请教ssh整合中的signer information does not match signer information错误问题
//JavaBean
package com.sysu.info.cs.six.net.vo;
import java.util.HashSet;
import java.util.Set;

public class Student1ntab implements java.io.Serializable {
private int studentid;
private String name;
private String password;
private String term;
private String classes;
private Set<Course1ntab> courses=new HashSet<Course1ntab>();
public int getStudentid() {
return studentid;
}
public void setStudentid(int studentid) {
this.studentid = studentid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getTerm() {
return term;
}
public void setTerm(String term) {
this.term = term;
}
public String getClasses() {
return classes;
}
public void setClasses(String classes) {
this.classes = classes;
}
public Set<Course1ntab> getCourses() {
return courses;
}
public void setCourses(Set<Course1ntab> courses) {
this.courses = courses;
}

}



package com.sysu.info.cs.six.net.vo;
public class Course1ntab implements java.io.Serializable {
private int courseid;
private String name;
private String description;
public int getCourseid() {
return courseid;
}
public void setCourseid(int courseid) {
this.courseid = courseid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}

}

-------------------------------------------------

//hibernate映射文件
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 
  Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
  <class name="com.sysu.info.cs.six.net.vo.Student1ntab" table="student_1ntab" catalog="test">
  <id name="studentid" type="java.lang.Integer">
  <column name="studentid" />
  <generator class="identity"></generator>
  </id>
  <property name="name" type="java.lang.String">
  <column name="name" length="20" not-null="true" />
  </property>
  <property name="password" type="java.lang.String">
  <column name="password" length="20" not-null="true" />
  </property>
  <property name="term" type="java.lang.String">
  <column name="term" length="20" />
  </property>
  <property name="classes" type="java.lang.String">
  <column name="classes" length="20" />
  </property>
  <set name="courses" table="student