"DocumentDto" : {
      "type" : "object",
      "properties" : {
        "uuid" : {
          "type" : "string",
          "format" : "uuid"
        },
        "creationDate" : {
          "type" : "string",
          "format" : "date-time"
        }
      }
    }

@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", date = "2019-05-21T13:07:21.639+02:00[Europe/Zurich]")
public class DocumentDto {
  public static final String SERIALIZED_NAME_UUID = "uuid";
  @SerializedName(SERIALIZED_NAME_UUID)
  private UUID uuid;


  public static final String SERIALIZED_NAME_TEST = "creationDate";
  @SerializedName(SERIALIZED_NAME_TEST)
  private OffsetDateTime creationDate;
}

<plugin>
    <groupId>org.openapitools</groupId>
    <artifactId>openapi-generator-maven-plugin</artifactId>
    <version>3.3.4</version>
    <executions>
        <execution>
            <id>test-service</id>
            <phase>validate</phase>
            <goals>
                <goal>generate</goal>
            </goals>
            <configuration>
                <inputSpec>
                    ${project.build.directory}/open-api/swagger.json
                </inputSpec>
                <generatorName>java</generatorName>
                <validateSpec>false</validateSpec>
                <generateApis>false</generateApis>
                <groupId>com.test</groupId>
                <artifactId>test-service</artifactId>
                <modelPackage>test.model</modelPackage>
                <apiPackage>test.api</apiPackage>
                <configOptions>
                    <sourceFolder>src/gen/java/main</sourceFolder>
                    <dateLibrary>java8</dateLibrary>
                    <java8>true</java8>
                </configOptions>
            </configuration>
        </execution>
    </executions>
</plugin>

<typeMappings>DateTime=Instant</typeMappings>
<importMappings>Instant=java.time.Instant</importMappings>