content: /**
   * Copyright (c) 2005-2012 springside.org.cn
   */
  package com.jeespring.common.mapper;
  
  import java.io.StringReader;
  import java.io.StringWriter;
  import java.util.Collection;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  import javax.xml.bind.JAXBContext;
  import javax.xml.bind.JAXBElement;
  import javax.xml.bind.JAXBException;
  import javax.xml.bind.Marshaller;
  import javax.xml.bind.Unmarshaller;
  import javax.xml.bind.annotation.XmlAnyElement;
  import javax.xml.namespace.QName;
  
  import org.springframework.http.converter.HttpMessageConversionException;
  import org.springframework.util.Assert;
  
  import com.jeespring.common.utils.Exceptions;
  import com.jeespring.common.utils.Reflections;
  import com.jeespring.common.utils.StringUtils;
  
  /**
   * 使用Jaxb2.0实现XML<->Java Object的Mapper.
   * 
   * 在创建时需要设定所有需要序列化的Root对象的Class.
   * 特别支持Root对象是Collection的情形.
   * 
   * @author calvin
   * @version 2013-01-15
   */
  @SuppressWarnings("rawtypes")
  public class JaxbMapper {
  
  	private static ConcurrentMap<Class, JAXBContext> jaxbContexts = new ConcurrentHashMap<Class, JAXBContext>();
  
  	/**
  	 * Java Object->Xml without encoding.
  	 */
  	public static String toXml(Object root) {
  		Class clazz = Reflections.getUserClass(root);
  		return toXml(root, clazz, null);
  	}
  
  	/**
  	 * Java Object->Xml with encoding.
  	 */
  	public static String toXml(Object root, String encoding) {
  		Class clazz = Reflections.getUserClass(root);
  		return toXml(root, clazz, encoding);
  	}
  
  	/**
  	 * Java Object->Xml with encoding.
  	 */
  	public static String toXml(Object root, Class clazz, String encoding) {
  		try {
  			StringWriter writer = new StringWriter();
  			createMarshaller(clazz, encoding).marshal(root, writer);
  			return writer.toString();
  		} catch (JAXBException e) {
  			throw Exceptions.unchecked(e);
  		}
  	}
  
  	/**
  	 * Java Collection->Xml without encoding, 特别支持Root Element是Collection的情形.
  	 */
  	public static String toXml(Collection<?> root, String rootName, Class clazz) {
  		return toXml(root, rootName, clazz, null);
  	}
  
  	/**
  	 * Java Collection->Xml with encoding, 特别支持Root Element是Collection的情形.
  	 */
  	public static String toXml(Collection<?> root, String rootName, Class clazz, String encoding) {
  		try {
  			CollectionWrapper wrapper = new CollectionWrapper();
  			wrapper.collection = root;
  
  			JAXBElement<CollectionWrapper> wrapperElement = new JAXBElement<CollectionWrapper>(new QName(rootName),
  					CollectionWrapper.class, wrapper);
  
  			StringWriter writer = new StringWriter();
  			createMarshaller(clazz, encoding).marshal(wrapperElement, writer);
  
  			return writer.toString();
  		} catch (JAXBException e) {
  			throw Exceptions.unchecked(e);
  		}
  	}
  
  	/**
  	 * Xml->Java Object.
  	 */
  	@SuppressWarnings("unchecked")
  	public static <T> T fromXml(String xml, Class<T> clazz) {
  		try {
  			StringReader reader = new StringReader(xml);
  			return (T) createUnmarshaller(clazz).unmarshal(reader);
  		} catch (JAXBException e) {
  			throw Exceptions.unchecked(e);
  		}
  	}
  
  	/**
  	 * 创建Marshaller并设定encoding(可为null).
  	 * 线程不安全，需要每次创建或pooling。
  	 */
  	public static Marshaller createMarshaller(Class clazz, String encoding) {
  		try {
  			JAXBContext jaxbContext = getJaxbContext(clazz);
  
  			Marshaller marshaller = jaxbContext.createMarshaller();
  
  			marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
  
  			if (StringUtils.isNotBlank(encoding)) {
  				marshaller.setProperty(Marshaller.JAXB_ENCODING, encoding);
  			}
  
  			return marshaller;
  		} catch (JAXBException e) {
  			throw Exceptions.unchecked(e);
  		}
  	}
  
  	/**
  	 * 创建UnMarshaller.
  	 * 线程不安全，需要每次创建或pooling。
  	 */
  	public static Unmarshaller createUnmarshaller(Class clazz) {
  		try {
  			JAXBContext jaxbContext = getJaxbContext(clazz);
  			return jaxbContext.createUnmarshaller();
  		} catch (JAXBException e) {
  			throw Exceptions.unchecked(e);
  		}
  	}
  
  	protected static JAXBContext getJaxbContext(Class clazz) {
  		Assert.notNull(clazz, "'clazz' must not be null");
  		JAXBContext jaxbContext = jaxbContexts.get(clazz);
  		if (jaxbContext == null) {
  			try {
  				jaxbContext = JAXBContext.newInstance(clazz, CollectionWrapper.class);
  				jaxbContexts.putIfAbsent(clazz, jaxbContext);
  			} catch (JAXBException ex) {
  				throw new HttpMessageConversionException("Could not instantiate JAXBContext for class [" + clazz
  						+ "]: " + ex.getMessage(), ex);
  			}
  		}
  		return jaxbContext;
  	}
  
  	/**
  	 * 封装Root Element 是 Collection的情况.
  	 */
  	public static class CollectionWrapper {
  
  		@XmlAnyElement
  		protected Collection<?> collection;
  	}
  	
  }
  