My rule is, don't use a dependency to implement your core business. Is JSON parsing our core business? No, so why would we ever write -- and thereby commit to supporting for its entire lifetime -- JSON parsing code? All the code you write and support should be directly tied to what you as a business decide are your fundamental value propositions. Everything else you write is just fat waiting to be cut by someone who knows how to write a business case.
To be clear, this is about the lifetime support of code. It's very, very rare that code can be written once and never touched. But that long tail of support eats up time and money, and is almost always discounted in these conversations. I don't even care that Jackson JSON parsing has years of work behind it, when I can hack together a JSON parser in a day. I care that Jackson will continue to improve their offering without any further input, while that's not true of my version.
To be clear, this is about the lifetime support of code. It's very, very rare that code can be written once and never touched. But that long tail of support eats up time and money, and is almost always discounted in these conversations. I don't even care that Jackson JSON parsing has years of work behind it, when I can hack together a JSON parser in a day. I care that Jackson will continue to improve their offering without any further input, while that's not true of my version.