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Objective: Introduction to the dblookup mediator

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Introduction

This sample demonstrates how to perform a simple database read operation database using the DBLookup mediator.

In this sample, when a message arrives at the DBLookup mediator, it opens a connection to the database and executes the SQL query. The SQL query uses the ? character for attributes that are specified at runtime, and the parameters define how to calculate the value of those attributes.Here, the DBLookup mediator is used to extract the id of the company from the company database using the symbol that is evaluated using an XPath against the SOAP envelope, and the id base switching is done by a Switch mediator.

Prerequisites

Set up the Apache Derby database. For information on how to set up the Derby database, see Setting up Derby.
For a list of general prerequisites, see Prerequisites to Start the ESB Samples.

Building the sample

The XML configuration for this sample is as follows:

Code Block

language	html/xml

<definitions xmlns="http://ws.apache.org/ns/synapse">

    <sequence name="myFaultHandler">
        <makefault>
            <code value="tns:Receiver" xmlns:tns="http://www.w3.org/2003/05/soap-envelope"/>
            <reason expression="get-property('ERROR_MESSAGE')"/>
        </makefault>

        <property name="RESPONSE" value="true"/>
        <header name="To" expression="get-property('ReplyTo')"/>
        <send/>
        <drop/>
    </sequence>

    <sequence name="main" onError="myFaultHandler">
        <in>
            <log level="custom">
                <property name="text"
                          value="** Looking up from the Database **"/>
            </log>
            <dblookup xmlns="http://ws.apache.org/ns/synapse">
                <connection>
                    <pool>
                        <driver>org.apache.derby.jdbc.ClientDriver</driver>
                        <url>jdbc:derby://localhost:1527/esbdb;create=false</url>
                        <user>esb</user>
                        <password>esb</password>
                    </pool>
                </connection>
                <statement>
                    <sql>select * from company where name =?</sql>
                    <parameter expression="//m0:getQuote/m0:request/m0:symbol"
                               xmlns:m0="http://services.samples/xsd" type="VARCHAR"/>
                    <result name="company_id" column="id"/>
                </statement>
            </dblookup>

            <switch source="get-property('company_id')">
                <case regex="c1">
                    <log level="custom">
                        <property name="text"
                                  expression="fn:concat('Company ID - ',get-property('company_id'))"/>
                    </log>
                    <send>
                        <endpoint>
                            <address uri="http://localhost:9000/services/SimpleStockQuoteService"/>
                        </endpoint>
                    </send>
                </case>
                <case regex="c2">
                    <log level="custom">
                        <property name="text"
                                  expression="fn:concat('Company ID - ',get-property('company_id'))"/>
                    </log>
                    <send>
                        <endpoint>
                            <address uri="http://localhost:9000/services/SimpleStockQuoteService"/>
                        </endpoint>
                    </send>
                </case>
                <case regex="c3">
                    <log level="custom">
                        <property name="text"
                                  expression="fn:concat('Company ID - ',get-property('company_id'))"/>
                    </log>
                    <send>
                        <endpoint>
                            <address uri="http://localhost:9000/services/SimpleStockQuoteService"/>
                        </endpoint>
                    </send>
                </case>
                <default>
                    <log level="custom">
                        <property name="text" value="** Unrecognized Company ID **"/>
                    </log>
                    <makefault>
                        <code value="tns:Receiver"
                              xmlns:tns="http://www.w3.org/2003/05/soap-envelope"/>
                        <reason value="** Unrecognized Company ID **"/>
                    </makefault>
                    <property name="RESPONSE" value="true"/>
                    <header name="To" action="remove"/>
                    <send/>
                    <drop/>
                </default>
            </switch>
            <drop/>
        </in>

        <out>
            <send/>
        </out>

    </sequence>

</definitions>

Prerequisites:

Setting up Derby database as explained above.
Start the Synapse configuration numbered 360: i.e. wso2esb-samples -sn 360
Start the Axis2 server and deploy the SimpleStockQuoteService if not already done

This sample demonstrates simple database read operations through ESB. When a message arrives at dblookup mediator, it opens a connection to the database and executes the SQL query. The SQL query use '?' character for attributes that will be filled at runtime. The parameters define how to calculate the value of those attributes at runtime. In this sample a dblookup mediator has been used to extract 'id' of the company from the company database using the symbol which is evaluated using an xpath against the SOAP envelope. Then 'id' base switching will be done by a switch mediator.

When the IBM stock quote is requested,

...

This configuration file synapse_sample_360.xml is available in the <ESB_HOME>/repository/samples directory.

To build the sample

Start the ESB with the sample 360 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."
Start the Axis2 server.
Deploy the back-end service SimpleStockQuoteService. For instructions on deploying sample back-end services, see Deploying sample back-end services.

Executing the sample

The sample client used here is 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

Run each of the following commands from the <ESB_HOME>/samples/axis2Client directory.
First, run the following command, specifying IBM as the stock symbol:
Code Block
language bash
ant stockquote -Daddurl=http://localhost:9000/services/SimpleStockQuoteService -Dtrpurl=http://localhost:8280/ -Dsymbol=IBM

ESB console shows

Code Block
INFO LogMediator text = Looking up from the Database INFO LogMediator text = Company ID ? c1

For the SUN stock quote,

...

Then, run the following command, specifying SUN as the stock symbol.

Code Block

language	bash

ant stockquote -Daddurl=http://localhost:9000/services/SimpleStockQuoteService -Dtrpurl=http://localhost:8280/ -Dsymbol=SUN

Next, run the following command, specifying MSFT as the stock symbol.

Code Block

language	bash

ant stockquote -Daddurl=http://localhost:9000/services/SimpleStockQuoteService -Dtrpurl=http://localhost:8280/ -Dsymbol=

...

MSFT

Analyzing the output

When you run the command that requests the IBM stock quote, you will see the following output on the ESB console:

Code Block
INFO LogMediator text = Looking up from the Database INFO LogMediator text = Company ID ? c2

...

c1

When you run the command that requests the SUN stock quote, you will see the following output on the ESB console:

Code Block

antINFO LogMediator stockquotetext -Daddurl=http://localhost:9000/services/SimpleStockQuoteService -Dtrpurl=http://localhost:8280/ -Dsymbol=MSFT
= ** Looking up from the Database **INFO LogMediator text = Company ID ? c2

When you run the command that requests the MSFT stock quote, you will see the following output on the ESB console:

Code Block
INFO LogMediator text = Looking up from the Database INFO LogMediator text = Company ID ? c2

For If you run a command for any other symbolssymbol, you will see that the ESB console showsdisplays the following:

Code Block
INFO LogMediator text = Unrecognized Company ID

and You will also observe that the client gets a response which has with the following message.

Code Block
Unrecognized Company ID

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Key

Introduction

Prerequisites

Building the sample

Executing the sample

Analyzing the output