dao层的泛型实现(2种方法)

package com.wzs.test2.dao;

import java.util.List;

public interface CommonDAO {
public <T> void sava(T entity); // 保存用户，无返回值；

public <T> void remove(T entity); // 删除用户

public <T> void update(T entity); // 更新用户

public <T> T findById(Class<T> entityClass, Integer id); // 通过id来查找某一个用户；

public <T> List<T> findAll(Class<T> entityclass); // 使用范型List<>。查询全部的用户信息

}

package com.wzs.test2.dao.impl;

import java.util.List;

import org.springframework.orm.hibernate3.support.HibernateDaoSupport;

import com.wzs.test2.dao.CommonDAO;

public class CommonDAOImpl extends HibernateDaoSupport implements CommonDAO {
@SuppressWarnings("unchecked")
public <T> List<T> findAll(Class<T> entityclass) {
String hql = "from " + entityclass.getName() + " as a order by a.id desc";
return this.getHibernateTemplate().find(hql);
}

@SuppressWarnings("unchecked")
public <T> T findById(Class<T> entityClass, Integer id) {
return (T) this.getHibernateTemplate().get(entityClass, id);
}

public <T> void remove(T entity) {
this.getHibernateTemplate().delete(entity);
}

public <T> void sava(T entity) {
this.getHibernateTemplate().save(entity);
}

public <T> void update(T entity) {
this.getHibernateTemplate().update(entity);
}

}

package com.wzs.test.dao;

import java.io.Serializable;
import java.util.Collection;

public interface BaseDao<T> {
public void saveEntity(T t);

public Collection<T> get();

public void updateEntity(T t);

public void deleteEntity(Serializable id);

public T getEntityById(Serializable id);

}

package com.wzs.test.dao.impl;

import java.io.Serializable;
import java.lang.reflect.ParameterizedType;
import java.util.Collection;

import org.springframework.orm.hibernate3.HibernateTemplate;

import com.wzs.test.dao.BaseDao;

public class BaseDaoImpl<T> implements BaseDao<T> {

private HibernateTemplate hibernateTemplate;

private Class classt;

public BaseDaoImpl() {
// ParameterizedType就是泛型，关键部分
ParameterizedType type = (ParameterizedType) this.getClass().getGenericSuperclass();
this.classt = (Class) type.getActualTypeArguments()[0];// <T>
System.out.println(type.getRawType());
}

public void deleteEntity(Serializable id) {
T t = this.getEntityById(id);
hibernateTemplate.delete(t);

}

public Collection<T> get() {
System.out.println(classt.getSimpleName());
return this.hibernateTemplate.find("from " + classt.getSimpleName());
}

public T getEntityById(Serializable id) {
return (T) this.hibernateTemplate.get(classt, id);
}

public void saveEntity(T t) {
this.hibernateTemplate.save(t);

}

public void updateEntity(T t) {
this.hibernateTemplate.update(t);
}

// set&&get
public HibernateTemplate getHibernateTemplate() {
return hibernateTemplate;
}

public void setHibernateTemplate(HibernateTemplate hibernateTemplate) {
this.hibernateTemplate = hibernateTemplate;
}

}

package com.wzs.test.dao;

public interface StudentDao<Student> extends BaseDao<Student> {

}

package com.wzs.test.dao.impl;

import org.springframework.stereotype.Component;

import com.wzs.test.dao.StudentDao;
import com.wzs.test.dao.bean.Student;

@Component
public class StudentDaoImpl extends BaseDaoImpl<Student> implements StudentDao<Student> {

}

package com.wzs.test.dao.bean;

public class Student {

}