使用泛型写了一个通用的Hibernate DAO类。

 

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GenericDao接口

package com.my.dao;import java.io.Serializable;import java.util.List;/** * Generic DAO interface * @author Robin * * @param 
     
       * @param 
      
        */public interface GenericDao
       
         {    /**     * Create entity     * @param entity     */    void create(T entity);        /**     * Update entity     * @param entity     */    void update(T entity);        /**     * Create or Update entity     * @param entity POJO     */    void saveOrUpdate(T entity);        /**     * Delete entity     * @param entity     */    void delete(T entity);        /**     * Find entity by id     * @param id ID     * @return Entity     */    T find(PK id);        /**     * Find all entities     * @return     */    List
        
          findAll();        /**     * Find all entities by paging     * @param pageNumber     * @param pageSize     * @return     */    List
         
           findList(int pageNumber, int pageSize);        /**     * All row count     * @return     */    Long count();}
         
        
       
      
     

 

GenericDaoSupport主类：

package com.my.dao;import javax.annotation.Resource;import org.hibernate.Session;import org.hibernate.SessionFactory;/** * Generic Dao Base Class * @author Robin * */public abstract class GenericDaoSupport {    @Resource    protected SessionFactory sessionFactory;        /**     * Get Hibernate Session     * @return     */    public Session getSession() {        return this.sessionFactory.getCurrentSession();    }}

 

通用DAO类实现：

package com.my.dao.impl;import java.io.Serializable;import java.lang.reflect.ParameterizedType;import java.lang.reflect.Type;import java.util.List;import org.hibernate.criterion.Projections;import com.my.dao.GenericDao;import com.my.dao.GenericDaoSupport;/** * Generic DAO class * @author Robin * * @param 
     
       * @param 
      
        */@SuppressWarnings("all")public class GenericDaoImpl
       
                extends GenericDaoSupport implements GenericDao
        
          {    // Entity class    private Class
         
           entityClass;    /**     * Constructor     */    public GenericDaoImpl() {        // 通过反射获取T的类型信息实例        this.entityClass = (Class
          
           ) ((ParameterizedType) this.getClass() .getGenericSuperclass()).getActualTypeArguments()[0]; } /** * Create entity * @param entity */ @Override public void create(T entity) { getSession().save(entity); } /** * Update entity * @param entity */ @Override public void update(T entity) { getSession().update(entity); } /** * Create or Update entity * @param entity */ @Override public void saveOrUpdate(T entity) { getSession().saveOrUpdate(entity); } /** * Delete entity * @param entity */ public void delete(T entity){ getSession().delete(entity); } /** * Find entity by id * @param id * @return Entity */ @Override public T find(PK id) { return (T) getSession().get(entityClass, id); } /** * Find all entities * @return */ @Override public List
           
             findAll() { return getSession().createCriteria(entityClass).list(); } /** * Find all entities by paging * @param pageNumber * @param pageSize * @return */ public List
            
              findList(int pageNumber, int pageSize) { return getSession().createCriteria(entityClass) .setFirstResult((pageNumber - 1) * pageSize) .setMaxResults(pageSize) .list(); } /** * All row count * @return */ public Long count() { Long count = (Long)getSession().createCriteria(entityClass) .setProjection(Projections.rowCount()) .uniqueResult(); if(count == null) { return (long)0; } else { return count; } }}
            
           
          
         
        
       
      
     

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Hibernate实体:

package com.my.entity;import java.io.Serializable;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.Table;@SuppressWarnings("serial")@Entity@Table(name = "account")public class Account implements Serializable {    @Id    @GeneratedValue(strategy = GenerationType.IDENTITY)    @Column(name = "id")    private long id;    @Column(name = "name", length = 200)    private String name;    public long getId() {        return id;    }    public void setId(long id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }}

实体类必需继承Serializable接口。

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使用方法例子：

写一个AccountDao接口

package com.my.dao;import org.springframework.stereotype.Repository;import com.my.entity.Account;@Repositorypublic interface AccountDao extends GenericDao
     
       {}
     

AccountDao接口的实现：

package com.my.dao.impl;import org.springframework.stereotype.Repository;import com.my.dao.AccountDao;import com.my.entity.Account;@Repository(value = "accountDao")public class AccountDaoImpl extends GenericDaoImpl
     
       implements AccountDao {}
     

 

Service的实现和使用：

package com.my.service;import java.util.List;import com.my.entity.Account;public abstract class AccountService {    /**     * Add new account     * @param account Account     */    public abstract void add(Account account);        /**     * Find entity by id     * @param id     * @return     */    public abstract Account find(long id);        /**     * Find all entities     * @return     */    public abstract List
     
       findAll();        /**     * Find all entities by paging     * @param pageNumber     * @param pageSize     * @return     */    public abstract List
      
        findList(int pageNumber, int pageSize);        /**     * All row count     * @return     */    public abstract long count();}
      
     

package com.my.service.impl;import java.util.List;import javax.annotation.Resource;import org.springframework.stereotype.Service;import com.my.dao.AccountDao;import com.my.entity.Account;import com.my.service.AccountService;@Service(value = "accountService")public class AccountServiceImpl extends AccountService {    @Resource(name = "accountDao")    private AccountDao accountDao;        public void add(Account account) {        accountDao.saveOrUpdate(account);    }    @Override    public Account find(long id) {        return accountDao.find(id);    }        @Override    public List
     
       findAll(){        return accountDao.findAll();    }    @Override    public List
      
        findList(int pageNumber, int pageSize) {        return accountDao.findList(pageNumber, pageSize);    }    @Override    public long count() {        return accountDao.count();    }}
      
     

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可以看到上面Service的调用对应的AccountDao中，不需要再写其它方法。因为在通用DAO中已经实现了。AccountDao只需要加入其它额外的方法即可，比如说特例的查询。

当然可以把通用DAO封装得更加“完美”，比如把查询条件都写上。

网上有一些通用的DAO写法，会把HQL写在Service层，这种破坏了BLL和DAO的分离。

 

附上Spring的xml配置：

     
         
              
               
               
               
           
          
              
               
                   
                        
         
          com.my.entity
                     
                
               
                   
        
                         hibernate.dialect=org.hibernate.dialect.MySQL5Dialect                hibernate.hbm2ddl.auto=update                hibernate.show_sql=true                hibernate.format_sql=false                hibernate.cache.use_second_level_cache=true                hibernate.cache.use_query_cache=false                hibernate.cache.provider_class=org.hibernate.cache.internal.NoCacheProvider                hibernate.current_session_context_class= org.springframework.orm.hibernate4.SpringSessionContext