利用泛型、反射、JPA、Spring技术实现增删改查通用类

最新推荐文章于 2022-07-28 19:50:19 发布

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#spring #jpa #string #delete #interface #exception

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本文介绍了如何通过定义DAO接口及其实现类，利用泛型、反射和Spring的JPA，创建一个可以进行增删改查操作的通用类。通过抽象基类`DaoSupport`，实现了`save`, `update`, `delete`, `find`和`getCount`方法，简化了业务操作类的编写。示例中展示了具体的接口、实现类、业务操作接口及其实现，以及测试类的代码结构。" 104336115,9323492,帆软报表自动填充用户姓名教程,"['数据库', '大数据', '程序人生', '经验分享', '数据填报']

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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());
}
}