added validation method

pom.xml

@@ -1,4 +1,5 @@
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 	<modelVersion>4.0.0</modelVersion>
 	<groupId>de.svenkubiak</groupId>
 	<artifactId>jpushover</artifactId>
@@ -104,6 +105,11 @@
 			<artifactId>fluent-hc</artifactId>
 			<version>4.3.6</version>
 		</dependency>
+		<dependency>
+			<groupId>org.apache.commons</groupId>
+			<artifactId>commons-lang3</artifactId>
+			<version>3.3.2</version>
+		</dependency>
 		<dependency>
 			<groupId>ch.qos.logback</groupId>
 			<artifactId>logback-classic</artifactId>

src/main/java/de/svenkubiak/jpushover/JPushover.java

@@ -4,6 +4,7 @@ import java.io.IOException;
 import java.util.List;
 
 import org.apache.commons.io.IOUtils;
+import org.apache.commons.lang3.StringUtils;
 import org.apache.http.Consts;
 import org.apache.http.HttpResponse;
 import org.apache.http.NameValuePair;
@@ -206,12 +207,52 @@ public class JPushover {
     }
     
     /**
-     * Send the message to pushover
+     * Sends a validation request to pushover ensuring that the token and user
+     * is correct, that there is at least one active device on the account.
+     * 
+     * Requires token parameter
+     * Requires user parameter
+     * Optional device parameter to check specific device
+     * 
+     * @return true if token and user are valid and at least on device is on the account, false otherwise
+     */
+    public boolean validate() {
+        Preconditions.checkNotNull(this.pushoverToken, "Token is required for validation");
+        Preconditions.checkNotNull(this.pushoverUser, "User is required for validation");
+        
+        List<NameValuePair> params = Form.form()
+                .add(Constants.TOKEN.get(), this.pushoverToken)
+                .add(Constants.USER.get(), this.pushoverUser)
+                .add(Constants.DEVICE.get(), this.pushoverDevice)
+                .build();
+        
+        HttpResponse httpResponse = null;
+        boolean valid = false;
+        try {
+            httpResponse = Request.Post(Constants.VALIDATION_URL.get()).bodyForm(params, Consts.UTF_8).execute().returnResponse();
+            
+            if (httpResponse != null && httpResponse.getStatusLine().getStatusCode() == 200) {
+                String response = IOUtils.toString(httpResponse.getEntity().getContent());
+                if (StringUtils.isNotBlank(response) && response.contains("\"status\":1")) {
+                    valid = true;
+                }
+            }
+        } catch (IOException e) {
+            LOG.error("Failed to send validation requeste to pushover", e);
+        }
+        
+        return valid;
+    }
+
+    /**
+     * Sends a message to pushover
+     * 
+     * @return JPushoverResponse instance
      */
     public JPushoverResponse push() {
-        Preconditions.checkNotNull(this.pushoverToken, "Token is required");
+        Preconditions.checkNotNull(this.pushoverToken, "Token is required for a message");
-        Preconditions.checkNotNull(this.pushoverUser, "User is required");
+        Preconditions.checkNotNull(this.pushoverUser, "User is required for a message");
-        Preconditions.checkNotNull(this.pushoverMessage, "Message is required");
+        Preconditions.checkNotNull(this.pushoverMessage, "Message is required for a message");
         
         if (Priority.EMERGENCY.equals(this.pushoverPriority)) {
             Preconditions.checkNotNull(this.pushoverRetry, "Retry is required on priority emergency");
@@ -237,7 +278,7 @@ public class JPushover {
         HttpResponse httpResponse = null;
         JPushoverResponse jPushoverResponse = null;
         try {
-            httpResponse = Request.Post(Constants.PUSHOVER_URL.get()).bodyForm(params, Consts.UTF_8).execute().returnResponse();
+            httpResponse = Request.Post(Constants.MESSAGES_URL.get()).bodyForm(params, Consts.UTF_8).execute().returnResponse();
             
             if (httpResponse != null) {
                 int status = httpResponse.getStatusLine().getStatusCode();

src/main/java/de/svenkubiak/jpushover/enums/Constants.java

@@ -6,7 +6,8 @@ package de.svenkubiak.jpushover.enums;
  *
  */
 public enum Constants {
-    PUSHOVER_URL("https://api.pushover.net/1/messages.json"),
+    MESSAGES_URL("https://api.pushover.net/1/messages.json"),
+    VALIDATION_URL("https://api.pushover.net/1/users/validate.json"),
     MESSAGE("message"),
     TITLE("title"),
     DEVICE("device"),