### Configure Maven Local Repository

Source: https://github.com/problem4j/problem4j-spring/blob/main/README.md

Example of how to configure repositories in a target project to use artifacts from the local Maven repository.

```kotlin
repositories {
    mavenLocal()
    mavenCentral()
}
```

--------------------------------

### Example Problem Response (application/problem+json)

Source: https://github.com/problem4j/problem4j-spring/blob/main/README.md

This JSON structure represents the problem response generated by the custom resolver for an invalid request.

```json
{
    "type": "errors/invalid-request",
    "title": "Invalid Request",
    "status": 400,
    "detail": "bad input for user u-456",
    "userId": "u-456"
}
```

--------------------------------

### DCO Sign-off with GitHub Nickname

Source: https://github.com/problem4j/problem4j-spring/blob/main/CONTRIBUTING.md

An example of a DCO sign-off using a GitHub nickname and a noreply email address, useful for maintaining privacy.

```text
Signed-off-by: nickname <12345678+nickname@users.noreply.github.com>
```

--------------------------------

### Generate Problem response from custom exception with @ProblemMapping

Source: https://github.com/problem4j/problem4j-spring/blob/main/README.md

Annotate a custom exception with @ProblemMapping to automatically generate a Problem response. This example shows how to map exception fields and extensions.

```java
@ProblemMapping(
    type = "errors/invalid-request",
    title = "Invalid Request",
    status = 400,
    detail = "{message}: {fieldName}",
    extensions = {"userId", "fieldName"})
public class ExampleException extends RuntimeException {

  private final String userId;
  private final String fieldName;

  public ExampleException(String userId, String fieldName) {
    super("bad input for user " + userId);
    this.userId = userId;
    this.fieldName = fieldName;
  }
}
```

--------------------------------

### Implement Custom ProblemResolver in Spring

Source: https://github.com/problem4j/problem4j-spring/blob/main/README.md

Implement the ProblemResolver interface to define custom logic for resolving exceptions into Problem objects. This example shows how to handle a specific ExampleException.

```java
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatusCode;
import org.springframework.stereotype.Component;

import io.github.problem4j.spring.ProblemResolver;
import io.github.problem4j.spring.ProblemContext;
import io.github.problem4j.core.Problem;

@Component
public class ExampleExceptionResolver implements ProblemResolver {

  @Override
  public Class<? extends Exception> getExceptionClass() {
    return ExampleException.class;
  }

  @Override
  public Problem resolve(
      ProblemContext context, Exception ex, HttpHeaders headers, HttpStatusCode status) {
    return Problem.builder()
        .type("errors/invalid-request")
        .title("Invalid Request")
        .status(400)
        .detail("bad input for user " + ((ExampleException) ex).getUserId())
        .extension("userId", ((ExampleException) ex).getUserId())
        .build();
  }
}
```

--------------------------------

### Gradle Dependencies for Problem4J Spring

Source: https://github.com/problem4j/problem4j-spring/blob/main/README.md

Add the problem4j-spring library as a dependency to your Gradle project using the Kotlin DSL. Select the artifact corresponding to your Spring Boot setup (webflux or webmvc). Java 17 or higher is required.

```groovy
dependencies {
       // pick the one for your project
       implementation("io.github.problem4j:problem4j-spring-webflux:${version}")
       implementation("io.github.problem4j:problem4j-spring-webmvc:${version}")
   }
```

--------------------------------

### Build the Project with Gradle

Source: https://github.com/problem4j/problem4j-spring/blob/main/README.md

The simplest command to build the project, which includes compilation and running tests.

```bash
./gradlew
```

--------------------------------

### Format Code with Gradle

Source: https://github.com/problem4j/problem4j-spring/blob/main/README.md

Apply code formatting rules defined in build.gradle.kts using the spotlessApply task. Building will fail if code is not properly formatted.

```bash
./gradlew spotlessApply
```

--------------------------------

### Build and Validate Project

Source: https://github.com/problem4j/problem4j-spring/blob/main/CLAUDE.md

Run these Gradle commands to format code, build, and test the project. Always validate changes with a full build and test run.

```shell
./gradlew                  # default: spotlessApply build (preferred)
./gradlew spotlessApply    # auto-format code
./gradlew build            # compile + test + spotlessCheck
./gradlew test             # tests only
```

--------------------------------

### Execute Tests with Gradle

Source: https://github.com/problem4j/problem4j-spring/blob/main/README.md

Use the 'test' task to run all project tests. Tests do not alter the release version of the bytecode.

```bash
./gradlew test
```

--------------------------------

### Format Code and Update License Year

Source: https://github.com/problem4j/problem4j-spring/blob/main/README.md

Use the spotlessApply task with the -Pspotless.license-year-enabled flag to update the year in license headers. This is important for publishing pipelines.

```bash
./gradlew spotlessApply -Pspotless.license-year-enabled
```

--------------------------------

### Environment Variables for Publishing

Source: https://github.com/problem4j/problem4j-spring/blob/main/RELEASING.md

Set these environment variables in your CI/CD system for publishing artifacts. These include Sonatype credentials and PGP keys for signing.

```bash
# generated tokens on Sonatype account, do not use real username/password
PUBLISHING_USERNAME=<username>
PUBLISHING_PASSWORD=<password>

# generated PGP key for signing artifacts
SIGNING_KEY=<PGP key>
SIGNING_PASSWORD=<PGP password>
```

--------------------------------

### Gradle Task for Publishing to Maven Central

Source: https://github.com/problem4j/problem4j-spring/blob/main/RELEASING.md

Use this Gradle task to publish artifacts to the Sonatype repository, which then allows them to be pushed to Maven Central. Ensure the version property is correctly set.

```bash
./gradlew -Pversion=<version> -Psign publishAggregationToCentralPortal
```

--------------------------------

### Publish to Local Maven Repository

Source: https://github.com/problem4j/problem4j-spring/blob/main/README.md

Use the publishToMavenLocal task to publish the built artifacts to your local Maven repository.

```bash
./gradlew publishToMavenLocal
```

--------------------------------

### Gradle (Kotlin DSL) Dependency Management

Source: https://github.com/problem4j/problem4j-spring/blob/main/problem4j-spring-bom/README.md

Add the Problem4J Spring BOM to your Gradle build using the Kotlin DSL. This allows you to declare individual problem4j-* Spring modules without specifying their versions.

```kotlin
dependencies {
    implementation(platform("io.github.problem4j:problem4j-spring-bom:{version}"))

    implementation("io.github.problem4j:problem4j-core")
    implementation("io.github.problem4j:problem4j-jackson2")
    implementation("io.github.problem4j:problem4j-jackson3")
    implementation("io.github.problem4j:problem4j-spring-web")
    implementation("io.github.problem4j:problem4j-spring-webmvc")
    implementation("io.github.problem4j:problem4j-spring-webflux")
}
```

--------------------------------

### Throw ProblemException with a Problem object

Source: https://github.com/problem4j/problem4j-spring/blob/main/README.md

Use this to throw a ProblemException with a manually constructed Problem object. The response will be in application/problem+json format.

```java
throw new ProblemException(Problem.of("Invalid Request", 400, "not a valid json"));
```

--------------------------------

### Add DCO Sign-off to Commit Message

Source: https://github.com/problem4j/problem4j-spring/blob/main/CONTRIBUTING.md

Append this line to your commit message to certify your contribution under the project's license.

```text
Signed-off-by: Your Name <your.email@example.com>
```

--------------------------------

### Maven Dependency Management

Source: https://github.com/problem4j/problem4j-spring/blob/main/problem4j-spring-bom/README.md

Configure your Maven project to use the Problem4J Spring BOM. Add the BOM to dependencyManagement with an import scope, then declare modules without versions.

```xml
<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>io.github.problem4j</groupId>
            <artifactId>problem4j-spring-bom</artifactId>
            <version>{version}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

<dependencies>
<dependency>
    <groupId>io.github.problem4j</groupId>
    <artifactId>problem4j-core</artifactId>
</dependency>
<dependency>
    <groupId>io.github.problem4j</groupId>
    <artifactId>problem4j-jackson2</artifactId>
</dependency>
<dependency>
    <groupId>io.github.problem4j</groupId>
    <artifactId>problem4j-jackson3</artifactId>
</dependency>
<dependency>
    <groupId>io.github.problem4j</groupId>
    <artifactId>problem4j-spring-web</artifactId>
</dependency>
<dependency>
    <groupId>io.github.problem4j</groupId>
    <artifactId>problem4j-spring-webmvc</artifactId>
</dependency>
<dependency>
    <groupId>io.github.problem4j</groupId>
    <artifactId>problem4j-spring-webflux</artifactId>
</dependency>
</dependencies>
```

--------------------------------

### Maven Dependencies for Problem4J Spring

Source: https://github.com/problem4j/problem4j-spring/blob/main/README.md

Add the problem4j-spring library as a dependency to your Maven project. Choose the appropriate artifact for your Spring Boot version (webflux or webmvc). Java 17 or higher is required.

```xml
<dependencies>
       <!-- pick the one for your project -->
       <dependency>
           <groupId>io.github.problem4j</groupId>
           <artifactId>problem4j-spring-webflux</artifactId>
           <version>${version}</version>
       </dependency>
       <dependency>
           <groupId>io.github.problem4j</groupId>
           <artifactId>problem4j-spring-webmvc</artifactId>
           <version>${version}</version>
       </dependency>
   </dependencies>
```

--------------------------------

### 404 Not Found Problem Object

Source: https://github.com/problem4j/problem4j-spring/blob/main/problem4j-spring-webmvc/README.md

This JSON represents the standard Problem object returned for 404 Not Found errors in Spring WebMVC when using this module.

```json
{
  "status": 404,
  "title": "Not Found"
}
```

--------------------------------

### Automatically Sign Git Commits

Source: https://github.com/problem4j/problem4j-spring/blob/main/CONTRIBUTING.md

Use this command to automatically add the DCO sign-off to your commit message if your Git user information is configured.

```bash
git commit -s -m "message"
```

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