Jaxb是JavaEE的规范.全称Java Architecture for XML Binding.

        
     
      org.hibernate.javax.persistence
         
     
      hibernate-jpa-2.0-api
         
     
      1.0.1.Final
     
    
        
     
      org.hibernate
         
     
      hibernate-validator
         
     
      5.0.1.Final
     
    

1. JDK中JAXB相关的重要Class和Interface：

• JAXBContext类，是应用的入口，用于管理XML/Java绑定信息。
• Marshaller接口，将Java对象序列化为XML数据。
• Unmarshaller接口，将XML数据反序列化为Java对象。

 这个是简单的入门demo.可以先运行试试,对JAXB有个大概的使用方法.下面例子将是系统正常做的.并对并发性进行处理的一个例子.

2. 常用注解说明

常用的annotation有：

1.@XmlType

• XmlAccessType.FIELD:java对象中的所有成员变量
• XmlAccessType.PROPERTY：java对象中所有通过getter/setter方式访问的成员变量
• XmlAccessType.PUBLIC_MEMBER：java对象中所有的public访问权限的成员变量和通过getter/setter方式访问的成员变量
• XmlAccessType.NONE:java对象的所有属性都不映射为xml的元素

注意：@XmlAccessorType的默认访问级别是XmlAccessType.PUBLIC_MEMBER，因此，如果java对象中的private成员变量设置了public权限的getter/setter方法，就不要在private变量上使用@XmlElement和@XmlAttribute注解，否则在由java对象生成xml时会报同一个属性在java类里存在两次的错误。同理，如果@XmlAccessorType的访问权限为XmlAccessType.NONE，如果在java的成员变量上使用了@XmlElement或@XmlAttribute注解，这些成员变量依然可以映射到xml文件。

注意：虽然@XmlAccessorType为XmlAccessType.NONE,但是在java类的私有属性上加了@XmlAttribute和@XmlElement注解后，这些私有成员会映射生成xml的元素

6.@XmlAccessorOrder

public abstract class XmlAdapter<ValueType,BoundType> {

实际案例:

package jaxb.shop;import java.util.Date;import java.text.SimpleDateFormat;import javax.xml.bind.annotation.adapters.XmlAdapter;public class DateAdapter extends XmlAdapter
    
      {    private String pattern = "yyyy-MM-dd HH:mm:ss";    SimpleDateFormat fmt = new SimpleDateFormat(pattern);    @Override    public Date unmarshal(String dateStr) throws Exception {        return fmt.parse(dateStr);    }    @Override    public String marshal(Date date) throws Exception {        return fmt.format(date);    }} //用于格式化日期在xml中的显示格式，并且由xml unmarshal为java对象时，将字符串解析为Date对象
    

在某个类中如下使用,解析出对应的时间格式.必须重载那2个方法,用于JAXB marshal xml,xml unmarshal object时候使用.

import javax.xml.bind.annotation.XmlSchemaType;import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;@XmlElement(name = "TransactionTime", required = true) @XmlSchemaType(name = "dateTime") @XmlJavaTypeAdapter(DatetimeAdapter.class) protected Date transactionTime;

9.但如果是和JPA一起使用的话,可以使用@Temporal(TemporalType.DATE)来格式时间,默认为TemporalType.TIMESTAMP类型.TemporalType属性如下:

10.在JAXB标准中，@XmlElementWrapper注解表示生成一个包装 XML 表示形式的包装器元素。 此元素主要用于生成一个包装集合的包装器 XML 元素。

3. 最终案例(模拟XML--系统 --DB)

例子XML示例.

    
    	
     
      110
     	
     
      Credo
     	
     
China BeiJing
	
     
      programmer
     	
     		
      			
       
        Accompany my girlfriend.
       			
       			
       
        2009-06-02T12:00:00
       			
       			
       
        2109-06-02T12:00:00
       		
      		
      			
       
        Write some code.
       			
       			
       
        2009-06-02T12:00:00
       			
       			
       
        2029-06-02T12:00:00
       		
      	
     
    

Model层(JAXB+JPA):

package org.credo.jaxb.model;import java.io.Serializable;import java.util.List;import javax.persistence.CascadeType;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.Id;import javax.persistence.OneToMany;import javax.persistence.Table;import javax.xml.bind.annotation.XmlAccessType;import javax.xml.bind.annotation.XmlAccessorType;import javax.xml.bind.annotation.XmlElement;import javax.xml.bind.annotation.XmlElementWrapper;import javax.xml.bind.annotation.XmlElements;import javax.xml.bind.annotation.XmlRootElement;import org.hibernate.validator.constraints.Length;/** * @author Credo */@XmlRootElement@XmlAccessorType(XmlAccessType.FIELD)@Entity@Table(name = "USERINFO")public class Userinfo implements Serializable{		private static final long serialVersionUID = 7870351249722416047L;		@Id	@Column(name = "ID", nullable = false)	private Long id;		@Column(name = "NAME", length = 50)	@Length(max = 50)	private String name;		@Column(name = "ADDRESS", length = 50)	@Length(max = 50)	private String address;		@Column(name = "JOB", length = 50)	@Length(max = 50)	private String job;		@XmlElementWrapper(name = "overinfos")	@OneToMany(cascade = CascadeType.ALL)	@XmlElements(value = { @XmlElement(name = "overinfo", type = Overinfo.class) })	private List
    
      overinfos;		public Long getId() {		return id;	}	public void setId(Long id) {		this.id = id;	}	public String getName() {		return name;	}	public void setName(String name) {		this.name = name;	}	public String getAddress() {		return address;	}	public void setAddress(String address) {		this.address = address;	}	public String getJob() {		return job;	}	public void setJob(String job) {		this.job = job;	}	public List
     
       getOverinfos() {		return overinfos;	}	public void setOverinfos(List
      
        overinfos) {		this.overinfos = overinfos;	}	}
      
     
    

Overinfo.class

package org.credo.jaxb.model;import java.io.Serializable;import java.util.Date;import javax.persistence.CascadeType;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.JoinColumn;import javax.persistence.ManyToOne;import javax.persistence.Table;import javax.persistence.Temporal;import javax.persistence.TemporalType;import javax.xml.bind.annotation.XmlAccessType;import javax.xml.bind.annotation.XmlAccessorType;import javax.xml.bind.annotation.XmlTransient;import javax.xml.bind.annotation.XmlType;@XmlAccessorType(XmlAccessType.FIELD)@XmlType(name = "overinfo")@Entity@Table(name = "OVERINFO")public class Overinfo implements Serializable {	private static final long serialVersionUID = 2579971237985854291L;	@XmlTransient	@Id	@GeneratedValue(strategy = GenerationType.IDENTITY)	@Column(name = "ID")	private Long id;		@XmlTransient	@ManyToOne(cascade = CascadeType.ALL)	@JoinColumn(name = "UserinfoId")	private Userinfo userinfo;		@Column(name = "hobby", length = 20)	private String hobby;		@Temporal(TemporalType.DATE)	@Column(name = "beginDate", length = 20)	private Date beginDate;		@Temporal(TemporalType.DATE)	@Column(name = "endDate", length = 20)	private Date endDate;	public String getHobby() {		return hobby;	}	public void setHobby(String hobby) {		this.hobby = hobby;	}	public Date getBeginDate() {		return beginDate;	}	public void setBeginDate(Date beginDate) {		this.beginDate = beginDate;	}	public Date getEndDate() {		return endDate;	}	public void setEndDate(Date endDate) {		this.endDate = endDate;	}	public Long getId() {		return id;	}	public void setId(Long id) {		this.id = id;	}	public Userinfo getUserinfo() {		return userinfo;	}	public void setUserinfo(Userinfo userinfo) {		this.userinfo = userinfo;	}}

JAXB并发处理:

package org.credo.jaxb;import java.util.concurrent.ConcurrentHashMap;import java.util.concurrent.ConcurrentMap;import javax.xml.bind.JAXBContext;import javax.xml.bind.JAXBException;public final class JAXBCache {	private static final JAXBCache instance = new JAXBCache();	private final ConcurrentMap
    
      contextCache = new ConcurrentHashMap
     
      ();	private JAXBCache() {	}	public static JAXBCache instance() {		return instance;	}	JAXBContext getJAXBContext(Class
       clazz) throws JAXBException {		JAXBContext context = contextCache.get(clazz.getName());		if ( context == null )		{			context = JAXBContext.newInstance(clazz);			contextCache.putIfAbsent(clazz.getName(), context);		}		return context;	}}
     
    

JAXBExportSchema 导出JAXB的 class的 结构

package org.credo.jaxb;import java.io.File;import java.io.IOException;import javax.xml.bind.JAXBContext;import javax.xml.bind.SchemaOutputResolver;import javax.xml.transform.Result;import javax.xml.transform.stream.StreamResult;import org.credo.jaxb.model.Userinfo;/** * JAXB 导出Schema。 *  * @author: Credo * @date: 2013-6-25 */public class JAXBExportSchema {	public static void main(String[] args) {		JAXBContext jct;		try		{			jct = JAXBContext.newInstance(Userinfo.class);			jct.generateSchema(new Resolver());		}		catch ( Exception ex )		{			ex.printStackTrace();		}	}}class Resolver extends SchemaOutputResolver {	@Override	public Result createOutput(String namespaceUri, String suggestedFileName) throws IOException {		File file = new File("d:\\", suggestedFileName);		StreamResult result = new StreamResult(file);		result.setSystemId(file.toURI().toURL().toString());		return result;	}}

JAXBUtil以及main方法测试:

package org.credo.jaxb;import java.io.ByteArrayInputStream;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.InputStream;import java.util.ArrayList;import java.util.List;import javax.xml.bind.JAXBContext;import javax.xml.bind.JAXBException;import javax.xml.bind.Marshaller;import javax.xml.bind.Unmarshaller;import org.apache.commons.io.IOUtils;import org.credo.jaxb.model.Overinfo;import org.credo.jaxb.model.Userinfo;/** * marshal对象和unmarshal对象都是由JAXBContext创建.所以一开始需要初始化JAXBContext. * @author Credo */public class JAXBUtil {	/**	 * 生成xml文件的二进制数据	 * @param obj 对象	 */	public static byte[] marshal(Object obj) throws JAXBException {		JAXBContext context = JAXBCache.instance().getJAXBContext(obj.getClass());		Marshaller m = context.createMarshaller();		ByteArrayOutputStream outputStream = new ByteArrayOutputStream();		m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);		m.marshal(obj, outputStream);		byte[] result = outputStream.toByteArray();		return result;	}	/**	 * @param data xml stream	 * @param classe 类	 * @return jaxb生成xml的java 类对象	 */	public static Object unmarshal(byte[] data, Class
     classe) throws JAXBException {		JAXBContext context = JAXBCache.instance().getJAXBContext(classe);		Unmarshaller m = context.createUnmarshaller();		ByteArrayInputStream inputStream = new ByteArrayInputStream(data);		Object obj = m.unmarshal(inputStream);		return obj;	}	/**	 * @param data xml stream	 * @param classe 类	 * @return jaxb生成xml的java 类对象	 */	public static Object unmarshal(InputStream in, Class
     classe) throws JAXBException, IOException {		JAXBContext context = JAXBCache.instance().getJAXBContext(classe);		byte[] data = IOUtils.toByteArray(in);		Unmarshaller m = context.createUnmarshaller();		ByteArrayInputStream inputStream = new ByteArrayInputStream(data);		Object obj = m.unmarshal(inputStream);		return obj;	}	public static void main(String[] args) throws JAXBException {		Userinfo userinfo = new Userinfo();		userinfo.setId(Long.valueOf(11));		List
    
      list = new ArrayList
     
      ();		Overinfo e = new Overinfo();		e.setHobby("陪女友");		list.add(e);		Overinfo e1 = new Overinfo();		e1.setHobby("写代码");		list.add(e1);		userinfo.setOverinfos(list);		byte[] b = JAXBUtil.marshal(userinfo);		System.out.println(new String(b));		userinfo = (Userinfo) JAXBUtil.unmarshal(b, Userinfo.class);		System.out.println(userinfo.getOverinfos().get(0).getHobby());	}}
     
    

就不说明了,仔细看代码的,一会就明白了.不看的运行下也明白了.下面是上面main方法测试的输出结果:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>

下面是使用JAXBExportSchema 导出JAXB的 class的 结构