From 373016ccdb6169cc0a118a519a905b09969ad9dc Mon Sep 17 00:00:00 2001
From: joehni <joerg.schaible@gmx.de>
Date: Wed, 14 Dec 2022 00:28:53 +0100
Subject: [PATCH] Add converter for Optional. Closes #293 and #294.

---
 xstream-distribution/src/content/changes.html |  4 +
 .../src/content/converters.html               | 11 +++
 xstream-distribution/src/content/team.html    |  3 +-
 .../com/thoughtworks/xstream/XStream.java     |  5 ++
 .../extended/OptionalConverter.java           | 73 +++++++++++++++++++
 .../acceptance/ExtendedTypesTest.java         | 48 +++++++++++-
 6 files changed, 142 insertions(+), 2 deletions(-)
 create mode 100644 xstream/src/java/com/thoughtworks/xstream/converters/extended/OptionalConverter.java
diff --git a/xstream-distribution/src/content/changes.html b/xstream-distribution/src/content/changes.html
index c81150490..acf3f3450 100644
--- a/xstream-distribution/src/content/changes.html
+++ b/xstream-distribution/src/content/changes.html
@@ -111,6 +111,7 @@ <h2>Major changes</h2>
 	<ul>
 		<li>GHI:#308: Add converter for AtomicBoolean, AtomicInteger, AtomicLong, and AtomicReference of
 		package java.util.concurrent.atomic.</li>
+		<li>GHI:#293: Add converter for Optional of package java.util.</li>
 	</ul>
 
 	<h2>Stream compatibility</h2>
@@ -118,6 +119,8 @@ <h2>Stream compatibility</h2>
 	<ul>
 		<li>The atomic types with new converters of package java.util.concurrent.atomic, that have been written with
 		previous versions of XStream, can still be deserialized.</li>
+		<li>The Optional types with new converters of package java.util, that have been written with previous versions
+		of XStream, can still be deserialized.</li>
 	</ul>
 
 	<h2>API changes</h2>
@@ -127,6 +130,7 @@ <h2>API changes</h2>
 		<li>Added c.t.x.converters.extended.AtomicIntegerConverter.</li>
 		<li>Added c.t.x.converters.extended.AtomicLongConverter.</li>
 		<li>Added c.t.x.converters.extended.AtomicReferenceConverter.</li>
+		<li>Added c.t.x.converters.extended.OptionalConverter.</li>
 	</ul>
 
 	<h1 id="1.4.19">1.4.19</h1>
diff --git a/xstream-distribution/src/content/converters.html b/xstream-distribution/src/content/converters.html
index 08829b806..a48f58323 100644
--- a/xstream-distribution/src/content/converters.html
+++ b/xstream-distribution/src/content/converters.html
@@ -425,6 +425,17 @@
                 <td>Available with Java 1.5 or greater.</td>
                 <td>normal</td>
             </tr>
+            <tr>
+                <td><a href="javadoc/com/thoughtworks/xstream/converters/extended/OptionalConverter.html">OptionalConverter</a></td>
+                <td>java.util.Optional</td>
+                <td class="example">
+                &lt;optional&gt;<br/>
+                &nbsp;&nbsp;&lt;value&nbsp;&nbsp;class=&quot;string&quot;&gt;test&lt;/value&gt;<br/>
+                &lt;/optional&gt;
+                </td>
+                <td>Available with Java 1.8 or greater.</td>
+                <td>normal</td>
+            </tr>
             <tr>
                 <td><a href="javadoc/com/thoughtworks/xstream/converters/enums/EnumMapConverter.html">EnumMapConverter</a></td>
                 <td>java.util.EnumMap</td>
diff --git a/xstream-distribution/src/content/team.html b/xstream-distribution/src/content/team.html
index 32d9116ea..d1cefbce8 100644
--- a/xstream-distribution/src/content/team.html
+++ b/xstream-distribution/src/content/team.html
@@ -1,7 +1,7 @@
 <html>
 <!--
  Copyright (C) 2005, 2006 Joe Walnes.
- Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2013, 2014, 2015, 2016, 2017, 2019, 2020, 2021 XStream committers.
+ Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2013, 2014, 2015, 2016, 2017, 2019, 2020, 2021, 2022 XStream committers.
  All rights reserved.
  
  The software in this package is published under the terms of the BSD
@@ -130,6 +130,7 @@ <h2 id="contributors">Contributors</h2>
       <li>Falko Modler</li>
       <li>Julia Boes of Oracle</li>
       <li>Chris Hegarty of Oracle</li>
+      <li>Emanuel Alves</li>
       <li>Basil Crow</li>
     </ul>
 
diff --git a/xstream/src/java/com/thoughtworks/xstream/XStream.java b/xstream/src/java/com/thoughtworks/xstream/XStream.java
index 1ae239908..e95346068 100644
--- a/xstream/src/java/com/thoughtworks/xstream/XStream.java
+++ b/xstream/src/java/com/thoughtworks/xstream/XStream.java
@@ -92,6 +92,7 @@
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Properties;
 import java.util.Set;
 import java.util.SortedSet;
@@ -162,6 +163,7 @@
 import com.thoughtworks.xstream.converters.extended.JavaMethodConverter;
 import com.thoughtworks.xstream.converters.extended.LocaleConverter;
 import com.thoughtworks.xstream.converters.extended.LookAndFeelConverter;
+import com.thoughtworks.xstream.converters.extended.OptionalConverter;
 import com.thoughtworks.xstream.converters.extended.PathConverter;
 import com.thoughtworks.xstream.converters.extended.RegexPatternConverter;
 import com.thoughtworks.xstream.converters.extended.SqlDateConverter;
@@ -758,6 +760,7 @@ protected void setupSecurity() {
         allowTypeHierarchy(Chronology.class);
         types.add(ValueRange.class);
         types.add(WeekFields.class);
+        types.add(Optional.class);
 
         types.remove(null);
         allowTypes(types.toArray(new Class[types.size()]));
@@ -901,6 +904,7 @@ protected void setupAliases() {
         alias("julian-field", JVM.loadClassForName("java.time.temporal.JulianFields$Field"));
         alias("temporal-value-range", ValueRange.class);
         alias("week-fields", WeekFields.class);
+        alias("optional", Optional.class);
         alias("serialized-lambda", SerializedLambda.class);
 
         aliasType("charset", Charset.class);
@@ -1014,6 +1018,7 @@ protected void setupConverters() {
         registerConverter(new YearMonthConverter(), PRIORITY_NORMAL);
         registerConverter(new ZonedDateTimeConverter(), PRIORITY_NORMAL);
         registerConverter(new ZoneIdConverter(), PRIORITY_NORMAL);
+        registerConverter(new OptionalConverter(mapper), PRIORITY_NORMAL);
         registerConverter(new DynamicProxyConverter(mapper, classLoaderReference), PRIORITY_NORMAL);
         registerConverter(new JavaClassConverter(classLoaderReference), PRIORITY_NORMAL);
         registerConverter(new JavaMethodConverter(classLoaderReference), PRIORITY_NORMAL);
diff --git a/xstream/src/java/com/thoughtworks/xstream/converters/extended/OptionalConverter.java b/xstream/src/java/com/thoughtworks/xstream/converters/extended/OptionalConverter.java
new file mode 100644
index 000000000..2174d675f
--- /dev/null
+++ b/xstream/src/java/com/thoughtworks/xstream/converters/extended/OptionalConverter.java
@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2022 XStream Committers.
+ * All rights reserved.
+ *
+ * The software in this package is published under the terms of the BSD
+ * style license a copy of which has been included with this distribution in
+ * the LICENSE.txt file.
+ *
+ * Created on 8. December 2022 by Joerg Schaible
+ */
+package com.thoughtworks.xstream.converters.extended;
+
+import java.util.Optional;
+
+import com.thoughtworks.xstream.converters.Converter;
+import com.thoughtworks.xstream.converters.MarshallingContext;
+import com.thoughtworks.xstream.converters.UnmarshallingContext;
+import com.thoughtworks.xstream.core.util.HierarchicalStreams;
+import com.thoughtworks.xstream.io.HierarchicalStreamReader;
+import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
+import com.thoughtworks.xstream.mapper.Mapper;
+
+
+/**
+ * Converts an Optional type.
+ *
+ * @since upcoming
+ * @author Emanuel Alves
+ * @author J&ouml;rg Schaible
+ */
+public class OptionalConverter implements Converter {
+
+    private final Mapper mapper;
+
+    public OptionalConverter(final Mapper mapper) {
+        this.mapper = mapper;
+    }
+
+    @Override
+    public boolean canConvert(final Class<?> type) {
+        return type != null && type == Optional.class;
+    }
+
+    @Override
+    public void marshal(final Object source, final HierarchicalStreamWriter writer, final MarshallingContext context) {
+        final Optional<?> optional = (Optional<?>)source;
+        if (optional.isPresent()) {
+            writer.startNode(mapper.serializedMember(Optional.class, "value"));
+
+            final Object object = optional.get();
+            final String name = mapper.serializedClass(object != null ? object.getClass() : null);
+            writer.addAttribute(mapper.aliasForSystemAttribute("class"), name);
+            context.convertAnother(optional.get());
+            writer.endNode();
+        }
+    }
+
+    @Override
+    public Object unmarshal(final HierarchicalStreamReader reader, final UnmarshallingContext context) {
+        final Object value;
+        if (reader.hasMoreChildren()) {
+            reader.moveDown();
+
+            final Class<?> type = HierarchicalStreams.readClassType(reader, mapper);
+            value = context.convertAnother(context, type);
+            reader.moveUp();
+            return Optional.of(value);
+        } else {
+            return Optional.empty();
+        }
+    }
+
+}
diff --git a/xstream/src/test/com/thoughtworks/acceptance/ExtendedTypesTest.java b/xstream/src/test/com/thoughtworks/acceptance/ExtendedTypesTest.java
index 5d58dd20a..3fc0072d0 100644
--- a/xstream/src/test/com/thoughtworks/acceptance/ExtendedTypesTest.java
+++ b/xstream/src/test/com/thoughtworks/acceptance/ExtendedTypesTest.java
@@ -1,6 +1,6 @@
 /*
  * Copyright (C) 2003, 2004, 2005 Joe Walnes.
- * Copyright (C) 2006, 2007, 2008, 2012, 2014, 2016, 2017, 2018, 2020 XStream Committers.
+ * Copyright (C) 2006, 2007, 2008, 2012, 2014, 2016, 2017, 2018, 2020, 2022 XStream Committers.
  * All rights reserved.
  *
  * The software in this package is published under the terms of the BSD
@@ -29,6 +29,7 @@
 import java.util.HashMap;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Optional;
 import java.util.TimeZone;
 import java.util.regex.Pattern;
 
@@ -288,4 +289,49 @@ public void testPathIsImmutable() {
             + "  <path>same</path>\n" //
             + "</path-array>");
     }
+
+    public void testEmptyOptional() {
+        final Optional<Object> optional = Optional.empty();
+        assertBothWays(optional, "<optional/>");
+    }
+
+    public void testOptional() {
+        final Optional<String> optional = Optional.of("test");
+        assertBothWays(optional, ("" //
+            + "<optional>\n" //
+            + "  <value class='string'>test</value>\n" //
+            + "</optional>").replace('\'', '"'));
+    }
+
+    public void testOptionalWithAlias() {
+        final Optional<String> optional = Optional.of("test");
+        xstream.aliasField("junit", Optional.class, "value");
+        assertBothWays(optional, ("" //
+            + "<optional>\n" //
+            + "  <junit class='string'>test</junit>\n" //
+            + "</optional>").replace('\'', '"'));
+    }
+
+    public void testOptionalIsRerenceable() {
+        @SuppressWarnings("unchecked")
+        final Optional<Object>[] array = new Optional[3];
+        array[0] = array[2] = Optional.of("test");
+        array[1] = Optional.empty();
+        assertBothWays(array, ("" //
+            + "<optional-array>\n" //
+            + "  <optional>\n" //
+            + "    <value class='string'>test</value>\n" //
+            + "  </optional>\n" //
+            + "  <optional/>\n" //
+            + "  <optional reference='../optional'/>\n" //
+            + "</optional-array>").replace('\'', '"'));
+    }
+
+    public void testOptionalWithOldFormat() {
+        assertEquals(Optional.of("test"), xstream.fromXML("" //
+            + "<java.util.Optional>\n" //
+            + "  <value class='string'>test</value>\n" //
+            + "</java.util.Optional>"));
+    }
+
 }
