JAXB how to marshall map into key value key

Question

The question is about JAXB Map marshalling - there is plenty of examples on how to marhsall a Map into a structure like follows    lt map gt     lt entry gt       lt key gt  KEY  lt  key gt       lt value gt  VALUE  lt  value gt     lt  entry gt     lt entry gt       lt key gt  KEY2  lt  key gt       lt value gt  VALUE2  lt  value gt     lt  entry gt     lt entry gt         lt  map gt    In fact  this is natively supported by JAXB  What I need  however  is the XML where key is the element name  and value is its content    lt map gt     lt key gt  VALUE  lt  key gt     lt key2 gt  VALUE2  lt  key2 gt        lt  map gt    I didn t succeed implementing my Map adapter the way it is recommended by JAXB developers  https   jaxb dev java net guide Mapping your favorite class html   as I need  he - dynamic attribute name      Is there any solution for that   P S  Currently I have to create a dedicated container class for each typical set of key-value pairs I want to marshall to XML - it works  but I have to create way too many of these helper containers

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Seems like this question is kind of duplicate with another one, where I've collect some marshal/unmarshal solutions into one post. You may check it here: Dynamic tag names with JAXB.

In short:

A container class for @xmlAnyElement should be created
An XmlAdapter can be used in pair with @XmlJavaTypeAdapter to convert between the container class and Map<>;

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There may be a valid reason why you want to do this  but generating this kind of XML is generally best avoided  Why  Because it means that the XML elements of your map are dependent on the runtime contents of your map  And since XML is usually used as an external interface or interface layer this is not desirable  Let me explain   The Xml Schema  xsd  defines the interface contract of your XML documents  In addition to being able to generate code from the XSD  JAXB can also generate the XML schema for you from the code  This allows you to restrict the data exchanged over the interface to the pre-agreed structures defined in the XSD   In the default case for a Map lt String  String gt   the generated XSD will restrict the map element to contain multiple entry elements each of which must contain one xs string key and one xs string value  That s a pretty clear interface contract   What you describe is that you want the xml map to contain elements whose name will be determined by the content of the map at runtime  Then the generated XSD can only specify that the map must contain a list of elements whose type is unknown at compile time  This is something that you should generally avoid when defining an interface contract   To achieve a strict contract in this case  you should use an enumerated type as the key of the map instead of a String  E g   public enum KeyType    KEY  KEY2      XmlJavaTypeAdapter MapAdapter class  Map lt KeyType   String gt  mapProperty    That way the keys which you want to become elements in XML are known at compile time so JAXB should be able to generate a schema that would restrict the elements of map to elements using one of the predefined keys KEY or KEY2   On the other hand  if you wish to simplify the default generated structure    lt map gt       lt entry gt           lt key gt KEY lt  key gt           lt value gt VALUE lt  value gt       lt  entry gt       lt entry gt           lt key gt KEY2 lt  key gt           lt value gt VALUE2 lt  value gt       lt  entry gt   lt  map gt    To something simpler like this   lt map gt       lt item key  KEY  value  VALUE   gt       lt item key  KEY2  value  VALUE2   gt   lt  map gt    You can use a MapAdapter that converts the Map to an array of MapElements as follows   class MapElements        XmlAttribute     public String key       XmlAttribute     public String value       private MapElements             Required by JAXB      public MapElements String key  String value            this key   key          this value   value            public class MapAdapter extends XmlAdapter lt MapElements    Map lt String  String gt  gt        public MapAdapter                public MapElements   marshal Map lt String  String gt  arg0  throws Exception           MapElements   mapElements   new MapElements arg0 size             int i   0          for  Map Entry lt String  String gt  entry   arg0 entrySet                mapElements i      new MapElements entry getKey    entry getValue              return mapElements             public Map lt String  String gt  unmarshal MapElements   arg0  throws Exception           Map lt String  String gt  r   new TreeMap lt String  String gt             for  MapElements mapelement   arg0              r put mapelement key  mapelement value           return r

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I didn t see anything that really answered this very well   I found something that worked pretty well here   Use JAXB XMLAnyElement type of style to return dynamic element names  I modified it a bit to support hashmap trees   You could add other collections   public class MapAdapter extends XmlAdapter lt MapWrapper  Map lt String  Object gt  gt         Override     public MapWrapper marshal Map lt String  Object gt  m  throws Exception           MapWrapper wrapper   new MapWrapper            List elements   new ArrayList            for  Map Entry lt String  Object gt  property   m entrySet                   if  property getValue   instanceof Map                  elements add new JAXBElement lt MapWrapper gt  new QName getCleanLabel property getKey                              MapWrapper class  marshal  Map  property getValue                   else                 elements add new JAXBElement lt String gt  new QName getCleanLabel property getKey                              String class  property getValue   toString                        wrapper elements   elements          return wrapper              Override     public Map lt String  Object gt  unmarshal MapWrapper v  throws Exception              TODO         throw new OperationNotSupportedException                  Return a XML-safe attribute   Might want to add camel case support     private String getCleanLabel String attributeLabel            attributeLabel   attributeLabel replaceAll             replaceAll      w  s         replaceAll                    return attributeLabel          class MapWrapper        XmlAnyElement     List elements      Then to implement it   static class myxml       String name    Full Name       String address    1234 Main St          I assign values to the map elsewhere  but it s just a simple        hashmap with a hashmap child as an example       XmlJavaTypeAdapter MapAdapter class      public Map lt String  Object gt  childMap      Feeding this through a simple Marshaller gives output that looks like this    lt  xml version  1 0  encoding  UTF-8  standalone  yes   gt   lt myxml gt       lt name gt Full Name lt  name gt       lt address gt 1234 Main St lt  address gt       lt childMap gt           lt key2 gt value2 lt  key2 gt           lt key1 gt value1 lt  key1 gt           lt childTree gt               lt childkey1 gt childvalue1 lt  childkey1 gt           lt  childTree gt       lt  childMap gt   lt  myxml gt

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Sorry  can t add comments   In Blaise s answer above  if you change    XmlJavaTypeAdapter MapAdapter class  public Map lt String  String gt  getMapProperty         return mapProperty      to    XmlJavaTypeAdapter MapAdapter class   XmlPath          lt  lt -- add this public Map lt String  String gt  getMapProperty         return mapProperty      then this should get rid of the  lt mapProperty gt  tag  and so give you    lt  xml version  1 0  encoding  UTF-8   gt   lt root gt       lt map gt           lt key gt value lt  key gt           lt key2 gt value2 lt  key2 gt       lt  map gt   lt  root gt    ALTERNATIVELY   You can also change it to    XmlJavaTypeAdapter MapAdapter class   XmlAnyElement     lt  lt -- add this public Map lt String  String gt  getMapProperty         return mapProperty      and then you can get rid of AdaptedMap altogether  and just change MapAdapter to marshall to a Document object directly  I ve only tested this with marshalling  so there may be unmarshalling issues   I ll try and find the time to knock up a full example of this  and edit this post accordingly

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I found easiest solution    XmlElement name  attribute       public String   getAttributes            return attributes keySet   toArray new String 1              Now it will generate in you xml output like this    lt attribute gt key1 lt attribute gt       lt attribute gt keyN lt attribute gt

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When using xml-apis-1 0  you can serialize and deserialize this    lt  xml version  1 0  encoding  UTF-8   gt   lt root gt       lt map gt           lt key gt value lt  key gt           lt key2 gt value2 lt  key2 gt       lt  map gt   lt  root gt    Using this code   import java io File  import java util HashMap  import java util List  import java util Map  import java util Map Entry   import javax xml bind JAXBContext  import javax xml bind Marshaller  import javax xml bind Unmarshaller  import javax xml bind annotation XmlAnyElement  import javax xml bind annotation XmlRootElement  import javax xml parsers DocumentBuilderFactory  import javax xml parsers ParserConfigurationException   import org w3c dom Document  import org w3c dom Element  import org w3c dom Node    XmlRootElement class Root        public XmlRawData map      public class Demo        public static void main String   args  throws Exception           JAXBContext jc   JAXBContext newInstance Root class            Unmarshaller unmarshaller   jc createUnmarshaller            Root root    Root  unmarshaller unmarshal new File  src input xml              System out println root map getAsMap              Marshaller marshaller   jc createMarshaller            marshaller setProperty Marshaller JAXB FORMATTED OUTPUT  true           marshaller marshal root  System out            class XmlRawData         XmlAnyElement     public List lt Element gt  elements       public void setFromMap Map lt String  String gt  values             Document document          try               document   DocumentBuilderFactory newInstance   newDocumentBuilder   newDocument              catch  ParserConfigurationException e                throw new RuntimeException e                      for  Entry lt String  String gt  entry   values entrySet                  Element mapElement   document createElement entry getKey                 mapElement appendChild document createTextNode entry getValue                  elements add mapElement                        public Map lt String  String gt  getAsMap             Map lt String  String gt  map   new HashMap lt String  String gt              for  Element element   elements                if  element getNodeType      Node ELEMENT NODE                    map put element getLocalName    element getFirstChild   getNodeValue                                      return map

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I have solution without adapter  Transient map converted to xml-elements and vise versa    XmlAccessorType XmlAccessType FIELD   XmlRootElement name    SchemaBasedProperties   public class SchemaBasedProperties      XmlTransient   Map lt String  Map lt String  String gt  gt  properties      XmlAnyElement lax   true    List lt Object gt  xmlmap     public Map lt String  Map lt String  String gt  gt  getProperties           if  properties    null        properties   new LinkedHashMap lt String  Map lt String  String gt  gt        I want same order      return properties         boolean beforeMarshal Marshaller m          try             if  properties    null  amp  amp   properties isEmpty                    if  xmlmap    null            xmlmap   new ArrayList lt Object gt             else           xmlmap clear             javax xml parsers DocumentBuilderFactory dbf   javax xml parsers DocumentBuilderFactory newInstance            javax xml parsers DocumentBuilder db   dbf newDocumentBuilder            org w3c dom Document doc   db newDocument            org w3c dom Element element           Map lt String  String gt  attrs           for  Map Entry lt String  Map lt String  String gt  gt  it  properties entrySet                        element   doc createElement it getKey               attrs   it getValue               if  attrs    null              for  Map Entry lt String  String gt  at  attrs entrySet                  element setAttribute at getKey    at getValue                xmlmap add element                           else         xmlmap   null            catch  Exception e              e printStackTrace          return false             return true         void afterUnmarshal Unmarshaller u  Object p          org w3c dom Node node      org w3c dom NamedNodeMap nodeMap       String name      Map lt String  String gt  attrs       getProperties   clear         if  xmlmap    null        for  Object xmlNode  xmlmap          if  xmlNode instanceof org w3c dom Node                      node    org w3c dom Node  xmlNode            nodeMap   node getAttributes               name   node getLocalName              attrs   new HashMap lt String  String gt                for  int i   0  l   nodeMap getLength    i  lt  l  i                            node   nodeMap item i               attrs put node getNodeName    node getNodeValue                            getProperties   put name  attrs                  xmlmap   null         public static void main String   args      throws Exception         SchemaBasedProperties props   new SchemaBasedProperties        Map lt String  String gt  attrs       attrs   new HashMap lt String  String gt         attrs put  ResId    A LABEL        props getProperties   put  LABEL   attrs        attrs   new HashMap lt String  String gt         attrs put  ResId    A TOOLTIP        props getProperties   put  TOOLTIP   attrs        attrs   new HashMap lt String  String gt         attrs put  Value    hide        props getProperties   put  DISPLAYHINT   attrs        javax xml bind JAXBContext jc   javax xml bind JAXBContext newInstance SchemaBasedProperties class        Marshaller marshaller   jc createMarshaller        marshaller setProperty Marshaller JAXB FORMATTED OUTPUT  true       marshaller marshal props  new java io File  test xml          Unmarshaller unmarshaller   jc createUnmarshaller        props    SchemaBasedProperties  unmarshaller unmarshal new java io File  test xml          System out println props getProperties             My output as espected    lt SchemaBasedProperties gt       lt LABEL ResId  A LABEL   gt       lt TOOLTIP ResId  A TOOLTIP   gt       lt DISPLAYHINT Value  hide   gt   lt  SchemaBasedProperties gt    LABEL  ResId A LABEL   TOOLTIP  ResId A TOOLTIP   DISPLAYHINT  Value hide     You can use element name value pair  I need attributes    Have fun

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I m still working on a better solution but using MOXy JAXB  I ve been able to handle the following XML    lt  xml version  1 0  encoding  UTF-8   gt   lt root gt      lt mapProperty gt         lt map gt            lt key gt value lt  key gt            lt key2 gt value2 lt  key2 gt         lt  map gt      lt  mapProperty gt   lt  root gt    You need to use an  XmlJavaTypeAdapter on your Map property   import java util HashMap  import java util Map   import javax xml bind annotation XmlRootElement  import javax xml bind annotation adapters XmlJavaTypeAdapter    XmlRootElement public class Root        private Map lt String  String gt  mapProperty       public Root             mapProperty   new HashMap lt String  String gt                 XmlJavaTypeAdapter MapAdapter class      public Map lt String  String gt  getMapProperty             return mapProperty             public void setMapProperty Map lt String  String gt  map            this mapProperty   map             The implementation of the XmlAdapter is as follows   import java util HashMap  import java util Map  import java util Map Entry   import javax xml bind annotation adapters XmlAdapter  import javax xml parsers DocumentBuilder  import javax xml parsers DocumentBuilderFactory   import org w3c dom Document  import org w3c dom Element  import org w3c dom Node  import org w3c dom NodeList   public class MapAdapter extends XmlAdapter lt AdaptedMap  Map lt String  String gt  gt          Override     public AdaptedMap marshal Map lt String  String gt  map  throws Exception           DocumentBuilderFactory dbf   DocumentBuilderFactory newInstance            DocumentBuilder db   dbf newDocumentBuilder            Document document   db newDocument            Element rootElement   document createElement  map            document appendChild rootElement            for Entry lt String String gt  entry   map entrySet                  Element mapElement   document createElement entry getKey                 mapElement setTextContent entry getValue                 rootElement appendChild mapElement                      AdaptedMap adaptedMap   new AdaptedMap            adaptedMap setValue document           return adaptedMap              Override     public Map lt String  String gt  unmarshal AdaptedMap adaptedMap  throws Exception           Map lt String  String gt  map   new HashMap lt String  String gt             Element rootElement    Element  adaptedMap getValue            NodeList childNodes   rootElement getChildNodes            for int x 0 size childNodes getLength    x lt size  x                  Node childNode   childNodes item x               if childNode getNodeType      Node ELEMENT NODE                    map put childNode getLocalName    childNode getTextContent                                     return map             The AdpatedMap class is where all the magic happens  we will use a DOM to represent the content   We will trick JAXB intro dealing with a DOM through the combination of  XmlAnyElement and a property of type Object   import javax xml bind annotation XmlAnyElement   public class AdaptedMap        private Object value        XmlAnyElement     public Object getValue             return value             public void setValue Object value            this value   value             This solution requires the MOXy JAXB implementation   You can configure the JAXB runtime to use the MOXy implementation by adding a file named jaxb properties in with your model classes with the following entry   javax xml bind context factory org eclipse persistence jaxb JAXBContextFactory   The following demo code can be used to verify the code   import java io File   import javax xml bind JAXBContext  import javax xml bind Marshaller  import javax xml bind Unmarshaller   public class Demo        public static void main String   args  throws Exception           JAXBContext jc   JAXBContext newInstance Root class            Unmarshaller unmarshaller   jc createUnmarshaller            Root root    Root  unmarshaller unmarshal new File  src forum74 input xml              Marshaller marshaller   jc createMarshaller            marshaller setProperty Marshaller JAXB FORMATTED OUTPUT  true           marshaller marshal root  System out

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the code provided didn t work for me  I found another way to Map    MapElements    package com cellfish mediadb rest lucene   import javax xml bind annotation XmlElement   class MapElements      XmlElement public String  key     XmlElement public Integer value     private MapElements        Required by JAXB    public MapElements String key  Integer value          this key     key      this value   value          MapAdapter    import java util HashMap  import java util Map   import javax xml bind annotation adapters XmlAdapter   class MapAdapter extends XmlAdapter lt MapElements    Map lt String  Integer gt  gt        public MapElements   marshal Map lt String  Integer gt  arg0  throws Exception           MapElements   mapElements   new MapElements arg0 size             int i   0          for  Map Entry lt String  Integer gt  entry   arg0 entrySet                mapElements i      new MapElements entry getKey    entry getValue              return mapElements             public Map lt String  Integer gt  unmarshal MapElements   arg0  throws Exception           Map lt String  Integer gt  r   new HashMap lt String  Integer gt             for  MapElements mapelement   arg0              r put mapelement key  mapelement value           return r            The rootElement     import java util HashMap  import java util Map   import javax xml bind annotation XmlRootElement  import javax xml bind annotation adapters XmlJavaTypeAdapter    XmlRootElement public class Root        private Map lt String  Integer gt  mapProperty       public Root             mapProperty   new HashMap lt String  Integer gt                 XmlJavaTypeAdapter MapAdapter class      public Map lt String  Integer gt  getMapProperty             return mapProperty             public void setMapProperty Map lt String  Integer gt  map            this mapProperty   map             I found the code in this website    http   www developpez net forums d972324 java general-java xml hashmap-jaxb

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Jackson has an XmlMapper which will support this out of the box  no need to write any code at all   Here s a nice tutorial https   www baeldung com jackson-xml-serialization-and-deserialization  Maven dependency    lt dependency gt       lt groupId gt com fasterxml jackson dataformat lt  groupId gt       lt artifactId gt jackson-dataformat-xml lt  artifactId gt       lt version gt 2 9 8 lt  version gt   lt  dependency gt    For writing a Map to xml   Map lt String  String gt  map   new HashMap lt  gt     map put  SomeKey    someValue     XmlMapper mapper   new XmlMapper    String xml   mapper writeValueAsString map     Will give you   lt HashMap gt  lt SomeKey gt someValue lt  SomeKey gt  lt  HashMap gt    I was able to customise the root element by creating a HashMap subclass   JacksonXmlRootElement localName    MyRootElement   public class XmlHashMap lt K  V gt  extends HashMap lt K  V gt         So now  Map lt String  String gt  map   new XmlHashMap lt  gt     map put  SomeKey    someValue     XmlMapper mapper   new XmlMapper    String xml   mapper writeValueAsString map     Will give you   lt MyRootElement gt  lt SomeKey gt someValue lt  SomeKey gt  lt  MyRootElement gt

[java] JAXB: how to marshall map into <key>value</key>

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