How To Integrate Model Mapper In Spring Boot

When building Spring Boot applications — especially microservices — we often need to convert DTOs into entities and vice versa. Writing manual mapping code quickly becomes repetitive and error‑prone.

ModelMapper solves this problem by automatically mapping objects with similar structures.

What is ModelMapper?

ModelMapper is a Java library that simplifies object mapping by automatically converting one object type into another based on matching fields.

Common use cases:

• Mapping Request DTO → Entity
• Mapping Entity → Response DTO
• Reducing boilerplate mapping code
• Cleaner service layer

Common Problem Developers Face

Many developers directly write this in their service:

But when the application starts, Spring throws:

Why does this happen?

Because Spring does not create ModelMapper automatically.

ModelMapper is a third‑party library, so you must explicitly tell Spring how to create it as a bean.

The Correct Solution (Minimal & Clean)

You only need one configuration file.

Step 0:Add ModelMapper Dependency (pom.xml)

Before writing any configuration or using ModelMapper in your code, you must add the library to your project.

Step 1: Create a config Package

Step 2: Create ModelMapperConfig.java

What This Configuration Does

Let’s break it down simply:

Spring stores this object in its Application Context and reuses it wherever required.

Step 4: Use ModelMapper in Your Service

Now you can safely inject ModelMapper using constructor injection:

Why Constructor Injection Works Now

Because of this chain:

@Bean → Spring knows how to create ModelMapper Spring stores it as a managed bean @RequiredArgsConstructor requests it Spring injects the same instance automatically