怎么用泛型对DAO层进行简化~~

[showtime520]

怎么用泛型对DAO层进行简化~~越详细越好

[jdlsfl]

想法不错，但真的能简化吗
DAO层跟具体的每张数据表都有关系的

[new_bird_0001]

[Quote=引用 1 楼 jdlsfl 的回复:]
想法不错，但真的能简化吗
DAO层跟具体的每张数据表都有关系的
[/Quote]
肯定是能够简化的：
basedao接口IBaseDAO:
package org.lidingzhong.util;

import java.util.List;

public interface IBaseDAO<T ,ID extends java.io.Serializable> {
public void save(T transientInstance);
public void delete(T persistentInstance);
public T findById(ID id);
public List<T> findByExample(T instance);
public List<T> findByProperty(String propertyName, Object value);
public List<T> findByHQLStr(String HQLStr);
public List<T> findAll();
public T merge(T detachedInstance);
public void attachDirty(T instance);
public void attachClean(T instance);
}
接口实现类：
package org.lidingzhong.util;

import java.util.List;

import org.apache.commons.logging.Log;
import org.hibernate.LockMode;
import org.springframework.orm.hibernate3.support.HibernateDaoSupport;

public abstract class BaseDAOImpl<T ,ID extends java.io.Serializable>
extends HibernateDaoSupport implements IBaseDAO<T,ID> {

private Log log ;

private Class<?> type ;
private String getTableClassName(){
return type.getName().substring(type.getName().lastIndexOf(".")+1);
}

protected void initDao() {
// do nothing
}

public void save(T transientInstance) {
log.debug("saving "+getTableClassName()+" instance");
try {
getHibernateTemplate().save(transientInstance);
log.debug("save successful");
} catch (RuntimeException re) {
log.error("save failed", re);
throw re;
}
}

public void delete(T persistentInstance) {
log.debug("deleting "+getTableClassName()+" instance");
try {
getHibernateTemplate().delete(persistentInstance);
log.debug("delete successful");
} catch (RuntimeException re) {
log.error("delete failed", re);
throw re;
}
}

public T findById(ID id) {
log.debug("getting "+getTableClassName()+" instance with id: " + id);
try {
T instance = (T) getHibernateTemplate().get(
type.getName(), id);
return instance;
} catch (RuntimeException re) {
log.error("get failed", re);
throw re;
}
}

public List<T> findByExample(T instance) {
log.debug("finding "+getTableClassName()+" instance by example");
try {
List<T> results = getHibernateTemplate().findByExample(instance);
log.debug("find by example successful, result size: "
+ results.size());
return results;
} catch (RuntimeException re) {
log.error("find by example failed", re);
throw re;
}
}

public List<T> findByProperty(String propertyName, Object value) {
log.debug("finding "+getTableClassName()+" instance with property: " + propertyName
+ ", value: " + value);
try {
String queryString = "from "+getTableClassName()+" as model where model."
+ propertyName + "= ?";
return getHibernateTemplate().find(queryString, value);
} catch (RuntimeException re) {
log.error("find by property name failed", re);
throw re;
}
}

public List<T> findAll() {
log.debug("finding all "+getTableClassName()+" instances");
try {
String queryString = "from "+getTableClassName();
return getHibernateTemplate().find(queryString);
} catch (RuntimeException re) {
log.error("find all failed", re);
throw re;
}
}

public T merge(T detachedInstance) {
log.debug("merging TabArticle instance");
try {
T result = (T) getHibernateTemplate().merge(
detachedInstance);
log.debug("merge successful");
return result;
} catch (RuntimeException re) {
log.error("merge failed", re);
throw re;
}
}

public void attachDirty(T instance) {
log.debug("attaching dirty TabArticle instance");
try {
getHibernateTemplate().saveOrUpdate(instance);
log.debug("attach successful");
} catch (RuntimeException re) {
log.error("attach failed", re);
throw re;
}
}

public void attachClean(T instance) {
log.debug("attaching clean TabArticle instance");
try {
getHibernateTemplate().lock(instance, LockMode.NONE);
log.debug("attach successful");
} catch (RuntimeException re) {
log.error("attach failed", re);
throw re;
}
}

public List<T> findByHQLStr(String HQLStr) {
log.debug("finding "+getTableClassName()+" instance with HQL: " + HQLStr) ;
try {
return getHibernateTemplate().find(HQLStr);
} catch (RuntimeException re) {
log.error("find by property name failed", re);
throw re;
}
}

public void setLog(Log log) {
this.log = log;
}

public void setType(Class<?> type) {
this.type = type;
}
}

[new_bird_0001]

某张表：
public class AnyTableDAO extends BaseDAOImpl<AnyTable ,Integer> {
private static final Log log = LogFactory.getLog(AnyTableDAO.class);

protected void initDao() {
super.setLog(log);
super.setType(AnyTable.class);

}
}

[M_song]

所谓泛型就是:将算法与其作用的数据结构分离，并将后者尽可能泛化，最大限度地实现算法重用。
所以可以实现对DAO层进行简化,就看做的粒度了!

楼上的代码可行!

[ChDw]

super.setType(AnyTable.class);

这个方法其实没有必要存在

改成这样：

public abstract class BaseDAOImpl <T ,ID extends java.io.Serializable> extends HibernateDaoSupport implements IBaseDAO <T,ID> {
	private Class<T> type = getTypeClass();
	private Class<T> getTypeClass() {
		if (type == null) {
			ParameterizedType thisType = (ParameterizedType) getClass().getGenericSuperclass();
			domainClass = (Class<T>) thisType.getActualTypeArguments()[0];
		}
		return type;
	}
}

public class AnyTableDAO extends BaseDAOImpl <AnyTable ,Integer> {
}

这样就可以了

[ChDw]

domainClass = (Class<T>) thisType.getActualTypeArguments()[0];

改成

type = (Class<T>) thisType.getActualTypeArguments()[0];

没有修改过来，呵呵