Support configuring the Jackson Object Mapper

[lorrin]

This change provides a getter for the Jackson Object Mapper so that Pippo applications can customize it as they need. E.g. I have this in my onInit:

ContentTypeEngineapplicationJsonEngine = getContentTypeEngine(APPLICATION_JSON);
if (applicationJsonEngineinstanceofJacksonJsonEngine) {
JacksonJsonEnginejacksonJsonEngine = (JacksonJsonEngine) applicationJsonEngine;
ObjectMapperobjectMapper = jacksonJsonEngine.getObjectMapper();
objectMapper.registerModule(newJdk8Module());
objectMapper.registerModule(newGuavaModule());
} else {
thrownewIllegalStateException(String.format(
"Cannot launch without Jackson engine registered to handle %s content.", APPLICATION_JSON));
}

[coveralls]

Coverage decreased (-0.003%) to 18.362% when pulling f97b923 on lorrin:jackson_om_config into f61b7d7 on decebals:master.

[decebals]

Thanks! I will take a look.
It's possible to customize Jackson Object Mapper, see #274.

[decebals]

In the end, I don't see the the difference. You replaced getObjectMapper method with constructObjectMapper (by the way, I believe that createObjectMapper is a better name for a factory method) .
Correct me if I am wrong?

[decebals]

It's enough to make this method public.

[lorrin]

Hi, I hadn't looked at #274 before submitting this. I agree create instead of construct would be a better name for the factory method.

It is not enough to make getObjectMapper public, because it creates a new ObjectMapper every time it is called. I wanted to be able to get the already-created ObjectMapper and make my own modifications to it.

I think the #274 pattern is probably cleanest, even though a bit more verbose. I propose the following:

1. rename the existing creation method to create
2. add a get that returns the previously created OM
3. leave get protected so that users are pushed to follow the customize jackson objectMapper #274 pattern

What would be different is that when I create my own ObjectMapper, I would just extend JacksonJsonEngine and override it's create method to do super, get the result, apply the changes. I don't have to care about the abstract parent class or reimplementing things it does that I want to preserve. I'll update this PR.

[lorrin]

Never mind, I hadn't fully understood the #274 pattern until I tried it. You're right, the changes I submitted weren't needed to customize Jackson easily. I've kept this PR alive as a simple rename from get to create for the factory method. Thanks for the help.

[coveralls]

Coverage remained the same at 18.365% when pulling ffdc51d on lorrin:jackson_om_config into f61b7d7 on decebals:master.

[decebals]

The rename is good but we have a problem because we brake the API, without a very good reason and I am sure that they are people that use this method (getObjectMapper) already.

[lorrin]

Alright, I'll close this then. Thanks for your help.

[lorrin]

BTW, if anyone stumbles across this looking for info on how to follow the #274 pattern, it's like this:

JacksonJsonEnginecustomEngine = newJacksonJsonEngine(){
@Overridepublicvoidinit(Applicationapplication) {
super.init(application);
objectMapper.registerModule(newJdk8Module());
objectMapper.registerModule(newGuavaModule());
}
};
customEngine.init(this);
getContentTypeEngines().setContentTypeEngine(customEngine);