泛型DAO在JPA中的应用

泛型DAO在JPA中的应用 收藏 import java.io.Serializable; import java.util.ArrayList; import java.util.List; import javax.persistence.EntityManager; import javax.persistence.PersistenceException; import javax.persistence.Query; import org.springframework.orm.jpa.JpaCallback; import org.springframework.orm.jpa.support.JpaDaoSupport; import com.easyjf.core.dao.CanotRemoveObjectException; import com.easyjf.core.dao.GenericDAO; public class GenericDAOImpl<T> extends JpaDaoSupport implements GenericDAO<T> { private Class<T> clazz; public GenericDAOImpl(Class<T> clazz) { this.clazz = clazz; } /* * public void setClazz(Class<T> clazz) { this.clazz = * clazz; } public Class<T> getClazz() { return clazz; } */ public T get(Serializable id) { if (id == null) return null; return this.getJpaTemplate().find(clazz, id); } public List<T> find(final String queryStr, final Object[] params, final int begin, final int max) { // TODO Auto-generated method stub List<T> ret = (List<T>) this.getJpaTemplate().execute( new JpaCallback() { public Object doInJpa(EntityManager em) throws PersistenceException { // TODO Auto-generated method stub String clazzName = clazz.getName(); StringBuffer sb = new StringBuffer("select obj from "); sb.append(clazzName).append(" obj").append(" where ") .append(queryStr); Query query = em.createQuery(sb.toString()); int parameterIndex = 1; if (params != null && params.length > 0) { for (Object obj : params) { query.setParameter(parameterIndex++, obj); } } if (begin >= 0 && max > 0) { query.setFirstResult(begin); query.setMaxResults(max); } if (begin >= 0 && max > 0) { query.setFirstResult(begin); query.setMaxResults(max); } return query.getResultList(); } }); if (ret != null && ret.size() >= 0) { return ret; } else { return new ArrayList<T>(); } } public List query(final String queryStr, final Object[] params, final int begin, final int max) { // TODO Auto-generated method stub List ret = (List) this.getJpaTemplate().execute(new JpaCallback() { public Object doInJpa(EntityManager em) throws PersistenceException { // TODO Auto-generated method stub Query query = em.createQuery(queryStr); int parameterIndex = 1; if (params != null && params.length > 0) { for (Object obj : params) { query.setParameter(parameterIndex++, obj); } } if (begin >= 0 && max > 0) { query.setFirstResult(begin); query.setMaxResults(max); } /* if (begin >= 0 && max > 0) { query.setFirstResult(begin); query.setMaxResults(max); }*/ return query.getResultList(); } }); if (ret != null && ret.size() >= 0) { return ret; } else { return new ArrayList(); } } public void remove(Serializable id) throws CanotRemoveObjectException { // TODO Auto-generated method stub if (id == null) throw new java.lang.IllegalArgumentException("id值不能为空!"); T object = this.get(id); if (object != null) { try { this.getJpaTemplate().remove(object); } catch (Exception e) { throw new CanotRemoveObjectException(); } } } public void save(T instance) { // TODO Auto-generated method stub // this.getJpaTemplate().getEntityManager().joinTransaction(); this.getJpaTemplate().persist(instance); } public T getBy(final String propertyName, final Object value) { if (propertyName == null || "".equals(propertyName) || value == null) throw new IllegalArgumentException("调用参数不正确，属性名称及值均不能为空!"); // TODO Auto-generated method stub List<T> ret = (List<T>) this.getJpaTemplate().execute( new JpaCallback() { public Object doInJpa(EntityManager em) throws PersistenceException { // TODO Auto-generated method stub String clazzName = clazz.getName(); StringBuffer sb = new StringBuffer("select obj from "); sb.append(clazzName).append(" obj"); Query query = null; if (propertyName != null && value != null) { sb.append(" where obj.").append(propertyName) .append(" = :value"); query = em.createQuery(sb.toString()).setParameter( "value", value); } else { query = em.createQuery(sb.toString()); } return query.getResultList(); } }); if (ret != null && ret.size() == 1) { return ret.get(0); } else if (ret != null && ret.size() > 1) { throw new java.lang.IllegalStateException( "worning --more than one object find!!"); } else { return null; } } public void update(T instance) { // TODO Auto-generated method stub this.getJpaTemplate().merge(instance); } public void setClazzType(Class clazz) { this.clazz = clazz; } public Class getClassType() { return this.clazz; } public List executeNativeNamedQuery(final String nnq) { Object ret = this.getJpaTemplate().execute(new JpaCallback() { public Object doInJpa(EntityManager em) throws PersistenceException { Query query = em.createNativeQuery(nnq); return query.getResultList(); } }); return (List) ret; } public int executeNativeSQL(final String nnq) { Object ret = this.getJpaTemplate().execute(new JpaCallback() { public Object doInJpa(EntityManager em) throws PersistenceException { Query query = em.createNativeQuery(nnq); query.executeUpdate(); return null; } }); return (Integer) ret; } public int batchUpdate(final String jpql, final Object[] params) { Object ret = this.getJpaTemplate().execute(new JpaCallback() { public Object doInJpa(EntityManager em) throws PersistenceException { Query query = em.createQuery(jpql); int parameterIndex = 1; if (params != null && params.length > 0) { for (Object obj : params) { query.setParameter(parameterIndex++, obj); } } return query.executeUpdate(); } }); return (Integer) ret; } public void flush() { this.getJpaTemplate().execute(new JpaCallback() { public Object doInJpa(EntityManager em) throws PersistenceException { em.getTransaction().commit(); return null; } }); } }

最后再说的是，通过上面的配置你可以知道在EasyJWeb 中的DAO 是通过JPA 实现的.

我想大家看了上面的代码以后也不会太明白. 我建议下载EasyJWeb 源代码看看. 里面有很好MVC 的实现. 真的是很不错的..

下载地址 : http://www.easyjf.com/download/easyjweb/easyjweb-1.0-m1-all.zip
SVN: http://svn.easyjf.com/repository/easyjf/easyjweb