[JavaSpring] Bug generating ApiException.java with useRuntimeException flag

Description

ApiException.java generation does not take in account useRuntimeException flag.

Swagger-codegen version

Checked on 2.3.1 and 3.0.1

Swagger declaration file content or url

Embedded swagger code generator files are affected.

Command line used for generation

    <build>
        <plugins>
            <plugin>
                <groupId>io.swagger.codegen.v3</groupId>
                <artifactId>swagger-codegen-maven-plugin</artifactId>
                <version>3.0.1</version>
                <executions>
                    <execution>
                        <id>default</id>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                        <configuration>
                            <language>spring</language>
                            <inputSpec>${project.basedir}/src/main/resources/api.yaml</inputSpec>
                            <apiPackage>com.my.api</apiPackage>
                            <modelPackage>com.my.model</modelPackage>
                            <ignoreFileOverride>${project.basedir}/src/main/resources/codegen-ignore</ignoreFileOverride>
                            <configOptions>
                                <useRuntimeException>true</useRuntimeException>
                                <recursiveBeanValidation>false</recursiveBeanValidation>
                                <useBeanValidation>false</useBeanValidation>
                                <performBeanValidation>false</performBeanValidation>
                            </configOptions>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

Steps to reproduce

Regular mvn clean generate-sources

Expected result:
public class ApiException extends RuntimeException {...}

Actual result:
public class ApiException extends Exception {...}

Related issues/PRs

Changes done for Java in https://github.com/swagger-api/swagger-codegen/issues/4376

Suggest a fix/enhancement

diff --git a/modules/swagger-codegen/src/main/resources/JavaSpring/apiException.mustache b/modules/swagger-codegen/src/main/resources/JavaSpring/apiException.mustache
index f61611477..c752b15c1 100644
--- a/modules/swagger-codegen/src/main/resources/JavaSpring/apiException.mustache
+++ b/modules/swagger-codegen/src/main/resources/JavaSpring/apiException.mustache
@@ -1,7 +1,7 @@
 package {{apiPackage}};
 
 {{>generatedAnnotation}}
-public class ApiException extends Exception{
+public class ApiException extends{{#useRuntimeException}} RuntimeException {{/useRuntimeException}}{{^useRuntimeException}} Exception {{/useRuntimeException}} {
     private int code;
     public ApiException (int code, String msg) {
         super(msg);

Start with modules/swagger-codegen/src/main/resources/JavaSpring/apiException.mustache and run the reported mvn clean generate-sources command. Verify that generated ApiException.java respects the useRuntimeException flag, extending RuntimeException when it is true and Exception otherwise.