利用JAXB可以实现XML与Java对象之间的转换。在转换时，可能会遇到交叉引用的情况，如果不做处理，提示为：

A cycle is detected in the object graph. This will cause infinitely deep XML:...

解决办法有两种：利用com.sun.xml.bind.CycleRecoverable和org.eclipse.persistence.oxm.annotations.XmlInverseReference。

以一个Student和SClass类为例。它们之间如果建立双向关系时会引起交叉引用。未处理前代码如下：

public class Student{
	
	private String num;
	private String name;

	private SClass sclass;


	public Student(){
		super();
	}
	
	public Student(String num,String name){
		super();
		this.num = num;
		this.name = name;
	}
	
	public SClass getSclass() {
		return sclass;
	}

	public void setSclass(SClass sclass) {
		this.sclass = sclass;
	}
	
	public String getNum(){
		return num;
	}
	
	public void setNum(String num){
		this.num = num;
	}
	
	public String getName(){
		return name;
	}
	
	public void setName(String name){
		this.name = name;
	}

}

@XmlRootElement
public class SClass{
	
	private String cnum;
	private List<Student> students;
	
	public SClass(){
		super();
	}
	
	public SClass(String cnum,List<Student> students){
		super();
		this.cnum = cnum;
		this.students = students;
	}
	
	
	public void addStudent(Student student){
		if(!this.students.contains(student)){
			student.setSclass(this);
			this.students.add(student);
		}
	}

	public String getCnum(){
		return cnum;
	}
	
	public void setCnum(String cnum){
		this.cnum = cnum;
	}
	
	public List<Student> getStudents(){
		return students;
	}
	
	public void setStudents(List<Student> students){
		this.students = students;
	}	
	
}

1.利用com.sun.xml.bind.CycleRecoverable。

需要让两个类都实现接口CycleRecoverable的方法onCycleDetected。以Student为例：

public class Student implements CycleRecoverable{
	
	private String num;
	private String name;
	private SClass sclass;

        ......
	public Object onCycleDetected(Context arg0) {
		// TODO Auto-generated method stub
		Student student=new Student();
		student.setNum(this.getNum());
		
		return student;
	}
}

这种方法中，如果是使用maven，需加入依赖：

	<dependency>
		<groupId>javax.xml</groupId>
		<artifactId>jaxb-impl</artifactId>
		<version>2.1</version>
	</dependency>

该方法中，要被引用的部分使用@XmlInverseReference标注。本文例中需要在Student部分加入：

SClass：
	private List<Student> students;

Student：
	@XmlInverseReference(mappedBy="students")
	private SClass sclass;

特别要注意的是，使用XmlInverseReference时，需要在数据模型类（本例中是Student和SClass）所在package下加入一个jaxb.properties属性文件，里面内容是：

javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory

	<dependency>
		<groupId>org.eclipse.persistence</groupId>
		<artifactId>org.eclipse.persistence.moxy</artifactId>
		<version>2.5.0</version>
	</dependency>