Jaxb是JavaEE的规范.全称Java Architecture for XML Binding.
可以根据XML Schema产生Java类的技术.JAXB也提供了将XML实例文档反向生成Java对象树的方法,并能将Java对象树的内容重新写到XML实例文档.
JAXB 2.0是JDK 1.6的组成部分。JAXB 2.2.3是JDK 1.7的组成部分。在实际使用不需要引入新的jar.
我一般使用都是配合JPA使用,下面例子也是按JPA+JAXB来说明.
因此我需要引入jpa的实现包.hibernate-validator随便.做验证用的.
<dependency> <groupId>org.hibernate.javax.persistence</groupId> <artifactId>hibernate-jpa-2.0-api</artifactId> <version>1.0.1.Final</version> </dependency> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-validator</artifactId> <version>5.0.1.Final</version> </dependency>
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。
http://my.oschina.net/zhaoqian/blog/89763 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:
@XmlType
@XmlElement
@XmlRootElement
@XmlAttribute
@XmlAccessorType
@XmlAccessorOrder
@XmlTransient
@XmlJavaTypeAdapter
@Temporal(TemporalType.XXXX) -->JPA中的时间处理注解,非JAXB
@XmlElementWrapper
1.@XmlType
@XmlType用在class类的注解,常与@XmlRootElement,@XmlAccessorType一起使用。它有三个属性:name、propOrder、namespace,经常使用的只有前两个属性。如:
同时使用了@XmlType(propOrder={})和@XmlAccessorOrder(XmlAccessOrder.ALPHABETICAL)的时候,生成的xml只按照propOrder定义的顺序生成元素
@XmlType(name = "basicStruct", propOrder = {
"intValue",
"stringArray",
"stringValue"
)
在使用@XmlType的propOrder 属性时,必须列出JavaBean对象中的所有属性,否则会报错。
2.@XmlRootElement
@XmlRootElement用于类级别的注解,对应xml的跟元素,常与 @XmlType 和 @XmlAccessorType一起使用。如:
@XmlType
@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement
public class Address {}
3.@XmlElement
@XmlElement将java对象的属性映射为xml的节点,在使用@XmlElement时,可通过name属性改变java对象属性在xml中显示的名称。如:
@XmlElement(name="Address")
private String yourAddress;
4.@XmlAttribute
@XmlAttribute用于把java对象的属性映射为xml的属性,并可通过name属性为生成的xml属性指定别名。如:
@XmlAttribute(name="Country")
private String state;
5.@XmlAccessorType
@XmlAccessorType用于指定由java对象生成xml文件时对java对象属性的访问方式。常与@XmlRootElement、@XmlType一起使用。它的属性值是XmlAccessType的4个枚举值,分别为:
- 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
@XmlAccessorOrder用于对java对象生成的xml元素进行排序。它有两个属性值:
AccessorOrder.ALPHABETICAL:对生成的xml元素按字母书序排序
XmlAccessOrder.UNDEFINED:不排序
7.@XmlTransient
@XmlTransient用于标示在由java对象映射xml时,忽略此属性。即,在生成的xml文件中不出现此元素。
8.@XmlJavaTypeAdapter
@XmlJavaTypeAdapter常用在转换比较复杂的对象时,如map类型或者格式化日期等。使用此注解时,需要自己写一个adapter类继承XmlAdapter抽象类,并实现里面的方法。
@XmlJavaTypeAdapter(value=xxx.class),value为自己定义的adapter类
XmlAdapter 抽象接口如下:
public abstract class XmlAdapter<ValueType,BoundType> { // Do-nothing constructor for the derived classes.
protected XmlAdapter() {}
// Convert a value type to a bound type.
public abstract BoundType unmarshal(ValueType v);
// Convert a bound type to a value type.
public abstract ValueType marshal(BoundType v);
}
实际案例:
<i>package jaxb.shop; import java.util.Date; import java.text.SimpleDateFormat; import javax.xml.bind.annotation.adapters.XmlAdapter; public class DateAdapter extends XmlAdapter<String, Date> { 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</i>
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.
@XmlJavaTypeAdapter(value=DateAdapter.class)
private Date purDate;
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:
public enum TemporalType {
DATE, //java.sql.Date
TIME, //java.sql.Time
TIMESTAMP //java.sql.Timestamp
}
java.sql.Date
日期型,精确到年月日,例如“2008-08-08”
java.sql.Time
时间型,精确到时分秒,例如“20:00:00”
java.sql.Timestamp
时间戳,精确到纳秒,例如“2008-08-08 20:00:00.000000001”
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。
注:@XmlElementWrapper仅允许出现在集合属性上。最后的案例将使用这个注解.
3. 最终案例(模拟XML--系统 --DB)
例子XML示例.
<?xml version="1.0" encoding="utf-8"?> <userinfo xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <id>110</id> <name>Credo</name> <address>China BeiJing</address> <job>programmer</job> <overinfos> <overinfo> <hobby>Accompany my girlfriend.</hobby> <!--开始日期 dateTime--> <beginDate>2009-06-02T12:00:00</beginDate> <!--结束日期 dateTime--> <endDate>2109-06-02T12:00:00</endDate> </overinfo> <overinfo> <hobby>Write some code.</hobby> <!--开始日期 dateTime--> <beginDate>2009-06-02T12:00:00</beginDate> <!--结束日期 dateTime--> <endDate>2029-06-02T12:00:00</endDate> </overinfo> </overinfos> </userinfo>
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<Overinfo> 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<Overinfo> getOverinfos() { return overinfos; } public void setOverinfos(List<Overinfo> 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<String, JAXBContext> contextCache = new ConcurrentHashMap<String, JAXBContext>(); 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<Overinfo> list = new ArrayList<Overinfo>(); 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"?>
<userinfo>
<id>11</id>
<overinfos>
<overinfo>
<hobby>陪女友</hobby>
</overinfo>
<overinfo>
<hobby>写代码</hobby>
</overinfo>
</overinfos>
</userinfo>
陪女友
下面是使用JAXBExportSchema 导出JAXB的 class的 结构
<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <xs:schema version="1.0" xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="userinfo" type="userinfo"/> <xs:complexType name="userinfo"> <xs:sequence> <xs:element name="id" type="xs:long" minOccurs="0"/> <xs:element name="name" type="xs:string" minOccurs="0"/> <xs:element name="address" type="xs:string" minOccurs="0"/> <xs:element name="job" type="xs:string" minOccurs="0"/> <xs:element name="overinfos" minOccurs="0"> <xs:complexType> <xs:sequence> <xs:element name="overinfo" type="overinfo" minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> <xs:complexType name="overinfo"> <xs:sequence> <xs:element name="hobby" type="xs:string" minOccurs="0"/> <xs:element name="beginDate" type="xs:dateTime" minOccurs="0"/> <xs:element name="endDate" type="xs:dateTime" minOccurs="0"/> </xs:sequence> </xs:complexType> </xs:schema>