How can I create a simple arithmetic operation (a b, for example)?

[Anon Anon]

I have to do some logic like "if x <= a + b { //do something }", and I can't find an easy way to do that?

 

Does anyone have a clue?

[Stephen Hughes]

This can be done using a few assertion to calculate the 2 numbers and then compare if the result is less than another number. Below you will find a policy fragment on how to do this.

<?xml version="1.0" encoding="UTF-8"?>

<wsp:Policy xmlns:L7p="http://www.layer7tech.com/ws/policy" xmlns:wsp="http://schemas.xmlsoap.org/ws/2002/12/policy">

    <wsp:All wsp:Usage="Required">

        <L7p:SetVariable>

            <L7p:Base64Expression stringValue="PGEvPg=="/>

            <L7p:ContentType stringValue="text/xml; charset=utf-8"/>

            <L7p:DataType variableDataType="message"/>

            <L7p:VariableToSet stringValue="math"/>

        </L7p:SetVariable>

        <L7p:SetVariable>

            <L7p:Base64Expression stringValue="MTU="/>

            <L7p:VariableToSet stringValue="a"/>

        </L7p:SetVariable>

        <L7p:SetVariable>

            <L7p:Base64Expression stringValue="MTI="/>

            <L7p:VariableToSet stringValue="b"/>

        </L7p:SetVariable>

        <L7p:SetVariable>

            <L7p:Base64Expression stringValue="MzA="/>

            <L7p:VariableToSet stringValue="result"/>

        </L7p:SetVariable>

        <L7p:ResponseXpathAssertion>

            <L7p:VariablePrefix stringValue="simpleMath"/>

            <L7p:XmlMsgSrc stringValue="math"/>

            <L7p:XpathExpression xpathExpressionValue="included">

                <L7p:Expression stringValue="$a + $b"/>

                <L7p:Namespaces mapValue="included">

                    <L7p:entry>

                        <L7p:key stringValue="s"/>

                        <L7p:value stringValue="http://schemas.xmlsoap.org/soap/envelope/"/>

                    </L7p:entry>

                </L7p:Namespaces>

                <L7p:XpathVersion xpathVersion="XPATH_1_0"/>

            </L7p:XpathExpression>

        </L7p:ResponseXpathAssertion>

        <L7p:ComparisonAssertion>

            <L7p:Expression1 stringValue="${simpleMath.results}"/>

            <L7p:Expression2 stringValue="${result}"/>

            <L7p:FailIfVariableNotFound booleanValue="false"/>

            <L7p:Operator operator="LE"/>

            <L7p:Predicates predicates="included">

                <L7p:item binary="included">

                    <L7p:Operator operator="LE"/>

                    <L7p:RightValue stringValue="${result}"/>

                </L7p:item>

            </L7p:Predicates>

        </L7p:ComparisonAssertion>

    </wsp:All>

</wsp:Policy>

[Anon Anon]

Its works perfectly!

 

Thank you very much!

 

Best regards.

[Derek Orr]

We do have a custom assertion that does this for us!

 

Sent from my iPhone

[mogol01]

The XPath assertion should cover your basic math needs.

 

If you're doing anything more sophisticated that XPath can't do - e.g. mathematical functions like SIN and LOG -  there's a Tactical "Evaluate Math Expression" assertion that might be of value. Talk to Support if you need it.

[Ozgur Anil Demir]

Hello,

I tried xpath assertion as you mentioned, but it is NOT RELIABLE. 

I need to calculate 86400 + ${gateway.time.seconds} for every request.

Let me explain;

Example for successful calculation;
when a = 86400 and b =1674554585

$a + $b = 1.674640985E9  --> the result is 1674640985, it works fine for this values
 
Example for wrong calculation;
when a = 86400 and b = 1674554480
it calculates;
$a + $b = 1.67464088E9 --> But the result is 1674640880, not 167464088. There is a missing zero.

It is very hard to understand that why are you so insistent about not developing an basic calculator for almost ten years?

[Aran White]

Did you try the Javascript assertion ? 

https://techdocs.broadcom.com/us/en/ca-enterprise-software/layer7-api-management/api-gateway/10-1/policy-assertions/assertion-palette/service-availability-assertions/execute-javascript-assertion.html

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Aran White - [JobTitle]
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[Ozgur Anil Demir]

Hello Aran,

Yes, after the situation about xPath I tried  javascript assertion and Perform JDBC Query assertion for calculation.

It is so simple to calculate with Perform JDBC Query Assertion.
Query could be like;
SELECT 360+86400 AS mathSum; 
But I am not sure about that could affect the performance seriously or not due to using database connection. 

Javascript assertion can be more effective.

Thanks

[Aran White]

policy might look like this

JS would look like this

var vara = context.getVariable('a');
var varb = context.getVariable('b');
var total = vara + varb;

context.setVariable("js.total", total);



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Aran White - [JobTitle]
[CompanyName]
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