Added additional converters.

core/src/main/java/hudson/util/XStream2.java

@@ -42,6 +42,8 @@ import com.thoughtworks.xstream.io.HierarchicalStreamReader;
 import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
 import com.thoughtworks.xstream.mapper.CannotResolveClassException;
 import hudson.diagnosis.OldDataMonitor;
+import hudson.util.xstream.ImmutableSetConverter;
+import hudson.util.xstream.ImmutableSortedSetConverter;
 import jenkins.model.Jenkins;
 import hudson.model.Label;
 import hudson.model.Result;
@@ -109,6 +111,8 @@ public class XStream2 extends XStream {
 
         registerConverter(new RobustCollectionConverter(getMapper(),getReflectionProvider()),10);
         registerConverter(new ImmutableMapConverter(getMapper(),getReflectionProvider()),10);
+        registerConverter(new ImmutableSortedSetConverter(getMapper(),getReflectionProvider()),10);
+        registerConverter(new ImmutableSetConverter(getMapper(),getReflectionProvider()),10);
         registerConverter(new ImmutableListConverter(getMapper(),getReflectionProvider()),10);
         registerConverter(new ConcurrentHashMapConverter(getMapper(),getReflectionProvider()),10);
         registerConverter(new CopyOnWriteMap.Tree.ConverterImpl(getMapper()),10); // needs to override MapConverter

core/src/main/java/hudson/util/xstream/ImmutableSetConverter.java

+package hudson.util.xstream;
+
+import com.google.common.collect.ImmutableSet;
+import com.thoughtworks.xstream.XStream;
+import com.thoughtworks.xstream.converters.UnmarshallingContext;
+import com.thoughtworks.xstream.converters.collections.CollectionConverter;
+import com.thoughtworks.xstream.converters.reflection.ReflectionProvider;
+import com.thoughtworks.xstream.converters.reflection.SerializableConverter;
+import com.thoughtworks.xstream.io.HierarchicalStreamReader;
+import com.thoughtworks.xstream.mapper.Mapper;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * @author Kohsuke Kawaguchi
+ */
+public class ImmutableSetConverter extends CollectionConverter {
+    private final SerializableConverter sc;
+
+    public ImmutableSetConverter(XStream xs) {
+        this(xs.getMapper(),xs.getReflectionProvider());
+    }
+
+    public ImmutableSetConverter(Mapper mapper, ReflectionProvider reflectionProvider) {
+        super(mapper);
+        sc = new SerializableConverter(mapper,reflectionProvider);
+    }
+
+    @Override
+    public boolean canConvert(Class type) {
+        return ImmutableSet.class.isAssignableFrom(type);
+    }
+
+    @Override
+    public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
+        return ImmutableSet.copyOf((List) super.unmarshal(reader, context));
+    }
+
+    @Override
+    protected Object createCollection(Class type) {
+        return new ArrayList();
+    }
+}

core/src/main/java/hudson/util/xstream/ImmutableSortedSetConverter.java

+package hudson.util.xstream;
+
+import com.google.common.collect.ImmutableSortedSet;
+import com.thoughtworks.xstream.XStream;
+import com.thoughtworks.xstream.converters.UnmarshallingContext;
+import com.thoughtworks.xstream.converters.collections.CollectionConverter;
+import com.thoughtworks.xstream.converters.reflection.ReflectionProvider;
+import com.thoughtworks.xstream.converters.reflection.SerializableConverter;
+import com.thoughtworks.xstream.io.HierarchicalStreamReader;
+import com.thoughtworks.xstream.mapper.Mapper;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * @author Kohsuke Kawaguchi
+ */
+public class ImmutableSortedSetConverter extends CollectionConverter {
+    private final SerializableConverter sc;
+
+    public ImmutableSortedSetConverter(XStream xs) {
+        this(xs.getMapper(),xs.getReflectionProvider());
+    }
+
+    public ImmutableSortedSetConverter(Mapper mapper, ReflectionProvider reflectionProvider) {
+        super(mapper);
+        sc = new SerializableConverter(mapper,reflectionProvider);
+    }
+
+    @Override
+    public boolean canConvert(Class type) {
+        return ImmutableSortedSet.class.isAssignableFrom(type);
+    }
+
+    @Override
+    public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
+        return ImmutableSortedSet.copyOf((List) super.unmarshal(reader, context));
+    }
+
+    @Override
+    protected Object createCollection(Class type) {
+        return new ArrayList();
+    }
+}