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This sample demonstrates the functionality of the Transaction Mediator using a sample distributed transaction. In this sample, a record is deleted from one database and added to a second database. If either of the operations (deleting from the first database and adding to the other) fails, all operations will roll backrollback, and the records will do not change.

Prerequisites

  • For a list of general prerequisites, see Setting Up the ESB Samples.
  • The sample configuration uses two data sources datasources and database instances to point to the sample databases. You have to manually create these in your environment for the sample to work.
    • For information on creating database instances, see Setting up the Physical Database
    • For information on how you can set up the Derby database server, see Setting Up the ESB Samples.
    • For information on creating the two sample XA data sources, see Adding Datasources and Transaction Examples.

      Setup two distributed Derby databases  esbdb and  esbdb1.  For instructions on setting up the Derby databases,  see Setting up Remote Derby.

    • Create a table in esbdb by executing the following statement.

      Code Block
      SQL
      SQL
      CREATE table company(name varchar(10) primary key, id varchar(10), price double);
    • Create a table in esbdb1 by executing the following statement.

      Code Block
      SQL
      SQL
      CREATE table company(name varchar(10) primary key, id varchar(10), price double);
    • Insert records into the two tables that you created by executing the following statements.

      To insert records into the table in esbdb

      Code Block
      SQL
      SQL
      INSERT into company values ('IBM','c1',0.0);
      INSERT into company values ('SUN','c2',0.0);
      

      To insert records into the table in esbdb1

      Code Block
      SQL
      SQL
      INSERT into company values ('SUN','c2',0.0);
      INSERT into company values ('MSFT','c3',0.0);
      
      Info
      titleNote

      When inserting records into the tables, the order of the record matters.

    • Add the required datasource via the Management Console or create datasource declarations for the distributed databases In the master-datasources.xml file. For information on how you can add datasources via the management console, see Adding DatasourcesTo create datasource declarations In the master-datasources.xml file, add the following code segments in the master-datasources.xml file located in the <ESB_HOME>/repository/conf/datasources directory, ensuring that the datasource file names are *-xa-ds.xml:

      Datasource1: esb-derby-xa-ds.xml

      Code Block
      XML
      XML
      <datasources>
          <xa-datasource>
              <jndi-name>jdbc/XADerbyDS</jndi-name>
              <isSameRM-override-value>false</isSameRM-override-value>
              <xa-datasource-class>org.apache.derby.jdbc.ClientXADataSource</xa-datasource-class>
              <xa-datasource-property name="portNumber">1527</xa-datasource-property>
              <xa-datasource-property name="DatabaseName">esbdb</xa-datasource-property>
              <xa-datasource-property name="user">esb</xa-datasource-property>
              <xa-datasource-property name="password">esb</xa-datasource-property>
              <metadata>
                  <type-mapping>Derby</type-mapping>
              </metadata>
          </xa-datasource>
      </datasources>
      

      Datasource2: esb-derby1-xa-ds.xml

      Code Block
      XML
      XML
      <datasources>
          <xa-datasource>
              <jndi-name>jdbc/XADerbyDS1</jndi-name>
              <isSameRM-override-value>false</isSameRM-override-value>
              <xa-datasource-class>org.apache.derby.jdbc.ClientXADataSource</xa-datasource-class>
              <xa-datasource-property name="portNumber">1527</xa-datasource-property>
              <xa-datasource-property name="DatabaseName">esbdb1</xa-datasource-property>
              <xa-datasource-property name="user">esb</xa-datasource-property>
              <xa-datasource-property name="password">esb</xa-datasource-property>
              <metadata>
                  <type-mapping>Derby</type-mapping>
              </metadata>
          </xa-datasource>
      </datasources>
      

Building the sample

The XML configuration for this sample is as follows: 

Code Block
languagehtml/xml
linenumberstrue
<definitions xmlns="http://ws.apache.org/ns/synapse"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://ws.apache.org/ns/synapse http://synapse.apache.org/ns/2010/04/configuration/synapse_config.xsd">
    <sequence name="myFaultHandler">
        <log level="custom">
            <property name="text" value="** Rollback Transaction**"/>
        </log>
        <transaction action="rollback"/>
        <send/>
    </sequence>
    <sequence name="main" onError="myFaultHandler">
        <in>
            <send>
                <endpoint>
                    <address uri="http://localhost:9000/services/SimpleStockQuoteService"/>
                </endpoint>
            </send>
        </in>
        <out>
            <transaction action="new"/>
            <log level="custom">
                <property name="text" value="** Reporting to the Database esbdb**"/>
            </log>
            <dbreport useTransaction="true" xmlns="http://ws.apache.org/ns/synapse">
                <connection>
                    <pool>
                        <dsName>jdbc/XADerbyDS</dsName>
                        <user>synapse<<user>esb</user>
                        <password>synapse<<password>esb</password>
                    </pool>
                </connection>
                <statement>
                    <sql>delete from company where name =?</sql>
                    <parameter expression="//m0:return/m1:symbol/child::text()"
                               xmlns:m0="http://services.samples"
                               xmlns:m1="http://services.samples/xsd"
                               type="VARCHAR"/>
                </statement>
            </dbreport>
            <log level="custom">
                <property name="text" value="** Reporting to the Database esbdb1**"/>
            </log>
            <dbreport useTransaction="true" xmlns="http://ws.apache.org/ns/synapse">
                <connection>
                    <pool>
                        <dsName>jdbc/XADerbyDS1</dsName>
                        <user>synapse<<user>esb</user>
                        <password>synapse<<password>esb</password>
                    </pool>
                </connection>
                <statement>
                    <sql>INSERT into company values ('IBM','c4',12.0)</sql>
                </statement>
            </dbreport>
            <transaction action="commit"/>
            <send/>
        </out>
    </sequence>
</definitions>

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To build the sample

  1. Start the ESB with the sample 657 configuration. For instructions on starting a sample ESB configuration, see Starting the ESB with a sample configuration.
    The operation log keeps running until the server starts, which usually takes several seconds. Wait until the server has fully booted up and displays a message similar to "WSO2 Carbon started in n seconds."server and log into the Management Console. Click the Main tab on the Management Console, go to Manage -> Service Bus and then click Source View. Next, copy and paste the above synapse configuration to the source view.

  2. Start the Axis2 server. For instructions on starting the Axis2 server, see Starting the Axis2 server.

  3. Deploy the back-end service SimpleStockQuoteService. For instructions on deploying sample back-end services, see Deploying sample back-end services.

Info
titleInfor

WSO2 ESB comes with a default JTA transaction manager (Atomikos), which allows you to run distributed transactions without deploying the ESB on an external application server.

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The sample client used here is the the Stock Quote Client, which can operate in several modes. For further details on this sample client and its operation modes, see Stock Quote Client.

To execute the sample client

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When you run the client to test the failure scenario, you will see that all operations roll back and none of the records are affected. you will see that a record is neither deleted from the first database nor added into the second database. That is because executing the command attempts to add an already existing record again to the second database, which results in the fault sequence being executed. Therefore, an exception raised for duplicate entries and results in an entire transaction rollback.