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Junit categories - which category I am in?

I am using JUNIT's #categories and want to check in a method which category I am in.
for example
if (category.name == "sanity")
//do something
Is there any way to do that?
I want to avoid having to pass a parameter to this method because I have over 800 calls to it in the project

I believe you can do that the same way that can be used to determine if any other class has specific annotation and its values - use Java reflection mechanism.
As a quick example for your specific case you can make it like this:
#Category(Sanity.class)
public class MyTest {
#Test
public void testWhatever() {
if (isOfCategory(Sanity.class)) {
// specific actions needed for any tests that falls into Sanity category:
System.out.println("Running Sanity Test");
}
// test whatever you need...
}
private boolean isOfCategory(Class<?> categoryClass) {
Class<? extends MyTest> thisClass = getClass();
if (thisClass.isAnnotationPresent(Category.class)) {
Category category = thisClass.getAnnotation(Category.class);
List<Class<?>> values = Arrays.asList(category.value());
return values.contains(categoryClass);
}
return false;
}
}

Method returning alternative data structures based on execution result

Say I have a function that looks at a file and returns two results: recognized and unrecognized. When it returns the recognized result, I want the result to also contain a message but when it is unrecognized, no message is necessary.
public Result checkFile(File file) {
...
}
There are two ways I can think of to accomplish this...
Have the Result class like so:
class Result {
private Type type;
private String message;
enum Type {
RECOGNIZED, UNRECOGNIZED
}
}
Or do it like so:
class Result {
}
class Unrecognized extends Result {
}
class Recognized extends Result {
private String message;
}
I'm inclined to use the second method, even though I'd have to check the result using instanceof and I've read that instanceof should be avoided whenever possible, but doing this avoids having a null message when the result is unrecognized. For this example a null message wouldn't be much of an issue, but what if there is a lot more data associated with a recognized result? It seems like worse practice to me to instantiate a class that could have all null fields.
What is the best practice to handle this situation? Is there some standard method or pattern?

Two classes might be overkill, because of it being one and the same class of object. Also an enum with two values which merely reassemble true and false is not required. One class Result should suffice and this would also remove the demand for a common interface. I'd be all for "no complexity beyond necessary" ...
class RecognitionResult {
private String message = "default message";
private boolean recognized = false;
public Result() {}
public Result(boolean value) {
this.setRecognised(value);
}
public boolean setRecognised(boolean value) {
this.recognized = value;
}
public boolean setMessage(#NonNull String value) {
this.message = value;
}
public boolean getRecognised() {
return this.recognized;
}
#Nullable
public String getMessage() {
return this.recognized ? this.message : null;
}
}
then one can simply do:
return new RecognitionResult(true);
an interface for asynchronous callbacks might look alike this:
interface Recognition {
void OnComplete(RecognitionResult result);
}
or if you really want to optimize:
interface Recognition {
void OnSuccess(RecognitionResult result);
void OnFailure(RecognitionException e);
}

Of course there's no 'correct' design here - it's going to be a matter of opinion which way you go. However my view is that the modern trend in OOD is to minimise the use of extension and to use delegation and implementation of interfaces wherever possible.
As a general rule, whenever you think of using instanceof, reconsider your design.
This would be my suggestion:
interface Result {
boolean isRecognised();
String getMessage();
}
class RecognisedResult implements Result {
private final String message;
public boolean isRecognised() {
return true;
}
public String getMessage() {
return message;
}
}
class UnrecognisedResult implements Result {
public boolean isRecognised() {
return false;
}
public String getMessage() {
throw new UnsupportedOperationException("No message for unrecognised results");
}
}

you can look at the way Retrofit implement your concept of "recognised" and "message"
https://square.github.io/retrofit/2.x/retrofit/retrofit2/Response.html. it is similar to your first method.
what they did is to have a class called Response, containing a method called isSuccessful(), and a method called body() containing the payload if it's successful (or null if it is unsuccessful.
you can try some thing like the following
class Result {
private Type type;
private String message;
public bool isSuccessful(){
return type == RECOGNIZED;
}
public String getMessage(){
return message; //null if unrecognized.
}
enum Type {
RECOGNIZED, UNRECOGNIZED
}
}

The functional way to do this would be to use an Either type, which doesn’t come with the JDK, but is available in vavr library. Based on your comments on this thread, it appears you don’t clearly understand how type inheritance works. In that case, a functional solution may be overkill, and I’d suggest going with #sprinter’s solution.

Checking an object is correctly built in Java

This is a general issue/problem that I have come across. I wondered if anyone knows of any well suited design patterns or techniques.
private ExternalObject personObject;
private String name;
private int age;
private String address;
private String postCode;
public MyBuilderClass(ExternalObject obj)
this.personObject=obj;
build();
}
public build() {
setName(personObject.getName());
setAge(personObject.getAge());
setAddress(personObject.getAddress());
setPostCode(personObject.getPostCode());
.
.
. many more setters
}
The class above takes external objects from a queue and constructs MyBuilderClass objects.
A MyBuilderClass object is successfully built if all of the fields have been set to non-null non-empty values.
There will be many MyBuilderClass objects that cannot be built because data will be missing from the ExternalObject.
My problem, what is the best way to detect if an object has been correctly built?
I could check for null or empty values in the set methods and throw an exception. The problem with this approach is throwing exceptions is expensive and it will clogg the log files up because there will be many instances where an object cannot be built;
What other approaches could I use?

Correct me if I'm wrong: you are trying to find a good way to check if an object is valid, and if it is not, tell the client code about this without using an exception.
You can try a factory method:
private MyBuilderClass(ExternalObject obj)
this.personObject=obj;
build();
}
public static MyBuilderClass initWithExternalObject(ExternalObject obj) {
// check obj's properties...
if (obj.getSomeProperty() == null && ...) {
// invalid external object, so return null
return null;
} else {
// valid
MyBuilderClass builder = new MyBuilderClass(obj);
return builder.build();
}
}
Now you know whether an object is valid without using an exception. You just need to check whether the value returned by initWithExternalObject is null.

I wouldn't throw exceptions in cases that aren't exceptional. And as the only way for a constructor not to produce an object is to throw, you should not delay validation to the constructor.
I'd still recommend the constructor to throw if its results were to be invalid, but there should be a validation before that, so you don't even call the constructor with an invalid ExternalObject.
It's up to you if you want to implement that as a static method boolean MyBuilderClass.validate(ExternalObject) or by using the builder pattern with this validation.

Another approach for such a validation is to use java Annotations:
Make a simple annotaion class, let's say Validate:
#Target({ElementType.FIELD})
#Retention(RetentionPolicy.RUNTIME)
#interface Validate {
boolean required() default true;
}
then annotate the fields you want to be present as #Validate(required=true):
class MyBuilderClass {
private ExternalObject externalObject;
#Validate(required=true)
private String name;
#Validate(required=false) /*since it's a primitive field*/
private int age;
#Validate(required=true)
private String address;
#Validate(required=true)
private String postCode;
MyBuilderClass(ExternalObject externalObject) {
this.externalObject = externalObject;
build();
}
public void build() {
setName(personObject.getName());
setAge(personObject.getAge());
setAddress(personObject.getAddress());
setPostCode(personObject.getPostCode());
}
//.
//.
//. many more setters
}
And then add this method in the MyBuilderClass class, in order to check if your Object is built correctly:
public boolean isCorrectlyBuilt() throws IllegalAccessException {
boolean retVal = true;
for (Field f : getClass().getDeclaredFields()) {
f.setAccessible(true);
boolean isToBeChecked = f.isAnnotationPresent(Validate.class);
if (isToBeChecked) {
Validate validate = f.getAnnotation(Validate.class);
if (validate.required()/*==true*/) {
if (f.get(this) == null) {
retVal = false;
break;
/* return false; */
}
}
}
}
return retVal;
}
Here is an example of use :
public static void main(String[] args) throws Exception {
ExternalObject personObject = new ExternalObject();
personObject.setAge(20);
personObject.setName("Musta");
personObject.setAddress("Home");
personObject.setPostCode("123445678");
MyBuilderClass myBuilderClass = new MyBuilderClass(personObject);
System.out.println(myBuilderClass.isCorrectlyBuilt());
}
Output : true because the object is correctly built.
This will allow you to choose the fields that you want to be in the structure by reflection, without bringing those inherited from a base class.

As this previous answer suggests, here are 2 options either of which should be added after you have tried to set the variables.
use reflection to check whether any of the variables are null. (As mentioned in comments this will check all fields in this object but be careful with fields in any superclasses).
public boolean checkNull() throws IllegalAccessException {
for (Field f : getClass().getDeclaredFields())
if (f.get(this) != null)
return false;
return true;
}
perform a null check on each variable.
boolean isValidObject = !Stream.of(name, age, ...).anyMatch(Objects::isNull);
Previous answer

From what I've come across you could overwrite the equals method of your object and compare it with a valid example object. Its dirty and might only work in some cases.
Your approach is the best I could think of. Write a seperate method or class that has for example a static validate method. You could reuse it anywhere.

How can we test an Enum like is valueOf()?

G'day, errata ... My plan was as shown below. This update is to clarify and apologise for a late night question. The compile error was due to a problem elsewhere in the file.
Clarification: a simple Java enum, like this:
public enum ServiceSource
{
NONE,
URL,
FILE;
}
Want to checking like, isURL():
public boolean isURL(){
return (URL == this);
}
This works (and compiles) ... There's no question -- Correctly answered by: dasblinkenlight and Elliott Frisch. Thank you very much for your time.
see also:
Lookup enum by string value
How to test enum types?

Since this is an instance method, you need to check that this is equal to URL, like this:
public boolean isURL(){
return (URL == this);
}
Demo on ideone.

If you want to have methods that are polymorphic - i.e. exhibit different behaviour for different instances (values) of your enum class, my preference is to override a common method:
public enum ServiceSource {
NONE("no_value"),
URL("url"){
#Override
public boolean isURL() {
return true;
}
},
FILE("file");
private final String val;
private ServiceSource(String val) {
this.val = val;
}
public boolean isURL() {
return false;
}
}
But for methods that check whether this is specific enum value then adding an isXXX method for each constant seems very wasteful. Really, the very reason to use an enum, is so that you can write
if(thing == ServiceSource.URL)
Elsewhere in your code.

If I understand your question, the correct method in your enum is to use this like so,
public enum ServiceSource
{
NONE( "no_value" ),
URL( "url" ),
FILE( "file" );
ServiceSource(String v) {
text =v;
}
private String text;
public boolean isURL() {
return this == URL;
}
}

You can make a method on your Enum to check the value of itself like this:
public boolean isURL(){
return (URL == this);
}
But it's hard to see the value in this approach since every Object has a built in equals() method that accomplishes the same thing.
if (serviceSource.equals(ServiceSource.URL)) { ... }
This would be a more common and obvious way to check the assigned value of an Enum variable (or any variable for that matter). Taking the first approach would require you to have a new isX() method on your Enum; every time you add an Enum constant, you would probably want a new method to accompany it.

Letting the code try different things until it succeeds, neatly

This is the second time I found myself writing this kind of code, and decided that there must be a more readable way to accomplish this:
My code tries to figure something out, that's not exactly well defined, or there are many ways to accomplish it. I want my code to try out several ways to figure it out, until it succeeds, or it runs out of strategies. But I haven't found a way to make this neat and readable.
My particular case: I need to find a particular type of method from an interface. It can be annotated for explicitness, but it can also be the only suitable method around (per its arguments).
So, my code currently reads like so:
Method candidateMethod = getMethodByAnnotation(clazz);
if (candidateMethod == null) {
candidateMethod = getMethodByBeingOnlyMethod(clazz);
}
if (candidateMethod == null) {
candidateMethod = getMethodByBeingOnlySuitableMethod(clazz);
}
if (candidateMethod == null) {
throw new NoSuitableMethodFoundException(clazz);
}
There must be a better way…
Edit: The methods return a method if found, null otherwise. I could switch that to try/catch logic, but that hardly makes it more readable.
Edit2: Unfortunately, I can accept only one answer :(

To me it is readable and understandable. I'd simply extract the ugly part of the code to a separate method (following some basic principles from "Robert C.Martin: Clean Code") and add some javadoc (and apologies, if necessary) like that:
//...
try {
Method method = MethodFinder.findMethodIn(clazz);
catch (NoSuitableMethodException oops) {
// handle exception
}
and later on in MethodFinder.java
/**
* Will find the most suitable method in the given class or throw an exception if
* no such method exists (...)
*/
public static Method findMethodIn(Class<?> clazz) throws NoSuitableMethodException {
// all your effort to get a method is hidden here,
// protected with unit tests and no need for anyone to read it
// in order to understand the 'main' part of the algorithm.
}

I think for a small set of methods what you're doing is fine.
For a larger set, I might be inclined to build a Chain of Responsibility, which captures the base concept of trying a sequence of things until one works.

I don't think that this is such a bad way of doing it. It is a bit verbose, but it clearly conveys what you are doing, and is easy to change.
Still, if you want to make it more concise, you can wrap the methods getMethod* into a class which implements an interface ("IMethodFinder") or similar:
public interface IMethodFinder{
public Method findMethod(...);
}
Then you can create instances of you class, put them into a collection and loop over it:
...
Method candidateMethod;
findLoop:
for (IMethodFinder mf: myMethodFinders){
candidateMethod = mf.findMethod(clazz);
if (candidateMethod!=null){
break findLoop;
}
}
if (candidateMethod!=null){
// method found
} else {
// not found :-(
}
While arguably somewhat more complicated, this will be easier to handle if you e.g. need to do more work between calling the findMethods* methods (such as more verification that the method is appropriate), or if the list of ways to find methods is configurable at runtime...
Still, your approach is probably OK as well.

I'm sorry to say, but the method you use seems to be the widely accepted one. I see a lot of code like that in the code base of large libraries like Spring, Maven etc.
However, an alternative would be to introduce a helper interface that can convert from a given input to a given output. Something like this:
public interface Converter<I, O> {
boolean canConvert(I input);
O convert(I input);
}
and a helper method
public static <I, O> O getDataFromConverters(
final I input,
final Converter<I, O>... converters
){
O result = null;
for(final Converter<I, O> converter : converters){
if(converter.canConvert(input)){
result = converter.convert(input);
break;
}
}
return result;
}
So then you could write reusable converters that implement your logic. Each of the converters would have to implement the canConvert(input) method to decide whether it's conversion routines will be used.
Actually: what your request reminds me of is the Try.these(a,b,c) method in Prototype (Javascript).
Usage example for your case:
Let's say you have some beans that have validation methods. There are several strategies to find these validation methods. First we'll check whether this annotation is present on the type:
// retention, target etc. stripped
public #interface ValidationMethod {
String value();
}
Then we'll check whether there's a method called "validate". To make things easier I assume, that all methods define a single parameter of type Object. You may choose a different pattern. Anyway, here's sample code:
// converter using the annotation
public static final class ValidationMethodAnnotationConverter implements
Converter<Class<?>, Method>{
#Override
public boolean canConvert(final Class<?> input){
return input.isAnnotationPresent(ValidationMethod.class);
}
#Override
public Method convert(final Class<?> input){
final String methodName =
input.getAnnotation(ValidationMethod.class).value();
try{
return input.getDeclaredMethod(methodName, Object.class);
} catch(final Exception e){
throw new IllegalStateException(e);
}
}
}
// converter using the method name convention
public static class MethodNameConventionConverter implements
Converter<Class<?>, Method>{
private static final String METHOD_NAME = "validate";
#Override
public boolean canConvert(final Class<?> input){
return findMethod(input) != null;
}
private Method findMethod(final Class<?> input){
try{
return input.getDeclaredMethod(METHOD_NAME, Object.class);
} catch(final SecurityException e){
throw new IllegalStateException(e);
} catch(final NoSuchMethodException e){
return null;
}
}
#Override
public Method convert(final Class<?> input){
return findMethod(input);
}
}
// find the validation method on a class using the two above converters
public static Method findValidationMethod(final Class<?> beanClass){
return getDataFromConverters(beanClass,
new ValidationMethodAnnotationConverter(),
new MethodNameConventionConverter()
);
}
// example bean class with validation method found by annotation
#ValidationMethod("doValidate")
public class BeanA{
public void doValidate(final Object input){
}
}
// example bean class with validation method found by convention
public class BeanB{
public void validate(final Object input){
}
}

You may use Decorator Design Pattern to accomplish different ways of finding out how to find something.
public interface FindMethod
{
public Method get(Class clazz);
}
public class FindMethodByAnnotation implements FindMethod
{
private final FindMethod findMethod;
public FindMethodByAnnotation(FindMethod findMethod)
{
this.findMethod = findMethod;
}
private Method findByAnnotation(Class clazz)
{
return getMethodByAnnotation(clazz);
}
public Method get(Class clazz)
{
Method r = null == findMethod ? null : findMethod.get(clazz);
return r == null ? findByAnnotation(clazz) : r;
}
}
public class FindMethodByOnlyMethod implements FindMethod
{
private final FindMethod findMethod;
public FindMethodByOnlyMethod(FindMethod findMethod)
{
this.findMethod = findMethod;
}
private Method findByOnlyMethod(Class clazz)
{
return getMethodOnlyMethod(clazz);
}
public Method get(Class clazz)
{
Method r = null == findMethod ? null : findMethod.get(clazz);
return r == null ? findByOnlyMethod(clazz) : r;
}
}
Usage is quite simple
FindMethod finder = new FindMethodByOnlyMethod(new FindMethodByAnnotation(null));
finder.get(clazz);

... I could switch that to try/catch logic, but that hardly makes it more readable.
Changing the signature of the get... methods so you can use try / catch would be a really bad idea. Exceptions are expensive and should only be used for "exceptional" conditions. And as you say, the code would be less readable.

What is bothering you is the repeating pattern used for flow control--and it should bother you--but there isn't too much to be done about it in Java.
I get really annoyed at repeated code & patterns like this, so for me it would probably be worth it to extract the repeated copy & paste control code and put it in it's own method:
public Method findMethod(Class clazz)
int i=0;
Method candidateMethod = null;
while(candidateMethod == null) {
switch(i++) {
case 0:
candidateMethod = getMethodByAnnotation(clazz);
break;
case 1:
candidateMethod = getMethodByBeingOnlyMethod(clazz);
break;
case 2:
candidateMethod = getMethodByBeingOnlySuitableMethod(clazz);
break;
default:
throw new NoSuitableMethodFoundException(clazz);
}
return clazz;
}
Which has the disadvantage of being unconventional and possibly more verbose, but the advantage of not having as much repeated code (less typos) and reads easier because of there being a little less clutter in the "Meat".
Besides, once the logic has been extracted into it's own class, verbose doesn't matter at all, it's clarity for reading/editing and for me this gives that (once you understand what the while loop is doing)
I do have this nasty desire to do this:
case 0: candidateMethod = getMethodByAnnotation(clazz); break;
case 1: candidateMethod = getMethodByBeingOnlyMethod(clazz); break;
case 2: candidateMethod = getMethodByBeingOnlySuitableMethod(clazz); break;
default: throw new NoSuitableMethodFoundException(clazz);
To highlight what's actually being done (in order), but in Java this is completely unacceptable--you'd actually find it common or preferred in some other languages.
PS. This would be downright elegant (damn I hate that word) in groovy:
actualMethod = getMethodByAnnotation(clazz) ?:
getMethodByBeingOnlyMethod(clazz) ?:
getMethodByBeingOnlySuitableMethod(clazz) ?:
throw new NoSuitableMethodFoundException(clazz) ;
The elvis operator rules. Note, the last line may not actually work, but it would be a trivial patch if it doesn't.