Micronaut Mappers

[prabalpsr]

We have just started to leverage @Mapper/@mapping mapping capability provided by Micronaut that leverages Introspection, since it meant that we don't have to use MapStruct (which is primarily Java and we use kotlin across the board).

Though this feature is experimental and has very high level documentation, our early evaluation found it to be working for our initial usecases. However, we have started facing issues with our more larger mappings that have > 50/60 fields with a mix of lists/sets/maps etc. The issue is getting more pronounced when:

1. We have Data classes that are spread between 2 Modules (even though they have @introspection annotations)
2. We have both KSP and KAPT annotation processing enabled or a mix
3. We have complex collection objects like lists/sets/maps
4. We have defaults of Null on the data class attributes

If anyone has faced and solved these issues, please let us know anything that you have learnt to fix these issues. Also if there are best practices, does/don'ts and reference implementation, it would be great to look at them.

Thanks in advance

[yawkat]

What do you mean specifically by "issues"?

[prabalpsr]

even though we have all the mappings verified, our test fail typically with error java.lang.ClassCastException: class java.util.ArrayList cannot be cast to class java.lang.String (java.util.ArrayList and java.lang.String are in module java.base of loader 'bootstrap')

We have been generally able to identify some issue with KSP generated intospected code like

public Object instantiateInternal(Object[] var1) {
        int var2 = 0;
        if ((String)var1[0] == null) {
            var2 |= 1;
        }

        if ((String)var1[1] == null) {
            var2 |= 2;
        }

        if ((String)var1[2] == null) {
            var2 |= 4;
        }

        if ((List)var1[3] == null) {
            var2 |= 8;
        }

        if ((String)var1[4] == null) {
            var2 |= 16;
        }
...
...
...
        if ((String)var1[31] == null) {
            var2 |= Integer.MIN_VALUE;
        }

        int var3 = 0;
        if ((String)var1[0] == null) {
            var3 |= 1;
        }

        if ((String)var1[1] == null) {
            var3 |= 2;
        }

        if ((String)var1[2] == null) {
            var3 |= 4;
        }

        if ((String)var1[3] == null) {
            var3 |= 8;
        }
...
...
...
        if ((Boolean)var1[30] == null) {
            var3 |= 1073741824;
        }

        if ((String)var1[31] == null) {
            var3 |= Integer.MIN_VALUE;
        }

        int var4 = 0;
        if ((String)var1[0] == null) {
            var4 |= 1;
        }

        if ((List)var1[1] == null) {
            var4 |= 2;
        }
return new CustomResponseObject((String)var1[0], (String)var1[1], (String)var1[2], (List)var1[3], (String)var1[4], (String)var1[5], (Map)var1[6], (String)var1[7], (String)var1[8], (DollarDueResponse)var1[9], (DollarDueResponse)var1[10], (String)var1[11], (String)var1[12], (String)var1[13], (Date)var1[14], (Date)var1[15], (String)var1[16], (String)var1[17], (String)var1[18], (String)var1[19], (String)var1[20], (String)var1[21], (String)var1[22], (String)var1[23], (String)var1[24], (LocationResponse)var1[25], (ProfileResponse)var1[26], (String)var1[27], (String)var1[28], (String)var1[29], (String)var1[30], (String)var1[31], (String)var1[32], (String)var1[33], (String)var1[34], (String)var1[35], (String)var1[36], (String)var1[37], (Boolean)var1[38], (Boolean)var1[39], (String)var1[40], (String)var1[41], (String)var1[42], (Map)var1[43], (List)var1[44], (List)var1[45], (List)var1[46], (DefaultResponse)var1[47], (Boolean)var1[48], (Integer)var1[49], (List)var1[50], (Cards)var1[51], (Boolean)var1[52], (List)var1[53], (Bags)var1[54], (List)var1[55], (Boolean)var1[56], (Boolean)var1[57], (Boolean)var1[58], (DeliveryResponse)var1[59], (Set)var1[60], (FullContentsResponse)var1[61], (Boolean)var1[62], (String)var1[63], (String)var1[64], (List)var1[65], var2, var3, var4, (DefaultConstructorMarker)null);
}

Please note that the var2, var3, var4 are being analysed for only till index field of 31 while the object has 66 fields. Plus the CustomResponseObject() is being created by passing additional values like var2, 3, 4 and null...

[prabalpsr]

Please note that the same mapping code worked fine when I removed the defaults for the attributes within CustomResponseObject. The instospected code in this case was

public Object instantiateInternal(Object[] var1) {
        byte var2 = 0;
        int var3 = 0;
        if ((String)var1[31] == null) {
            var3 |= Integer.MIN_VALUE;
        }

        byte var4 = 0;

       return new CustomResponseObject((String)var1[0], (String)var1[1], (String)var1[2], (List)var1[3], (String)var1[4], (String)var1[5], (Map)var1[6], (String)var1[7], (String)var1[8], (DollarDueResponse)var1[9], (DollarDueResponse)var1[10], (String)var1[11], (String)var1[12], (String)var1[13], (Date)var1[14], (Date)var1[15], (String)var1[16], (String)var1[17], (String)var1[18], (String)var1[19], (String)var1[20], (String)var1[21], (String)var1[22], (String)var1[23], (String)var1[24], (LocationResponse)var1[25], (ProfileResponse)var1[26], (String)var1[27], (String)var1[28], (String)var1[29], (String)var1[30], (String)var1[31], (String)var1[32], (String)var1[33], (String)var1[34], (String)var1[35], (String)var1[36], (String)var1[37], (Boolean)var1[38], (Boolean)var1[39], (String)var1[40], (String)var1[41], (String)var1[42], (Map)var1[43], (List)var1[44], (List)var1[45], (List)var1[46], (DefaultResponse)var1[47], (Boolean)var1[48], (Integer)var1[49], (List)var1[50], (Cards)var1[51], (Boolean)var1[52], (List)var1[53], (Bags)var1[54], (List)var1[55], (Boolean)var1[56], (Boolean)var1[57], (Boolean)var1[58], (DeliveryResponse)var1[59], (Set)var1[60], (FullContentsResponse)var1[61], (Boolean)var1[62], (String)var1[63], (String)var1[64], (List)var1[65], var2, var3, var4, (DefaultConstructorMarker)null);
}

[prabalpsr]

the same Object when introspected with Kapt generates as

public Object instantiateInternal(Object[] var1) {
        return new CustomResponseObject((String)var1[0], (String)var1[1], (String)var1[2], (List)var1[3], (String)var1[4], (String)var1[5], (Map)var1[6], (String)var1[7], (String)var1[8], (DollarDueResponse)var1[9], (DollarDueResponse)var1[10], (String)var1[11], (String)var1[12], (String)var1[13], (Date)var1[14], (Date)var1[15], (String)var1[16], (String)var1[17], (String)var1[18], (String)var1[19], (String)var1[20], (String)var1[21], (String)var1[22], (String)var1[23], (String)var1[24], (LocationResponse)var1[25], (ProfileResponse)var1[26], (String)var1[27], (String)var1[28], (String)var1[29], (String)var1[30], (String)var1[31], (String)var1[32], (String)var1[33], (String)var1[34], (String)var1[35], (String)var1[36], (String)var1[37], (Boolean)var1[38], (Boolean)var1[39], (String)var1[40], (String)var1[41], (String)var1[42], (Map)var1[43], (List)var1[44], (List)var1[45], (List)var1[46], (DefaultResponse)var1[47], (Boolean)var1[48], (Integer)var1[49], (List)var1[50], (Cards)var1[51], (Boolean)var1[52], (List)var1[53], (Bags)var1[54], (List)var1[55], (Boolean)var1[56], (Boolean)var1[57], (Boolean)var1[58], (DeliveryResponse)var1[59], (Set)var1[60], (FullContentsResponse)var1[61], (Boolean)var1[62], (String)var1[63], (String)var1[64], (List)var1[65]);
    }

[graemerocher]

if you have spotted differences please report issues and attach examples. Thanks.