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Handle duplicate code in concrete implementations of an interface in Spring boot application

I am working on a spring boot application, where I have an interface I as follows:
public interface I {
String getType();
void f1();
}
There are two classes implementing interface I as follows:
#Component
class A implements I {
private final MyRepo1 myRepo1;
private final Helper helper;
public A(MyRepo1 myRepo1, Helper helper) {
this.myRepo1 = myRepo1;
this.helper = helper;
}
#Override
public String getType() {
return "type1";
}
#Override
public void f1(String type) {
int response = helper.f1(type);
if(response != -1) {
return;
}
//Add type1 specific handling here
}
}
One more class B implementing interface I as follows:
#Component
class B implements I {
private final MyRepo2 myRepo2;
private final Helper helper;
public B(MyRepo2 myRepo2, Helper helper) {
this.myRepo2 = myRepo2;
this.helper = helper;
}
#Override
public String getType() {
return "type2";
}
#Override
public void f1(String type) {
int response = helper.f1(type);
if(response != -1) {
return;
}
//Add type2 specific handling here
}
}
Helper is as follows:
#Component
class Helper {
public int f1(String type) {
...
}
}
I have a factory class as follows, that is used to fetch an object of the appropriate type:
#Component
public class ServiceFactory {
private final Map<String, I>
typeToClassMap = new HashMap<>();
public ServiceFactory(List<I> components) {
for(I component : components) {
typeToClassMap.put(component.getType(), component);
}
}
}
This ServiceFactory is basically used to get objects according to the type.
Now, the problem is, here for sake of simplicity I have just shown two classes implementing the interface. But actually, I have a lot more classes than this, implementing the interface I.
Some of the classes may have the same implementation of f1(), resulting in duplicate code.
I cannot make f1() as the default method in interface I as this requires the dependent bean.
I cannot understand what is the best way to handle this.
Could anyone please help here?

How to implement factory pattern with generics in Java?

I have a generic interface Handler
public interface Handler<T> {
void handle(T obj);
}
I can have n implementations of this interface. Let's say I have following 2 implementations for now. One which handles String objects and another handles Date
public class StringHandler implements Handler<String> {
#Override
public void handle(String str) {
System.out.println(str);
}
}
public class DateHandler implements Handler<Date> {
#Override
public void handle(Date date) {
System.out.println(date);
}
}
I want to write a factory which will return handler instances based on the class type. Something like this :
class HandlerFactory {
public <T> Handler<T> getHandler(Class<T> clazz) {
if (clazz == String.class) return new StringHandler();
if (clazz == Date.class) return new DateHandler();
}
}
I get following error in this factory :
Type mismatch: cannot convert from StringHandler to Handler<T>
How to fix this?

SIMPLE SOLUTION
You could save your mappings Class<T> -> Handler<T> in a Map. Something like:
Map<Class<T>, Handler<T>> registry = new HashMap<>();
public void registerHandler(Class<T> dataType, Class<? extends Handler> handlerType) {
registry.put(dataType, handlerType);
}
public <T> Handler<T> getHandler(Class<T> clazz) {
return registry.get(clazz).newInstance();
}
In some place, initialize handlers (could be in the factory itself):
factory.registerHandler(String.class, StringHandler.class);
factory.registerHandler(Date.class, DateHandler.class);
And in another place, you create and use them:
Handler<String> stringhandler = factory.getHandler(String.class);
Handler<Date> dateHandler = factory.getHandler(Date.class);
MORE COMPLEX SOLUTION
You can "scan" classes using reflection and, instead of register manually the mappings Class<T> -> Handler<T>, do it using reflection.
for (Class<? extends Handler> handlerType : getHandlerClasses()) {
Type[] implementedInterfaces = handlerType.getGenericInterfaces();
ParameterizedType eventHandlerInterface = (ParameterizedType) implementedInterfaces[0];
Type[] types = eventHandlerInterface.getActualTypeArguments();
Class dataType = (Class) types[0]; // <--String or Date, in your case
factory.registerHandler(dataType, handlerType);
}
Then, you create and use them like above:
Handler<String> stringhandler = factory.getHandler(String.class);
Handler<Date> dateHandler = factory.getHandler(Date.class);
To implement getHandlerClasses(), look at this to scan all classes in your jar. For each class, you have to check if it is a Handler:
if (Handler.class.isAssignableFrom(scanningClazz) //implements Handler
&& scanningClazz.getName() != Handler.class.getName()) //it is not Handler.class itself
{
//is a handler!
}
Hope it helps!

Your problem is that the compiler cannot make the leap to the fact thet the type of the result is correct.
To help the compiler you can make the factory delegate the construction. Although this looks strange and unwieldly it does manage to properly maintain type safety without sacrifices such as casting or using ? or raw types.
public interface Handler<T> {
void handle(T obj);
}
public static class StringHandler implements Handler<String> {
#Override
public void handle(String str) {
System.out.println(str);
}
}
public static class DateHandler implements Handler<Date> {
#Override
public void handle(Date date) {
System.out.println(date);
}
}
static class HandlerFactory {
enum ValidHandler {
String {
#Override
Handler<String> make() {
return new StringHandler();
}
},
Date {
#Override
Handler<Date> make() {
return new DateHandler();
}
};
abstract <T> Handler<T> make();
}
public <T> Handler<T> getHandler(Class<T> clazz) {
if (clazz == String.class) {
return ValidHandler.String.make();
}
if (clazz == Date.class) {
return ValidHandler.Date.make();
}
return null;
}
}
public void test() {
HandlerFactory factory = new HandlerFactory();
Handler<String> stringHandler = factory.getHandler(String.class);
Handler<Date> dateHandler = factory.getHandler(Date.class);
}

The whole point of using a generic type is to share the implementation. If the n implementation of your Handler interface are so different that they can't be shared, then I don't think there is any reason to use define that generic interface at the first place. You'd rather just have StringHandler and DateHandler as top level classes.
On the other hand, if the implementation can be shared, as is the case of your example, then the factory works naturally:
public class Main {
static public interface Handler<T> {
void handle(T obj);
}
static public class PrintHandler<T> implements Handler<T> {
#Override
public void handle(T obj) {
System.out.println(obj);
}
}
static class HandlerFactory {
public static <T> Handler<T> getHandler() {
return new PrintHandler<T>();
}
}
public static void main(String[] args) {
Handler<String> stringHandler = HandlerFactory.getHandler();
Handler<Date> dateHandler = HandlerFactory.getHandler();
stringHandler.handle("TEST");
dateHandler.handle(new Date());
}
}

You can use something like:
class HandlerFactory {
public <T> Handler<T> getHandler(Class<T> clazz) {
if (clazz.equals(String.class)) return (Handler<T>) new StringHandler();
if (clazz.equals(Date.class)) return (Handler<T>) new DateHandler();
return null;
}
}
T is generic and the compiler can't map that at compile time. Also it is safer to use .equals instead of ==.

Define an interface for creating an object, but let subclasses decide which class to instantiate.
Factory method lets a class defer instantiation to subclasses.
Define generic abstract class
public abstract class Factory<T> {
public abstract T instantiate(Supplier<? extends T> supplier);
}
And a generic supplier
public class SupplierFactory<T> extends Factory<T> {
#Override
public T instantiate(Supplier<? extends T> supplier) {
return supplier.get();
}
}
Then an implementation needs to have concrete classes to implement the base interface and a main class to show class defer instantiation . i.e
The base interface (desired interface of the requirement)
public interface BaseInterface {
void doAction();
}
The first concrete class
public class Alpha implements BaseInterface {
#Override
public void doAction() {
System.out.println("The Alpha executed");
}
}
And the second one
public class Beta implements BaseInterface {
#Override
public void doAction() {
System.out.println("The Beta executed");
}
}
The main
public class Main {
public static void main(String[] args) {
Factory<BaseInterface> secondFactory = new SupplierFactory<>();
secondFactory.instantiate(Beta::new).doAction();
secondFactory.instantiate(Alpha::new).doAction();
}
}

Basically you can do:
public Handler getHandler( Class clazz ){
if( clazz == String.class ) return new StringHandler();
if( clazz == Date.class ) return new DateHandler();
return null;
}
public static void main( String[] args ){
HandlerFactory handlerFactory = new HandlerFactory();
StringHandler handler = ( StringHandler )handlerFactory.getHandler( String.class );
handler.handle( "TEST" );
DateHandler handler2 = ( DateHandler )handlerFactory.getHandler( Date.class );
handler2.handle( new Date() );
}
Output:
TEST
Tue Dec 15 15:31:00 CET 2015
But instead writing two different methods to get handlers separately always is a better way.

I edited your code and allowed Eclipse to "fix" the errors and it came up with this.
public Handler<?> getHandler(Class<?> clazz) {
if (clazz == String.class)
return new StringHandler();
if (clazz == Date.class)
return new DateHandler();
return null;
}

Yout HandlerFactory don't know about T. Use your factory like below-
public class HandlerFactory {
public Handler<?> getHandler(Class<?> clazz) {
if (clazz == String.class) {
return new StringHandler();
}
if (clazz == Date.class) {
return new DateHandler();
}
return null;
}
}

Nice way of factory method pattern with inheritance

Suppose I have following class hierarchy:
class abstract Parent{}
class FirstChild extends Parent {}
class SecondChild extends Parent {}
And I'd like to create DTO objects from each child:
class abstract ParentDTO {}
class FirstChildDTO extends ParentDTO{}
class SecondChildDTO extends ParentDTO{}
I think I need a factory method something like this:
ParentDTO createFrom(Parent source);
Is there any nice way to do this in Java without instanceof checks and if/else statements?
EDIT:
This factory method does not work:
public ParentDTO create(Parent source)
{
return _create(source);
}
private FirstChildDTO _create(FirstChild source)
{
return new FirstDTO();
}
private SecondChildDTO _create(SecondChild source)
{
return new SecondDTO();
}
private ParentDTO _create(Parent source)
{
return new ParentDTO();
}
It only generates ParentDTOs and here is why:
Parent p = new FirstChild();
System.out.println(factory.create(p)); //ParentDTO
FirstChild f = new FirstChild();
System.out.println(factory.create(f)); //FirstChildDTO

If you insist on using a factory for DTO creation you can use simple method overloading. Example follows:
public class Factory {
public ParentDTO createDTO(Parent parent) {
return new ParentDTO();
}
public FirstChildDTO createDTO(FirstChild firstChild) {
return new FirstChildDTO();
}
public SecondChildDTO createDTO(SecondChild SecondChild) {
return new SecondChildDTO();
}
}
public class Parent {
}
public class FirstChild extends Parent {
}
public class SecondChild extends Parent {
}
public class ParentDTO {
#Override
public String toString() {
return this.getClass().getSimpleName();
}
}
public class FirstChildDTO extends ParentDTO {
#Override
public String toString() {
return this.getClass().getSimpleName();
}
}
public class SecondChildDTO extends ParentDTO {
#Override
public String toString() {
return this.getClass().getSimpleName();
}
}
public class App {
public static void main(String[] args) {
Factory factory = new Factory();
ParentDTO parentDTO = factory.createDTO(new Parent());
System.out.println(parentDTO);
FirstChildDTO firstChildDTO = factory.createDTO(new FirstChild());
System.out.println(firstChildDTO);
SecondChildDTO secondChildDTO = factory.createDTO(new SecondChild());
System.out.println(secondChildDTO);
}
}
Running the App as Java application in my IDE outputs:
ParentDTO
FirstChildDTO
SecondChildDTO

That's quite a complex question. I'd resolve this in few steps.
Parent class should have some kind of interface that would allow your factory to recognize, what data should your DTO object contain, like this (in PHP language):
class Parent
{
abstract function getDataFields();
}
class FirstChild extends Parent
{
function getDataFields()
{
return ['id' => $this->id, 'name' => $this->name, 'email' => $this->email];
}
}
class SecondChild extends Parent
{
function getDataFields()
{
return ['id' => $this->id, 'brand' => $this->brand, 'model' => $this->model];
}
}
Now, you only need a single factory, AND i would use a single class for DTO too, since you know what subclass of Parent
class DTOFactory
{
function createFromParent(Parent $parent)
{
return new DTO($parent);
}
}
class DTO
{
private $fields = [];
function __construct(Parent $parent)
{
foreach ($parent->getDataFields() as $field => $value) {
$this->fields[$field] = $value
}
}
function __get($field)
{
return $this->fields[$field];
}
}
Of course, there are a lot of ways to make DTO's in various languages, i can't cover this in detail, that's up to you.
You could do your factory method static, but if you want to avoid that, you have to use Dependency Injection of some sorts:
class MyController
{
private $dtoFactory;
function __construct(DTOFactory $factory)
{
$this->dtoFactory = $factory;
}
function returnDTOAction()
{
$object = new FirstChild(); // or some other way to get your child;
return $this->factory->createFromParent($object);
}
}
class DIContainer
{
private $instances = [];
function get($className)
{
if (!is_object($this->instances[$className]) {
$this->instances[$className] = new $className;
}
return $this->instances[$className] = new $className;
}
}
$container = new DIContainer;
$controller = new MyController($container->get('DTOFactory'));
This is a very simple example of DI Container, better examples have automatic dependency resolution, so you simply call them like $container->get('MyController'); and get a class with automatically resolved dependencies, but i won't go into further detail on this, since their implementation is heavily language-dependent, and i only stuck with a basic one.
Anyways, hope this helps. If you need some clarifications - feel free to comment.

You can code the factory method directly into the model class and utilize Java's covariant return type to return the correct type of DTO, for example:
public class Parent {
public ParentDTO createDTO() {
return new ParentDTO();
}
}
public class FirstChild extends Parent {
#Override
public FirstChildDTO createDTO() {
return new FirstChildDTO();
}
}
public class SecondChild extends Parent {
#Override
public SecondChildDTO createDTO() {
return new SecondChildDTO();
}
}

Is it possible to parcel a generic class?

I'm trying to create public class MyClass<T extends Parcelable> implements Parcelable. I'm having trouble implementing Parcelable. Is it possible to create a generic class that implements Parcelable? (Note that T is bounded so that it also must implement Parcelable).
I am running into trouble with the fact that the Parcelable interface requires a static variable: public static final Parcelable.Creator<MyParcelable> CREATOR. Thus I cannot do public static final Parcelable.Creator<MyClass<T>> CREATOR because MyParcelable<T> is nonstatic.
André

I had similar issues with implementing Parcelable on a class with a generic, the first issue was the same as what you were experiencing:
Thus I cannot do public static final Parcelable.Creator> CREATOR because MyParcelable is nonstatic.
The second was to read in a Parcelable object you need access to the ClassLoader which cannot be gotten from T due to type erasure.
The class below is an adaption of a class I am using in production which overcomes both issues. Note: I have not tested this class specifically, so let me know if you have any issues.
public class TestModel<T extends Parcelable> implements Parcelable {
private List<T> items;
private String someField;
public List<T> items() {
return items;
}
public void setItems(List<T> newValue) {
items = newValue;
}
public String someField() {
return someField;
}
public void setSomeField(String newValue) {
someField = newValue;
}
//region: Parcelable implementation
public TestModel(Parcel in) {
someField = in.readString();
int size = in.readInt();
if (size == 0) {
items = null;
}
else {
Class<?> type = (Class<?>) in.readSerializable();
items = new ArrayList<>(size);
in.readList(items, type.getClassLoader());
}
}
#Override
public int describeContents() {
return 0;
}
#Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(someField);
if (items == null || items.size() == 0)
dest.writeInt(0);
else {
dest.writeInt(items.size());
final Class<?> objectsType = items.get(0).getClass();
dest.writeSerializable(objectsType);
dest.writeList(items);
}
}
public static final Parcelable.Creator<TestModel> CREATOR = new Parcelable.Creator<TestModel>() {
public TestModel createFromParcel(Parcel in) {
return new TestModel(in);
}
public TestModel[] newArray(int size) {
return new TestModel[size];
}
};
//endregion
}

Write the generic data member class name to the parcel and then read it back in order to create its class loader. Example,
public class MyClass<T> implements Parcelable {
T data;
#Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(data.getClass().getName());
dest.writeParcelable((Parcelable) data, 0);
}
private MyClass(Parcel in) {
final String className = in.readString();
try {
data = in.readParcelable(Class.forName(className).getClassLoader());
} catch (ClassNotFoundException e) {
Log.e("readParcelable", className, e);
}
}

Yes you can. You just need to store the class name or class loader during the construction of your subclass object and then you can pass it during the read/write operation of the parcelable.
Step by step instructions:
Step 1. Store the class name that extends from your Generic class like this:
public abstract class GenericClass<T> implements Parcelable {
private String className;
Step 2. Any classes that extends from your generic class must specify the class name during its construction like this:
public class MyClass extends GenericClass<MyClass> {
public MyClass () {
super();
setClassName(MyClass.class.getName()); // Generic class setter method
}
Step 3. In your generic class, you can then read/write your class names to getClassLoader() like this:
public abstract class GenericClass<T> implements Parcelable {
private String className;
T myGenericObject;
protected MyClass (Parcel in) {
super(in);
this.className = in.readString();
ClassLoader classLoader;
try {
classLoader = Class.forName(this.className).getClassLoader();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
myGenericObject = in.readParcelable(classLoader);
//... Other class members can go here
}
#Override
public void writeToParcel(Parcel dest, int flags) {
super.writeToParcel(dest, flags);
dest.writeString(className);
//... Other class members can go here
}
}

Based on answers above, have created extension functions for this.
fun <T : Parcelable> Parcel.writeGenericParcelable(data: T, flags: Int) {
writeString(data::class.java.name)
writeParcelable(data, flags)
}
fun <T : Parcelable> Parcel.readGenericParcelable(): T {
val className = readString()!!
val classNameLoader = Class.forName(className).classLoader
return readParcelable(classNameLoader)!!
}

How to 'wrap' two classes with identical methods?

I have to handle two classes with identical methods but they don't implement the same interface, nor do they extend the same superclass. I'm not able / not allowed to change this classes and I don't construct instances of this classes I only get objects of this.
What is the best way to avoid lots of code duplication?
One of the class:
package faa;
public class SomethingA {
private String valueOne = null;
private String valueTwo = null;
public String getValueOne() { return valueOne; }
public void setValueOne(String valueOne) { this.valueOne = valueOne; }
public String getValueTwo() { return valueTwo; }
public void setValueTwo(String valueTwo) { this.valueTwo = valueTwo; }
}
And the other...
package foo;
public class SomethingB {
private String valueOne;
private String valueTwo;
public String getValueOne() { return valueOne; }
public void setValueOne(String valueOne) { this.valueOne = valueOne; }
public String getValueTwo() { return valueTwo; }
public void setValueTwo(String valueTwo) { this.valueTwo = valueTwo; }
}
(In reality these classes are larger)
My only idea is now to create a wrapper class in this was:
public class SomethingWrapper {
private SomethingA someA;
private SomethingB someB;
public SomethingWrapper(SomethingA someA) {
//null check..
this.someA = someA;
}
public SomethingWrapper(SomethingB someB) {
//null check..
this.someB = someB;
}
public String getValueOne() {
if (this.someA != null) {
return this.someA.getValueOne();
} else {
return this.someB.getValueOne();
}
}
public void setValueOne(String valueOne) {
if (this.someA != null) {
this.someA.setValueOne(valueOne);
} else {
this.someB.setValueOne(valueOne);
}
}
public String getValueTwo() {
if (this.someA != null) {
return this.someA.getValueTwo();
} else {
return this.someB.getValueTwo();
}
}
public void setValueTwo(String valueTwo) {
if (this.someA != null) {
this.someA.setValueTwo(valueTwo);
} else {
this.someB.setValueTwo(valueTwo);
}
}
}
But I'm not realy satisfied with this solution. Is there any better / more elegant way to solve this problem?

A better solution would be to create an interface to represent the unified interface to both classes, then to write two classes implementing the interface, one that wraps an A, and another that wraps a B:
public interface SomethingWrapper {
public String getValueOne();
public void setValueOne(String valueOne);
public String getValueTwo();
public void setValueTwo(String valueTwo);
};
public class SomethingAWrapper implements SomethingWrapper {
private SomethingA someA;
public SomethingWrapper(SomethingA someA) {
this.someA = someA;
}
public String getValueOne() {
return this.someA.getValueOne();
}
public void setValueOne(String valueOne) {
this.someA.setValueOne(valueOne);
}
public String getValueTwo() {
return this.someA.getValueTwo();
}
public void setValueTwo(String valueTwo) {
this.someA.setValueTwo(valueTwo);
}
};
and then another class just like it for SomethingBWrapper.

There, a duck-typed solution. This will accept any object with valueOne, valueTwo properties and is trivially extensible to further props.
public class Wrapper
{
private final Object wrapped;
private final Map<String, Method> methods = new HashMap<String, Method>();
public Wrapper(Object w) {
wrapped = w;
try {
final Class<?> c = w.getClass();
for (String propName : new String[] { "ValueOne", "ValueTwo" }) {
final String getter = "get" + propName, setter = "set" + propName;
methods.put(getter, c.getMethod(getter));
methods.put(setter, c.getMethod(setter, String.class));
}
} catch (Exception e) { throw new RuntimeException(e); }
}
public String getValueOne() {
try { return (String)methods.get("getValueOne").invoke(wrapped); }
catch (Exception e) { throw new RuntimeException(e); }
}
public void setValueOne(String v) {
try { methods.get("setValueOne").invoke(wrapped, v); }
catch (Exception e) { throw new RuntimeException(e); }
}
public String getValueTwo() {
try { return (String)methods.get("getValueTwo").invoke(wrapped); }
catch (Exception e) { throw new RuntimeException(e); }
}
public void setValueTwo(String v) {
try { methods.get("setValueTwo").invoke(wrapped, v); }
catch (Exception e) { throw new RuntimeException(e); }
}
}

You can use a dynamic proxy to create a "bridge" between an interface you define and the classes that conform but do not implement your interface.
It all starts with an interface:
interface Something {
public String getValueOne();
public void setValueOne(String valueOne);
public String getValueTwo();
public void setValueTwo(String valueTwo);
}
Now you need an InvocationHandler, that will just forward calls to the method that matches the interface method called:
class ForwardInvocationHandler implements InvocationHandler {
private final Object wrapped;
public ForwardInvocationHandler(Object wrapped) {
this.wrapped = wrapped;
}
#Override
public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable {
Method match = wrapped.getClass().getMethod(method.getName(), method.getParameterTypes());
return match.invoke(wrapped, args);
}
}
Then you can create your proxy (put it in a factory for easier usage):
SomethingA a = new SomethingA();
a.setValueOne("Um");
Something s = (Something)Proxy.newProxyInstance(
Something.class.getClassLoader(),
new Class[] { Something.class },
new ForwardInvocationHandler(a));
System.out.println(s.getValueOne()); // prints: Um
Another option is simpler but requires you to subclass each class and implement the created interface, simply like this:
class SomethingAImpl extends SomethingA implements Something {}
class SomethingBImpl extends SomethingB implements Something {}
(Note: you also need to create any non-default constructors)
Now use the subclasses instead of the superclasses, and refer to them through the interface:
Something o = new SomethingAImpl(); // o can also refer to a SomethingBImpl
o.setValueOne("Uno");
System.out.println(o.getValueOne()); // prints: Uno

i think your original wrapper class is the most viable option...however it can be done using reflection, your real problem is that the application is a mess...and reflection is might not be the method you are looking for
i've another proposal, which might be help: create a wrapper class which has specific functions for every type of classes...it mostly copypaste, but it forces you to use the typed thing as a parameter
class X{
public int asd() {return 0;}
}
class Y{
public int asd() {return 1;}
}
class H{
public int asd(X a){
return a.asd();
}
public int asd(Y a){
return a.asd();
}
}
usage:
System.out.println("asd"+h.asd(x));
System.out.println("asd"+h.asd(y));
i would like to note that an interface can be implemented by the ancestor too, if you are creating these classes - but just can't modify it's source, then you can still overload them from outside:
public interface II{
public int asd();
}
class XI extends X implements II{
}
class YI extends Y implements II{
}
usage:
II a=new XI();
System.out.println("asd"+a.asd());

You probably can exploit a facade along with the reflection - In my opinion it streamlines the way you access the legacy and is scalable too !
class facade{
public static getSomething(Object AorB){
Class c = AorB.getClass();
Method m = c.getMethod("getValueOne");
m.invoke(AorB);
}
...
}

I wrote a class to encapsulate the logging framework API's. Unfortunately, it's too long to put in this box.
The program is part of the project at http://www.github.com/bradleyross/tutorials with the documentation at http://bradleyross.github.io/tutorials. The code for the class bradleyross.library.helpers.ExceptionHelper in the module tutorials-common is at https://github.com/BradleyRoss/tutorials/blob/master/tutorials-common/src/main/java/bradleyross/library/helpers/ExceptionHelper.java.
The idea is that I can have the additional code that I want to make the exception statements more useful and I won't have to repeat them for each logging framework. The wrapper isn't where you eliminate code duplication. The elimination of code duplication is in not having to write multiple versions of the code that calls the wrapper and the underlying classes. See https://bradleyaross.wordpress.com/2016/05/05/java-logging-frameworks/
The class bradleyross.helpers.GenericPrinter is another wrapper that enables you to write code that works with both the PrintStream, PrintWriter, and StringWriter classes and interfaces.