Johnzon 1.0.1 change in behaviour for final objects

[dave]

Hi,

I am attempting to upgrade from TomEE 7.0.4 (Johnzon 1.0.0) to TomEE 7.1.0
(Johnzon 1.0.1) and have encountered a change in behaviour with JSON
deserialization. The below test passes with Johnzon 1.0.0 but fails with
1.0.1.

Tracing this through with the different Johnzon versions it appears the
cause is FieldAccessMode.field() method excluding final fields in 1.0.1.
Johnzon no longer regards the map field "m" as writeable so silently skips
attempting to put its contents. Removing the final modifier from the map
avoids the issue.

Is this behaviour considered erroneous?

Thanks,
Dave

public class JohnzonMapperTest
{
@Test
public void testFinalMap()
throws Exception
{
WithFinalMap o = new
MapperBuilder().build().readObject("{\"m\":{\"A\":\"a\"}}", WithMap.class);
assertEquals("a", o.m.get("A"));
}


public static class WithFinalMap
{
public final Map<String, Object> m = new HashMap<>();
}
}




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[Romain Manni-Bucau]

Hi Dave,

yes this is tracked in https://issues.apache.org/jira/browse/JOHNZON-142
and 77

long story short setting final fields was not intended and lead to
inconsistencies so this behavior has been dropped.

if you need the previous behavior and are sure it is intended you can get
it back using:

WithFinalMap o = new MapperBuilder()
.setAccessMode(new FieldAccessMode(true, true) {
@Override
protected Map<String, Field> fields(Class<?> clazz,
boolean includeFinalFields) {
return super.fields(clazz, true);
}
})
.build().readObject("{\"m\":{\"A\":\"a\"}}", WithFinalMap.class);


That said i wouldnt recommand you to do it and maybe use the constructor
rather than this old hack

Romain Manni-Bucau
@rmannibucau <https://twitter.com/rmannibucau> | Blog
<https://rmannibucau.metawerx.net/> | Old Blog
<http://rmannibucau.wordpress.com> | Github <https://github.com/rmannibucau> |
LinkedIn <https://www.linkedin.com/in/rmannibucau> | Book
<https://www.packtpub.com/application-development/java-ee-8-high-performance>

Post by dave
Hi,
I am attempting to upgrade from TomEE 7.0.4 (Johnzon 1.0.0) to TomEE 7.1.0
(Johnzon 1.0.1) and have encountered a change in behaviour with JSON
deserialization. The below test passes with Johnzon 1.0.0 but fails with
1.0.1.
Tracing this through with the different Johnzon versions it appears the
cause is FieldAccessMode.field() method excluding final fields in 1.0.1.
Johnzon no longer regards the map field "m" as writeable so silently skips
attempting to put its contents. Removing the final modifier from the map
avoids the issue.
Is this behaviour considered erroneous?
Thanks,
Dave
public class JohnzonMapperTest
{
@Test
public void testFinalMap()
throws Exception
{
WithFinalMap o = new
MapperBuilder().build().readObject("{\"m\":{\"A\":\"a\"}}", WithMap.class);
assertEquals("a", o.m.get("A"));
}
public static class WithFinalMap
{
public final Map<String, Object> m = new HashMap<>();
}
}
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[dave]

Thanks for the explanation Romain.

In this case I have been able to remove the final modifiers from the
affected fields. This was the simplest thing to do as the mapping was being
done automatically in REST API calls rather than explicitly via Johnzon.

The problem did take some tracking down. I can understand the Map field m
not being settable if final, but this also has the effect of causing Johnzon
to silently not set the values within the map even if the map has been
initialised. I presume the same would apply for any nested final objects
containing settable non-final fields. From my perspective it would be
preferable to either support this, or fail fast with an error in such cases.

Regards,
Dave

Post by Romain Manni-Bucau
Hi Dave,
yes this is tracked in https://issues.apache.org/jira/browse/JOHNZON-142
and 77
long story short setting final fields was not intended and lead to
inconsistencies so this behavior has been dropped.
if you need the previous behavior and are sure it is intended you can get
WithFinalMap o = new MapperBuilder()
.setAccessMode(new FieldAccessMode(true, true) {
@Override
boolean includeFinalFields) {
return super.fields(clazz, true);
}
})
.build().readObject("{\"m\":{\"A\":\"a\"}}", WithFinalMap.class);
That said i wouldnt recommand you to do it and maybe use the constructor
rather than this old hack
Romain Manni-Bucau
Le lun. 29 oct. 2018 à 00:10, dave &lt;

Post by dave
Hi,
I am attempting to upgrade from TomEE 7.0.4 (Johnzon 1.0.0) to TomEE 7.1.0
(Johnzon 1.0.1) and have encountered a change in behaviour with JSON
deserialization. The below test passes with Johnzon 1.0.0 but fails with
1.0.1.
Tracing this through with the different Johnzon versions it appears the
cause is FieldAccessMode.field() method excluding final fields in 1.0.1.
Johnzon no longer regards the map field "m" as writeable so silently skips
attempting to put its contents. Removing the final modifier from the map
avoids the issue.
Is this behaviour considered erroneous?
Thanks,
Dave
public class JohnzonMapperTest
{
@Test
public void testFinalMap()
throws Exception
{
WithFinalMap o = new
MapperBuilder().build().readObject("{\"m\":{\"A\":\"a\"}}",
WithMap.class);
assertEquals("a", o.m.get("A"));
}
public static class WithFinalMap
{
}
}
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[Romain Manni-Bucau]

Failling fast is not really an option since it is the correct behavior and
does not violate java contract.

We can tune some config like the extsing readAttributeBeforeWrite to reuse
it to read your map and enrich it instead of overwriting it but it can also
lead to inconsistent values when reusing mapped objects.
Getting the map then clearing it before setting it is an option but not
sure it does worth it since the fix is very easy (a setter, dropping final,
@JohnzonAny in an object etc).

Post by dave
Thanks for the explanation Romain.
In this case I have been able to remove the final modifiers from the
affected fields. This was the simplest thing to do as the mapping was being
done automatically in REST API calls rather than explicitly via Johnzon.
The problem did take some tracking down. I can understand the Map field m
not being settable if final, but this also has the effect of causing Johnzon
to silently not set the values within the map even if the map has been
initialised. I presume the same would apply for any nested final objects
containing settable non-final fields. From my perspective it would be
preferable to either support this, or fail fast with an error in such cases.
Regards,
Dave

Post by Romain Manni-Bucau
Hi Dave,
yes this is tracked in https://issues.apache.org/jira/browse/JOHNZON-142
and 77
long story short setting final fields was not intended and lead to
inconsistencies so this behavior has been dropped.
if you need the previous behavior and are sure it is intended you can get
WithFinalMap o = new MapperBuilder()
.setAccessMode(new FieldAccessMode(true, true) {
@Override
boolean includeFinalFields) {
return super.fields(clazz, true);
}
})
.build().readObject("{\"m\":{\"A\":\"a\"}}", WithFinalMap.class);
That said i wouldnt recommand you to do it and maybe use the constructor
rather than this old hack
Romain Manni-Bucau
&lt;

https://www.packtpub.com/application-development/java-ee-8-high-performance&gt
;

Post by Romain Manni-Bucau
Le lun. 29 oct. 2018 à 00:10, dave &lt;

Post by dave
Hi,
I am attempting to upgrade from TomEE 7.0.4 (Johnzon 1.0.0) to TomEE 7.1.0
(Johnzon 1.0.1) and have encountered a change in behaviour with JSON
deserialization. The below test passes with Johnzon 1.0.0 but fails with
1.0.1.
Tracing this through with the different Johnzon versions it appears the
cause is FieldAccessMode.field() method excluding final fields in 1.0.1.
Johnzon no longer regards the map field "m" as writeable so silently skips
attempting to put its contents. Removing the final modifier from the map
avoids the issue.
Is this behaviour considered erroneous?
Thanks,
Dave
public class JohnzonMapperTest
{
@Test
public void testFinalMap()
throws Exception
{
WithFinalMap o = new
MapperBuilder().build().readObject("{\"m\":{\"A\":\"a\"}}",
WithMap.class);
assertEquals("a", o.m.get("A"));
}
public static class WithFinalMap
{
}
}
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