XStream处理null值的问题

使用XStream把javaBean转化成xml文件时，当JavaBean的某些变量为null是，将在xml文件中不输出这个属性！如

Class Person{

        String name;
        String sex;
}

当sex为null时，那么输出的xml文件为

<person>
     <name>***</name>
</person>

如果我们希望能把全部变量输出，需要给XStream实例注册一个转化器，实现Converter接口，这个接口提供三个方法，在它的官方文档中有详细介绍。 http://xstream.codehaus.org/javadoc/index.html


这里我们需要实现的功能是，把null值的属性都在xml文件中输出！如上面的Person输出为

<person>
      <name>***</name>
      <sex></sex>
</person>

那么我们需要新建一个实现Converter接口的类，如

package com.asrfid.jay.action;

import java.lang.reflect.Method;
import java.util.List;

import com.asrfid.jay.dto.Consignee;
import com.asrfid.jay.dto.Consignor;
import com.asrfid.jay.dto.Goods;
import com.asrfid.jay.dto.SendXML;
import com.thoughtworks.xstream.converters.Converter;
import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;

public class NullConverter implements Converter{

	@Override
	public void marshal(Object source, HierarchicalStreamWriter writer,
			MarshallingContext context) {
		SendXML obj = (SendXML)source;
		
		Method[] methods = SendXML.class.getMethods();
		for(Method m : methods){
			String methodName = m.getName();
			if (methodName.indexOf("get") != -1 && methodName != "getClass") {
				String name = methodName.substring(3);
				Object o = null;
				try {
					o = m.invoke(obj, new Object[0]);
				} catch (Exception e) {
					e.printStackTrace();
				}
				if (o instanceof Consignee) {
					writer.startNode("ConsigneeInfomation");
					Consignee consignee = (Consignee)o;
					Method[] methods2 = Consignee.class.getMethods();
					for (Method m2 : methods2) {
						methodName = m2.getName();
						if (methodName.indexOf("get") != -1 && methodName != "getClass") {
							name = methodName.substring(3);
							writer.startNode(name);
							Object con1 = null;
							try {
								con1 = m2.invoke(consignee, new Object[0]);
							} catch (Exception e) {
								// TODO Auto-generated catch block
								e.printStackTrace();
							}
							writer.setValue(con1==null?"":con1.toString());
							writer.endNode();
						}
					}
					writer.endNode();
				}else if (o instanceof Consignor) {
					writer.startNode("ConsignorInfomation");
					Consignor consignor = (Consignor)o;
					Method[] methods2 = Consignor.class.getMethods();
					for (Method m2 : methods2) {
						methodName = m2.getName();
						if (methodName.indexOf("get") != -1 && methodName != "getClass") {
							name = methodName.substring(3);
							writer.startNode(name);
							Object con1 = null;
							try {
								con1 = m2.invoke(consignor, new Object[0]);
							} catch (Exception e) {
								// TODO Auto-generated catch block
								e.printStackTrace();
							}
							writer.setValue(con1==null?"":con1.toString());
							writer.endNode();
						}
					}
					writer.endNode();
				}else if(o instanceof java.util.List){
					writer.startNode("goodsInformations");
					List lists = (java.util.List)o;
					for(int i =0;i<lists.size();i++){
						Goods goods = (Goods)lists.get(i);
						Method[] methods3 = Goods.class.getMethods();
						for (Method m3 : methods3) {
							methodName = m3.getName();
							if (methodName.indexOf("get") != -1 && methodName != "getClass") {
								name = methodName.substring(3);
								writer.startNode(name);
								Object con1 = null;
								try {
									con1 = m3.invoke(goods, new Object[0]);
								} catch (Exception e) {
									e.printStackTrace();
								}
								writer.setValue(con1==null?"":con1.toString());
								writer.endNode();
							}
						}
					}
					writer.endNode();//goodsInformations
				}else {
					writer.startNode(name);
					writer.setValue(o==null?"":o.toString());
					writer.endNode();//
				}
				
				
			}
		}
		
	}

	@Override
	public Object unmarshal(HierarchicalStreamReader reader,
			UnmarshallingContext context) {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public boolean canConvert(Class type) {
		// TODO Auto-generated method stub
		return type.equals(SendXML.class);
	}

}

另外我们还需要注册这个类，如

		SendXML sendXML = this.sendXMLManager.getSendXML(shippingId);
		XStream xStream = new XStream(new DomDriver());
		xStream.alias("ShippingOrder", SendXML.class);
		xStream.alias("consigneeInfomation", Consignee.class);
		xStream.alias("consignorInfomation", Consignor.class);
		xStream.alias("GoodsInfomation", Goods.class);
		xStream.registerConverter(new com.asrfid.jay.action.NullConverter());
		String xml = xStream.toXML(sendXML);