下面是JAVA代码中学生信息DAO方法，帮忙详细说说每个函数是做什么的
package cn.myexam.model;

import cn.myexam.hibernate.BaseHibernateDAO;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.LockMode;
import org.hibernate.Query;
import org.hibernate.Transaction;
import org.hibernate.criterion.Example;


public class StudentDAO extends BaseHibernateDAO {

    private static final Log log = LogFactory.getLog(StudentDAO.class);


public static final String STU_ID = "stuId";
public static final String PASSWORD = "password";
public static final String NAME = "name";
public static final String SEX = "sex";
public static final String TEL = "tel";
public static final String ADDRESS = "address";
public static final String EMAIL = "email";
public static final String TYPE = "type";

    
    public boolean save(Student transientInstance) {
        log.debug("saving Student instance");
        boolean passed = false;
        try {
         Transaction tx = getSession().beginTransaction();
            getSession().save(transientInstance);
            tx.commit();
            log.debug("save successful");
            passed = true;
        } catch (RuntimeException re) {
            log.error("save failed", re);
            passed = false;
            throw re;
        }finally{
         closeSession();
        }
        return passed;
    }
    
public boolean delete(Student persistentInstance) {
        log.debug("deleting Student instance");
        boolean passed = false;
        try {
         Transaction tx = getSession().beginTransaction();
            getSession().delete(persistentInstance);
            tx.commit();
            log.debug("delete successful");
            passed = t