String concatenation in Script Mediator of WSO2 ESB 5.0.0

[Article moved from ajanthane.blogspot.com]

If you are using String concatenation inside Javascript mediator, as the Rhino engine ( Rhino JavaScript engine (1.74) ) has been updated in WSO2 ESB5.0.0, the same concatenation functionality worked in ESB4.9.0 will not work in ESB5.0.0. As it is a problem in Rhino Engine, to overcome the issue you need to follow the below. To get more understanding you can refer [1] also.

[1] https://www-01.ibm.com/support/docview.wss?uid=swg1JR55739

When you set up proxy as below:

<?xml version="1.0" encoding="UTF-8"?>
<proxy xmlns="http://ws.apache.org/ns/synapse"
       name="StringConcatenationJS"
       startOnLoad="true"
       statistics="disable"
       trace="disable"
       transports="http,https">
   <target>
      <inSequence>
         <property name="STATUS"
                   value="--------------------StringConcatenationJS Proxy Invoked-------------------"/>
         <script language="js">var log = mc.getServiceLog();         
          log.info("-----------Executing Script Mediator-------------------- ");
          var name = 'ajanthan';
var addres = 'batticaloa'; 
var cconcatenatedString = name + addres;
           log.info("Concatenated string: " + cconcatenatedString);
           
           mc.setProperty('concatString',cconcatenatedString);</script>
         <log level="custom">
            <property expression="get-property('concatString')"
                      name="Concatenated String @ Property: "/>
         </log>
      </inSequence>
   </target>
   <description/>
</proxy>

You will get and Empty Result as below:

[2017-01-28 14:20:29,382]  INFO - ScriptMessageContext -----------Executing Script Mediator-------------------- 
[2017-01-28 14:20:29,383]  INFO - ScriptMessageContext Concatenated string: ajanthanbatticaloa
[2017-01-28 14:20:29,387]  INFO - LogMediator Concatenated String @ Property:  =

To overcome this when you set the property cconcatenatedString.toString().

Updated proxy as below:

<?xml version="1.0" encoding="UTF-8"?>
<proxy xmlns="http://ws.apache.org/ns/synapse"
       name="StringConcatenationJS"
       startOnLoad="true"
       statistics="disable"
       trace="disable"
       transports="http,https">
   <target>
      <inSequence>
         <property name="STATUS"
                   value="--------------------StringConcatenationJS Proxy Invoked-------------------"/>
         <script language="js">var log = mc.getServiceLog();         
          log.info("-----------Executing Script Mediator-------------------- ");
          var name = 'ajanthan';
var addres = 'batticaloa'; 
var cconcatenatedString = name + addres;
           log.info("Concatenated string: " + cconcatenatedString);
           
           mc.setProperty('concatString',cconcatenatedString.toString());</script>
         <log level="custom">
            <property expression="get-property('concatString')"
                      name="Concatenated String @ Property: "/>
         </log>
      </inSequence>
   </target>
   <description/>
</proxy>

The Result will be:

[2017-01-28 14:27:21,679]  INFO - ScriptMessageContext -----------Executing Script Mediator-------------------- 
[2017-01-28 14:27:21,679]  INFO - ScriptMessageContext Concatenated string: ajanthanbatticaloa
[2017-01-28 14:27:21,680]  INFO - LogMediator Concatenated String @ Property:  = ajanthanbatticaloa