Add XmlPrettyPrinter

build.gradle

@@ -104,6 +104,11 @@ allprojects {
 			// uses generated Java source code which is prone to Error
 			// Prone bug patterns.
 			toolChain ErrorProneToolChain.create(project)
+			options.compilerArgs = [
+				// Disable MissingCasesInEnumSwitch error prone check
+				// because this check is already done by javac as incomplete-switch.
+				'-Xep:MissingCasesInEnumSwitch:OFF',
+			]
 		}
 	}
 	if (JavaVersion.current().isJava8Compatible()) {

jxmpp-core/src/main/java/org/jxmpp/xml/splitter/XmlPrettyPrinter.java

@@ -0,0 +1,305 @@
+/**
+ *
+ * Copyright 2018 Florian Schmaus
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.jxmpp.xml.splitter;
+
+import java.io.IOException;
+import java.io.Writer;
+
+import org.jxmpp.xml.splitter.XmlSplitter.State;
+
+public class XmlPrettyPrinter extends XmlPrinter {
+
+	private final int indent;
+	private final int attributeIndent;
+	private final int tabWidth;
+
+	private final PrettyPrintedXmlChunkCallback newChunkCallback;
+	private final PrettyPrintedXmlPartCallback newPartCallback;
+	private final Writer prettyWriter;
+
+	private StringBuilder currentPart;
+	private StringBuilder currentChunk;
+
+	/**
+	 * Construct a new XML pretty printer.
+	 *
+	 * @param partCallback a part callback.
+	 */
+	public XmlPrettyPrinter(PrettyPrintedXmlPartCallback partCallback) {
+		this(builder().setPartCallback(partCallback));
+	}
+
+	/**
+	 * Construct a new XML pretty printer.
+	 *
+	 * @param prettyWriter a writer for the pretty printed XML stream.
+	 */
+	public XmlPrettyPrinter(Writer prettyWriter) {
+		this(builder().setPrettyWriter(prettyWriter));
+	}
+
+	private XmlPrettyPrinter(Builder builder) {
+		this.indent = builder.indent;
+		this.attributeIndent = builder.attributeIndent;
+		this.tabWidth = builder.tabWidth;
+		this.newChunkCallback = builder.newChunkCallback;
+		this.newPartCallback = builder.newPartCallback;
+		this.prettyWriter = builder.prettyWriter;
+	}
+
+	@Override
+	void onChunkStart() {
+		if (newChunkCallback == null) {
+			return;
+		}
+		currentChunk = new StringBuilder(currentPart.length() + 1024);
+		currentChunk.append(currentPart);
+		currentChunk.append('[');
+	}
+
+	@Override
+	void onChunkEnd() {
+		if (newChunkCallback == null) {
+			return;
+		}
+		currentChunk.append(']');
+		newChunkCallback.onPrettyPrintedXmlChunk(currentChunk);
+		currentChunk = null;
+	}
+
+	@SuppressWarnings("incomplete-switch")
+	@Override
+	void onNextChar(char c, int depth, State initialState, State currentState) throws IOException {
+		final boolean stateChange = initialState != currentState;
+		final StringBuilder sb = new StringBuilder(stateChange ? 16 : 1);
+
+		if (stateChange) {
+			boolean deferredLeftAngle = false;
+			int indent = 0;
+			switch (currentState) {
+			case TAG_LEFT_ANGLE_BRACKET:
+				// Note that we return here because we need to see if this is a start tag or end tag.
+				return;
+			case END_TAG_SOLIDUS:
+				indent = getElementIndent(depth - 1);
+				deferredLeftAngle = true;
+				break;
+			case IN_TAG_NAME:
+				indent = getElementIndent(depth);
+				deferredLeftAngle = true;
+				break;
+			case IN_ATTRIBUTE_NAME:
+				if (attributeIndent > 0) {
+					indent = getAttributeIndent(depth);
+				}
+				break;
+			case START:
+				indent = getElementIndent(depth);
+				break;
+			}
+
+			if (indent > 0 || deferredLeftAngle) {
+				sb.append('\n');
+			}
+
+			appendIndent(sb, indent);
+
+			if (deferredLeftAngle) {
+				sb.append('<');
+			}
+		}
+
+		sb.append(c);
+
+		if (currentChunk != null) {
+			currentChunk.append(sb);
+		}
+		if (newPartCallback != null) {
+			if (currentPart == null) {
+				currentPart = new StringBuilder(1024);
+			}
+			currentPart.append(sb);
+		}
+		if (prettyWriter != null) {
+			prettyWriter.append(sb);
+		}
+	}
+
+	@Override
+	void onCompleteElement() {
+		if (newPartCallback == null) {
+			return;
+		}
+		if (currentPart.charAt(0) == '\n') {
+			currentPart.deleteCharAt(0);
+		}
+		newPartCallback.onPrettyPrintedXmlPart(currentPart);
+		currentPart = null;
+	}
+
+	private int getElementIndent(int depth) {
+		return indent * depth;
+	}
+
+	private int getAttributeIndent(int depth) {
+		return getElementIndent(depth) + attributeIndent;
+	}
+
+	private void appendIndent(StringBuilder sb, int indent) {
+		int spaces = indent;
+		if (tabWidth > 0) {
+			spaces = indent % tabWidth;
+			int tabs = indent / tabWidth;
+			for (int i = 0; i < tabs; i++) {
+				sb.append('\t');
+			}
+		}
+		for (int i = 0; i < spaces; i++) {
+			sb.append(' ');
+		}
+	}
+
+	public interface PrettyPrintedXmlChunkCallback {
+
+		/**
+		 * Invoked after the XML pretty printer handled a chunk. The pretty printed chunk will contain the current part
+		 * and the newly handled chunk enclosing in '[' and ']'.
+		 *
+		 * @param chunk the state of the current part with the newly handled chunk marked.
+		 */
+		void onPrettyPrintedXmlChunk(StringBuilder chunk);
+	}
+
+	public interface PrettyPrintedXmlPartCallback {
+
+		/**
+		 * Invoked after a part was completed.
+		 *
+		 * @param part the pertty printed part.
+		 */
+		void onPrettyPrintedXmlPart(StringBuilder part);
+	}
+
+	/**
+	 * Create a new builder.
+	 *
+	 * @return a new builder.
+	 */
+	public static Builder builder() {
+		return new Builder();
+	}
+
+	public static final class Builder {
+		private int indent = 2;
+		private int attributeIndent;
+		private int tabWidth;
+
+		private PrettyPrintedXmlChunkCallback newChunkCallback;
+		private PrettyPrintedXmlPartCallback newPartCallback;
+		private Writer prettyWriter;
+
+		private Builder() {
+		}
+
+		/**
+		 * Set the indent for elements in whitespace characters.
+		 *
+		 * @param indent the indent for elements in whitespace characters.
+		 * @return a reference to this builders.
+		 */
+		public Builder setIndent(int indent) {
+			ensureNotNegative(indent);
+
+			this.indent = indent;
+			return this;
+		}
+
+		/**
+		 * Set the attribute indent in whitespace characters. Use a value smaller one to disable attribute indentation.
+		 *
+		 * @param attributeIndent the attribute indent in whitespace characters.
+		 * @return a reference to this builder.
+		 */
+		public Builder setAttributeIndent(int attributeIndent) {
+			ensureNotNegative(attributeIndent);
+
+			this.attributeIndent = attributeIndent;
+			return this;
+		}
+
+		/**
+		 * Set the tab width in whitespace characters. Use a value smaller one to disable pretty printing with tabs.
+		 *
+		 * @param tabWidth the tab width in whitespace characters.
+		 * @return a reference to this builder.
+		 */
+		public Builder setTabWidth(int tabWidth) {
+			ensureNotNegative(tabWidth);
+
+			this.tabWidth = tabWidth;
+			return this;
+		}
+
+		/**
+		 * Set a chunk callback.
+		 *
+		 * @param chunkCallback the cunk callback.
+		 * @return a reference to this builder.
+		 */
+		public Builder setChunkCallback(PrettyPrintedXmlChunkCallback chunkCallback) {
+			this.newChunkCallback = chunkCallback;
+			return this;
+		}
+
+		/**
+		 * Set a part callback.
+		 *
+		 * @param partCallback the part callback.
+		 * @return a reference to this builder.
+		 */
+		public Builder setPartCallback(PrettyPrintedXmlPartCallback partCallback) {
+			this.newPartCallback = partCallback;
+			return this;
+		}
+
+		/**
+		 * Set a {@link Writer} for the pretty printed XML stream.
+		 *
+		 * @param prettyWriter the writer to pretty print to.
+		 * @return a reference to this builder.
+		 */
+		public Builder setPrettyWriter(Writer prettyWriter) {
+			this.prettyWriter = prettyWriter;
+			return this;
+		}
+
+		/**
+		 * Build an XML pretty printer.
+		 *
+		 * @return the newly build XML pretty printer.
+		 */
+		public XmlPrettyPrinter build() {
+			return new XmlPrettyPrinter(this);
+		}
+
+		private static void ensureNotNegative(int i) {
+			if (i < 0) {
+				throw new IllegalArgumentException();
+			}
+		}
+	}
+}

jxmpp-core/src/main/java/org/jxmpp/xml/splitter/XmlPrinter.java

@@ -0,0 +1,32 @@
+/**
+ *
+ * Copyright 2018 Florian Schmaus
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.jxmpp.xml.splitter;
+
+import java.io.IOException;
+
+import org.jxmpp.xml.splitter.XmlSplitter.State;
+
+public abstract class XmlPrinter {
+
+	abstract void onChunkStart();
+
+	abstract void onChunkEnd();
+
+	abstract void onNextChar(char c, int depth, State initialState, State currentState) throws IOException;
+
+	abstract void onCompleteElement();
+}