dao

Dependency injection using Guice with the DAO pattern

由 别来无恙 提交于 2019-12-20 03:21:37
问题 For a small side project I'm working on I've been trying to implement something of a DAO pattern for my interactions with the DB, and have started using Guice (for my first time) to handle the DI for me. Right now I have this class hierarchy: DAOImpl takes a reference to a class type so my database client (mongo/morphia) can do some initialization work and instantiate a BasicDAO provided by morphia. Here's snippets of the relevant classes: public class DAOImpl<T> implements DAO<T> { private

JAVA--高级基础开发--分页技术

由 ∥☆過路亽．° 提交于 2019-12-20 00:14:56
【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> =========《分页技术:》============== 前端代码: <%@ page contentType="text/html;charset=UTF-8" language="java" %> <%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <html> <head> <title>分页技术</title> <script src="js/jquery-3.4.1.js"></script> </head> <body> <h2 style="color: darkmagenta">分页技术的展示页面</h2> <table border="100%" width="100%"> <h2 style="color: firebrick;" align="center">省份信息的展示</h2> <tr> <th>ID</th> <th>省份的代号</th> <th>省份</th> </tr> <c:forEach items="${pp.datas}" var="ss"> <tr align="center"> <td> ${ss.id} </td> <td> ${ss.provinceid} </td> <td> $

Spring框架

由 血红的双手。 提交于 2019-12-19 12:48:43
---恢复内容开始--- Spring框架：Spring框架的核心 代理模式，AOP，JDBC支持 Spring事务管理 Spring与Mybatis整合 传统开发模式 基于项目框架架构：entity/dao/service/action 1、实体类 class user{} 2、dao class userdao｛ 访问数据库｝ 3、Service class UserService｛ UserDao userdao=new……（）； ｝ 4、action class userAction｛ UserService userservice=new ……()； public void setUserService（UserService userservice）｛ this.userservice=userservice; ｝ //由别人来创建：控制反转 ｝ 用户访问：user.action--->Tomcat(服务器创建Action，Service，dao) 思考：1、对象创建创建能否写死 2、对象创建细节，对象的个数？创建的时间 3、对象之间的依赖 总结：Spring解决对象的创建，以及对象依赖关系管理 Spring框架：了解专业术语 组件/框架设计:侵入式：对现有的类的结构有影响，需要实现或继承 非侵入式：对现有的类的结构没有影响 控制反转（IOC）

Struts 2 Hibernate null pointer exception while submitting the form

由 浪尽此生 提交于 2019-12-19 10:18:15
问题 I am trying to create a registration page by integrating Struts 2 & Hibernate. But when I am running the below code , I am getting a null pointer exception when I click the register button. hibernate configuration file: <hibernate-configuration> <session-factory> <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property> <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property> <property name="hibernate.connection.url">jdbc:mysql://localhost/db

Mybatis框架介绍及其入门

由 人走茶凉 提交于 2019-12-19 05:44:46
在前面介绍了原生JDBC的缺陷，那么对于弥补相应缺陷的框架：就是目前最流行的————Mybatis框架 Mybatis框架介绍及其入门 Mybatis框架介绍 Mybatis原本是Apache软件基金会的一个开源项目叫做iBatis，2010年这个项目由Apache迁移到了goole code管理才改名为Mybatis，2013年又迁移到了GitHub。 #Github代码托管平台：就是互联网网站，上面放东西的 注意：如果以后想从事开发工作的话，在招聘信息和面试时候可能问你会ibatis吗 ？记得它就是Mybatis Mybatis是一个优秀的持久层框架（Dao层框架），它是对JDBC的封装，使得开发者只需要关注Sql语句（业务）本身即可，无需开发者处理加载驱动、获取连接、创建Statement等繁琐的过程。 Mybatis 最大的特点是把Sql 语句写在XML 配置文件当中 。而且Mybatis执行完Sql语句之后可以以对象形式返回（实体类/实体类集合等） ORM：Object/Relation Mapping 对象/关系映射 ORM思想：将数据库中的关系数据表映射为JAVA中的对象，把对数据表的操作转换为对对象的操作，实现面向对象编程。因此ORM的目的是使得开发人员以面向对象的思想来操作数据库 Hibernate框架是一个 全自动的 ORM 持久层框架，只需要编写POJO

Java Remove repeated try, catch, finally boilerplate from DAO

由 ぃ、小莉子 提交于 2019-12-19 03:54:26
问题 I have a DAO class with many methods that have a lot of repeated code along the lines of: - public void method1(...) { Connection conn = null; try { //custom code here } catch (SQLException e) { LOG.error("Error accessing the database.", e); throw new DatabaseException(); } catch (QueryNotFoundException e) { LOG.error("Error accessing the database.", e); throw new DatabaseException(); } finally { if (conn != null) connectionPool.returnConnection(conn); } public void method2(...) { Connection

使用Maven构建多模块项目

由 孤者浪人 提交于 2019-12-19 00:15:24
【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 在平时的Javaweb项目开发中为了便于后期的维护，我们一般会进行分层开发，最常见的就是分为domain（域模型层）、dao（数据库访问层）、service（业务逻辑层）、web（表现层），这样分层之后，各个层之间的职责会比较明确，后期维护起来也相对比较容易，今天我们就是使用Maven来构建以上的各个层。 　　项目结构如下： 　　system-parent 　　　　|----pom.xml 　　　　|----system-domain 　　　　　　　　|----pom.xml 　　　　|----system-dao 　　　　　　　　|----pom.xml 　　　　|----system-service 　　　　　　　　|----pom.xml 　　　　|----system-web 　　　　　　　　|----pom.xml 一、创建system-parent项目 　　创建system-parent，用来给各个子模块继承。 　　进入命令行，输入以下命令： mvn archetype:create -DgroupId=me.gacl -DartifactId=system-parent -DarchetypeArtifactId=maven-archetype-quickstart

Will existing DAO code work against a SQL Server?

由 拥有回忆 提交于 2019-12-18 17:38:13
问题 If I transfer data from a Access MDB into a SQL Server, will DAO code in a VB app work against the SQL Server. I realise there will need to be changes to the initial connection calls but will anything else need to change? 回答1: A number of issues here. if you're using an ADP for your front end to SQL Server, you won't be using DAO, as you can't, since ADPs don't use Jet/ACE. You'll then have a direct ADO connection to the SQL Server. However, for the last 5 years or so MS has been deprecating

Calling one DAO from another DAO?

由 风流意气都作罢 提交于 2019-12-18 13:30:49
问题 Can this ever make sense? Say I need to fetch an object from the DB which has a relation to another object (represented by a foreign key in the DB, and by a composition in my domain object). If in my first DAO I fetch the data for object 1, then call the dao for object 2, and finally (from within the first DAO, call the setter in object 1 and give it the previously fetched object 2). I know I could do a join instead, but it just seems more logical to me to decouple the functionality (which is

MS Access Batch Update via ADO.Net and COM Interoperability

由 时光怂恿深爱的人放手 提交于 2019-12-18 12:40:37
问题 This is kind of a follow-up to this thread. This is all with .Net 2.0 ; for me, at least. Essentially, Marc (OP from above) tried several different approaches to update an MS Access table with 100,000 records and found that using a DAO connection was roughly 10 - 30x faster than using ADO.Net. I went down virtually the same path (examples below) and came to the same conclusion. I guess I'm just trying to understand why OleDB and ODBC are so much slower and I'd love to hear if anyone has found
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