（二十八）分类信息的curd-分类信息删除

删除分类步骤分析:
        1.在list.jsp上编写 删除连接
            /store/adminCategory?method=delete&cid=??
        2.在delete方法中
            获取cid
            调用service的delete方法
            页面重定向/store/adminCategory?method=findAll
        3.service中delete
            添加事务
            通过cid先更新所有的商品分类信息 ，删除后分类信息为null
            调用dao(商品表、分类表) 删除分类
            事务控制
            清空缓存

/store/WebContent/admin/category/list.jsp

/store/src/com/louis/web/servlet/AdminCategoryServlet.java

/**
     * 删除分类
     * @param request
     * @param response
     * @return
     * @throws Exception
     */
    public String delete(HttpServletRequest request, HttpServletResponse response) throws Exception {
        //1.获取cid
        String cid = request.getParameter("cid");

        //2.调用service 完成删除
        CategoryService cs=(CategoryService) BeanFactory.getBean("CategoryService");
        cs.delete(cid);

        //3.重定向
        response.sendRedirect(request.getContextPath()+"/adminCategory?method=findAll");
        return null;
    }

/store/src/com/louis/service/impl/CategoryServiceImpl.java

public void delete(String cid) throws Exception{
        try {
            //1.开启事务
            DataSourceUtils.startTransaction();

            //2.更新商品
            ProductDao pd=(ProductDao) BeanFactory.getBean("ProductDao");
            pd.updateCid(cid);

            //3.删除分类
            CategoryDao cd=(CategoryDao) BeanFactory.getBean("CategoryDao");
            cd.delete(cid);

            //4.事务控制
            DataSourceUtils.commitAndClose();

            //5.清空缓存
            CacheManager cm = CacheManager.create(CategoryServiceImpl.class.getClassLoader().getResourceAsStream("ehcache.xml"));
            Cache cache = cm.getCache("categoryCache");
            cache.remove("clist");
        } catch (Exception e) {
            e.printStackTrace();
            DataSourceUtils.rollbackAndClose();
            throw e;
        }

    }

/store/src/com/louis/dao/impl/ProductDaoImpl.java

/**
     * 更新商品的cid 为删除分类的时候准备
     */
    @Override
    public void updateCid(String cid) throws Exception {
        QueryRunner qr = new QueryRunner();
        String sql="update product set cid = null where cid = ?";
        qr.update(DataSourceUtils.getConnection(), sql, cid);
    }

/store/src/com/louis/dao/impl/CategoryDaoImpl.java

/**
     * 删除分类
     */
    @Override
    public void delete(String cid) throws Exception {
        QueryRunner qr = new QueryRunner();
        String sql="delete from category where cid = ?";
        qr.update(DataSourceUtils.getConnection(), sql, cid);

    }