addition of maven entries at the README

README.md

@@ -21,6 +21,17 @@ You can find examples on how to use the framework at <a href="https://github.com
         System.out.println(response);
 ```
 
+The component is on Maven central repo; to use it, you only need to add the following piece of code to your pom.xml:
+
+```
+<dependency>
+    <groupId>br.com.autonomiccs</groupId>
+    <artifactId>apache-cloudstack-java-client</artifactId>
+    <version>1.0.0</version>
+</dependency>
+```
+
+
 # License
  Apache CloudStack Java Client
 

src/main/java/br/com/autonomiccs/apacheCloudStack/client/beans/ApacheCloudStackUser.java

@@ -21,9 +21,12 @@
  */
 package br.com.autonomiccs.apacheCloudStack.client.beans;
 
+import org.apache.commons.lang3.StringUtils;
 import org.apache.commons.lang3.builder.EqualsBuilder;
 import org.apache.commons.lang3.builder.HashCodeBuilder;
 
+import br.com.autonomiccs.apacheCloudStack.exceptions.ApacheCloudStackClientRuntimeException;
+
 /**
  * This class represent an Apache CloudStack users. It holds the user data that is needed to execute the authentication process.
  * We can use either the username/password  or the secret key and API key authentication mechanism.
@@ -52,15 +55,25 @@ public class ApacheCloudStackUser {
      */
     private String apiKey;
 
+    private void validatePropertiesOnNewlyCreatedObject() {
+        boolean isAuthenticationUsingUserCredentialsConfigured = StringUtils.isNotBlank(username) && StringUtils.isNotBlank(password) && StringUtils.isNotBlank(domain);
+        boolean isAuthenticationUsingKeysConfigured = StringUtils.isNotBlank(apiKey) && StringUtils.isNotBlank(secretKey);
+        if (!isAuthenticationUsingKeysConfigured && !isAuthenticationUsingUserCredentialsConfigured) {
+            throw new ApacheCloudStackClientRuntimeException("You should either configure authentication using user credentials or user private and API keys.");
+        }
+    }
+
     public ApacheCloudStackUser(String secretKey, String apiKey) {
         this.secretKey = secretKey;
         this.apiKey = apiKey;
+        validatePropertiesOnNewlyCreatedObject();
     }
 
     public ApacheCloudStackUser(String username, String password, String domain) {
         this.username = username;
         this.password = password;
         this.domain = domain;
+        validatePropertiesOnNewlyCreatedObject();
     }
 
     public String getUsername() {

src/main/java/br/com/autonomiccs/apacheCloudStack/exceptions/ApacheCloudStackClientRequestRuntimeException.java

@@ -28,7 +28,7 @@
  *   It contains the returned status code and the server response.
  */
 @SuppressWarnings("serial")
-public class ApacheCloudStackClientRequestRuntimeException extends RuntimeException {
+public class ApacheCloudStackClientRequestRuntimeException extends ApacheCloudStackClientRuntimeException {
 
     /**
      * Status of the HTTP request that generated this exception

src/main/java/br/com/autonomiccs/apacheCloudStack/exceptions/ApacheCloudStackClientRuntimeException.java

@@ -27,6 +27,10 @@
 @SuppressWarnings("serial")
 public class ApacheCloudStackClientRuntimeException extends RuntimeException {
 
+    public ApacheCloudStackClientRuntimeException() {
+        super();
+    }
+
     public ApacheCloudStackClientRuntimeException(Exception e) {
         super(e);
     }

src/test/java/br/com/autonomiccs/apacheCloudStack/client/beans/ApacheCloudStackUserTest.java

@@ -0,0 +1,50 @@
+/*
+ * Apache CloudStack Java Client
+ * Copyright (C) 2016 Autonomiccs, Inc.
+ *
+ * Licensed to the Autonomiccs, Inc. under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The Autonomiccs, Inc. licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package br.com.autonomiccs.apacheCloudStack.client.beans;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.runners.MockitoJUnitRunner;
+
+import br.com.autonomiccs.apacheCloudStack.exceptions.ApacheCloudStackClientRuntimeException;
+
+@RunWith(MockitoJUnitRunner.class)
+public class ApacheCloudStackUserTest {
+
+    @Test(expected = ApacheCloudStackClientRuntimeException.class)
+    public void contructorTestUsingNeitherOneOfTheConfigurations() {
+        new ApacheCloudStackUser("", "");
+        new ApacheCloudStackUser("", "", "");
+    }
+
+    @Test
+    public void contructorTestUsingKeys() {
+        new ApacheCloudStackUser("secretKey", "API-key");
+    }
+
+    @Test
+    public void contructorTestUsingUserCredentials() {
+        new ApacheCloudStackUser("username", "pass", "/");
+    }
+
+}