JAXB：使用annotation绑定XML(xmlns)

在java开发中使用XML几乎是每个程序员都会碰到的，目前可供我们选择的库也有很多，包括，dom4j， jaxen,  SAX等等，本文将介绍如何使用JAXB进行Object-XML mapping.

 

JAXB目前已经集成到了JDK6中，但是还是推荐下载使用最新版的jaxb库， https://jaxb.dev.java.net/

 

从JAXB2.0开始，可以通过使用annotation进行Object-XMl mapping。

 

本文将通过以下步骤演示如何使用JAXB annotation绑定使用了namespace的XML文件

1. 创建employees.xml文件

2. 创建Employees.java和Employee.java绑定employees.xml

3. 创建package-info.java和jaxb.index文件

4. 创建XMLParser.java封装marshal/unmarshal操作

5. 创建Test.java运行测试

 

现在将逐步展开演示

1. 创建employees.xml文件

<?xml version="1.0" encoding="utf-8" ?>
<employees xmlns:admin="http://www.company.com/management/employees/admin">
	<admin:employee>
		<admin:userId>[e-mail]</admin:userId>
		<admin:password>abc123_</admin:password>
		<admin:name>John Smith</admin:name>
		<admin:age>24</admin:age>
		<admin:gender>Male</admin:gender>
	</admin:employee>
	<admin:employee>
		<admin:userId>[e-mail]</admin:userId>
		<admin:password>123456</admin:password>
		<admin:name>Christine Chen</admin:name>
		<admin:age>27</admin:age>
		<admin:gender>Female</admin:gender>
	</admin:employee>
</employees>

 这是一个很普通的xml文件，用于展示组织内部的成员（employee）状况，这里有一点需要注意的是使用了namespace，这也是本文将要演示的重点。

 

2. 创建Employees.java和Employee.java绑定employees.xml

 

package com.javaeye.terrencexu.jaxb;

import java.util.ArrayList;
import java.util.List;

import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement(name = "employees")
public class Employees {

	@XmlElement(name = "employee", namespace=NameSpace.ADMIN_URI)
	private List<Employee> employees;

	public Employees() {
		employees = new ArrayList<Employee>();
	}

	public List<Employee> getEmployees() {
		return employees;
	}
	
	public void addEmployee(Employee employee) {
		employees.add(employee);
	}

}

 

 

package com.javaeye.terrencexu.jaxb;

import javax.xml.bind.annotation.XmlElement;

public class Employee {

	@XmlElement(name = "userId", namespace=NameSpace.ADMIN_URI)
	private String userId;

	@XmlElement(name = "password", namespace=NameSpace.ADMIN_URI)
	private String password;

	@XmlElement(name = "name", namespace=NameSpace.ADMIN_URI)
	private String name;

	@XmlElement(name = "age", namespace=NameSpace.ADMIN_URI)
	private int age;

	@XmlElement(name = "gender", namespace=NameSpace.ADMIN_URI)
	private String gender;

	public Employee() {
	}

	public Employee(String userId, String psw, String name, int age, Gender gender) {
		this.userId = userId;
		this.password = psw;
		this.name = name;
		this.age = age;
		this.gender = gender.getValue();
	}

	public String getUserId() {
		return userId;
	}

	public String getPassword() {
		return password;
	}

	public String getName() {
		return name;
	}

	public int getAge() {
		return age;
	}

	public String getGender() {
		return gender;
	}

}

 

 

package com.javaeye.terrencexu.jaxb;

public class NameSpace {

	public static final String ADMIN_PREFIX = "admin";
	public static final String ADMIN_URI = "http://www.company.com/management/employees/admin";

}

 

package com.javaeye.terrencexu.jaxb;

public enum Gender {

	MALE("Male"),
	FEMALE("Female");
	
	private String value;
	
	private Gender(String value) {
		this.value = value;
	}
	
	public String getValue() {
		return this.value;
	}
	
}

 

3. 创建package-info.java和jaxb.index文件

创建package-info.java注册xmlns, 将该文件放在当前source code的package下面，如果不使用namespace可以不创建该文件

@XmlSchema(
xmlns={
		@XmlNs(prefix=NameSpace.ADMIN_PREFIX, namespaceURI=NameSpace.ADMIN_URI)
}
)
package com.javaeye.terrencexu.jaxb;
import javax.xml.bind.annotation.XmlNs;
import javax.xml.bind.annotation.XmlSchema;

 

创建jaxb.index注册Employees, Employee，如果不使用包级context，可以不创建该文件

Employees
Employee

 

 

4. 创建XMLParser.java封装marshal/unmarshal操作

 

package com.javaeye.terrencexu.jaxb;

import java.io.InputStream;
import java.io.StringWriter;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;

public final class XMLParser {

	private XMLParser() {}
	
	public static Object unmarshal(InputStream xml, Class<?> clazz) {
		Object obj = null;
		
		try {
			JAXBContext jc = JAXBContext.newInstance(clazz.getPackage().getName());
			Unmarshaller u = jc.createUnmarshaller();
			obj = u.unmarshal(xml);
		} catch (JAXBException e) {
			throw new RuntimeException("Can't unmarshal the XML file, error message: " + e.getMessage());
		}
		
		return obj;
	}
	
	public static String marshal(Object obj, Class<?> clazz) {
		String result = null;
		
		try {
			JAXBContext jc = JAXBContext.newInstance(clazz.getPackage().getName());
			Marshaller m = jc.createMarshaller();
			
			StringWriter writer = new StringWriter();
			
			m.marshal(obj, writer);
			
			result = writer.toString();
		} catch (JAXBException e) {
			throw new RuntimeException("Can't marshal the XML file, error message: " + e.getMessage());
		}
		
		
		return result;
	}
	
}

 

 

5. 创建Test.java运行测试

 

package com.javaeye.terrencexu.jaxb;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.util.List;

public class Test {

	public static void main(String[] args) throws FileNotFoundException {
		testUnmarshal();
		testMarshal();
	}

	public static void testUnmarshal() throws FileNotFoundException {
		Employees employees = (Employees) XMLParser.unmarshal(
		  new FileInputStream(new File("F:\\workspace\\JavaStudy\\test\\employees.xml")),
		  Employees.class);

		List<Employee> employeeList = employees.getEmployees();

		if (employeeList != null && employeeList.size() > 0) {
			for (Employee employee : employeeList) {
				StringBuilder builder = new StringBuilder();
				builder.append("[UserID: ").append(employee.getUserId()).append(", ")
				       .append("Password: ").append(employee.getPassword()).append(", ")
				       .append("Name: ").append(employee.getName()).append(", ")
				       .append("Age: ").append(employee.getAge()).append(", ")
				       .append("Gender").append(employee.getGender()).append("]");

				System.out.println(builder.toString());
			}
		}
	}
	
	public static void testMarshal() {
		Employees employees = new Employees();
		employees.addEmployee(new Employee("[e-mail]", "abc123_", "John Smith", 24, Gender.MALE));
		employees.addEmployee(new Employee("[e-mail]", "123456", "Christine Chen", 27, Gender.FEMALE));
		
		String result = XMLParser.marshal(employees, Employees.class);
		System.out.println(result);
	}
}

 

6. 运行结果：

[UserID: [e-mail], Password: abc123_, Name: John Smith, Age: 24, GenderMale]
[UserID: [e-mail], Password: 123456, Name: Christine Chen, Age: 27, GenderFemale]
<?xml version="1.0" encoding="UTF-8" standalone="yes"?><employees xmlns:admin="http://www.company.com/management/employees/admin"><admin:employee><admin:userId>[e-mail]</admin:userId><admin:password>abc123_</admin:password><admin:name>John Smith</admin:name><admin:age>24</admin:age><admin:gender>Male</admin:gender></admin:employee><admin:employee><admin:userId>[e-mail]</admin:userId><admin:password>123456</admin:password><admin:name>Christine Chen</admin:name><admin:age>27</admin:age><admin:gender>Female</admin:gender></admin:employee></employees>

 

评论

2 楼 Welcome鹏友 2014-10-11  

为什么用你的代码，我输出的结果是这样的：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<employees xmlns:ns2="http://www.company.com/management/employees/admin">
	<ns2:employee>
		<ns2:userId>[e-mail]</ns2:userId>
		<ns2:password>abc123_</ns2:password>
		<ns2:name>John Smith</ns2:name>
		<ns2:age>24</ns2:age>
		<ns2:gender>Male</ns2:gender>
	</ns2:employee>
	<ns2:employee>
		<ns2:userId>[e-mail]</ns2:userId>
		<ns2:password>123456</ns2:password>
		<ns2:name>Christine Chen</ns2:name>
		<ns2:age>27</ns2:age>
		<ns2:gender>Female</ns2:gender>
	</ns2:employee>
</employees>

为什么是xmlns:ns2?不是xmlns:admin

1 楼 java_pad 2011-10-26  

JAXBContext jc = JAXBContext.newInstance(clazz.getPackage().getName());  
抛出异常,

java.lang.RuntimeException: Can't unmarshal the XML file, error message: 6 counts of IllegalAnnotationExceptions


我没有使用 namespace .

- <musicinfo>
+ <accompanyinfo>
  <name>伴奏版_试听地址</name>
  <value>kala/2011/09/29/banchangrunawayAvrilLavigne.mp3</value>
  <anchor>823287</anchor>
  </accompanyinfo>
+ <actorinfo>
  <name>艺人</name>
  <value>Avril Lavigne</value>
  <anchor>10110369</anchor>
  </actorinfo>
- <addrinfo>
  <name>Mp3_试听地址</name>
  <value>kalaori/2011/09/29/yuanchangrunawayAvrilLavigne.mp3</value>
  <anchor>823286</anchor>
  </addrinfo>
- <albuminfo>
  <name>专辑</name>
  <value />
  <anchor />
  </albuminfo>
- <music>
  <id>10088552</id>
  <name>Runaway</name>
  </music>
- <picinfo>
  <name>图片地址</name>
  <value />
  <anchor />
  </picinfo>
  </musicinfo>
------------------------xml



@XmlRootElement(name = "total")
public class MusicInfos {
@XmlElement(name = "musicinfo")
private List<MusicInfo>  musicInfos;
------------------------------------------------------------java


public class MusicInfo {
@XmlElement(name = "actorinfo")  
private ActorInfo actorinfo;
----------------------------------------------------java
如果看到,麻烦回复一下好么?谢谢!