derive invoker package name from api/modoel package name

Author: wing328

modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/AbstractJavaCodegen.java

@@ -117,6 +117,18 @@ public void processOpts() {
 
         if (additionalProperties.containsKey(CodegenConstants.INVOKER_PACKAGE)) {
             this.setInvokerPackage((String) additionalProperties.get(CodegenConstants.INVOKER_PACKAGE));
+        } else if (additionalProperties.containsKey(CodegenConstants.API_PACKAGE)) {
+            // guess from api package
+            String derviedInvokerPackage = deriveInvokerPackageName((String)additionalProperties.get(CodegenConstants.API_PACKAGE));
+            this.additionalProperties.put(CodegenConstants.INVOKER_PACKAGE, derviedInvokerPackage);
+            this.setInvokerPackage((String) additionalProperties.get(CodegenConstants.INVOKER_PACKAGE));
+            LOGGER.info("Invoker Package Name, originally not set, is now dervied from api package name: " + derviedInvokerPackage);
+        } else if (additionalProperties.containsKey(CodegenConstants.MODEL_PACKAGE)) {
+            // guess from model package
+            String derviedInvokerPackage = deriveInvokerPackageName((String)additionalProperties.get(CodegenConstants.MODEL_PACKAGE));
+            this.additionalProperties.put(CodegenConstants.INVOKER_PACKAGE, derviedInvokerPackage);
+            this.setInvokerPackage((String) additionalProperties.get(CodegenConstants.INVOKER_PACKAGE));
+            LOGGER.info("Invoker Package Name, originally not set, is now dervied from model package name: " + derviedInvokerPackage);
         } else {
             //not set, use default to be passed to template
             additionalProperties.put(CodegenConstants.INVOKER_PACKAGE, invokerPackage);
@@ -845,4 +857,23 @@ public String escapeUnsafeCharacters(String input) {
         return input.replace("*/", "*_/").replace("/*", "/_*");
     }
 
+    /*
+     * Derive invoker package name based on the input
+     * e.g. foo.bar.model => foo.bar
+     *
+     * @param input API package/model name
+     * @return Derived invoker package name based on API package/model name
+     */
+    private String deriveInvokerPackageName(String input) {
+        String[] parts = input.split(Pattern.quote(".")); // Split on period.
+
+        StringBuilder sb = new StringBuilder();
+        String delim = "";
+        for (String p : Arrays.copyOf(parts, parts.length-1)) {
+            sb.append(delim).append(p);
+            delim = ".";
+        }
+        return sb.toString();
+    }
+
 }