@Bean
public RestTemplate restTemplate() throws KeyManagementException, NoSuchAlgorithmException, KeyStoreException {
    final RestTemplate restTemplate = new RestTemplate(sslFactory());
    return restTemplate;
}

@Bean
public HttpComponentsClientHttpRequestFactory sslFactory() throws KeyManagementException, NoSuchAlgorithmException, KeyStoreException {
    final TrustStrategy acceptingTrustStrategy = (X509Certificate[] chain, String authType) -> true;

    final SSLContext sslContext = org.apache.http.ssl.SSLContexts.custom()
                    .loadTrustMaterial(null, acceptingTrustStrategy)
                    .build();

    final SSLConnectionSocketFactory csf = new SSLConnectionSocketFactory(sslContext);

    final CloseableHttpClient httpClient = HttpClients.custom()
                    .setMaxConnPerRoute(250)
                    .setMaxConnTotal(250)
                    .setSSLSocketFactory(csf)
                    // during the SSL check we have also the verification of the host name,
                    // this can be skipped to like this:
                    .setSSLHostnameVerifier(NoopHostnameVerifier.INSTANCE)
                    .build();

    final HttpComponentsClientHttpRequestFactory requestFactory =
                    new HttpComponentsClientHttpRequestFactory();

    requestFactory.setHttpClient(httpClient);

    return requestFactory;
}

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
</dependency>

// If a using spring rest template assign here the RestTemplate
final XyzApi result = new XyzApi(new ApiClient(restTemplate));

<plugin>
    <groupId>org.openapitools</groupId>
    <artifactId>openapi-generator-maven-plugin</artifactId>
    <executions>
        <execution>
            <id>xyz-client</id>
          <goals>
            <goal>generate</goal>
          </goals>
          <configuration>
          	    <!-- use Spring RestTemaplte, optional -->
                <library>resttemplate</library>
	            <!-- skip SSL check -->
                <environmentVariables>
                    <io.swagger.parser.util.RemoteUrl.trustAll>true</io.swagger.parser.util.RemoteUrl.trustAll>
                </environmentVariables>