[Spring] Improve CI and maven integration: regenerate all files depending on swagger specs at every build

Description

As a best practice for code generation with a CI pipeline driven by maven, it should be able to regenerate every file that depends on Swagger spec file.

Speaking about Spring Boot, these files are:

• API Interfaces
• Model classes
• SwaggerDocumentationConfig.java (defines API info based on the Swagger specs)

Using Maven, these files should be regenerated at every build, into ./target/generated-sources (usually ignored in VCS).

Any other file might be optionally generated, on demand (as opposed as automatically at every build), only on the developer's machine and into ./src.

Currently, this only partially works using the swagger-codegen-maven-plugin and spring language.

Specifyng interfaceOnly=true, the following files are generated:

• API Interfaces
• Model classes
• pom.xml
• README.md
• .swagger-codegen-ignore

By default, swagger-codegen-maven-plugin correctly generates into ./target/generated-sources

I see two distinct problems here:

1. pom.xml, README.md, .swagger-codegen-ignore should not be generated when interfaceOnly=true (and it also doen't make sense generating them into ./target/generated-sources)
2. It should be possible to regnerate also SwaggerDocumentationConfig.java

The .swagger-codegen-ignore file is not useful, as you only may ignore files, not selectively activate their generation.

Swagger-codegen version

Verified using Swagger Codegen Maven plugin 2.2.2 (release) and CLI 2.2.2

Swagger declaration file content or url

It does not depend on Swagger specs. I used this for testing: https://github.com/OAI/OpenAPI-Specification/blob/master/examples/v2.0/json/petstore-minimal.json

Command line used for generation

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.example</groupId>
    <artifactId>example</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>sample</name>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.3.RELEASE</version>
        <relativePath/>
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
        <application.package>com.example</application.package>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jersey</artifactId>
        </dependency>
        <dependency>
            <groupId>io.swagger</groupId>
            <artifactId>swagger-annotations</artifactId>
            <version>1.5.13</version>
        </dependency>
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger2</artifactId>
            <version>2.6.1</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>io.swagger</groupId>
                <artifactId>swagger-codegen-maven-plugin</artifactId>
                <version>2.2.2</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                        <configuration>
                            <inputSpec>src/main/resources/swagger.json</inputSpec>
                            <language>spring</language>
                            <configOptions>
                                <interfaceOnly>true</interfaceOnly>
                                <dateLibrary>java8</dateLibrary>
                                <java8>true</java8>
                            </configOptions>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

The effect is reproducible with the following CLI, but as the build is controlled by Maven, only the Maven plugin should be used.

swagger-codegen -l spring -i src/main/resources/swagger.json -o src/ -c config.json

using the following config.json:

{
  "dateLibrary" : "java8",
  "java8" : true,
  "interfaceOnly" : true  
}

Steps to reproduce

1. Create a maven project using the pom.xml file above
2. Copy a specs file into ./src/main/resources/ project subdirectory
3. run mvn clean generate-sources

Related issues

None AFAIK

Suggest a Fix

The current SpringCodegen.java implementation might be easily modified not to generate pom.xml, README.md, .swagger-codegen-ignore when interfaceOnly=true

Selectively regenerating SwaggerDocumentationConfig.java might need a separage, language specific option.

Start by reproducing the issue with the provided pom.xml, swagger.json, config.json, and mvn clean generate-sources. Read SpringCodegen.java to trace the interfaceOnly=true path and generated files. Done means Maven generation produces the requested API interfaces, model classes, and SwaggerDocumentationConfig.java under target/generated-sources without the unwanted project files.