BaseDao基于JPA的实现

一，说明

基本DAO的实现也是基于上一篇文章，Spring3+Hibernate4+JPA2.0整合之后，DAO层的实现

二，DAO层的功能

      这里要简单提一下MVC模式了，MVC本身不是一种设计模式，只是在程序开发过程中逐渐形成的一种模式，也可以说是一种结构，它的目的就是为了分层解耦。

      spring框架也有自己的MVC开发模式，spring是面向接口编程（切面），View层调用Controller，Controller调用Service，而Service又调用数据访问层,Model即实体类

      更加详细的介绍可以参考这篇文章，应该是比较循序渐进的入门级的http://jinnianshilongnian.iteye.com/blog/1594806。如果英文比较好，建议直接读英文API文档

      DAO接口代码：

public interface DAO {

    public void save(Object entity);

    public void update(Object entity);

    public  void delete(Class entityClass,Object entityid);

    public  void delete(Class entityClass,Object[] entityids);

    public  T find(Class entityClass,Object entityid);

    /**
     * 获取分页数据的封装
     * @param
     * @param entityClass 实体类
     * @param firstindex 开始索引
     * @param maxresult 需要获取的记录数
     * @return
     */
    public  QueryResult getScrollData(Class entityClass,int firstindex,int maxresult);

    /**
     * 带排序功能的分页实现
     * @param
     * @param entityClass
     * @param firstindex
     * @param maxresult
     * @param orderby 按照添加的key的顺序排序
     * @return
     */
    public  QueryResult getScrollData(
Class entityClass,int firstindex,int maxresult,LinkedHashMap orderby);

    /**
     * 带排序功能的分页实现
     * @param
     * @param entityClass
     * @param firstindex
     * @param maxresult
     * @param wheresql 添加限制条件
     * @param orderby
     * @return
     */
    public  QueryResult getScrollData(
Class entityClass,int firstindex,int maxresult,String wheresql,Object[] queryParams,LinkedHashMap orderby);

}

 

DAO实现层代码：

@Transactional
public abstract class DaoSupport implements DAO {

    @PersistenceContext
    protected EntityManager em;

    @Override
    public void save(Object entity) {
        em.persist(entity);
    }

    @Override
    public void update(Object entity) {
        em.merge(entity);
    }

    @Override
    public  void delete(Class entityClass, Object entityid) {
        delete(entityClass, new Object[]{entityid});
    }

    @Override
    public  void delete(Class entityClass, Object[] entityids) {
        for(Object id : entityids) {
            em.remove(em.getReference(entityClass, id));
        }
    }

    @Override
    public  T find(Class entityClass, Object entityid) {
        return em.find(entityClass, entityid);
    }

    @SuppressWarnings({ "unchecked", "rawtypes" })
    @Override
    @Transactional(readOnly=true,propagation=Propagation.NOT_SUPPORTED)
    public  QueryResult getScrollData(Class entityClass,
            int firstindex, int maxresult) {
        QueryResult qr = new QueryResult();
        String entityname = getEntityName(entityClass);
        Query query = em.createQuery("select o from "+entityname+" o ");
        query.setFirstResult(firstindex).setMaxResults(maxresult);
        qr.setResultlist(query.getResultList());
        query = em.createQuery("select count(o) from " + entityname + " o ");
        qr.setTotalrecord((Long)query.getSingleResult());
        return qr;
    }

    @SuppressWarnings({ "unchecked", "rawtypes" })
    @Override
    public  QueryResult getScrollData(Class entityClass,
            int firstindex, int maxresult,String wheresql,Object[] queryParams, LinkedHashMap orderby) {
        QueryResult qr = new QueryResult();
        String entityname = getEntityName(entityClass);
        Query query = em.createQuery("select o from "+entityname+" o " + (wheresql == null ? "" : " where " + wheresql) + buildOrderby(orderby));
        setQueryParams(query,queryParams);
        query.setFirstResult(firstindex).setMaxResults(maxresult);
        List list = query.getResultList();
        qr.setResultlist(list);
        qr.setTotalrecord(list.size());
        return qr;
    }

    protected void setQueryParams(Query query,Object[] queryParams) {
        if(null != queryParams && 0 < queryParams.length) {
            for (int i = 0; i < queryParams.length; i++) {
                query.setParameter(i+1, queryParams[i]);
            }
        }
    }

    @Override
    public  QueryResult getScrollData(Class entityClass,
            int firstindex, int maxresult, LinkedHashMap orderby) {
        return getScrollData(entityClass, firstindex, maxresult, null,null, orderby);
    }

    protected String buildOrderby(LinkedHashMap orderby) {
        StringBuffer sb = new StringBuffer();
        if(null != orderby && 0 != orderby.size()) {
            sb.append(" order by ");
            for (String key : orderby.keySet()) {
                sb.append("o.").append(key).append(" ").append(orderby.get(key)).append(",");
            }
            sb.deleteCharAt(sb.length() - 1);
        }
        return sb.toString();
    }

    /**
     * 获取实体的名称
     * @param
     * @param entityClass 实体类
     * @return
     */
    protected  String getEntityName(Class entityClass) {
        String entityname = entityClass.getSimpleName();
        Entity entity = entityClass.getAnnotation(Entity.class);
        if(entity.name() != null && !"".equals(entity.name())) {
            entityname = entity.name();
        }
        return entityname;
    }

}

三，添加Service层

public interface JMusicService extends DAO {

}

 

Service实现

@Service(value="jMusicServiceBean")
@Transactional
public class JMusicServiceBean extends DaoSupport implements JMusicService {



}

 

可以看到，dao层利用泛型的方式来实现，使Service层代码非常简单，但是，这里没有利用依赖注入的方式将dao层和Service层分离，后续中有待处理

四，测试dao层的实现

public class SpringJpaTest {

    private static ApplicationContext cxt;
    private static JMusicService jmService;

    @BeforeClass
    public static void setUpBeforeClass() throws Exception {
        //WebRoot/WEB-INF/
        cxt=  new ClassPathXmlApplicationContext("spring-mvc.xml");
        jmService = (JMusicService) cxt.getBean("jMusicServiceBean");
    }

    @Test
    public void testsave() {

        for(int i = 0;i < 15;i++) {
            JMusic jm = new JMusic();
            jm.setAlbum("BigBun");
            jm.setDistributeDate(Timestamp.valueOf(DateUtil.getNowDate()));
            String uuid = UUID.randomUUID().toString().replaceAll("-", "");
            jm.setMusicname(uuid.substring(3, 10));
            jm.setMusicurl("http://www.baidu.com/music/20150308/"+uuid.substring(3, 10)+".mp3");
            jm.setSinger("Johns Brooks");
            jmService.save(jm);
        }
    }

    @Test
    public void testfind() throws UnsupportedEncodingException {
        JMusic jm = jmService.find(JMusic.class, 1000);
        if(null != jm)
            System.out.println(jm.getSinger());
    }


    @Test
    public void testdelete () {
        jmService.delete(JMusic.class, 1);
        jmService.delete(JMusic.class, 2);
    }
    /***
     * 测试分页
     */
    @Test
    public void testPages() {
        QueryResult qr = jmService.getScrollData(JMusic.class, 11, 10);
        for(JMusic jm : qr.getResultlist()) {
            System.out.println(jm.getId());
        }
    }

    /***
     * 测试带有排序的分页
     */
    @Test
    public void testOrderPages() {
        LinkedHashMap orderby = new LinkedHashMap();
        orderby.put("musicname", "desc");
        orderby.put("id", "asc");
        //JPA占位符
        QueryResult qr = jmService.getScrollData(JMusic.class, 0, 100," singer=?1",new Object[]{"Jay"},orderby);
        for(JMusic jm : qr.getResultlist()) {
            System.out.println(jm.getMusicname() + "-" + jm.getId());
        }
    }

}