[java-client] WebClient requires java8 (OpenAPITools#460)

* Usage of webclient library forces java8 to be true

* Run bin/java-petstore-webclient.sh

Author: jmini

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaClientCodegen.java

@@ -17,6 +17,10 @@
 
 package org.openapitools.codegen.languages;
 
+import static com.google.common.base.CaseFormat.LOWER_CAMEL;
+import static com.google.common.base.CaseFormat.UPPER_UNDERSCORE;
+import static java.util.Collections.sort;
+
 import org.apache.commons.lang3.BooleanUtils;
 import org.apache.commons.lang3.StringUtils;
 import org.openapitools.codegen.CliOption;
@@ -45,10 +49,6 @@
 import java.util.Map;
 import java.util.regex.Pattern;
 
-import static com.google.common.base.CaseFormat.LOWER_CAMEL;
-import static com.google.common.base.CaseFormat.UPPER_UNDERSCORE;
-import static java.util.Collections.sort;
-
 public class JavaClientCodegen extends AbstractJavaCodegen
         implements BeanValidationFeatures, PerformBeanValidationFeatures,
         GzipFeatures {
@@ -287,6 +287,8 @@ public void processOpts() {
             additionalProperties.put("jackson", "true");
             supportingFiles.add(new SupportingFile("auth/Authentication.mustache", authFolder, "Authentication.java"));
         } else if (WEBCLIENT.equals(getLibrary())) {
+            setJava8Mode(true);
+            additionalProperties.put("java8", "true");
             additionalProperties.put("jackson", "true");
         } else if (VERTX.equals(getLibrary())) {
             typeMapping.put("file", "AsyncFile");

samples/client/petstore/java/webclient/README.md

@@ -12,7 +12,7 @@ This spec is mainly for testing Petstore server and contains fake endpoints, mod
 ## Requirements
 
 Building the API client library requires:
-1. Java 1.7+
+1. Java 1.8+
 2. Maven/Gradle
 
 ## Installation