writer = new java.io.StringWriter() builder = new groovy.xml.MarkupBuilder(writer) customers = builder.customers() { acustomer = builder.cusomer(name:"John") builder.setCurrent(acustomer) builder.order() } println writer.toString() /* the output is <customers> <customer name='John' /> <order /> </customers> */ But if I let builder be NodeBuilder. e.g. builder = new groovy.util.NodeBuilder() the logic of customers is like <customers> <customer name='John' > <order/> </customer> </customers>