Reflection Free Parsing
&
Immutable Data Model
Moshi Code Gen
=
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ELI5 Definitions
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Immutable
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Immutable
Not Mutable
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Immutable
Not Mutable
Hard to change
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Reflection Free
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Reflection Free
Not Dynamic
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Reflection Free
Not Dynamic
Compiled
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Why does
this matter?
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Mike’s first
month at the
New York
Times
Application startup time
was horrible. He started
digging and found some
issues.
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One big culprit was
parsing a configuration
file that we needed for
Application start up
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One big culprit was
parsing a configuration
file that we needed for
Application start up
Roughly 700ms wasted!
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What was the
issue? Why did it
take so long?
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What was the issue?
Why did it take so
long?
Reflection!
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How shall we fix this?
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We could write our own
type adapters
How shall we fix this?
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Annotation Processing
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Annotation Processing
•AutoValue
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Annotation Processing
•AutoValue
•Immutables.org
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Unfun stuff taken care
of for us
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Unfun stuff taken care
of for us
•toString()
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Unfun stuff taken care
of for us
•toString()
•equals()
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Unfun stuff taken care
of for us
•toString()
•equals()
•hashCode()
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Copy methods for
mutate
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Immutable Data Model
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Immutable Data Model
•Thread safety
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Immutable Data Model
•Thread safety
•Reduced Complexity
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Immutable Data Model
•Thread safety
•Reduced Complexity
•No more bugs caused by
mutation
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Reflection free type
adapters
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All was well!
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Kotlin came and we
have data classes
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Data classes give us
most of what we
needed
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Data classes give us
most of what we
needed
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Data classes give us
most of what we
needed
•Unfun methods
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Data classes give us
most of what we
needed
•Unfun methods
•Copy methods
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Data classes give us
most of what we
needed
•Unfun methods
•Copy methods
•Immutability
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Data classes give us
most of what we
needed
•Unfun methods
•Copy methods
•Immutability
•Reflection free parsing
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Moshi to the rescue!
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data class Book (
val title: String?,
val authors: List,
val isbn: String
)
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@JsonClass(generateAdapter = true)
data class Book (
val title: String?,
val authors: List,
val isbn: String
)
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That’s it!
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Really really it..besides
adding it as a dependency
in gradle of course!
That’s it!
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implementation "com.squareup.moshi:moshi:$moshi_version"
kapt("com.squareup.moshi:moshi-kotlin-codegen:$moshi_version")
Really really it..besides
adding it as a dependency
in gradle of course!
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That sounds too good to
be true.
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How does it work?
That sounds too good to
be true.
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Annotation processing
How does it work?
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Type adapter resolves at
runtime so you don’t
have to do anything else
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Uses reflection once to
lookup, caches it for use.
Good across modules!