最近在用HttpClien来调用Rest服务，在其中要用到XML与java对象之间的转换，发现用JAXB非常方便。现整理如下。具体应用例子转帖自http://terrencexu.javaeye.com/blog/702089
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，但还是推荐下载使用最新版的jaxb库， https://jaxb.dev.java.net/，本文下载的是2.2.3，下载安装后将安装后的lib目录中的jaxb-impl.jar拷贝到项目的lib目录中，引用即可，即可使用该下载的JAXB包。
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.java和Employee.java
2. 创建package-info.java和jaxb.index文件
3. 创建XMLParser.java封装marshal/unmarshal操作
4. 创建employees.xml文件
5. 创建Test.java运行测试
6. 运行结果：
1. 创建Employees.java和Employee.java
Java代码
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 {
private List<Employee> employees;
public Employees() {
employees = new ArrayList<Employee>();
}
@XmlElement(name = "employee" , namespace=NameSpace.ADMIN_URI)
public List<Employee> getEmployees() {
return employees;
}
public void setEmployees(List<Employee> employees) {
this.employees = employees;
}
public void addEmployee(Employee employee) {
employees.add(employee);
}
}
Java代码
package com.javaeye.terrencexu.jaxb;
import javax.xml.bind.annotation.XmlElement;
public class Employee {
private String userId;
private String password;
private String name;
private int age;
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();
}
@XmlElement(name = "userId", namespace=NameSpace.ADMIN_URI)
public String getUserId() {
return userId;
}
public void setUserId(String userId) {
this.userId = userId;
}
@XmlElement(name = "password", namespace=NameSpace.ADMIN_URI)
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@XmlElement(name = "name", namespace=NameSpace.ADMIN_URI)
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@XmlElement(name = "age", namespace=NameSpace.ADMIN_URI)
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@XmlElement(name = "gender", namespace=NameSpace.ADMIN_URI)
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
}
Java代码 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"; } Java代码 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; } }2. 创建package-info.java和jaxb.index文件
创建package-info.java文件是为了注册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
3. 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 static final String PACKAGE_NAME = "com.javaeye.terrencexu.jaxb";
private JAXBContext jc;
public XMLParser() {
try {
jc = JAXBContext.newInstance(PACKAGE_NAME, getClass().getClassLoader());
} catch (JAXBException e) {
e.printStackTrace();
}
}
public Object unmarshal(InputStream xml,Class objclass) {
Object obj = null;
try {
Unmarshaller u = jc.createUnmarshaller();
Reader reader = new InputStreamReader(xml,"utf-8");
StreamSource source = new StreamSource(reader);
obj = u.unmarshal(source,objclass).getValue();
} catch (JAXBException e) {
e.printStackTrace();
throw new RuntimeException(
"Can't unmarshal the XML file, error message: " + e.getMessage());
}catch(UnSupportedEncodingException e){
e.printStackTrace();}
return obj;
}
public String marshal(Object obj) {
String result = null;
try {
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;
}
}
4. 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>johnsmith@company.com</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>christinechen@company.com</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，主要是为了后面的测试，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。
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 {
XMLParser xMLParser = new XMLParser();
Employees employees = (Employees) xMLParser.unmarshal(
new FileInputStream(new File("D:/eclipse 3.6/workspace/JAXB-test/src/xml/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("johnsmith@company.com", "abc123_", "John Smith", 24, Gender.MALE));
employees.addEmployee(new Employee("christinechen@company.com", "123456", "Christine Chen", 27, Gender.FEMALE));
XMLParser xMLParser = new XMLParser();
String result = xMLParser.marshal(employees);
System.out.println(result);
}
}
6. 运行结果：
[UserID: johnsmith@company.com, Password: abc123_, Name: John Smith, Age: 24, GenderMale]
[UserID: christinechen@company.com, 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>johnsmith@company.com</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>christinechen@company.com</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>
