BaseDao基於JPA的實現
阿新 • • 發佈：2019-01-30
一，說明
二，DAO層的功能
這裡要簡單提一下MVC模式了，MVC本身不是一種設計模式，只是在程式開發過程中逐漸形成的一種模式，也可以說是一種結構，它的目的就是為了分層解耦。
spring框架也有自己的MVC開發模式，spring是面向介面程式設計（切面），View層呼叫Controller，Controller呼叫Service，而Service又呼叫資料訪問層,Model即實體類
DAO介面程式碼：
public interface DAO { public void save(Object entity); public void update(Object entity); public <T> void delete(Class<T> entityClass,Object entityid); public <T> void delete(Class<T> entityClass,Object[] entityids); public <T> T find(Class<T> entityClass,Object entityid); /** * 獲取分頁資料的封裝 * @param <T> * @param entityClass 實體類 * @param firstindex 開始索引 * @param maxresult 需要獲取的記錄數 * @return */ public <T> QueryResult<T> getScrollData(Class<T> entityClass,int firstindex,int maxresult); /** * 帶排序功能的分頁實現 * @param <T> * @param entityClass * @param firstindex * @param maxresult * @param orderby 按照新增的key的順序排序 * @return */ public <T> QueryResult<T> getScrollData(Class<T> entityClass,int firstindex,int maxresult,LinkedHashMap<String, String> orderby); /** * 帶排序功能的分頁實現 * @param <T> * @param entityClass * @param firstindex * @param maxresult * @param wheresql 新增限制條件 * @param orderby * @return */ public <T> QueryResult<T> getScrollData(Class<T> entityClass,int firstindex,int maxresult,String wheresql,Object[] queryParams,LinkedHashMap<String, String> orderby); }
DAO實現層程式碼：
@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 <T> void delete(Class<T> entityClass, Object entityid) { delete(entityClass, new Object[]{entityid}); } @Override public <T> void delete(Class<T> entityClass, Object[] entityids) { for(Object id : entityids) { em.remove(em.getReference(entityClass, id)); } } @Override public <T> T find(Class<T> entityClass, Object entityid) { return em.find(entityClass, entityid); } @SuppressWarnings({ "unchecked", "rawtypes" }) @Override @Transactional(readOnly=true,propagation=Propagation.NOT_SUPPORTED) public <T> QueryResult<T> getScrollData(Class<T> entityClass, int firstindex, int maxresult) { QueryResult qr = new QueryResult<T>(); 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 <T> QueryResult<T> getScrollData(Class<T> entityClass, int firstindex, int maxresult,String wheresql,Object[] queryParams, LinkedHashMap<String, String> orderby) { QueryResult qr = new QueryResult<T>(); 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<T> 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 <T> QueryResult<T> getScrollData(Class<T> entityClass, int firstindex, int maxresult, LinkedHashMap<String, String> orderby) { return getScrollData(entityClass, firstindex, maxresult, null,null, orderby); } protected String buildOrderby(LinkedHashMap<String, String> 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(); } /** * 獲取實體的名稱 * @param <T> * @param entityClass 實體類 * @return */ protected <T> String getEntityName(Class<T> entityClass) { String entityname = entityClass.getSimpleName(); Entity entity = entityClass.getAnnotation(Entity.class); if(entity.name() != null && !"".equals(entity.name())) { entityname = entity.name(); } return entityname; } }
三，新增Service層
public interface JMusicService extends DAO {
}Service實現
@Service(value="jMusicServiceBean")
@Transactional
public class JMusicServiceBean extends DaoSupport implements JMusicService {
}可以看到，dao層利用泛型的方式來實現，使Service層程式碼非常簡單，但是，這裡沒有利用依賴注入的方式將dao層和Service層分離，後續中有待處理
四，測試dao層的實現
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); } /*** * 測試分頁 */ @Test public void testPages() { QueryResult<JMusic> qr = jmService.getScrollData(JMusic.class, 11, 10); for(JMusic jm : qr.getResultlist()) { System.out.println(jm.getId()); } } /*** * 測試帶有排序的分頁 */ @Test public void testOrderPages() { LinkedHashMap<String, String> orderby = new LinkedHashMap<String, String>(); orderby.put("musicname", "desc"); orderby.put("id", "asc"); //JPA佔位符 QueryResult<JMusic> 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()); } } }
這裡可以測試一下，增刪改查的各個功能，還有各種分頁的效果的測試