xml与java技术用Castor进行数据绑定
Castor简介：
Castor是OXM的一个实现，主要完成XML文件数据与Java类实体间的映射。（实际上，Castor的功能远远不止这些，只不过这个是被人熟知和常用的罢了）。如果你现在还在使用dom和sax处理xml文档，只能说你太落伍了！！！
废话不多说，下面开始正题
功能说明：这里有一个student类，当执行createStudent时，会将一个student实体转化输出到一个XML文档中。当执行readStudent时，将会从xml文档中读取信息并生成一个student实体。
Student实体类很简单，就是平常的实体，没有任何特殊标记：
Student.java
package com.guan.castorTest.xmodel;
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import java.util.Date;
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public class Student {
??? private String studentName;
??? private String studentId;
??? private Date birthDay;
??? private int id;
??? public String getStudentName() {
?????? return studentName;
??? }
??? public void setStudentName(String studentName) {
?????? this.studentName = studentName;
??? }
??? public String getStudentId() {
?????? return studentId;
??? }
??? public void setStudentId(String studentId) {
?????? this.studentId = studentId;
??? }
??? public Date getBirthDay() {
?????? return birthDay;
??? }
??? public void setBirthDay(Date birthDay) {
?????? this.birthDay = birthDay;
??? }
??? public int getId() {
?????? return id;
??? }
??? public void setId(int id) {
?????? this.id = id;
??? }
}
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需要写一个mapping，完成Student类和xml文档之间的具体映射，就是Student属性和xml文档的属性和字段之间的映射。
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<!DOCTYPE databases PUBLIC
"-//EXOLAB/Castor Mapping DTD Version 1.0//EN"
"http://castor.exolab.org/mapping.dtd">
<mapping>
<!—class标签指明需要映射的类，name是这个类的类名，注意要写全哦！
Map-to只有根源素对应的类才配置这个属性
Field 类字段和xml字段之间的映射 filed中的name是类字段的名字
Bind-xml 是xml文档中对应的字段信息，name是名字，node指明是element还是attribute，默认是element -->
??? <class name="com.guan.castorTest.xmodel.Student">
?????? <map-to xml="student"/>
?????? <field name="birthDay">
?????????? <bind-xml name="birth-day" node="attribute"/>
?????? </field>
?????? <field name="id">
?????????? <bind-xml name="id" node="attribute"/>
?????? </field>
?????? <field name="studentName">
?????????? <bind-xml name="student-name"/>
?????? </field>
?????? <field name="studentId">
?????????? <bind-xml name="student-id" node="attribute"/>
?????? </field>?????????
??? </class>
</mapping>
需要注意的是，一个映射文件可以映射多个类。并且Castor可以提供一个默认的mapping（如果你不想写这个文件的话，但是一般对负责的结构，还是要写这样的mapping文件的），在默认的映射中要遵守相应的命名规则，就是说java中studentName（驼峰表示法）映射到xml中的student-name。
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就这样我们的主要工作完成，下面是写测试，本次示例仍然使用junit。测试代码如下：
StudentTest.java
package com.guan.castorTest.xmodel;
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import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Reader;
import java.io.Writer;
import java.util.Date;
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import org.exolab.castor.mapping.Mapping;
import org.exolab.castor.mapping.MappingException;
import org.exolab.castor.xml.MarshalException;
import org.exolab.castor.xml.Marshaller;
import org.exolab.castor.xml.Unmarshaller;
import org.exolab.castor.xml.ValidationException;
import org.junit.Test;
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public class StudentTest {
??? @Test
??? public void createStudent() throws IOException, MappingException, MarshalException, ValidationException
??? {
?????? Student student = new Student();//创建一个学生实例
?????? student.setBirthDay(new Date());
?????? student.setId(1);
?????? student.setStudentId("S05080444");
?????? student.setStudentName("张三");
??????
?????? Mapping mapping = new Mapping();//创建一个mapping，载入mapping文件
?????? mapping.loadMapping("mapping.xml");
??????
?????? File file = new File("student.xml");//输出的xml文件，以覆写方式写入
?????? Writer writer = new FileWriter(file);
?????? Marshaller marshaller = new Marshaller(writer);//编组
?????? marshaller.setMapping(mapping);//设置mapping
?????? marshaller.marshal(student);//将student输出到xml文档中
??? }
???
??? @Test
??? public void readStudent() throws IOException, MappingException, MarshalException, ValidationException
??? {
?????? Student student;
??????
?????? Mapping mapping = new Mapping();
?????? mapping.loadMapping("mapping.xml");
??????
?????? File file = new File("student.xml");//读取的文档
?????? Reader reader = new FileReader(file);
?????? Unmarshaller umarshaller = new Unmarshaller(mapping);//解组
?????? student = (Student) umarshaller.unmarshal(reader);//得到实体
??????
?????? System.out.println(student.getId());//输出实体
?????? System.out.println(student.getStudentId());
?????? System.out.println(student.getStudentName());
?????? System.out.println(student.getBirthDay());
??????
??? }
}
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通过junit test 执行createStudent得到下面结果：
Log输出：
2010-8-4 22:58:59 org.exolab.castor.mapping.Mapping setBaseURL
信息: mapping.xml is not a URL, trying to convert it to a file URL
2010-8-4 22:58:59 org.exolab.castor.mapping.Mapping loadMapping
信息: Loading mapping descriptors from mapping.xml
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获得的xml中的信息：
<?xml version="1.0" encoding="UTF-8"?>
<student birth-day="2010-08-04T22:58:59.281+08:00" id="1" student-id="S05080444">
<student-name>张三</student-name>
</student>
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执行readStudent得到：
信息: mapping.xml is not a URL, trying to convert it to a file URL
2010-8-4 23:00:41 org.exolab.castor.mapping.Mapping loadMapping
信息: Loading mapping descriptors from mapping.xml
1
S05080444
张三
Wed Aug 04 22:58:59 CST 2010
更多复杂操作可以参考：http://hi.baidu.com/higuang/blog/item/7d63cbc4de9fecc639db4904.html
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需要的jar包：
castor-1.3.jar
castor-1.3-core.jar
commons-logging.jar