How to Serialize Maps?

[Siegfried Heintze]

Can someone help me modify my program below so it will serialize a map to standard output? Sun had documented a bug several years ago concerning the serialization of maps and I am hoping it has been fixed by now.
Thanks,
Siegfried

/*
 * Begin commands to execute this file using Java with bash
 * if [ `uname` == 'Linux' ]
 * then
 * export CLASSPATH=bin:.
 * else
 * export CLASSPATH=bin\;.
 * fi
 * pushd ../../
 * if [ -e "bin" ]
 * then
 * echo "already have build (bin) directory"
 * else
 * echo "mkdir bin"
 * mkdir bin
 * fi
 * javac -g com/heintze/DemoMaps.java -d bin
 * java  com.heintze.DemoMaps <<EOF 
 * ><?xml version="1.0" encoding="UTF-8" standalone="yes"?>
 * <demoMaps>
 *   <datum name="xyz"><value>Insert your sample data here</value></datum>
 *   <datum name="abc"><value>def</value></datum>
 * </demoMaps>
 * EOF
 * rm bin/com/heintze/DemoMaps.class
 * popd
 * End commands to execute this file using Java with bash
 *
 */

package com.heintze;
import java.io.FileReader;
import java.util.TreeMap;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;

@XmlType
class Pair{
  Pair(){}
  Pair(String name, String value){ this.name = name; this.value = value; }
  @XmlAttribute
  String name;
  @XmlElement
  String value;
}

@XmlRootElement
public class DemoMaps {
  static java.io.PrintStream out = System.out;
  public static void main(String[] args) {
    DemoMaps data = new DemoMaps();
    try {
      JAXBContext context = JAXBContext.newInstance(DemoMaps.class);
      Marshaller m = context.createMarshaller();
      Unmarshaller um = context.createUnmarshaller();
      data = (DemoMaps)um.unmarshal(new FileReader(java.io.FileDescriptor.in) );
      data.datum[0].name+="_modified";
      data.datum[0].value+="_modified";
      data.map.put("hello", "world");
      m.marshal(data, System.out);
    } catch (JAXBException e) {
      e.printStackTrace();
    }
  }
  @XmlElement
  Pair[] datum =new Pair[0];
  @XmlElement(nillable=true, required=false)
  TreeMap<String,String> map=new TreeMap<String,String>();
 }

[Paul Clapham]

I ran that code (with the XML from the comments before it) and it produced this:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?><demoMaps><datum name="xyz_modified"><value>Insert your sample data here_modified</value></datum><datum name="abc"><value>def</value></datum><map/></demoMaps>

Looks okay to me, except for that empty <map> element at the end. Was that what you were referring to? Is it a problem?

Edit: looking at your code it looks like you were expecting the contents of the map to be serialized as well. At least that's what I would expect. So if that's the bug (you didn't say what this bug was) then it's still there.

[David Newton]

It'd be easier if you just said what issue you're having. The code works as-is for me once the command is fixed:

java  com.heintze.DemoMaps <<EOF  
><?xml version="1.0" encoding="UTF-8" standalone="yes"?> 

That ">" at the beginning of line 2 shouldn't be there.

[David Newton]

Oh, the map.

Don't you need @XmlJavaTypeAdapter to do maps?

http://www.caucho.com/resin/doc/jaxb-annotations.xtp#@XmlJavaTypeAdapter

[Siegfried Heintze]

Sorry -- yup. The map is empty. That is the problem I was hoping was fixed by now. Wow! sun sure is slow at fixing these things.

[Siegfried Heintze]

I'm trying to implement the suggested code at http://www.caucho.com/resin/doc/jaxb-annotations.xtp#@XmlJavaTypeAdapter and I need some help.

Can someone help me implement the marshal and unmarshal methods? I'm having trouble understand how class Temp works. Why would marshal return a single temp? Wouldn't it return a java.util.list<Temp>?

Perhaps the problem is that eclipse generated the stub for marshal and unmarshal incorrectly?

Thanks,
Siegfried

/*
 * Begin commands to execute this file using Java with bash
 * if [ `uname` == 'Linux' ]
 * then
 * export CLASSPATH=bin:.
 * else
 * export CLASSPATH=bin\;.
 * fi
 * pushd ../../
 * if [ -e "bin" ]
 * then
 * echo "already have build (bin) directory"
 * else
 * echo "mkdir bin"
 * mkdir bin
 * fi
 * javac -g com/heintze/DemoMaps.java -d bin
 * java  com.heintze.DemoMaps "/demoMaps/datum[1]/value/text()" '/demoMaps/datum[@name="abc"]' <<EOF 
 * ><?xml version="1.0" encoding="UTF-8" standalone="yes"?>
 * <demoMaps>
 *   <datum name="xyz"><value>Insert your sample data here</value></datum>
 *   <datum name="abc"><value>def</value></datum>
 * </demoMaps>
 * EOF
 * rm bin/com/heintze/DemoMaps.class
 * popd
 * End commands to execute this file using Java with bash
 *
 */

package com.heintze;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;
import javax.xml.bind.annotation.adapters.XmlAdapter;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;

@XmlType
class Pair{
  Pair(){}
  Pair(String name, String value){ this.name = name; this.value = value; }
  @XmlAttribute
  String name;
  @XmlElement
  String value;
}

// http://www.caucho.com/resin/doc/jaxb-annotations.xtp#@XmlJavaTypeAdapter

class Bean {
  @XmlJavaTypeAdapter(MyMapAdapter.class)
	  public HashMap<String,String> map = new HashMap<String,String>();
}

class MyMapAdapter
  extends XmlAdapter<Temp,java.util.Map><String,String>> {

	@Override
	public Temp marshal(Map<String, String> arg0) throws Exception {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public Map<String, String> unmarshal(Temp v) throws Exception {
		// TODO Auto-generated method stub
		return null;
	}
}

class Item {
  @XmlAttribute
	  private String key;

  @XmlAttribute
	  private String value;
}

class Temp {
  @XmlElement
	  private List<Item> entry = new java.util.ArrayList<Item>();
}

@XmlRootElement
public class DemoMaps {
  static java.io.PrintStream out = System.out;
  public static void main(String[] args) {
    DemoMaps data = new DemoMaps();
    try {
      JAXBContext context = JAXBContext.newInstance(DemoMaps.class);
      Marshaller m = context.createMarshaller();
      Unmarshaller um = context.createUnmarshaller();
      data = (DemoMaps)um.unmarshal(new FileReader(java.io.FileDescriptor.in) );
      data.datum[0].name+="_modified";
      data.datum[0].value+="_modified";
      data.map.put("hello", "world");
      data.map2.map.put("hello", "world");
      m.marshal(data, System.out);
    } catch (JAXBException e) {
      e.printStackTrace();
    }
  }
  @XmlElement
  Pair[] datum =new Pair[0];
  @XmlElement(nillable=true, required=false)
  TreeMap<String,String> map=new TreeMap<String,String>();
  Bean map2 = new Bean();
 }

[Siegfried Heintze]

I figured it out.

I have a new question now! See my new post.

Thanks,
Siegfried