dao | 易学教程

EntityManager injection - NullPointerException

阅读更多关于 EntityManager injection - NullPointerException

In my Spring+JPA/Hibernate+Wicket app, I have a QueryBuilder bean that I want to use in one of my DAOs which generates a typed query with the help of Criteria API: @Service(value="inboxQueryBuilder") public class InboxQueryBuilder { @PersistenceContext EntityManager em; CriteriaBuilder cb; public InboxQueryBuilder() { cb = em.getCriteriaBuilder(); } public TypedQuery<App> getQueryForApps(AppSearchObject aso) { ... } ... } However, when I run the app, I get a null pointer exception for line: cb = em.getCriteriaBuilder(); i.e. the EntityManager doesn't get injected. Do you know why? Also, is

品优购(IDEA版)-第一天

阅读更多关于品优购(IDEA版)-第一天

# 品优购(IDEA版)-第一天品优购IDEA版应该是2019年的新项目。目前只有视频。资料其他都还是旧的。 ## 1.学习目标 1：了解电商行业特点以及理解电商的模式 2：了解整体品优购的架构特点 3：能够运用 Dubbo+SSM 搭建分布式应用 4：搭建工程框架，完成品牌列表后端代码 ## 2. 电商概述 ## 3. 品优购需求分析与设计 ### 3.1. 品优购简介品优购商城主要分为网站前台、网站后台、商家后台三类系统。 #### 3.1.1. 网站前台主要包括网站首页、商家首页、商品详情、搜索、会员中心、订单与支付相关页面、秒杀频道等。 ![在这里插入图片描述](https://img2018.cnblogs.com/blog/756375/201911/756375-20191103021804323-1727543117.png) #### 3.1.2. 网站后台运营该电商平台的运营人员的管理后台。主要包括商家审核、品牌管理、规格管理、模板管理、商品分类管理、商品审核、广告类型管理、广告管理、订单查询、商家结算等。 ![在这里插入图片描述](https://img2018.cnblogs.com/blog/756375/201911/756375-20191103021806534-1852194779.png) #### 3.1.3. 商家管理后台

Is it correct to access the DAO layer from the Controller layer?

阅读更多关于 Is it correct to access the DAO layer from the Controller layer?

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: In my applications I usually access the DAO layer in order to obtain/save or update objects to it's repository, and I use a Service layer to perform more complex operations. So my question is this: Is it correct (according to best practices and design/architecture patterns) to access the DAO layer from the Controller layer, or should I bypass it through the Service layer? Thanks! 回答1: In theory: within the context of the MVC architectural pattern, there is no clear distinction between a data access layer (DAO) and a service layer. The

Spring_Bean配置_入门

阅读更多关于 Spring_Bean配置_入门

　Spring 的入门案例:(IOC) 　　 IOC 的底层实现原理（结构图2.01）　　　　　　　　　　　　　　　　　　　　　　　　　　　　图：2.01 　　　　 IOC ：Inversion of Control 控制反转，指的是对象的创建权反转(交给)给Spring，　　　　　　作用是实现了程序的解耦合　　步骤一: 下载 Spring 的开发包: 　　　　官网：http://spring.io/ 　　　　下载地址：　 http://repo.springsource.org/libs-release-local/org/springframework/spring 　　创建 web 项目, 引入 Spring 的开发包: 　　　　　　　　导入基本的jar包（4+2）　　　　　　　　　　　　　　　　　图：2.02 　　　引入相关配置文件: 　　　　　　log4j.properties　　//日志文件　　　　　　applicationContext.xml 　　　　引入约束: 　　　　　　spring-framework-4.2.4.RELEASE\docs\spring-framework-reference\html\xsd-configur ation.html 　　　　　　　　　　 <beans xmlns= "http://www

handling GWT RequestFactory server error responses

阅读更多关于 handling GWT RequestFactory server error responses

问题 I have a newly coded GWT/GAE app that uses RequestFactory and Editors on the client and a custom Objectify DAO Service on the back. The flush() then persist() paths work fine on success. Client side JSR 303 works as well as can be expected too. My question is how to trigger server warnings/errors and handle UI updates? I am using Chandler's Generic DAO for Objectify 2 at http://turbomanage.wordpress.com/2010/02/09/generic-dao-for-objectify-2/ my gwt activity is calling persist( myProxy ).fire

call service vs dao from another service

阅读更多关于 call service vs dao from another service

I have User And Role entities and Service, DAO layers for them. I need Role list from UserService. Which layer should I use from UserService? Call list method of RoleService vs RoleDAO ? Which one is common use and why? Normally DAO layer is close to database, Service layer is encapsulating your business logic, performing any transactions or other things rather than just calling DAO. Service calling another service is more common because Your RoleService can have some business code evaluated, you can benefit from transactions or passing messages via JMS or you can have some security on service

DAO generator for java [closed]

阅读更多关于 DAO generator for java [closed]

问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed last year . I'm searching for free and simple DAO generator for java (it needs to create entities/bens from db tables/views and generate basic CRUD code). Currently, I`m using DAO4J which lacks some functionality like views mapping. I know that there are frameworks like Hibernate but I dont need such robust framework. Some

Generic DAO pattern in Hibernate

阅读更多关于 Generic DAO pattern in Hibernate

问题 While working on hibernate we are following generic Hibernate DAO pattern as mentioned in Hibernate Doc also. So as per this we are currently maintaining two parallel hirarchies 1) for interfaces 2) for Implimentation so if we work on this the way even if there is no proposed new method beside standard persistannce methods we need to create a marker interface for that entiry as well its Implimentation. Though there seems no problem in this approach and its clear seperation. my question is if

Spring session-scoped beans as dependencies in prototype beans?

阅读更多关于 Spring session-scoped beans as dependencies in prototype beans?

问题 I read spring docs on this subject several times, but some things are still unclear to me. Documentation states: If you want to inject (for example) an HTTP request scoped bean into another bean, you must inject an AOP proxy in place of the scoped bean. That is, you need to inject a proxy object that exposes the same public interface as the scoped object but that can also retrieve the real, target object from the relevant scope (for example, an HTTP request) and delegate method calls onto the

开发springboot项目基本思路

阅读更多关于开发springboot项目基本思路

开发springboot项目基本思路一、先跳转到前端页面，再通过前端ajax来拿数据到前端填充网页数据二、数据库Dao层的CRUD不能直接在业务层Service层调用，应该将其包装好放在Service层中再去调用，要将Dao层的方法进行隔离。嗯嗯，基本就这样！来源： CSDN 作者：宇宙第零帅链接： https://blog.csdn.net/qq_42039738/article/details/103217808