added environment variable support

Author: fehguy

modules/swagger-codegen-maven-plugin/src/main/java/io/swagger/codegen/plugin/CodeGenMojo.java

@@ -36,6 +36,7 @@
 import config.ConfigParser;
 
 import java.io.File;
+import java.util.HashMap;
 import java.util.Map;
 import java.util.ServiceLoader;
 
@@ -112,6 +113,9 @@ public class CodeGenMojo extends AbstractMojo {
     @Parameter(defaultValue = "true")
     private boolean addCompileSourceRoot = true;
 
+    @Parameter
+    protected Map<String, String> environmentVariables = new HashMap<String, String>();
+
     /**
      * The project being built.
      */
@@ -125,6 +129,12 @@ public void execute() throws MojoExecutionException {
         CodegenConfig config = CodegenConfigLoader.forName(language);
         config.setOutputDir(output.getAbsolutePath());
 
+        if (environmentVariables != null) {
+            for(String key : environmentVariables.keySet()) {
+                System.setProperty(key, environmentVariables.get(key));
+            }
+        }
+
         if (null != templateDirectory) {
             config.additionalProperties().put(TEMPLATE_DIR_PARAM, templateDirectory.getAbsolutePath());
         }