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https://github.com/chrimle/openapi-to-java-records-mustache-templates

Generate Java Records from OpenAPI Specifications
https://github.com/chrimle/openapi-to-java-records-mustache-templates

java java-17 mustache mustache-templates openapi openapi-generator openapi-generator-maven-plugin openapi-specification openapi3

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Generate Java Records from OpenAPI Specifications

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README

        

# openapi-to-java-records-mustache-templates
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Project containing [Mustache-templates](https://mustache.github.io/) used by [openapi-generator-maven-plugin](https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator-maven-plugin/README.md) to generate [Java Records](https://docs.oracle.com/en/java/javase/17/language/records.html) from [OpenAPI Specifications](https://swagger.io/specification/).

This project contains the **mustache templates**.

## Apache License 2.0
Starting with project version **2.0.0**, the project is licensed under the **Apache License 2.0**.
> [!NOTE]
> Prior to version **2.0.0**, the project was licensed under the **MIT License**. See [License](#license).

## Support the Project
If you find this project useful, please ⭐ **Star** ⭐ it and share it with others!
This is the best way to show appreciation for this project - Thank you! ❤️

If you have feedback or suggestions, please share it in either [Discussions](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/discussions) or [Issues](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/issues)!

> [!NOTE]
> This project is, _and will continue to be_, solely maintained by [Chrimle](https://github.com/Chrimle).
> While _direct_ code contributions are disallowed, your feedback is the most valuable contribution - please share it!

# Getting Started
The mustache templates are best acquired by importing the project as a dependency.

> [!TIP]
> If you want a more detailed guide with simple examples to get started, check out the Wiki-page
> [Beginner Guide (Step-by-Step)](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/wiki/Beginner-Guide-%28Step‐by‐Step%29).

## Import Dependency
> [!NOTE]
> The Maven artifact **only** contains the `.mustache` template files and a `LICENSE.txt`. No other files are included in the imported artifact.

```xml

io.github.chrimle
openapi-to-java-records-mustache-templates
2.8.2

```
It is **strongly recommended** to import the project as a dependency. It has officially been published to:
- [Maven Central Repository](https://central.sonatype.com/artifact/io.github.chrimle/openapi-to-java-records-mustache-templates)
- [GitHub Packages](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/packages/)

> [!WARNING]
> While it is _possible_ to download the Mustache templates directly
> from [GitHub](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/tree/main/mustache-templates/target/classes/templates),
> this approach is **not recommended**. Templates obtained this way are not guaranteed to be versioned correctly and
> is explicitly **exempt** from the [Semantic Versioning](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/wiki/Semantic-Versioning) considerations.

## Use the `.mustache` templates when generating
Place the file(s) in desired directory. Then, in the Maven build configuration, set the property `` to the directory path. Example:
```xml



org.openapitools
openapi-generator-maven-plugin



generate









```
## Additional Configurations
The generated classes are customizable by using ``-properties.

In this example, each generated class field will be annotated with [Jakarta Bean Validation annotations](https://jakarta.ee/specifications/bean-validation/3.0/jakarta-bean-validation-spec-3.0.html#builtinconstraints).
```xml



true



```

> [!TIP]
> See [Supported 'openapi‐generator‐maven‐plugin' Configuration options](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/wiki/Supported-%27openapi‐generator‐maven‐plugin%27-Configuration-options)

## OpenAPI Specification

Example OpenAPI Specification

```yaml
components:
schemas:
Name:
description: Name Information
type: object
required:
- firstName
- lastName
properties:
firstName:
description: First Name
type: string
minLength: 2
lastName:
description: Last Name
type: string
minLength: 2
middleName:
description: Middle Name
type: string
nullable: true
Person:
description: Personal information
deprecated: true
type: object
required:
- name
- age
- gender
- height
- ssn
- aliases
- email
- trackingCode
- uuid
properties:
name:
description: Name
type: object
$ref: '#/components/schemas/Name'
age:
description: Age (years)
type: integer
minimum: 0
maximum: 100
gender:
description: Gender
type: string
enum:
- Male
- Female
height:
description: Height (m)
type: number
pattern: float
minimum: 0
legalGuardian:
description: Legal Guardian
type: object
$ref: '#/components/schemas/Person'
ssn:
description: Social Security Number
type: string
pattern: '^\d{3}-\d{2}-\d{4}$'
aliases:
description: Known Aliases
type: array
uniqueItems: true
minItems: 1
maxItems: 3
items:
type: string
telephoneNumber:
description: Telephone Number
type: string
nullable: true
email:
description: Email Address
type: string
format: email
trackingCode:
description: Tracking code for Web analytics
type: string
minLength: 5
maxLength: 50
default: "utm_source=default"
uuid:
description: An Universally Unique Identifier
type: string
format: uuid
```

> [!TIP]
> See [Supported OpenAPI Specification properties](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/wiki/Supported-OpenAPI-Specification-properties)

## Generate models
Compile the project, for example via:
```console
mvn compile
```

> [!TIP]
> Further information about how to generate models can be found on [openapi-generator-maven-plugin](https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator-maven-plugin/README.md).

## Generated Java Record
Unless the configuration property `` has been set, the generated classes should be found under `./target/generated-sources/openapi`.


Resulting Java record from example OpenAPI spec.

```java
package io.github.chrimle.o2jrm;

/**
* Personal information
*
* @deprecated
* @param name Name.
* @param age Age (years)
* @param gender Gender
* @param height Height (m)
* @param legalGuardian Person.
* @param ssn Social Security Number
* @param aliases Known Aliases
* @param telephoneNumber Telephone Number
* @param email Email Address
* @param trackingCode Tracking code for Web analytics
* @param uuid An Universally Unique Identifier
*/
@Deprecated
public record Person(
@javax.annotation.Nonnull @Valid @NotNull Name name,
@javax.annotation.Nonnull @NotNull @Min(0) @Max(100) Integer age,
@javax.annotation.Nonnull @NotNull GenderEnum gender,
@javax.annotation.Nonnull @NotNull @DecimalMin("0") BigDecimal height,
@javax.annotation.Nonnull @Valid Person legalGuardian,
@javax.annotation.Nonnull @NotNull @Pattern(regexp = "^\\d{3}-\\d{2}-\\d{4}$") String ssn,
@javax.annotation.Nonnull @NotNull @Size(min = 1, max = 3) Set aliases,
@javax.annotation.Nullable String telephoneNumber,
@javax.annotation.Nonnull @NotNull @Email String email,
@javax.annotation.Nonnull @NotNull @Size(min = 5, max = 50) String trackingCode,
@javax.annotation.Nonnull @NotNull UUID uuid) {

public Person(
@javax.annotation.Nonnull final Name name,
@javax.annotation.Nonnull final Integer age,
@javax.annotation.Nonnull final GenderEnum gender,
@javax.annotation.Nonnull final BigDecimal height,
@javax.annotation.Nonnull final Person legalGuardian,
@javax.annotation.Nonnull final String ssn,
@javax.annotation.Nullable final Set aliases,
@javax.annotation.Nullable final String telephoneNumber,
@javax.annotation.Nonnull final String email,
@javax.annotation.Nullable final String trackingCode,
@javax.annotation.Nonnull final UUID uuid) {
this.name = name;
this.age = age;
this.gender = gender;
this.height = height;
this.legalGuardian = legalGuardian;
this.ssn = ssn;
this.aliases = Objects.requireNonNullElse(aliases, new LinkedHashSet<>());
this.telephoneNumber = telephoneNumber;
this.email = email;
this.trackingCode = Objects.requireNonNullElse(trackingCode, "utm_source=default");
this.uuid = uuid;
}

/**
* Gender
*/
public enum GenderEnum {
MALE("Male"),
FEMALE("Female");

private final String value;

GenderEnum(final String value) {
this.value = value;
}

/**
* Gets the {@code value} of this enum.
*
* @return the value of this enum.
*/
public String getValue() {
return value;
}

/**
* Case-sensitively matches the given {@code value} to an enum constant using {@link
* #getValue()}.
*
*

NOTE: if multiple enum constants have a matching value, the first enum constant is
* returned, by the order they are declared.
*
* @param value of the enum.
* @return a {@link GenderEnum } with the matching value.
* @throws IllegalArgumentException if no enum has a value matching the given value.
*/
public static GenderEnum fromValue(final String value) {
for (final GenderEnum constant : GenderEnum.values()) {
if (constant.getValue().equals(value)) {
return constant;
}
}
throw new IllegalArgumentException("Unexpected value '" + value + "'");
}
}
}
```

## Further examples

Refer to the test-cases for generated classes, as these list supported plugin ``-options and OpenAPI
Specification-properties. The unit-tests could clarify expected behaviors, and the OpenAPI Specification could also
provide concrete examples and use-cases. For reference:

- [OpenAPI Specification](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/blob/main/tests/src/main/resources/api.yaml)

Used as the input schema to generate **all** classes used in testing.
- [Maven plugin executions](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/blob/main/tests/pom.xml#L139)

Generates classes from the OpenAPI spec, with different `openapi-generator-maven-plugin` configuration options. The
resulting classes are placed in sub-packages, named after the plugin-execution.
- [Generated classes](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/tree/main/tests/target/generated-sources/openapi/src/src/gen/java/main/io/github/chrimle/o2jrm)

The resulting classes are organized into sub-packages, which facilitates testing. These files are - _albeit in no way
necessary_ - tracked and versioned in order to be accessible without needing to compile anything. Furthermore, it
makes it easier to spot differences in generated classes after making a change to the mustache templates.
- [Test Suite](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/tree/main/tests/src/test/java/io/github/chrimle/o2jrm/tests)

Contains all test-cases for generated `record` and `enum` classes. These tests are _parameterized_, to test **all**
classes in the OpenAPI Specification in combination with **all** plugin-executions.

## Encountered an issue?
Firstly, make a minimal reproducible example - it will greatly facilitate troubleshooting!

Please, verify these steps _without_ custom mustache-template files:
1. Verify that the Maven Build Configuration is correct.
2. Verify that the OpenAPI Specification is valid.
3. Verify that classes are generated successfully.
4. Verify that needed dependencies are imported.

Once verified, use the custom mustache-template files and verify the following:
1. Verify that the `openapi-generator-maven-plugin` configuration options are supported. See [Supported 'openapi‐generator‐maven‐plugin' Configuration options](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/wiki/Supported-%27openapi‐generator‐maven‐plugin%27-Configuration-options).
- If no configuration options are set, please proceed to the next step.
- If the configuration option is not listed as supported - please request it via [open an issue](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/issues/new/choose).
2. Verify that the OpenAPI Specification properties are supported. See [Supported OpenAPI Specification properties](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/wiki/Supported-OpenAPI-Specification-properties).
- If the property is not listed as supported - please request it via [open an issue](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/issues/new/choose).
3. Compare `openapi-generator-maven-plugin` versions
- As a last resort, it could be due to using an older/newer version than what is used within this project for testing.
Even if this would solve the issue - please report it via [open an issue](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/issues/new/choose).

If problems persist, check the [open issues](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/issues).
If the problem you are facing has not already been reported, please [open an issue](https://github.com/Chrimle/openapi-to-java-records-mustache-templates/issues/new/choose) with details and instructions to reproduce.

### Useful Resources

- [Maven in 5 minutes](https://maven.apache.org/guides/getting-started/maven-in-five-minutes.html)
- [OpenAPI Basic Structure](https://swagger.io/docs/specification/basic-structure/)
- [openapi-generator-maven-plugin](https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator-maven-plugin/README.md)
- [Mustache](https://mustache.github.io/)

# License
Apache License
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http://www.apache.org/licenses/

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