mapstruct

A tool for generating Java code that converts data-transfer objects (DTOs) to database entities and back, field by field. A DTO is an object used to carry data between parts of an application; an entity represents stored data.

In plain words
What is it for?
Use it to create, review, or refactor DTO-to-entity and entity-to-DTO mappings, including create and merge operations, constructor injection, update targets, and named custom mapping methods.
Why use it?
It removes repetitive hand-written getter and setter code and keeps conversions consistent. Generated mappings can also support updating an existing entity and applying custom steps afterward.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/snk-devcenter/addon-studio/mapstruct
Any agent
npx skills add snk-devcenter/addon-studio --skill mapstruct
Clone the repo
git clone --depth 1 https://github.com/snk-devcenter/addon-studio

Made for: Claude Code, Codex.

Per session 169 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,803 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00169 $0.03803
Opus 5 $0.00084 $0.01902
Sonnet 5 $0.00034 $0.00761
Haiku 4.5 $0.00017 $0.00380

Measured yesterday against content hash 639a708e1443, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

mapstruct scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/addon-studio/skills/mapstruct/SKILL.md · 321 lines

How it starts

The opening of the file, as written. The whole thing — 321 lines — stays where its author put it; the contents beside it link to each section on GitHub.

MapStruct — Addon Studio 2.0

MapStruct = biblioteca padrao pra conversao DTO <-> entidade. Nunca faca mapper manual — use MapStruct.

"Dominio", nesta skill e nas demais do plugin, e a entidade @JapeEntity. Os metodos toDomain/fromDomain convertem DTO <-> entidade — nao existe um terceiro modelo entre eles. Criar POJO de dominio separado da entidade e decisao explicita do projeto (ver skill controller, "O que atravessa controller -> service"), nunca inferida a partir do nome dos metodos.

Referencia complementar: veja dependency-injection pra como mappers registram no container Guice.

Escopo: arquivo define so regras genericas MapStruct. Regras negocio, filtros plataforma, convencoes dominio especificas ficam em override por projeto (fora desta skill).


1. Configuracao Global do Projeto

Projeto ja define flags globais compilacao no build.gradle:

dependencies {
    implementation 'org.mapstruct:mapstruct:1.5.5.Final'
    annotationProcessor 'org.mapstruct:mapstruct-processor:1.5.5.Final'

    compileOnly 'org.projectlombok:lombok:1.18.30'
    annotationProcessor 'org.projectlombok:lombok:1.18.30'
    annotationProcessor 'org.projectlombok:lombok-mapstruct-binding:0.2.0'
}

tasks.withType(JavaCompile) {
    options.compilerArgs += [
        "-Amapstruct.defaultComponentModel=jakarta",
        "-Amapstruct.unmappedTargetPolicy=IGNORE"
    ]
}

O que cada flag faz

Flag Valor Efeito
defaultComponentModel jakarta MapStruct gera implementacoes com @Named pra registro automatico Guice. NAO sobrescrever nos mappers.
unmappedTargetPolicy IGNORE Campos target sem mapeamento explicito ignorados sem erro compilacao.
lombok-mapstruct-binding 0.2.0 Garante compatibilidade Lombok (getters/setters gerados) com MapStruct (annotation processor).

ATENCAO — Nao confunda componentModel com injectionStrategy:

Parametro Configurado globalmente? Regra
componentModel SIMjakarta no build.gradle NUNCA declare no @Mapper individual. Declarar sobrescreve global.
injectionStrategy NAO — sem flag global SEMPRE declare InjectionStrategy.CONSTRUCTOR em mapper abstract class (com @Inject repository) ou que use uses = {...}.
repositories em abstract class N/A SEMPRE use field injection (@Inject no campo). Limitacao MapStruct: processador nao gera super(...) com parametros construtor classe abstrata, impossibilita constructor injection pra repositorios.

IMPORTANTE — componentModel: componentModel NUNCA declare no @Mapper individual. Ja global como jakarta em build.gradle. Declarar — mesmo com mesmo valor "jakarta" — sobrescreve global, causa conflitos injecao ou falhas silenciosas no Guice.

IMPORTANTE — injectionStrategy: injectionStrategy NAO global. Declare explicito como InjectionStrategy.CONSTRUCTOR em mapper que:

  • abstract class com @Inject (repositorios ou deps), OU
  • use uses = {...} com componentes externos.

Omitir = field injection Guice sem garantia ordem inicializacao.

Read the full file on GitHub · 321 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 321 lines · 0 tokens per session scan A 639a708e1443

Subscribe to this mod's changes

mapstruct is a skill published in the GitHub repository snk-devcenter/addon-studio (5 stars, last pushed yesterday), licensed MIT. It adds 169 tokens to every session and 3,803 once invoked, about $0.0008 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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