> For the complete documentation index, see [llms.txt](https://result.leakyabstractions.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://result.leakyabstractions.com/extra/demo/spring-boot.md).

# Spring Boot Demo Project

Take a look at a Spring Boot-based REST API leveraging Result objects

This demo project demonstrates how to handle and serialize `Result` objects within a [Spring Boot](https://spring.io/projects/spring-boot) application. It provides a working example of a "pet store" web service that exposes a REST API for managing pets.

## Generating the Project

The project was generated via [Spring Initializr](https://start.spring.io/) including features: *web* and *cloud-feign*.

## Adding Serialization Support

Then [Jackson datatype module for Result objects](/add-ons/jackson.md) was manually added as a dependency to serialize and deserialize `Result` objects.

{% code title="build.gradle" %}

```groovy
dependencies {
  // ...
  implementation platform('com.leakyabstractions:result-bom:1.0.0.0')
  implementation 'com.leakyabstractions:result'
  implementation 'com.leakyabstractions:result-jackson'
}
```

{% endcode %}

We use a `@Bean` to register the datatype module.

{% code title="JacksonConfig.java" %}

```java
@Configuration
public class JacksonConfig {
  @Bean
  public Module registerResultModule() {
    return new ResultModule();
  }
}
```

{% endcode %}

## API Responses

API responses contain a `Result` field, encapsulating the outcome of the requested operation.

{% code title="ApiResponse.java" %}

```java
public class ApiResponse<S> {

  @JsonProperty String version;
  @JsonProperty Instant generatedOn;
  @JsonProperty Result<S, ApiError> result;
}
```

{% endcode %}

Results have different success types, depending on the specific endpoint. Failures will be encapsulated as instances of `ApiError`.

## Controllers

Controllers return instances of `ApiResponse` that will be serialized to JSON by Spring Boot.

{% code title="PetController.java" %}

```java
@RestController
public class PetController {
  // ...
  @GetMapping("/pet")
  ApiResponse<Collection<Pet>> list(@RequestHeader("X-Type") RepositoryType type) {
    log.info("List all pets in {} pet store", type);
    return response(locate(type)
      .flatMapSuccess(PetRepository::listPets)
      .ifSuccess(x -> log.info("Listed {} pet(s) in {}", x.size(), type))
      .ifFailure(this::logError));
  }
}
```

{% endcode %}

Since failures are expressed as `ApiError` objects, endpoints invariably return HTTP status `200`.

## Running the Application

The application can be built and run with Gradle.

```
./gradlew bootRun
```

This will start a stand-alone server on port 8080.

## Testing the Server

Once started, you can interact with the API.

```bash
curl -s -H 'x-type: local' http://localhost:8080/pet/0
```

You should see a JSON response like this:

```json
{
  "version": "1.0",
  "result": {
    "success":{
      "id": 0,
      "name": "Rocky",
      "status": "AVAILABLE"
    }
  }
}
```

## Using Swagger-UI

You can navigate to <http://localhost:8080/> to inspect the API using an interactive UI

![Swagger-UI](https://dev.leakyabstractions.com/result-example-spring-boot/swagger-ui.png)

{% hint style="success" %}
The full source code for the example application is [available on GitHub](https://github.com/LeakyAbstractions/result-example-spring-boot).
{% endhint %}


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://result.leakyabstractions.com/extra/demo/spring-boot.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.