如何通过Swagger Codegen 2.3.1从YAML 2.0文件生成自定义Java构造方法？

Yep, you absolutely can generate custom Java constructors with Swagger Codegen 2.3.1 from an OpenAPI 2.0 (YAML) spec—though it’s not an out-of-the-box feature. You’ll need to tweak the code generation templates to make it happen. Here’s a step-by-step breakdown:

1. Export the Default Java Model Template #

First, grab a copy of the default Java model template Swagger Codegen uses. If you’re using the CLI, run this command to export all Java-related templates to a local folder:

swagger-codegen-cli templates -l java -o ./custom-java-templates

This will create a custom-java-templates directory, and inside it you’ll find model.mustache—the template responsible for generating Java model classes.

2. Modify the Template to Add Custom Constructors #

Open custom-java-templates/model.mustache in your editor. You can add custom constructors in two ways: statically (for all models) or dynamically (based on extensions in your YAML spec).

Option A: Static Custom Constructor (All Models) #

If every model needs the same style of custom constructor, hardcode it into the template. For example, add this after the default full-parameter constructor:

// Custom constructor: accepts core fields only
public {{classname}}(Long id, String name) {
    this.id = id;
    this.name = name;
}

The {{classname}} variable will auto-replace with the actual model class name during generation.

Option B: Dynamic Constructor (Model-Specific) #

If you want constructors tailored to specific models, use OpenAPI extensions (fields prefixed with x-) in your YAML, then reference them in the template.

First, add an extension to your model schema in the YAML:

schemas:
  User:
    type: object
    x-custom-constructor:
      fields:
        - name: id
          type: Long
        - name: email
          type: String
    properties:
      id:
        type: integer
        format: int64
      name:
        type: string
      email:
        type: string

Then update the model.mustache template to check for this extension and generate the constructor dynamically:

{{#model.x-custom-constructor}}
    // Custom constructor generated from spec extension
    public {{classname}}({{#fields}}{{type}} {{name}}{{#hasMore}}, {{/hasMore}}{{/fields}}) {
        {{#fields}}this.{{name}} = {{name}};
        {{/fields}}
    }
{{/model.x-custom-constructor}}

This will only generate the custom constructor for models that have the x-custom-constructor extension.

3. Generate Code with Your Custom Template #

Once your template is ready, run the code generation command and specify your custom template directory:

swagger-codegen-cli generate -i your-openapi-spec.yaml -l java -o ./generated-java-code -t ./custom-java-templates

If you’re using Maven, configure the plugin to use your custom template by adding this to your pom.xml:

<plugin>
    <groupId>io.swagger</groupId>
    <artifactId>swagger-codegen-maven-plugin</artifactId>
    <version>2.3.1</version>
    <executions>
        <execution>
            <goals>
                <goal>generate</goal>
            </goals>
            <configuration>
                <inputSpec>${project.basedir}/src/main/resources/your-spec.yaml</inputSpec>
                <language>java</language>
                <templateDirectory>${project.basedir}/src/main/resources/custom-java-templates</templateDirectory>
                <output>${project.build.directory}/generated-sources/swagger</output>
            </configuration>
        </execution>
    </executions>
</plugin>

Quick Notes #

• Swagger Codegen 2.3.1 is an older version, so some newer template features from later releases won’t work here. Stick to the template variables available in this version.
• Always test your modified template with a small spec first to ensure the generated code compiles correctly.

内容的提问来源于stack exchange，提问作者Charaviz