Table of contents

1. Objects
   1. properties to map
      1. can also use slurper
2. Object Extensions
   1. if you don’t know the name of method at runtime
3. MetaProgramming
   1. Create Class Prop Dynamically
   2. to invoke a property dynamically
   3. iterate over an objects properties
   4. check if property exists
   5. iterate through objects methods
   6. iterate through methods
   7. check if method exists
   8. invoke method dynamically
4. Class object – reflection
   1. dynamically create class

---

Objects

properties to map

intCmd.class
        .declaredFields
        .findAll { !it.synthetic }
        .collectEntries { [it.name, intCmd."$it.name"] }

can also use slurper

class BaseObject {
    Map asMap() {
        def jsonSlurper = new groovy.json.JsonSlurperClassic()
        Map map = jsonSlurper.parseText(this.asJson())
        return map
    }

    String asJson() {
        def jsonOutput = new groovy.json.JsonOutput()
        String json = jsonOutput.toJson(this)
        return json
    }
}

Object Extensions

if you don’t know the name of method at runtime

peter.invokeMethod("walk", 10)

MetaProgramming

Create Class Prop Dynamically

code example from class constructor

dynamicProperties.eachWithIndex { String newProp, Integer index ->
    if (index < 4) {
        String propName = newProp.substring(1).replaceAll("\\s", "")
        String propNameCamelCased = Character.toString(newProp.charAt(0)).toUpperCase() + noWhite
        this.metaClass["get${propNameCamelCased}"] = raw.get(newProp)
    }
}

to invoke a property dynamically

 def x = vobj[usrRequestedProperty]
def y = vobj."${usrRequestedProperty}"

iterate over an objects properties

obj.properties.each {}

check if property exists

 object.hasProperty(methodName)

iterate through objects methods

object.methods.each {}

iterate through methods

test.metaClass.methods.each { method -> if (method.name == 'thismethod') method.invoke(arg) }

check if method exists

 object.respondsTo(methodName)

invoke method dynamically

if (methodUsed) returnSet = invokeMethod(methodUsed as String, group) as Set

Class object – reflection

dynamically create class

public class Example {
    Class<?> clazz = Class.forName("java.util.Date");
    Object date = clazz.newInstance();
}

public class Example {
    Class<?> clazz = Class.forName("com.foo.MyClass");
    Constructor<?> constructor = clazz.getConstructor(String.class, Integer.class);
    Object instance = constructor.newInstance("stringparam", 42);
}

def p3 = Class.forName("Person").newInstance()
assert p3

using groovy classLoader

def instance = this.class.classLoader.loadClass('Item', true, false)?.newInstance()

Code Example

// expected configmap
// Map configMap = [rest: RESTClientResultConfig, soap: SOAPClientResultConfig, ftp: FTPClientResultConfig, email: EmailClientResultConfig]

Class clazz = configMap.get(name)
Object typeConfigProps = wSConfigCommand.getProperty(name)
Object newInstance = clazz.newInstance([*: newClientOrderConfig.properties, *: typeConfigProps.properties] as Object)
newInstance.wSConfigType = type
newInstance.clientSetup = newClientSetup
def err = validatingClosure(newInstance)
if (err) {
    returnObj.errors = [(err.name): err]
} else {
    returnObj = [(type.getKey()): newInstance.save(flush: true).id]
}

possible errors

1. the JVM can’t find or can’t load your class
2. the class you’re trying to instantiate doesn’t have the right sort of constructors
3. the constructor itself threw an exception
4. the constructor you’re trying to invoke isn’t public
5. a security manager has been installed and is preventing reflection from occurring