Updating README about Sensitive Logging in JavaSdk

Author: vijayabraj

README.md

@@ -114,6 +114,34 @@ To create the javadocs...
 ### Testing Guide
 For additional help in testing your own code, Authorize.Net maintains a [comprehensive testing guide](http://developer.authorize.net/hello_world/testing_guide/) that includes test credit card numbers to use and special triggers to generate certain responses from the sandbox environment.
 
+## Logging Sensitive Data
+The Authorize.Net Java SDK uses Log4J framework for logging purposes and it can be enabled by keeping a configuration file `Log4j.properties` in the resources folder of the application. A sample [Log4.properties](https://github.com/AuthorizeNet/sdk-java/blob/master/resources/log4j.properties) file has been provided as a reference. 
+
+The possible log levels are `DEBUG, INFO, WARN, ERROR` and `FATAL`. 
+
+There is a new pattern layout introduced to mask sensitive data while logging and can be used with the application by providing the following configurations in the `Log4j.properties` file:  
+```
+// Default configuration which logs the entries in clear text
+log4j.appender.S.layout = org.apache.log4j.PatternLayout
+log4j.appender.R.layout = org.apache.log4j.PatternLayout
+
+// Configuration which masks the sensitive data in the log entries
+log4j.appender.S.layout = net.authorize.util.SensitiveFilterLayout
+log4j.appender.R.layout = net.authorize.util.SensitiveFilterLayout
+```
+By default the logger comes with two appenders i.e **console** and **file transport**. 
+
+The list of sensitive fields which can be masked during logging are:
+* Card Number,
+* Card Code,
+* Expiration Date,
+* Name on Account,
+* Transaction Key, and
+* Account Number. 
+
+There is also a list of regular expressions which the sensitive logger uses to mask credit card numbers while logging. 
+
+Further information on the sensitive data logging and regular expressions can be found at this [location](https://github.com/AuthorizeNet/sdk-java/blob/master/resources/AuthorizedNetSensitiveTagsConfig.json).
 
 ## License
 This repository is distributed under a proprietary license. See the provided [`LICENSE.txt`](/LICENSE.txt) file.