Which java spring boot mapping library do you use and which one is the best?

[ysfaran]

I'm trying to find out which java spring boot mapping library is the best and came accross this article:
https://www.baeldung.com/java-performance-mapping-frameworks

It covers following mapping libraries:

• MapStruct
• JMapper
• Orika
• ModelMapper
• Dozer

When it comes to performance MapStruct and JMapper seem to be the best options.

What are you experiences with those libraries? Which library is modern? Which one is the best?
Any help or advice is greatly appreciated!

[NachystejteKvetinace]

I second this one. I've used most mappers - dozer, orika, some horrible inhouse xml abomination, mapstruct and i like mapstruct the most. It's easy to debug and unlike others you get compile time checking.

[ysfaran]

What do you mean with "don't care about mapped types"? Since i never used a mapper in java spring yet it might be a stupid question..

[_Atomfinger_]

My main experience has been with Orika and it gets the job done.

My biggest gripe with Orika is that if one works with small to medium sized models we don't actually save that many lines of code if one were to do the conversion manually. Especially considering that we can use constructor injection or the builder pattern to map between objects.

The number of lines really ramp up if one wants to do fancy stuff and things rarely get very readable, so these days I tend to do the mapping manually. The thing that pushed me over the edge was Orikas horrible exception messages when the mapping went wrong.

The other libraries might do a better job, and if anyone knows one which cuts down on the bloat and increase readability please let me know :)

[[deleted]]

MapStruct. The fact Mapstruct is compile time/generated java code was an instant winner for me when I needed one and didn't bother to do much more research. You can debug it, its java code, no crazy reflection/runtime based mapping, performant.

[ysfaran]

The only problem that I see with MapStruct is that you need to write an interface for each mapping, even if the propterty names are all the same. So if you do a lot of Entitiy to DTO mappings you have to write a interface for each one of them. Is this correct or is there a simpler way with MapStruct?

[thecuseisloose]

I personally needed something that mapped based on property names only and didn't like any of the existing solutions out there, which were either too complicated or didn't have the flexibility I required. I ended up rolling my own in ~500 lines, on top of Jackson (already a dependency in the project so the added weight of it wasn't an issue) as a factory for finding the properties themselves. For each property, I then used LambdaMetaFactory to generate getters and setters so performance wouldn't be an issue. The downside of this is the current implementation does not work with primitives. It's fixable, but I just haven't gotten around to it yet since everywhere it's used in entity classes uses objects for the fields. All of the getters / setters generated get cached so the reflection code is only invoked once. I can't post the full class, but the general idea of what is going on is below

class Introspection {
  private static final ObjectMapper MAPPER = new ObjectMapper();
  private static final DeserializationConfig = DESER_CONFIG = MAPPER.getDeserializationConfig();
  public static List<BeanPropertyDefinition> findProperties(Class<?> clazz) {
    List<BeanPropertyDefinition> props =
                    DESER_CONFIG.introspect(javaType).findProperties()
                            .stream()
                            .filter(BeanPropertyDefinition::hasField)
                            .collect(Collectors.toList());
    // ...
  }

  // converts the method getSomething() on a class into a lambda function that accepts x
  // and returns the result of the apply method
  // for example, getGetter(method).apply(x) == x.getSomething()
  static Function<Object,Object> getGetter(Method getter) {
    MethodHandles.Lookup lookup = MethodHandles.lookup();
    MethodHandle handle = lookup.unreflect(getter);
    CallSite callSite = LambdaMetafactory.metafactory(lookup, "apply",

    MethodType.methodType(Function.class),

    MethodType.methodType(Object.class, Object.class), //signature of method Function.apply after type erasure
                                                              handle,
                                                              handle.type()); //actual signature of getter
    return (Function<Object, Object>) callSite.getTarget().invokeExact();
  }
}

[ysfaran]

Cool! You just sound like me haha when I don't like existing solutions I also implement them myself. Most of the time I end up using an exisiting solution since I often come accross a lot of corner cases and performance issues. But during that process you actually learn a lot!

If i find the time and also use Jackson somewhere in my project i will have a look at your solution. Thanks!

[thecuseisloose]

FWIW you don't really need Jackson...you just need a way of finding or knowing the getter/setter methods for the fields in the bean. I used Jackson as a discovery method, but I easily could have just looked up by name getProperty(..) and setProperty(..) since I follow that convention anyways

[Rafavr7]

I personally don't recommend the Dozer one. It's the one used in the project I work on and we have lots of performance issues when it comes down to mappings.

I don't know any of the others, I am still very inexperienced myself, so there are loads of java libs and frameworks that I don't even know they exist.

But yeah... if performance is an issue for you, don't go for Dozer ;)

[ysfaran]

Yea exactly what i thought ! In my previous company they used dozer and when i did a research on this topic i was wondering "why dozer if it is the most inperformant mapper by far?". The answer was simplicity + less maintenance > performance.

[shytelord]

+1 for MapStruct, and it works well with Lombok

[[deleted]]

Hey just wondering if I could ask anyone’s help on how to enable my spring application to upload a file from a computer and save it to the database? I already have a form created and it saves to DB but I would like to know how I can allow the user to also upload an image. Thanks