Pretty print XML

src/main/java/starter/Server.kt

@@ -23,7 +23,8 @@ class Server(private val views: Views, private val conf: StarterConfig) {
                 ctx.formParam(it.name) != null
             }
 
-            ctx.result(views.pom(deps, name, basePackage))
+            val generatedPom = views.pom(deps, name, basePackage)
+            ctx.result(prettyPrintXml(generatedPom))
             ctx.contentType("text/xml")
         }
     }

src/main/java/starter/Utils.kt

@@ -0,0 +1,49 @@
+package starter
+
+import org.w3c.dom.Document
+import org.w3c.dom.NodeList
+import org.xml.sax.InputSource
+import java.io.ByteArrayInputStream
+import java.io.StringWriter
+import javax.xml.parsers.DocumentBuilderFactory
+import javax.xml.transform.OutputKeys
+import javax.xml.transform.TransformerFactory
+import javax.xml.transform.dom.DOMSource
+import javax.xml.transform.stream.StreamResult
+import javax.xml.xpath.XPathConstants
+import javax.xml.xpath.XPathFactory
+
+
+/*
+    @see https://stackoverflow.com/a/33541820
+ */
+fun prettyPrintXml(xml: String, indent: Int = 4): String {
+    // Turn xml string into a document
+    val document: Document = DocumentBuilderFactory.newInstance()
+            .newDocumentBuilder()
+            .parse(InputSource(ByteArrayInputStream(xml.encodeToByteArray())))
+
+    // Remove whitespaces outside tags
+    document.normalize()
+    val xPath = XPathFactory.newInstance().newXPath()
+    val nodeList = xPath.evaluate("//text()[normalize-space()='']",
+            document,
+            XPathConstants.NODESET) as NodeList
+    for (i in 0 until nodeList.length) {
+        val node = nodeList.item(i)
+        node.parentNode.removeChild(node)
+    }
+
+    // Setup pretty print options
+    val transformerFactory = TransformerFactory.newInstance()
+    transformerFactory.setAttribute("indent-number", indent)
+    val transformer = transformerFactory.newTransformer()
+    transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8")
+    transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes")
+    transformer.setOutputProperty(OutputKeys.INDENT, "yes")
+
+    // Return pretty print xml string
+    val stringWriter = StringWriter()
+    transformer.transform(DOMSource(document), StreamResult(stringWriter))
+    return stringWriter.toString()
+}