读取xml对于应用软件来说是一个必不可少的工作,当然现在的jdk也提供了很好的处理xml方式,读写xml的库也挺多,包括有名的dom4j,不管使用任何的代码库,对于xml只是一个解析工作而已,不能马上绑定到java 对象。对于对象,每次都需要set 或者get相应的属性,当然也可以使用map 来保存xml配置。
于是,一种新的处理方式用于对象和xml之间的映射就变得非常需要,还好sun提供了jaxb,一种很方便的方式来处理java对象和xml内容。下面通过一个实例来体会一下。
看一下如下的xml
<?xml version="1.0"?>
<customer id="No1">
<name>Alice Smith</name>
<address>
<street>123 Maple Street</street>
<city>Cambridge</city>
<zip>12345</zip>
</address>
</customer>
别忘了生成相应的xsd,或者dtd文件,这是主要的配置:
xsd:
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:complexType name="Customer">
<xs:sequence>
<xs:element name="address" type="Address"/>
<xs:element name="name" type="xs:string"/>
</xs:sequence>
<xs:attribute name="id" type="xs:string"/>
</xs:complexType>
<xs:complexType name="Address">
<xs:sequence>
<xs:element name="street" type="xs:string"/>
<xs:element name="city" type="xs:string"/>
<xs:element name="zip" type="ZipCodeType"/>
</xs:sequence>
</xs:complexType>
<xs:simpleType name="ZipCodeType">
<xs:restriction base="xs:integer">
<xs:minInclusive value="10000"/>
<xs:maxInclusive value="99999"/>
</xs:restriction>
</xs:simpleType>
<xs:element name="customer" type="Customer"/>
<xs:element name="address" type="Address"/>
</xs:schema>
需要映射两个java对象,CustomerBo和AddressBo
java 对象可以通过xjc来生成。
或者自己定义(但需要增加相应的java注释,如@XmlAccessorType,@XmlType,这是给引擎使用的)
所以一般通过xjd自动生成
@XmlAccessorType(AccessType.FIELD)
@XmlType(name = "Customer", propOrder = {
"address",
"customerName"
})
public class CustomerBo {
protected Address address;
@XmlElement(name = "name")
protected String customerName;
@XmlAttribute
protected String id;
public Address getAddress() {
return address;
}
public String getCustomerName() {
return customerName;
}
public String getId() {
return id;
}
public void setAddress(Address value) {
this.address = value;
}
public void setCustomerName(String value) {
this.customerName = value;
}
public void setId(String value) {
this.id = value;
}
}
public class Address {
protected String street;
protected String city;
@XmlElement(name = "zip")
protected BigInteger zipCode;
public String getStreet() {
return street;
}
public void setStreet(String value) {
this.street = value;
}
public String getCity() {
return city;
}
public void setCity(String value) {
this.city = value;
}
public BigInteger getZipCode() {
return zipCode;
}
public void setZipCode(BigInteger value) {
this.zipCode = value;
}
}
定义jxb绑定文件:
<jxb:bindings version="1.0"
xmlns:jxb="http://java.sun.com/xml/ns/jaxb"
xmlns:xs="http://www.w3.org/2001/XMLSchema">
<jxb:bindings schemaLocation="customer.xsd" node="/xs:schema">
<jxb:globalBindings
fixedAttributeAsConstantProperty="false"
collectionType="java.util.Vector"
typesafeEnumBase="xs:NCName"
choiceContentProperty="false"
typesafeEnumMemberName="generateError"
enableFailFastCheck="false"
generateIsSetMethod="false"
underscoreBinding="asCharInWord"/>
<jxb:schemaBindings>
<jxb:package name="mycompany.demo">
<jxb:javadoc><![CDATA[<body>Package level documentation for generated package mycompany.demo.</body>]]>
</jxb:javadoc>
</jxb:package>
<jxb:nameXmlTransform>
<jxb:elementName suffix="Element"/>
</jxb:nameXmlTransform>
</jxb:schemaBindings>
//需要绑定的元素
<jxb:bindings
node="//xs:complexType[@name='Customer']">
//绑定的类
<j
xb:class name="CustomerBo">
<jxb:javadoc>A <b>todo..</jxb:javadoc>
</jxb:class>
<jxb:bindings node=".//xs:element[@name='name']">
//绑定的属性
<jxb:property name="customerName"/> </jxb:bindings>
</jxb:bindings>
<jxb:bindings node="//xs:complexType[@name='Address']">
<jxb:class name="AddressBo">
<jxb:javadoc><![CDATA[First line of documentation for a <b>Address</b>.]]></jxb:javadoc>
</jxb:class>
<jxb:bindings node=".//xs:element[@name='zip']">
<jxb:property name="zipCode"/>
</jxb:bindings>
</jxb:bindings>
</jxb:bindings>
</jxb:bindings>
看着比较复杂,其实挺好理解,当然可以不需要这个绑定文件,也可以绑定相应的java 类,但需要元素名称和类名称完全一致,而且属性也要一致。
看一下jaxb是如何来读入xml的:
//主要的环境类,主要读取ObjectFactory这个类,这是由xjc生成的。
JAXBContext jc = JAXBContext.newInstance("mycompany.demo");
Unmarshaller u = jc.createUnmarshaller();
JAXBElement customerE = (JAXBElement) u.unmarshal(new FileInputStream(
"customer.xml"));
CustomerBo bo = (CustomerBo) customerE.getValue();
就是这么简单
写入也比较简单:
JAXBContext jc = JAXBContext.newInstance("mycompany.demo");
Marshaller marshaller=jc.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
customerE.setValue(bo);
marshaller.marshal( customerE,new FileOutputStream("test.xml"));
在webservices中jaxb的作用是明显的,当然也有不方便的地方,比如定义binding.jaxb文件时,如果没有工具支持,手工写,还是比较困难。
posted on 2006-11-11 20:20
布衣郎 阅读(4379)
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