This is a workflow xml example for Liferay DXP (7.0) to sent form data through a workflow to an external rest service.

form-data-to-rest.xml

<?xml version="1.0"?>
<!-- this workflow will sent data from a simple form (subject and description field) to an external rest service -->
<workflow-definition
	xmlns="urn:liferay.com:liferay-workflow_7.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:liferay.com:liferay-workflow_7.0.0 http://www.liferay.com/dtd/liferay-workflow-definition_7_0_0.xsd">
	<name>Logger</name>
	<description></description>
	<version>1</version>
	<state>
		<name>Start</name>
		<metadata>
			<![CDATA[{"xy":[100,40]}]]>
		</metadata>
		<actions>
			<action>
				<name>Log</name>
				<description></description>
				<script>
					<![CDATA[
						import com.liferay.portal.kernel.util.GetterUtil;
						import com.liferay.portal.kernel.workflow.WorkflowConstants;
						import com.liferay.portal.kernel.service.ServiceContext;
						import com.liferay.dynamic.data.lists.model.DDLRecord;
						import com.liferay.dynamic.data.lists.service.DDLRecordLocalServiceUtil;
						import com.liferay.dynamic.data.lists.service.DDLRecordVersionLocalServiceUtil
						import com.liferay.dynamic.data.lists.model.DDLRecordVersion;
						import com.liferay.dynamic.data.mapping.storage.DDMFormFieldValue;
						import java.net.HttpURLConnection;
						import java.net.URL;
						import java.net.URLEncoder;
						import java.io.DataOutputStream;
						import java.util.List;
						import java.util.Locale;

						long companyId = GetterUtil.getLong((String) workflowContext.get(WorkflowConstants.CONTEXT_COMPANY_ID));
						System.out.println("companyID: " + companyId);

						ServiceContext serviceContext = (ServiceContext) workflowContext.get(WorkflowConstants.CONTEXT_SERVICE_CONTEXT);

        				long classPK = GetterUtil.getLong((String)workflowContext.get(WorkflowConstants.CONTEXT_ENTRY_CLASS_PK));
						System.out.println("original classPK: " + classPK);

						DDLRecordVersion ddlRecordVersion = DDLRecordVersionLocalServiceUtil.getRecordVersion(classPK);
        				DDLRecord ddlRecord = DDLRecordLocalServiceUtil.getRecord(ddlRecordVersion.getRecordId());

						Locale locale = new Locale("en", "US");

						List<DDMFormFieldValue> values;
						values = ddlRecord.getDDMFormFieldValues("Subject");
						String subject = "";
        				for(DDMFormFieldValue value : values){
							subject = value.getValue().getString(locale);
							System.out.println("subject: " + subject);
						}

						values = ddlRecord.getDDMFormFieldValues("Description");
						String description = "";
        				for(DDMFormFieldValue value : values){
							description = value.getValue().getString(locale);
							System.out.println("description: " + description);
						}

						// checkout http://mockbin.org/bin/14f67c2e-66d3-47dd-b715-083d7b7d6d57/log for actual request
						URL obj = new URL("http://mockbin.org/bin/14f67c2e-66d3-47dd-b715-083d7b7d6d57");
						HttpURLConnection con = (HttpURLConnection) obj.openConnection();
						
						//add request header
						con.setRequestMethod("POST");
						con.setRequestProperty("User-Agent", "LiferayDXP");
						con.setRequestProperty("Accept-Language", "en-US,en;q=0.5");
						
						String urlParameters = "";
						urlParameters += "subject=" + URLEncoder.encode(subject,"utf-8");
						urlParameters += "&description=" + URLEncoder.encode(description,"utf-8");
						
						// Send post request
						con.setDoOutput(true);
						DataOutputStream wr = new DataOutputStream(con.getOutputStream());
						wr.writeBytes(urlParameters);
						wr.flush();
						wr.close();

						int responseCode = con.getResponseCode();

						System.out.println("Responsecode: " + responseCode);

					]]>
				</script>
				<script-language>groovy</script-language>
				<execution-type>onEntry</execution-type>
			</action>
			<notification>
				<name>Notifier</name>
				<description></description>
				<template>
					<![CDATA[Hi, you just received a message from the workflow]]>
				</template>
				<template-language>text</template-language>
				<notification-type>user-notification</notification-type>
				<recipients>
					<user/>
				</recipients>
				<execution-type>onEntry</execution-type>
			</notification>
		</actions>
		<initial>true</initial>
		<transitions>
			<transition>
				<name>connector135430</name>
				<target>End</target>
				<default>true</default>
			</transition>
		</transitions>
	</state>
	<state>
		<name>End</name>
		<metadata>
			<![CDATA[{"terminal":true,"xy":[100,500]}]]>
		</metadata>
		<actions>
			<action>
				<name>Approve</name>
				<description>Approve</description>
				<script>
					<![CDATA[com.liferay.portal.kernel.workflow.WorkflowStatusManagerUtil.updateStatus(com.liferay.portal.kernel.workflow.WorkflowConstants.getLabelStatus("approved"), workflowContext);]]>
				</script>
				<script-language>groovy</script-language>
				<execution-type>onEntry</execution-type>
			</action>
		</actions>
	</state>
</workflow-definition>