Hibernate之实体类设计基本步骤

1、先设计一个基类BaseBean

(1)@MappedSuperclass表示实体类父类

(2)也可以加上版本列字段version，但是注意，在save对象时如果version的值有改动，将执行insert操作而不是update，即使id是原来的id

package com.life.hibernate.bean;

import java.util.Date;

import javax.persistence.Column;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.MappedSuperclass;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@MappedSuperclass
public class BaseBean {

    /**
     * 自增长主键
     */
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;

    /**
     * 删除位
     */
    @Column(nullable = false,columnDefinition="BOOLEAN default false")
    private boolean deleted;
    /**
     * 创建时间戳，默认当前时间，不可修改，不为空
     * 注意，表示CURRENT_TIMESTAMP的字段一张表只能有一个
     */
    @Column(updatable = false, nullable = false, columnDefinition = "timestamp default CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP")
    @Temporal(TemporalType.TIMESTAMP)
    private Date dateCreated;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public boolean isDeleted() {
        return deleted;
    }

    public void setDeleted(boolean deleted) {
        this.deleted = deleted;
    }

    public Date getDateCreated() {
        return dateCreated;
    }

    public void setDateCreated(Date dateCreated) {
        this.dateCreated = dateCreated;
    }

}

2、通用Dao层设计

package com.life.dao;

import java.util.List;
import java.util.Map;

import org.hibernate.Query;

public interface IDao<T> {

    /**
     * 根据id查找实体
     * 
     * @param clazz
     * @param id
     * @return
     */
    public T find(Class<T> clazz, int id);

    public void create(T t);

    public void save(T t);

    public void delete(T t);

    /**
     * 查询某页实体
     * @param hql 查询语句
     * @param firstResult 从第几条开始，注意索引从0开始
     * @param maxResults 最多返回的数据条数
     * @param map 参数键值对
     * @return
     */
    public List<T> list(String hql, int firstResult, int maxResults,
            Map<String, Object> map);

    public Query createQuery(String hql, Map<String, Object> map);

    /**
     * 查询实体
     * @param hql
     * @param map
     * @return
     */
    public List<T> list(String hql, Map<String, Object> map);

    /**
     * 获取记录总数
     * @param hql
     * @param map
     * @return
     */
    public int getTotalCount(String hql, Map<String, Object> map);
    
}

3、实现Dao层接口

（1）getSession() throws CannotCreateTransactionException，当连接不上数据库时会抛出异常，可以在struts.xml配置异常页面

package com.life.dao.impl;

import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.springframework.transaction.CannotCreateTransactionException;

import com.life.dao.IDao;

public class DaoImpl<T> implements IDao<T> {
    private SessionFactory sessionFactory;

    @Override
    public T find(Class<T> clazz, int id) {
        // TODO Auto-generated method stub
        return (T) getSession().get(clazz, id);
    }

    @Override
    public void create(T t) {
        // TODO Auto-generated method stub
        getSession().persist(t);
    }

    @Override
    public void save(T t) {
        // TODO Auto-generated method stub
        getSession().saveOrUpdate(t);

    }

    @Override
    public void delete(T t) {
        // TODO Auto-generated method stub
        getSession().delete(t);
    }

    @Override
    public List<T> list(String hql, Map<String, Object> map) {
        // TODO Auto-generated method stub
        Query query = createQuery(hql, map);
        List<T> list = query.list();
        return list;
    }

    @Override
    public int getTotalCount(String hql, Map<String, Object> map) {
        // TODO Auto-generated method stub
        Query query = createQuery(hql, map);
        Object obj = query.uniqueResult();
        return ((Long) obj).intValue();
    }

    @Override
    public List<T> list(String hql, int firstResult, int maxResults,
            Map<String, Object> map) {
        // TODO Auto-generated method stub
        Query query = createQuery(hql, map);

        List<T> list = query.setFirstResult(firstResult)
                .setMaxResults(maxResults).list();
        System.out.println("起始:"+firstResult);
        System.out.println("最大值:"+maxResults);
        System.out.println("实际值:"+list.size());

        return list;
    }
    

    public Session getSession() throws CannotCreateTransactionException{
        return sessionFactory.getCurrentSession();
    }

    public SessionFactory getSessionFactory() {
        return sessionFactory;
    }

    public void setSessionFactory(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    @Override
    public Query createQuery(String hql, Map<String, Object> map) {
        Query query = getSession().createQuery(hql);
        // TODO Auto-generated method stub
        if (map != null) {  
            Set<String> keySet = map.keySet();  
            for (String string : keySet) {  
                Object obj = map.get(string);  
                //这里考虑传入的参数是什么类型，不同类型使用的方法不同  
                if(obj instanceof Collection<?>){  
                    query.setParameterList(string, (Collection<?>)obj);  
                }else if(obj instanceof Object[]){  
                    query.setParameterList(string, (Object[])obj);  
                }else{  
                    query.setParameter(string, obj);  
                }  
            }  
        }  
        return query;  
    }

}

 4、service层接口

IService.class

package com.life.service;

import java.util.List;
import java.util.Map;

/**
 * 这个父接口不能作为bean在applicationContext.xml中，因为serviceImpl是虚函数
 * 
 * @author JL Service接口，基本方法
 */
public interface IService<T> {

    /**
     * 根据id和对象类查找实体
     */
    public T find(Class<T> clazz, int id);

    /**
     * 创建实体
     */
    public void create(T t);

    /**
     * 保存实体
     */
    public void save(T t);

    /**
     * 删除实体
     */
    public void delete(T t);

    /**
     * 分页实体
     */
    public List<T> list(String hql, int firstResult, int maxResults,
            Map<String, Object> map);

    public int getTotalCount(String hql, Map<String, Object> map);

    List<T> list(String hql, Map<String, Object> map);

    List<T> listPage(String hql, int page, int maxResults,
            Map<String, Object> map);
}

service层接口实现IServiceImpl.class

package com.life.service.impl;

import java.util.List;
import java.util.Map;

import com.life.dao.IDao;
import com.life.service.IService;

/**
 * 由于各个实体类的create（）方法有不同的业务逻辑（例如创建用户前需要检查账号是否已经存在），所以把类定义成abstract
 * 把create（）方法定义成abstract，由具体的Service单独实现
 * @author JL
 */
public abstract class ServiceImpl<T> implements IService<T>{

    /**
     * 通过spring的IoC注射进来
     */
    protected IDao<T> dao; 
    
    public IDao<T> getDao() {
        return dao;
    }

    public void setDao(IDao<T> dao) {
        this.dao = dao;
    }

    @Override
    public T find(Class<T> clazz, int id) {
        // TODO Auto-generated method stub
        return dao.find(clazz, id);
    }
    
    @Override
    public void create(T t){
        dao.create(t);
    }; 
    
    @Override
    public void save(T t) {
        // TODO Auto-generated method stub
        dao.save(t);
    }

    @Override
    public void delete(T t) {
        // TODO Auto-generated method stub
        
        dao.delete(t);
    }

    @Override
    public List<T> list(String hql, Map<String, Object> map) {
        // TODO Auto-generated method stub
        return dao.list(hql, map);
    }
    
    @Override
    public int getTotalCount(String hql, Map<String, Object> map) {
        // TODO Auto-generated method stub
        return dao.getTotalCount(hql, map);
    }

    @Override
    public List<T> list(String hql, int firstResult, int maxResults,
            Map<String, Object> map) {
        // TODO Auto-generated method stub
        return dao.list(hql, firstResult, maxResults, map);
    }

    @Override
    public List<T> listPage(String hql, int page, int maxResults,
            Map<String, Object> map) {
        // TODO Auto-generated method stub
        return dao.list(hql, maxResults*(page-1), maxResults, map);

    }
}

Done