How to Set Query Parameters on Outgoing Messages

REST clients use query parameters to provide inputs for the relevant operation. These query parameters may be required to carry out the back-end operations either in a REST service or a proxy service.

Shown below is an example request that uses query parameters.

curl -v -X GET "http://localhost:8290/stockquote/view/IBM?param1=value1&param2=value2"

Synapse configuration

Following is a sample REST API configuration that can be used to implement this scenario. See the instructions on how to build and run this example.

There are two query parameters (customer name and ID) that must be set in the outgoing message from the Micro Integrator. We can configure the API to set those parameters as shown below. The path and query parameter values can be accessed through expressions.

REST APIEndpoint

<api name="StockQuoteAPI" context="/stockquote" xmlns="http://ws.apache.org/ns/synapse">
    <resource methods="GET" uri-template="/view/{symbol}?param1={param1}&amp;param2={param2}">
        <inSequence>
            <payloadFactory media-type="xml" template-type="default">
                <format>
                    <m0:getQuote xmlns:m0="http://services.samples">
                        <m0:request>
                            <m0:symbol>${params.uriParams.symbol}</m0:symbol>
                            <m0:customerName>${params.queryParams.param1}</m0:customerName>
                            <m0:customerId>${params.queryParams.param2}</m0:customerId>
                        </m0:request>
                    </m0:getQuote>
                </format>
            </payloadFactory>
            <property name="SOAPAction" scope="transport" type="STRING" value="urn:getQuote" />
            <call>
                <endpoint key="SimpleStockQuoteService"/>
            </call>
            <respond/>
        </inSequence>
        <faultSequence>
        </faultSequence>
    </resource>
</api>

<endpoint name="SimpleStockQuoteService" xmlns="http://ws.apache.org/ns/synapse">
    <address format="soap11" uri="http://localhost:9000/services/SimpleStockQuoteService"/>
</endpoint>

Reading a query or path parameter

You can define a REST API and access the query parameters or path parameters by defining them in expressions. The following is a sample code that shows how the resource is defined.

<resource methods="GET" uri-template="/{val1}/groups/{val2}/json?q1={v1}&amp;q2={v2}">

Reading a query parameter

The following sample indicates how the expressions can be defined using ${params.queryParams.param1} to read a query parameter.

<property name="queryParam" expression="${params.queryParams.param1}"></property>

Reading a path parameter

The following sample indicates how the expressions can be defined using ${params.uriParams.symbol} to read a path parameter.

<property name="pathParam" expression="${params.uriParams.symbol}"></property>

Build and run

Create the artifacts:

1. Launch Visual Studio Code with the Micro Integrator for VS Code extension (MI for VS Code) installed.

   Info

   Follow the Install Micro Integrator for VS Code documentation for a complete installation guide.

2. Create an integration project.

3. Create the REST API with the configurations given above.
4. Deploy the artifacts in your Micro Integrator.

Set up the back-end service:

1. Download the back-end service.
2. Extract the downloaded zip file.
3. Open a terminal, navigate to the axis2Server/bin/ directory inside the extracted folder.

4. Execute the following command to start the axis2server with the SimpleStockQuote back-end service:

   On MacOS/LinuxOn Windows

   sh axis2server.sh
   

   axis2server.bat
   

Invoke the sample API by executing the following command:

curl -v -X GET "http://localhost:8290/stockquote/view/IBM?param1=value1&param2=value2"

You will receive the following response:

<soapenv:Body>
    <ns:getQuoteResponse>
        <ax21:change>-2.86843917118114</ax21:change>
        <ax21:earnings>-8.540305401672558</ax21:earnings>
        <ax21:high>-176.67958828498735</ax21:high>
        <ax21:last>177.66987465262923</ax21:last>
        <ax21:low>-176.30898912339075</ax21:low>
        <ax21:marketCap>5.649557998178506E7</ax21:marketCap>
        <ax21:name>IBM Company</ax21:name>
        <ax21:open>185.62740369461244</ax21:open>
        <ax21:peRatio>24.341353665128693</ax21:peRatio>
        <ax21:percentageChange>-1.4930577008849097</ax21:percentageChange>
        <ax21:prevClose>192.11844053187397</ax21:prevClose>
        <ax21:symbol>IBM</ax21:symbol>
        <ax21:volume>7791</ax21:volume>
    </ns:getQuoteResponse>
</soapenv:Body>