feat(#64): Add Output abstraction

src/main/java/org/xembly/Output.java

@@ -0,0 +1,48 @@
+package org.xembly;
+
+import java.util.HashMap;
+import java.util.Map;
+import javax.xml.transform.OutputKeys;
+import javax.xml.transform.Transformer;
+
+public interface Output {
+
+
+    void prepareTransformer(final Transformer transformer);
+
+
+    final class Document implements Output {
+
+        private final Map<String, String> properties;
+
+        public Document() {
+            this((Document.defaultProperties()));
+        }
+
+        public Document(final Map<String, String> properties) {
+            this.properties = properties;
+        }
+
+        @Override
+        public void prepareTransformer(final Transformer transformer) {
+            this.properties.entrySet().stream()
+                .forEach((e) -> transformer.setOutputProperty(e.getKey(), e.getValue()));
+        }
+
+        private static Map<String, String> defaultProperties() {
+            final HashMap<String, String> res = new HashMap<>();
+            res.put(OutputKeys.INDENT, "yes");
+            res.put(OutputKeys.ENCODING, "UTF-8");
+            return res;
+        }
+    }
+
+    final class Node implements Output {
+
+        @Override
+        public void prepareTransformer(final Transformer transformer) {
+            transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
+        }
+    }
+
+}

src/main/java/org/xembly/Xembler.java

@@ -101,6 +101,8 @@ public final class Xembler {
      */
     private final Iterable<Directive> directives;
 
+    private final Output output;
+
     static {
         Xembler.BFACTORY.setNamespaceAware(true);
         Xembler.BFACTORY.setValidating(false);
@@ -112,7 +114,17 @@ public final class Xembler {
      * @param dirs Directives
      */
     public Xembler(final Iterable<Directive> dirs) {
-        this.directives = dirs;
+        this(dirs, new Output.Document());
+    }
+
+    /**
+     * Public ctor.
+     * @param directives Directives
+     * @param output Output type
+     */
+    public Xembler(final Iterable<Directive> directives, final Output output) {
+        this.directives = directives;
+        this.output = output;
     }
 
     /**
@@ -247,8 +259,9 @@ public String xml() throws ImpossibleModificationException {
                 ex
             );
         }
-        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
-        transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
+        this.output.prepareTransformer(transformer);
+//        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
+//        transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
         final StringWriter writer = new StringWriter();
         try {
             transformer.transform(

src/test/java/org/xembly/XemblerTest.java

@@ -208,4 +208,19 @@ void concurrentInvocationWithNoExceptions() throws Exception {
             )
         );
     }
+
+    @Test
+    void omitsHeader() {
+        MatcherAssert.assertThat(
+            "Xembler should omit XML header for Node output type",
+            new Xembler(
+                new Directives()
+                    .add("animals")
+                    .add("cow")
+                    .set("mu-mu"),
+                new Output.Node()
+            ).xmlQuietly(),
+            Matchers.equalTo("<animals><cow>mu-mu</cow></animals>")
+        );
+    }
 }