Boolean conversion for maven plugin (#1252)

* saving the fixes.
Used commons-configuration2 for
org.apache.commons.configuration2.PropertiesConfiguration.
It makes the configuration easier to read amongst other benefits

* removing tabs

* updating and simplifying based on sugegstion from William. This should
now fix across all generators

* upgraded pom

* added some javadocs for the new method

modules/openapi-generator-maven-plugin/src/main/java/org/openapitools/codegen/plugin/CodeGenMojo.java

@@ -35,6 +35,7 @@ import java.io.File;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 import org.apache.maven.plugin.AbstractMojo;
 import org.apache.maven.plugin.MojoExecutionException;
@@ -571,6 +572,7 @@ public class CodeGenMojo extends AbstractMojo {
             }
             return;
         }
+        adjustAdditionalProperties(config);
         try {
             new DefaultGenerator().opts(input).generate();
         } catch (Exception e) {
@@ -608,4 +610,30 @@ public class CodeGenMojo extends AbstractMojo {
             }
         }
     }
+    /**
+     * This method enables conversion of true/false strings in 
+     * config.additionalProperties (configuration/configOptions) to proper booleans.
+     * This enables mustache files to handle the properties better.
+     * 
+     * @param config
+     */
+    private void adjustAdditionalProperties(final CodegenConfig config) {
+        Map<String, Object> configAdditionalProperties = config.additionalProperties();
+        Set<String> keySet = configAdditionalProperties.keySet();
+        for (String key : keySet) {
+            Object value = configAdditionalProperties.get(key);
+            if (value != null) {
+                if (value instanceof String) {
+                    String stringValue = (String) value;
+                    if (stringValue.equalsIgnoreCase("true")) {
+                        configAdditionalProperties.put(key, Boolean.TRUE);
+                    } else if (stringValue.equalsIgnoreCase("false")) {
+                        configAdditionalProperties.put(key, Boolean.FALSE);
+                    }
+                }
+            } else {
+                configAdditionalProperties.put(key, Boolean.FALSE);
+            }
+        }
+    }
 }