hibernate报错,该如何解决

hibernate报错
错误如下：
org.hibernate.exception.ConstraintViolationException: could not insert: [orm.Userinfo]
org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:71)
org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43

Userinfo.hbm.xml代码：

<hibernate-mapping>
    <class name="orm.Userinfo" table="Userinfo" schema="dbo" catalog="woniu">
        <id name="id" type="java.lang.Integer">
            <column name="id" />
            <generator class="native" />
        </id>
        <property name="username" type="java.lang.String">
            <column name="username" length="50" not-null="true" />
        </property>
        <property name="password" type="java.lang.String">
            <column name="password" length="50" not-null="true" />
        </property>
        <property name="age" type="java.lang.Integer">
            <column name="age" />
        </property>
    </class>
</hibernate-mapping>

Insert.java代码：

package controller;

import orm.Userinfo;
import orm.UserinfoDAO;

public class Insert {
	
	public String execute(){
		Userinfo userinfo = new Userinfo();
		userinfo.setUsername("woniu");
		userinfo.setPassword("000123");
		userinfo.setAge(10);
		
		
		UserinfoDAO userinfoDAO = new UserinfoDAO();
		userinfoDAO.getSession().beginTransaction();
		userinfoDAO.attachDirty(userinfo);
		userinfoDAO.getSession().getTransaction().commit();
		userinfoDAO.getSession().close();
		return "";
		
	}
}