey", type = "There")
String fielda
#MyAnnot(used = "denn", type = "Ton")
String fieldc
}
def findAllPropertiesForClassWithAnotation(obj, annotClass) {
def op = []
def annos = []
def i = 0
obj.properties.findAll { prop ->
obj.getClass().declaredFields.find {
it.name == prop.key && annotClass in it.declaredAnnotations*.annotationType()
annos=it.declaredAnnotations
i++
if(annos)
op << annos[0] as Set
// println"Props ${annos[0]}"
}
}
op.each{ println "${it} and i is ${i}"}
}
// Then, define an instance of our class
MyClass a = new MyClass(fielda: 'tim', fieldc: 'dennisStar')
// And print the results of calling our method
println findAllPropertiesForClassWithAnotation(a, MyAnnot)
First of all you need to mark you annotation with: #Retention(RetentionPolicy.RUNTIME) to make it available for processing at runtime, so it will be:
#Retention(RetentionPolicy.RUNTIME)
#interface MyAnnot {
String used()
String type()
}
Then, used and type are not fields, nor properties but methods, so they must be invoked and get.
The script will be:
import java.lang.annotation.RetentionPolicy
import java.lang.annotation.Retention
#Retention(RetentionPolicy.RUNTIME)
#interface MyAnnot {
String used()
String type()
}
class MyClass {
#MyAnnot(used="Hey" ,type="There")
String fielda
#MyAnnot(used="denn", type="Ton")
String fieldc
}
def findAllPropertiesForClassWithAnotation( obj, annotClass ) {
def c = obj.getClass()
c.declaredFields.findAll { field ->
field.isAnnotationPresent(annotClass)
}.collect { found ->
def a = found.getAnnotation(annotClass)
[(a.used()): a.type()]
}.sum()
}
MyClass a = new MyClass(fielda: 'tim', fieldc: 'dennisStar')
println findAllPropertiesForClassWithAnotation(a, MyAnnot)
Mind that passing only a class of annotation is not sufficient, since you don't know the methods (used and type) to be invoked on the annotation. The following method will work only for MyAnnot class.
I'd like to create a simple wrapper, which would allow calling objects methods as a fluent interface. I've been thinking about rewriting methods of a class upon creation, but this doesn't seem to work. Is this possible in some way with groovy metaprograming?
I have this kind of code snippet so far:
class FluentWrapper {
def delegate
FluentWrapper(wrapped) {
delegate = wrapped
delegate.class.getMethods().each { method ->
def name = method.getName()
FluentWrapper.metaClass."$name" = { Object[] varArgs ->
method.invoke(wrapped, name, varArgs)
return this
}
}
}
def methodMissing(String name, args) {
def method = delegate.getClass().getDeclaredMethods().find { it.match(name) }
if(method) {
method.invoke(delegate,name, args)
return FluentWrapper(delegate)
}
else throw new MissingMethodException(name, delegate, args)
}
}
Assuming example Java class:
class Person {
void setAge()
void setName()
}
I'd like to be able to execute the following piece of code:
def wrappedPerson = new FluentWrapper(new Person())
wrappedPerson.setAge().setName()
I'm using Groovy 1.6.7 for this.
This is all Groovy, and I'm using 1.8.6 (the current latest), but given this Person Class:
class Person {
int age
String name
public void setAge( int age ) { this.age = age }
public void setName( String name ) { this.name = name }
public String toString() { "$name $age" }
}
And this FluentWrapper class:
class FluentWrapper {
def delegate
FluentWrapper(wrapped) {
delegate = wrapped
}
def methodMissing(String name, args) {
def method = delegate.getClass().declaredMethods.find { it.name == name }
if(method) {
method.invoke( delegate, args )
return this
}
else throw new MissingMethodException(name, delegate, args)
}
}
Then, you should be able to do:
def wrappedPerson = new FluentWrapper(new Person())
Person person = wrappedPerson.setAge( 85 ).setName( 'tim' ).delegate
And person should have the age and name specified
I find #tim_yates' answer nice, but you couldn't access delegate methods' return values (something one usually likes doing, even for Builders in the case of build() :)
Moreover, if this wasn't intended for a Builder but for an object with a chainable interface (like that of jQuery wrapped objects in JS), it would be a serious issue.
So I'd put the wrapper like this:
class FluentWrapper {
def delegate
FluentWrapper(wrapped) {
delegate = wrapped
}
def methodMissing(String name, args) {
def method = delegate.getClass().declaredMethods.find { it.name == name }
if(method) {
def result = method.invoke(delegate, args)
return result != null ? result : this
}
else throw new MissingMethodException(name, delegate, args)
}
}
Note the elvis operator is unsuitable since a falsy value would never get returned.
Of course, it's up to the invoker to know wether a method is chainable or not, but that could be overcome with method annotations if neccesary.
Assuming that I have an object someObj of indeterminate type, I'd like to do something like:
def value = someObj.someMethod()
Where there's no guarantee that 'someObj' implements the someMethod() method, and if it doesn't, just return null.
Is there anything like that in Groovy, or do I need to wrap that in an if-statement with an instanceof check?
Use respondsTo
class Foo {
String prop
def bar() { "bar" }
def bar(String name) { "bar $name" }
}
def f = new Foo()
// Does f have a no-arg bar method
if (f.metaClass.respondsTo(f, "bar")) {
// do stuff
}
// Does f have a bar method that takes a String param
if (f.metaClass.respondsTo(f, "bar", String)) {
// do stuff
}
Just implement methodMissing in your class:
class Foo {
def methodMissing(String name, args) { return null; }
}
And then, every time you try to invoke a method that doesn't exist, you will get a null value.
def foo = new Foo();
assert foo.someMethod(), null
For more information, take a look here: http://groovy.codehaus.org/Using+methodMissing+and+propertyMissing
You should be able to do something like:
SomeObj.metaClass.getMetaMethod("someMethod")
Or you can fall back to the good old Java reflection API.
You can achieve this by using getMetaMethod together with the safe navigation operator ?.:
def str = "foo"
def num = 42
def methodName = "length"
def args = [] as Object[]
assert 3 == str.metaClass.getMetaMethod(methodName, args)?.invoke(str, args);
assert null == num.metaClass.getMetaMethod(methodName, args)?.invoke(num, args);
if class :
MyClass.metaClass.methods*.name.any{it=='myMethod'}//true if exist
if object :
myObj.class.metaClass.methods*.name.any{it=='myMethod'}//true if exist
In very concise way you can use this:
if(someObj.&methodName){
//it means someObj has the method
}