Wednesday, October 29, 2014

[WSO2 ESB] Comparing two XMLs and find matching elements using WSO2 ESB 4.8.0

Imagine we are getting a list of xml data from an external service and it is required to match this response against another xml payload and find the matching xml elements inside ESB 4.8.0. For e.g. a user send the below request into ESB.

Inside ESB we are calling an Account DB service which retrieves all the Account elements inside the database and return us. Assume the BE response with Account details is as follows.

<a123: Accounts xmlns:a123=">


Once this response comes into ESB it is required to compare the two xmls and retrieve Account elements that matches with account numbers which are in incoming request. We can do this through an iterate mediator inside ESB too, however the way that is explained here is rather simple to be used, specially for a scenario when it is not possible to use Iterate mediator.

1. When the incoming request comes, we can use xpath to get a comma separated String with all account numbers in the request. Then assign it to a Property mediator.

<property name="accountsList" expression="string-join(//Accounts/acctNum, ',')" scope="default" type="STRING"/>
This XPath expression uses string-join() function from Xpath 2.0. Therefore it is required to enable the below property in ESB/repository/conf/ file in order to support Xpath 2.0

# Uncomment following to support fallback XPATH 2.0 support with DOM and Saxon
2. Once this property is set we can call the BE and get the Account details response. Then the response payload will be passed to the given XSLT stylesheet using XSLT mediator in ESB.
Also as there is comparison needs to be done here, i am passing the previous 'accountsList' property as a parameter into XSLT stylesheet as well.

<xslt key="MatchingAccounts">
    <property name="AccountsList" expression="$ctx:accountsList"

3. The stylesheet is added as a local-entry in the ESB with the name 'MatchingAccounts'. If needed you can add this as a Registry resource too.

<localEntry xmlns="" key="MatchingAccounts">
<xsl:stylesheet xmlns:xsl="" xmlns:a123=" xmlns:fn="" version="2.0">
        <xsl:param name="AccountsList"/>
        <xsl:output method="xml" indent="yes"/>
        <xsl:template match="/">
            <Result xmlns="">
                <xsl:for-each select="//a123:Account">
                    <xsl:if test="matches($AccountsList,
                        <xsl:copy-of select="."/>

4. Inside the style sheet if process through each a123:Account/a123:AcctNum element and checks whether the 'accountsList' String contains that account number. If there is a match that <Account> node is taken as results.

5. For the above two XMLs the final payload that comes outside XSLT mediator will be like this, with one matching Account node.
<Result xmlns="">

Sunday, September 7, 2014

[WSO2 ESB] Sending Form Data through WSO2 ESB with x-www-form-urlencoded content type

This post is about how to post form data into a REST service from WSO2 ESB 4.8.1.
Imagine that we have the following key values pairs to be passed into a REST service  which accepts x-www-form-urlencoded type data.


Now when we going to send these data into ESB, it is needed to set them as key values pairs through adding a PayloadFactory mediator in the following format.  

<property name="name" value="ishara" scope="default" type="STRING"/>
<property name="company" value="wso2" scope="default" type="STRING"/>/>
<property name="country" value="srilanka" scope="default" type="STRING"/>/>

<payloadFactory media-type="xml">
                    <soapenv:Envelope xmlns:soapenv="">
                    <arg evaluator="xml" expression="$ctx:name"/>
                    <arg evaluator="xml" expression="$ctx:company"/>
                    <arg evaluator="xml" expression="$ctx:country"/>


Then set the messageType property as 'application/x-www-form-urlencoded'. This is how ESB can identify these key-value pairs as form data and it will do the transformations. Then it is also required to disable chunking too.
<property name="messageType" value="application/x-www-form-urlencoded" scope="axis2" type="STRING"/>
<property name="DISABLE_CHUNKING" value="true" scope="axis2" type="STRING"/>

Now we are all set to call the REST endpoint with this message data as below. You can use either send or a call mediator.

   <endpoint key="conf:endpoints/EmployeeDataServiceEndpoint.xml"/>


Sunday, August 31, 2014

[WSO2 ESB] Enrich Mediator Patterns

WSO2 ESB Enrich Mediator can process a message based on a given source configuration and then perform the specified action on the message by using the target configuration. The following post specifies some of the source/target patterns that can be used with Enrich mediator. The flow is explained in 'description' element of each mediator entry to make it easily understandable.

1. Adding a property value into message body as a sibling

<property name="failureResultProperty" scope="default" description="FailureResultProperty">
        <result xmlns="">failure</result> 

        <source xpath="$ctx:failureResultProperty"/>
        <target type="body" action="sibling"/> 

2. Append new elements into a property using two enrichs

<property name="testMessages" scope="default" description="Test Messages Property">
<property name="testMsg" expression="//testMessage" scope="default" type="OM"/>

<enrich description="Get testMessages into current msg body">
            <source type="property" property="testMessages"/>
            <target type="body"/> 

<enrich description="Append testMsg into testMessages property">
            <source xpath="$ctx:testMsg"/>
            <target type="body" action="child"/> 


<property name="testMessages" description="Set testMessages property back"  expression="//testMessages" scope="default" type="OM"/>
The final output for 'testMessages' property after enriching will be like this.


3 . Append direct to a property using single Enrich.
<property name="testMessages" scope="default" description="Test Messages Property">
            <source xpath="//testMessage"/>
            <target action="child" xpath="$ctx:testMessages"/>


[WSO2 ESB] How to Read Local Entries and Registry Entries

This post is rather a quick note to my self. In WSO2 ESB we can have external reference to a file using either a local entry or a registry entry. 

Local-entry :

An entry stored in the local registry. The local registry acts as a memory registry where you can store text strings, XML strings, and URLs. These entries can be retrieved from a mediator.

Registry-entry :
WSO2 ESB makes use of a registry to store various configurations and artifacts such as sequences and endpoints. A registry is a content store and a metadata repository. Various SOA artifacts such as services, WSDLs, and configuration files can be stored in a registry and referred to by a key, which is a path similar to a UNIX file path.

1. This is how we can read some value stores in a local-entry. Let's say i have a value stored in local-entry file 'testEntry'.

<localEntry xmlns="" key="testEntry">12345</localEntry>

 This is how we can read this value into a mediator.

<property name="testProp" expression="get-property('testEntry')" scope="default" type="STRING"/>

2. If this 'testEntry' file is stored in the registry we have to use 'registry' scope with get-property() XPath extension function and read entry as below.

<property name="testProp" expression="get-property('registry', 'conf://custom/testEntry')" scope="default" type="STRING"/>

[WSO2 ESB] Property mediator : Performing XPath Expressions with and without Namespaces

Assume that we have an XML payload where there are several namespaces defined and we need to retrieve values of some elements from the payload into Properties using XPath. There are several ways to do this. We can either define the namespace in the property mediator and then refer to XML element via XPath with adding the namespace itself into the Xpath operation. let's get started with this.

Below is our payload.

<abc  xmlns="" >

For e.g i need to read the value 'A' into a property.  Following are the two ways for this However the 2nd option is more cleaner approach since we can get rid of adding namespace references every where. In addition to Property mediator, this can be used with other mediators in WSO2 ESB whether XPath operations are supported.

1. Use name space entries with property mediator

<property  xmlns:ns="" name="aValue" expression="//ns:abc/ns:A" scope="default" type="STRING"/>

2. Use local-name() option in XPath in order to avoid name spaces and get the same element value with property mediator.

<property name="aValueWithoutNS" expression="//*[local-name()='A']" scope="default" type="STRING"/>


[WSO2 ESB] XSLT mediator : Writing a simple style sheet

The XSLT Mediator of WSO2 ESB applies a specified XSLT transformation to a selected element of the current message payload. In this post i am going to write a simple XSLT style sheet which will read values from the current XML payload inside ESB using XPath and populate them into style sheet to create a new or different payload.

Below is our original XML payload.

We will be passing this payload into XSLT mediator with specifying a certain drink name as a parameter to the style sheet. For e.g i am passing drink name as 'Coffee'. At the style sheet it will traverse through incoming payload and find the <lunch> elements which contains 'Coffee' as drink name. If matches found we add the prices of those elements under a new <Payment> element. So when we come out of XSLT mediator the payload will be now changed to the <Payment> entry where it contains drinkPrices of matching elements.

The style sheet 'discountPayment.xsl' is like this.

<xsl:stylesheet xmlns:xsl="" xmlns:fn="" xmlns:m0="http://services.samples" version="2.0" exclude-result-prefixes="m0 fn">
        <xsl:output method="xml" omit-xml-declaration="yes" indent="yes"/>
        <xsl:param name="drink_name"/>
        <xsl:template match="/">
                <xsl:for-each select="//Order/lunch[contains(drinkName, $drink_name)]">
                        <xsl:value-of select="drinkPrice"/>

Add this style sheet into local-entries of ESB and it can be referred from XSLT mediator as this.

After coming out from XSLT mediator now our current message payload is changed to below.

[WSO2 ESB] Using [resource] attribute for [xsd:import] elements in a scheme file with Validate Mediator

The Validate Mediator in WSO2 ESB is used for schema validation of messages. Then this message is validated against the schema specified.

When we use validate mediator against a schema that schema file itself can contain some other schema references under <xsd:import> elements like below.

If our schema file is like this, in this scenario validate mediator tries to map and find the internal schemas which are defined in <xsd:import> elements. If these cannot be found, ESB will log an error saying that "The resource "{resource_file_name} can not be located"

Therefore in order to use these schema files with validate mediator follow the steps given below.

1. First add all the xsd files as local entries to ESB. These is no relative paths or nested folders supported so the xsd files has to be in local-entries folder itself. However if you put the schemas into registry nested folders are supported.

2. In the validate mediator there is an attribute called <resource>. Use this option to tell the validate mediator on where to find the files to import as below. Make sure ‘location’ and ‘schemaLocation’ entries has the same file name in order to map those correctly. Then the 'key' attribute is used to specify the current location of this schema file as shown in the given exmaple.

If you have added the schema files as registry entries, and when there are relative paths mentioned in parent schema, validate mediator can be used in  the following manner.

Sunday, May 25, 2014

WSO2 Message Broker 2.2.0 - An Overview of Newest WSO2 MB Release

After months of hard work we, WSO2 Message Broker team finally completed and released the version 2.2.0 of WSO2 MB, with several community demanded new features and improvements.

The release was initially planned to be go out with two main features namely Dead Letter Channel and Publisher Flow Control. However as the time goes we were able to introduce several more features listed as Cassandra and Zookeeper Profiles support with MB, Message Selectors and Dynamic Queue Support as well as improved SSL and Failover support and a lot more. Below is a quick overview of the newly released WSO2 MB 2.2.0 version. 

The complete information can be found in MB 2.2.0 official documentation which describes each of below feature in detail.

WS02 MB 2.2.0 New Admin Console

What comes new ???

First let's download WSO2 MB 2.2.0 version to experience the new features. Now we are ready go through the list  :)

๏ Dead Letter Channel implementation
The Dead Letter Channel (DLC) is specifically designed to persist messages that are faulty or rejected by the message receivers, providing you with a choice on whether to delete, retrieve or reroute the messages from the DLC. If the subscriber rejected the message, did not ack the sever within a configured time or could not receive message due to connection fail first MB erver will try to resend the message.After doing this for a maximum number of configured times  the message will be routed to DLC.

A user can perform following actions on DLC messages
  • Delete (discard mal-formatted message)
  • Restore message to the original queue 
  • Re-route the message to any other existing queue in MB cluster

๏ Publisher Flow control implementation
Flow control ensures that the rate at which messages are transmitted from the publisher to the receiver is controlled. Back-pressure is exerted when the defined global memory threshold or message count threshold per connection is exceeded. At this point, message acceptance is blocked until the sender is notified of memory recovery.  If the memory is not recovered within a specified time interval 'qpid.flow_control_wait_failure' which is by default 120s (2 mins), all currently publishing clients will be disconnected. But the subscriber clients will be able to continue.
The users are able to increase/decrease this wait time as needed by setting system property 'qpid.flow_control_wait_failure' at client-side. This value is 'long' type.

WSO2 MB 2.2.0 comes with following flow control mechanisms.
1. Throttling based on global memory threshold
2. Throttling based on message count per connection

๏ MB profile support for Cassandra and Zookeeper
With the previous MB releases it was required to download Cassandra and Zookeeper from external sites and point MB to be run with those. From 2.2.0 onwards this is no longer needed and you can start WSO2 MB purely as a Apache Cassandra server. All configurations files of Cassandra are there plus the port is configurable with an offset. The logs related to Cassandra are written to wso2carbon.log file as well as we have introduced a new log file specially for Cassandra system logs, as <MB_HOME>/repository/logs/cassandra_system.log file. Cassandra tools such as nodetool,cassandra-cli scripts are also packed inside MB. Also now you can start WSO2 MB purely as a Apache Zookeeper server. Hence in order to create a complete message broker cluster the users only need a WSO2 MB distribution.

๏ JMS message selectors support
Message selectors allow you to filter specific messages using a selector string. The message consumer will then receive only messages whose headers and properties match the selector. There are different patterns that can be used in selector strings, and the broker (JMS provider) filters messages according to that query. It is not possible for a message selector to filter messages on the basis of the content of the message body.

๏ Queue/Topic Permission model 
The role permission list is modified now the admin can explicitly set the each permissions like create queue/browse queue etc. inside a role. Therefore now when you create a queue/topic it can be selected whether this user can publish/subscribe to the created queue or topic.

WSO2 MB 2.2.0 Permission Model

๏ Dynamic queue support
In previous Message Broker releases users needed to create a subscriber or create the queue from admin console before start publishing messages to that queue and if not messages will be lost. Now this is  improved with dynamic queue support that when the publisher client initiates the queue is created in the broker, even if there are no consumers. The create queue segmant of message publisher would be as follows.
        QueueConnectionFactory connFactory = (QueueConnectionFactory) ctx.lookup(CF_NAME);
        QueueConnection queueConnection = connFactory.createQueueConnection();
        QueueSession queueSession =
                queueConnection.createQueueSession(false, QueueSession.AUTO_ACKNOWLEDGE);
        // create queue
        Queue queue =  queueSession.createQueue("Queue-MB");
        // create the message producer for queue
        javax.jms.QueueSender queueSender = queueSession.createSender(queue);

๏ Improved SSL support
The wire level connection between client-server of broker can be encrypted using SSL to provide maximum protection where this is supported in both standalone and clustered mode with failover as well. The SSL properies are easily configurable at the client side using AMQP connection url.

๏ Improved logging 
Trace level logs are now separated for easy debugging. In addition there are two more log files have been introduced for Cassandra and Zookeeper profiles named, cassandra_system.log and zookeeper.log file.

๏ Queue/Topics Subscription UI
A new segmant is introdued to WSO2 MB 2.2.0 admin console as shown in above image to view active/inactive queue and topic subscriptions for whole MB cluster. The following details are displayed in the new UI.
  • View active topic subscriptions in whole MB cluster 
  • View inactive durable topic subscriptions specifically.
  • Ability to unsubscribe inactive durable topic subscriptions with UI.

Queue/Topic Subscriptions UI

Apart from these major changes there are a lot of bug fixes and improvements in the new release. It was a great and hard team work for the last few months for all of us ( there are a lot in the team including our QA crew) to finally get the 2.2.0 release out. It is really proud to be a part of my team and we are now gearing up for WSO2 MB 3.0.0 which will be coming out as a complete revamped architecture. Looking forward for 3.0.0 :) :)

[Quick Note] Modifying Git Configurations in Ubuntu and Windows

OS : Ubuntu 13.10 or Windows 7

This is a brief post on how to change default configuration entries for Git.

There might be requirements that you need to change the default username where the commits get written to github, specially if you created a new github account, changed email etc.

Git uses global configuration file called .gitconfig in order to store the global credentials. To change the default user you can simply edit this file.

isha@thinkpad:~$ vim .gitconfig

For Windows this file can be found in file: git/etc/.config location.
I have set the following three properties here.

 1. username: github username of author.
 2. user email: github email address of user.
 3. credential helper: turn on the credential helper so that Git will save your password in memory for some time. By default Git will cache your password for 15 minutes. You can change this by changing --timeout property in the command.

        name = ishadil
        email =
        helper = cache --timeout=3600  // i have changed timeout for 1 hour

Other option is doing this using the command prompt as below.

git config --global "ishadil"

git config --global ""

git config --global credential.helper 'cache --timeout=3600'

After that use git config --global --list command to verify whether the properties are reset correctly.

git config --global --list

In a similar manner there are lot more configuration entries that can be set into this file. For e.g. let's set a proxy url in to git .config file.

    proxy =

Wednesday, February 19, 2014

WSO2 ESB Performance Round 7.5 is now released ......

As the Enterprise Service Bus 4.8.1 version was out in early February this year WSO2 ESB team has carried out a latest ESB Performance round, which results in that the newly released WSO2 ESB clearly outperforms other ESBs in the current market. The ESB Performance round 7.5 testing was conducted on an Amazon c1.xlarge EC2 instance of a 64-bit instance with 8 cores, 20 ECUs, and 7GB of memory.

The following table and graph show the summary results which is drawn against 'Average TPS Values' per 'Proxy Service' of the performance test. In summary it can be stated that,

As shown in the graphs below, WSO2 ESB 4.8.1 is the fastest in performance compared to all the other ESBs here, except for the security scenario.



The 'ESB Performance Round 7.5' article in the WSO2 Library provides a comprehensive report of the complete test round.