Fix for FasterXML#336, multiple class adapted for the feature.

- Accepts new annotation for collection type.

.gitignore

@@ -19,3 +19,4 @@ target
 *.iml
 *.ipr
 *.iws
+.idea

src/main/java/com/fasterxml/jackson/dataformat/xml/JacksonXmlAnnotationIntrospector.java

@@ -1,7 +1,9 @@
 package com.fasterxml.jackson.dataformat.xml;
 
 import com.fasterxml.jackson.databind.PropertyName;
-import com.fasterxml.jackson.databind.introspect.*;
+import com.fasterxml.jackson.databind.introspect.Annotated;
+import com.fasterxml.jackson.databind.introspect.AnnotatedClass;
+import com.fasterxml.jackson.databind.introspect.JacksonAnnotationIntrospector;
 import com.fasterxml.jackson.dataformat.xml.annotation.*;
 
 /**
@@ -80,6 +82,15 @@ public PropertyName findRootName(AnnotatedClass ac)
         }
         return super.findRootName(ac);
     }
+
+    @Override
+    public String getWrapperForIndexedType(AnnotatedClass ac){
+        JacksonXmlRootElement root = ac.getAnnotation(JacksonXmlRootElement.class);
+        if (root != null) {
+            return root.wrapperForIndexedType();
+        }
+        return JacksonXmlRootElement.DEFAULT_WRAPPER_NAME;
+    }
 
     /*
     /**********************************************************************

src/main/java/com/fasterxml/jackson/dataformat/xml/XmlAnnotationIntrospector.java

@@ -2,7 +2,9 @@
 
 import com.fasterxml.jackson.databind.AnnotationIntrospector;
 import com.fasterxml.jackson.databind.introspect.Annotated;
+import com.fasterxml.jackson.databind.introspect.AnnotatedClass;
 import com.fasterxml.jackson.databind.introspect.AnnotationIntrospectorPair;
+import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlRootElement;
 import com.fasterxml.jackson.module.jaxb.JaxbAnnotationIntrospector;
 
 /**
@@ -43,6 +45,8 @@ public interface XmlAnnotationIntrospector
     public Boolean isOutputAsCData(Annotated ann);
 
     public void setDefaultUseWrapper(boolean b);
+
+    public String getWrapperForIndexedType(AnnotatedClass ac);
 
     /*
     /**********************************************************************
@@ -135,6 +139,15 @@ public void setDefaultUseWrapper(boolean b) {
                 _xmlSecondary.setDefaultUseWrapper(b);
             }
         }
+
+        @Override
+        public String getWrapperForIndexedType(AnnotatedClass ac) {
+            String value = (_xmlPrimary == null) ? null : _xmlPrimary.getWrapperForIndexedType(ac);
+            if ((value == null) && (_xmlSecondary != null)) {
+                value = _xmlSecondary.getWrapperForIndexedType(ac);
+            }
+            return value;
+        }
     }
 
     /*
@@ -183,5 +196,10 @@ public Boolean isOutputAsCData(Annotated ann) {
         public void setDefaultUseWrapper(boolean b) {
             // not used with JAXB
         }
+
+        @Override
+        public String getWrapperForIndexedType(AnnotatedClass ac) {
+            return JacksonXmlRootElement.DEFAULT_WRAPPER_NAME;
+        }
     }
 }

src/main/java/com/fasterxml/jackson/dataformat/xml/annotation/JacksonXmlRootElement.java

@@ -14,6 +14,9 @@
 @Retention(RetentionPolicy.RUNTIME)
 public @interface JacksonXmlRootElement
 {
+    public static String DEFAULT_WRAPPER_NAME="item";
+
     String namespace() default "";
     String localName() default "";
+    String wrapperForIndexedType() default DEFAULT_WRAPPER_NAME;
 }

src/main/java/com/fasterxml/jackson/dataformat/xml/jaxb/XmlJaxbAnnotationIntrospector.java

@@ -2,6 +2,7 @@
 
 import com.fasterxml.jackson.databind.introspect.*;
 import com.fasterxml.jackson.dataformat.xml.XmlAnnotationIntrospector;
+import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlRootElement;
 import com.fasterxml.jackson.module.jaxb.JaxbAnnotationIntrospector;
 
 /**
@@ -57,4 +58,9 @@ public Boolean isOutputAsCData(Annotated ann) {
     public void setDefaultUseWrapper(boolean b) {
         // nothing to do with JAXB
     }
+
+    @Override
+    public String getWrapperForIndexedType(AnnotatedClass ac) {
+        return JacksonXmlRootElement.DEFAULT_WRAPPER_NAME;
+    }
 }

src/main/java/com/fasterxml/jackson/dataformat/xml/ser/XmlSerializerProvider.java

@@ -1,22 +1,23 @@
 package com.fasterxml.jackson.dataformat.xml.ser;
 
-import java.io.IOException;
-
-import javax.xml.namespace.QName;
-import javax.xml.stream.XMLStreamException;
-
-import com.fasterxml.jackson.core.*;
-
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.core.TokenStreamFactory;
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.cfg.GeneratorSettings;
-import com.fasterxml.jackson.databind.ser.SerializerFactory;
 import com.fasterxml.jackson.databind.ser.DefaultSerializerProvider;
 import com.fasterxml.jackson.databind.ser.SerializerCache;
+import com.fasterxml.jackson.databind.ser.SerializerFactory;
 import com.fasterxml.jackson.databind.util.TokenBuffer;
 import com.fasterxml.jackson.dataformat.xml.util.StaxUtil;
 import com.fasterxml.jackson.dataformat.xml.util.TypeUtil;
 import com.fasterxml.jackson.dataformat.xml.util.XmlRootNameLookup;
 
+import javax.xml.namespace.QName;
+import javax.xml.stream.XMLStreamException;
+import java.io.IOException;
+import java.util.Collection;
+import java.util.Iterator;
+
 /**
  * We need to override some parts of
  * {@link com.fasterxml.jackson.databind.SerializerProvider}
@@ -68,7 +69,8 @@ public void serializeValue(JsonGenerator gen, Object value) throws IOException
             _initWithRootName(xgen, rootName);
             asArray = TypeUtil.isIndexedType(cls);
             if (asArray) {
-                _startRootArray(xgen, rootName);
+                String indexedRootName = _rootNameLookup.findWrapperForIndexedType(getTypeOfCollection(value), _config);
+                _startRootArray(xgen, indexedRootName);
             }
         }
 
@@ -107,7 +109,8 @@ public void serializeValue(JsonGenerator gen, Object value, JavaType rootType,
             _initWithRootName(xgen, rootName);
             asArray = TypeUtil.isIndexedType(rootType);
             if (asArray) {
-                _startRootArray(xgen, rootName);
+                String indexedRootName = _rootNameLookup.findWrapperForIndexedType(getTypeOfCollection(rootType), _config);
+                _startRootArray(xgen, indexedRootName);
             }
         }
         if (ser == null) {
@@ -125,6 +128,17 @@ public void serializeValue(JsonGenerator gen, Object value, JavaType rootType,
         }
     }
 
+    protected Class<?> getTypeOfCollection(Object value){
+        Class<?> eleClass = value.getClass();
+        if(Collection.class.isAssignableFrom(eleClass)) {
+            Collection<?> collection = (Collection<?>) value;
+            Iterator<?> iterator = collection.iterator();
+            if (iterator.hasNext())
+                eleClass = iterator.next().getClass();
+        }
+        return eleClass;
+    }
+
     protected void _serializeXmlNull(JsonGenerator jgen) throws IOException
     {
         // 14-Nov-2016, tatu: As per [dataformat-xml#213], we may have explicitly
@@ -139,11 +153,11 @@ protected void _serializeXmlNull(JsonGenerator jgen) throws IOException
         super.serializeValue(jgen, null);
     }
 
-    protected void _startRootArray(ToXmlGenerator xgen, QName rootName) throws IOException
+    protected void _startRootArray(ToXmlGenerator xgen, String rootName) throws IOException
     {
         xgen.writeStartObject();
         // Could repeat root name, but what's the point? How to customize?
-        xgen.writeFieldName("item");
+        xgen.writeFieldName(rootName);
     }    
 
     protected void _initWithRootName(ToXmlGenerator xgen, QName rootName) throws IOException

src/main/java/com/fasterxml/jackson/dataformat/xml/util/XmlRootNameLookup.java

@@ -8,6 +8,7 @@
 import com.fasterxml.jackson.databind.type.ClassKey;
 import com.fasterxml.jackson.databind.util.SimpleLookupCache;
 import com.fasterxml.jackson.dataformat.xml.XmlAnnotationIntrospector;
+import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlRootElement;
 
 /**
  * Helper class used for efficiently finding root element name used with
@@ -26,6 +27,7 @@ public class XmlRootNameLookup
      * state
      */
     protected final transient SimpleLookupCache<ClassKey,QName> _rootNames = new SimpleLookupCache<>(40, 200);
+    protected final transient SimpleLookupCache<ClassKey,String> _indexedWrapperNames = new SimpleLookupCache<>(10, 200);
 
     public XmlRootNameLookup() { }
 
@@ -57,6 +59,27 @@ public QName findRootName(Class<?> rootType, MapperConfig<?> config)
         }
         return name;
     }
+
+    public String findWrapperForIndexedType(JavaType rootType, MapperConfig<?> config) {
+        return findWrapperForIndexedType(rootType.getRawClass(), config);
+    }
+
+    public String findWrapperForIndexedType(Class<?> rootType, MapperConfig<?> config)
+    {
+        ClassKey key = new ClassKey(rootType);
+        String wrapperName;
+        synchronized (_indexedWrapperNames) {
+            wrapperName = _indexedWrapperNames.get(key);
+        }
+        if (wrapperName != null) {
+            return wrapperName;
+        }
+        wrapperName = findWrapperName(rootType, config);
+        synchronized (_indexedWrapperNames) {
+            _indexedWrapperNames.put(key, wrapperName);
+        }
+        return wrapperName;
+    }
 
     // NOTE: needed to be synchronized in 2.6.4, but 2.7.0 adds a proper fix
     // for annotation introspection hence not needed any more
@@ -102,4 +125,20 @@ private String findNamespace(AnnotationIntrospector ai, AnnotatedClass ann)
         }
         return null;
     }
+
+    private String findWrapperName(Class<?> rootType, MapperConfig<?> config)
+    {
+        BeanDescription beanDesc = config.introspectClassAnnotations(rootType);
+        AnnotationIntrospector annotationIntrospector = config.getAnnotationIntrospector();
+        AnnotatedClass annotatedClass = beanDesc.getClassInfo();
+        for (AnnotationIntrospector intr : annotationIntrospector.allIntrospectors()) {
+            if (intr instanceof XmlAnnotationIntrospector) {
+                String ns = ((XmlAnnotationIntrospector) intr).getWrapperForIndexedType(annotatedClass);
+                if (ns != null) {
+                    return ns;
+                }
+            }
+        }
+        return JacksonXmlRootElement.DEFAULT_WRAPPER_NAME;
+    }
 }

src/test/java/com/fasterxml/jackson/dataformat/xml/ser/TestSerializationCollection.java

@@ -0,0 +1,45 @@
+package com.fasterxml.jackson.dataformat.xml.ser;
+
+import com.fasterxml.jackson.dataformat.xml.XmlMapper;
+import com.fasterxml.jackson.dataformat.xml.XmlTestBase;
+import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlProperty;
+import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlRootElement;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+public class TestSerializationCollection extends XmlTestBase {
+
+
+    @JacksonXmlRootElement(localName="person", namespace="http://example.org/person", wrapperForIndexedType = "Person")
+    static class Person {
+
+        @JacksonXmlProperty(isAttribute = true)
+        public Integer id;
+
+        public String n;
+
+        public Person(Integer id, String name) {
+            this.id = id;
+            this.n = name;
+        }
+    }
+
+    @JacksonXmlRootElement(localName = "persons")
+    static class PersonList extends ArrayList<Person>{}
+
+    public void testList() throws Exception
+    {
+        List<String> personNames = Arrays.asList("A", "B", "C");
+        PersonList personList = IntStream.range(0, personNames.size())
+                .mapToObj(count -> new Person(count, personNames.get(count)))
+                .collect(Collectors.toCollection(PersonList::new));
+        XmlMapper xmlMapper = new XmlMapper();
+        String xml = xmlMapper.writeValueAsString(personList);
+        assertEquals("<persons><Person id=\"0\"><n>A</n></Person><Person id=\"1\"><n>B</n></Person><Person id=\"2\"><n>C</n></Person></persons>",
+                xml);
+    }
+}