泛型DAO在JPA中的应用
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