Export to Excel Using ScriptRunner

import com.atlassian.jira.component.ComponentAccessor
String fileName = 'filename.xls'
String userName = 'admin'
Long structureId = 1L
Long viewId = 2L
String viewSpec = null
String expandState = null
String clientFilter = null
def plugin = ComponentAccessor.pluginAccessor.getPlugin('com.almworks.jira.structure')
def helper = plugin.getModuleDescriptor('helper').module
def ExcelExporter = plugin.classLoader.loadClass('com.almworks.jira.structure.export.excel.ExcelExporter')
def exporter = helper.instantiate(ExcelExporter)
def ForestSpec = plugin.classLoader.loadClass('com.almworks.jira.structure.api.forest.ForestSpec')
def spec = ForestSpec.structure(structureId, helper.userManager.getUser(userName))
exporter.configure(viewId, viewSpec, spec, expandState, clientFilter)
exporter.prepareExport()
exporter.createWorkbook({null})
def stream = new FileOutputStream(fileName)
try {
    exporter.writeWorkbookTo(stream)
} finally {
    stream.close()
    return new File(fileName).toPath().toAbsolutePath()
}