利用泛型、反射、JPA、Spring技术实现增删改查通用类

1、定义接口

package cn.joeho.base;

import java.io.Serializable;

public interface DAO<T> {

public String getSubClass();

public Class<T> getEntityClass();

public void save(T entity);

public void update(T entity);

public void delete(Serializable id);

public T find(Serializable id);

public long getCount();

}

2、接口的实现类

package cn.joeho.base;

import java.io.Serializable;

import java.lang.reflect.ParameterizedType;

import java.lang.reflect.Type;

import javax.persistence.Entity;

import javax.persistence.EntityManager;

import javax.persistence.PersistenceContext;

import org.springframework.transaction.annotation.Propagation;

import org.springframework.transaction.annotation.Transactional;

@Transactional

public abstract class DaoSupport<T> implements DAO<T> {

@PersistenceContext protected EntityManager em;

protected Class<T> entityClass=getEntityClass();

@Override

public String getSubClass(){

return super.getClass().getName();

}

@Override

public Class<T> getEntityClass(){

Type parentType =getClass().getGenericSuperclass();

if(parentType instanceof ParameterizedType){

ParameterizedType type=(ParameterizedType)parentType;

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

}

return null;

}

public String getEntityName(){

String entityName=this.entityClass.getSimpleName();

Entity entity=this.entityClass.getAnnotation(Entity.class);

String ename=entity.name();

if(ename!=null&&!"".equals(ename)){

entityName=ename;

}

return entityName;

}

@Override

public void save(T entity) {

em.persist(entity);

}

@Override

public void update(T entity) {

em.merge(entity);

}

@Override

public void delete(Serializable id) {

em.remove(em.getReference(entityClass, id));

}

@Override

@Transactional(propagation=Propagation.NOT_SUPPORTED)

public T find(Serializable id) {

return em.find(entityClass, id);

}

@Override

@Transactional(propagation=Propagation.NOT_SUPPORTED)

public long getCount() {

return (Long) em.createQuery("select count(o) from "+getEntityName()+" o").getSingleResult();

}

}

3、业务操作类接口

package cn.joeho.service;

import cn.joeho.base.DAO;

import cn.joeho.entity.Buyer;

public interface BuyerService extends DAO<Buyer>{

}

4、业务操作类实现

package cn.joeho.service.impl;

import org.springframework.stereotype.Service;

import cn.joeho.base.DaoSupport;

import cn.joeho.entity.Buyer;

import cn.joeho.service.BuyerService;

@Service

public class BuyerServiceBean extends DaoSupport<Buyer> implements BuyerService {

}

5、测试类

package junit.test;

import org.junit.BeforeClass;

import org.junit.Test;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import cn.joeho.entity.Buyer;

import cn.joeho.service.BuyerService;

public class BuyerTest {

public static ApplicationContext act =null;

public static BuyerService buyerService = null;

@BeforeClass

public static void setUpBeforeClass() throws Exception {

act = new ClassPathXmlApplicationContext("beans.xml");

buyerService=(BuyerService)act.getBean("buyerServiceBean");

}

@Test

public void aaa(){

System.out.println(buyerService.getSubClass());

}

@Test

public void save(){

Buyer buyer=new Buyer();

buyer.setName("xupeng1");

buyer.setPassword("123344");

buyer.setEmail("xupeng@hotmail.com");

buyerService.save(buyer);

}

@Test

public void update(){

Buyer buyer=new Buyer();

buyer.setName("lisi");

buyer.setPassword("123456");

buyer.setEmail("xupeng@hotmail.com");

buyerService.update(buyer);

}

@Test

public void delete(){

buyerService.delete("xupeng1");

}

@Test

public void find(){

Buyer buyer=buyerService.find("xupeng");

System.out.println(buyer.getName()+"="+buyer.getEmail());

}

@Test

public void count(){

System.out.println(buyerService.getCount());

}

}