[BUG] instantiationTypes not taken into account

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

I want to instantiate a Set from a type: array in my OpenAPI file. The controller is correctly generated with a Set<MyType> types. However, the model is generated with a line this.mySet = new ArrayList();, causing a compile error.

I have the following in my pom.xml:

<plugin>
    <groupId>org.openapitools</groupId>
    <artifactId>openapi-generator-maven-plugin</artifactId>
    <version>7.1.0</version>
    <executions>
        <execution>
            <id>generate-client</id>
            <goals>
                <goal>generate</goal>
            </goals>
            <configuration>
                <inputSpec>${project.basedir}/../apidocs/technical/openapi.yml</inputSpec>
                <generatorName>spring</generatorName>
                <library>spring-boot</library>
                <generateApiTests>false</generateApiTests>
                <generateModelTests>false</generateModelTests>
                <generateSupportingFiles>false</generateSupportingFiles>
                <configOptions>
                    <sourceFolder>src/gen/java/main</sourceFolder>
                    <basePackage>com.mycompany.myproject.domain.api.gen</basePackage>
                    <modelPackage>com.mycompany.myproject.domain.api.gen.models</modelPackage>
                    <apiPackage>com.mycompany.myproject.domain.api.gen</apiPackage>
                    <configPackage>com.mycompany.myproject.domain.api.config</configPackage>
                    <dateLibrary>java17</dateLibrary>
                    <interfaceOnly>true</interfaceOnly>
                    <skipDefaultInterface>true</skipDefaultInterface>
                    <useTags>true</useTags>
                    <useSpringBoot3>true</useSpringBoot3>
                </configOptions>
                <modelNameSuffix>Dto</modelNameSuffix>
                <typeMappings>
                    <typeMapping>array=Set</typeMapping>
                </typeMappings>
                <importMappings>
                    <importMapping>Set=java.util.Set</importMapping>
                </importMappings>
                <instantiationTypes>
                    <instantiationType>array=HashSet</instantiationType>
                </instantiationTypes>
            </configuration>
        </execution>
    </executions>
</plugin>

openapi-generator version

I'm using 7.1.0 and the issue was not present in 6.4.0.

OpenAPI declaration file content or url

Unfortunately, I can't paste code as it's confidential, but I'm more than happy to help troubleshoot this issue.

Generation Details

Steps to reproduce

Related issues/PRs

Suggest a fix

I'm guessing the <instantionTypes> parameter is not read correctly, because it seems like the array is correctly understood as a Set in my controller.

Start with the Java Spring generator's model-generation path and the Maven configuration shown in the report, focusing on how typeMappings and instantiationTypes are consumed for array properties. Build a minimal OpenAPI reproduction because the original schema is unavailable, compare generated model output between 6.4.0 and 7.1.0, and define done as generating a Set field initialized with the configured HashSet.