how to use macro in ftl - freemarker

Question

I have full of confusion in implementing the macro and functions in ftl.
can any one please add some useful information.
and what is the difference between macro and function in ftl
Thanks

Answer 1

The difference between macros and functions: macros are for generating markup (or other long text) and for flow-control and side-effects in general. Functions are for calculating other kind of values, including short plain text, and usually has no side-effects. These are reflected by that fact that macros has no return value, they just directly print to the output. Also the output of macros is not escaped by #escape. That's also why they look similar to HTML tags, while ${myFunction()} doesn't.
Other than that, what are you confused about? I assume you have found the FreeMarker Manual.

Answer 2

Below is the answer how to use macros in FTL :)
Input-smooks.Json:
{
"title": "Payment Received",
"firstName": "vijay",
"lastName": "dwivedi",
"accountId": "123",
"paymentId": "456",
"accounts": [
{
"accountId": "1111",
"paymentId": "1112"
},
{
"accountId": "2111",
"paymentId": "2112"
},
{
"accountId": "3111",
"paymentId": "3112"
}
]
}
Smook-config.xml file:
Define macros once and use as function whenever required
<smooks-resource-list xmlns="http://www.milyn.org/xsd/smooks-1.1.xsd"
xmlns:json="http://www.milyn.org/xsd/smooks/json-1.1.xsd" xmlns:ftl="http://www.milyn.org/xsd/smooks/freemarker-1.1.xsd">
<params>
<param name="stream.filter.type">SAX</param>
<param name="default.serialization.on">false</param>
</params>
<json:reader rootName="json" keyWhitspaceReplacement="_">
<json:keyMap>
<json:key from="date&time" to="date_and_time" />
</json:keyMap>
</json:reader>
<resource-config selector="json">
<resource>org.milyn.delivery.DomModelCreator</resource>
</resource-config>
<ftl:freemarker applyOnElement="json">
<ftl:template>
<!--
<#macro PopulateTasks task_list>
<#list task_list as att1>
"accountId": "${att1.accountId}"
"paymentId": "${att1.paymentId}"
</#list>
</#macro>
<#PopulateTasks json.accounts.element/>
-->
</ftl:template>
</ftl:freemarker>
</smooks-resource-list>
public static void main(String[] args) throws SmooksException, IOException, SAXException {
long start = System.currentTimeMillis();
Smooks smooks = new Smooks("src/main/resources/smooks-config.xml");
try {
smooks.filterSource(new StreamSource(new
FileInputStream("src/main/resources/input_smooks.json")), new
StreamResult(System.out));
} finally {
smooks.close();
}
}
<#PopulateTasks json.accounts.element/> this is the way to call macros