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());
}
}
}
这里可以测试一下，增删改查的各个功能，还有各种分页的效果的测试