dao

Session factories to handle multiple DB connections

由 别来无恙 提交于 2019-12-22 18:29:22
问题 I have a task to create multiple session factories for different Data Sources. One data source will be used for read requests and another for read-write requests. Each API of our Database Service(a wrapper over DAO) is executed as a transaction. Single API may call multiple DAO functions having different Read/Write property. What is the best possible way to perform this task? 回答1: I am assuming that the different datasources are different DBs . Else you could use the readOnly attribute with

Session factories to handle multiple DB connections

由 牧云@^-^@ 提交于 2019-12-22 18:29:18
问题 I have a task to create multiple session factories for different Data Sources. One data source will be used for read requests and another for read-write requests. Each API of our Database Service(a wrapper over DAO) is executed as a transaction. Single API may call multiple DAO functions having different Read/Write property. What is the best possible way to perform this task? 回答1: I am assuming that the different datasources are different DBs . Else you could use the readOnly attribute with

Difference between Active Record and DAO?

由 心不动则不痛 提交于 2019-12-22 01:25:30
问题 What's the difference between a Data Access Object and Active Record? They seem to be quite the same, as both built a layer between the application and persistence layer, and abstract away direct database access using SQL queries. 回答1: Data Access Object (DAO) refers to an object in your data layer responsible for persisting a separate entity in your domain. Active Record is a specific method of doing a DAO where the class containing the values of a single row from a table is also responsible

passing value to a jsp page from a java class using DAO

由 假如想象 提交于 2019-12-22 01:06:50
问题 I wanted to pass the value retrieved on a java class to a page.I am using DAO classes. I have retrieved the values from the database and stored them on String variables.Now I want to set them to the text boxes in my view.jsp page.I am new to this area,can anyone help me out?? View.jsp is as <%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html

Spring中的事务操作

由 ↘锁芯ラ 提交于 2019-12-22 00:52:00
事务的特性 原子性：强调事务的不可分割。 一致性：事务的执行的前后数据的完整性保持一致。 隔离性：一个事务执行的过程中，不应该受到其他事务的干扰。 持久性：事务一旦结束，数据就持久化到数据库。 如果不考虑隔离性会引发的安全性问题 脏读：一个事务读到了另一个事务的未提交的数据。 不可重复读：一个事务读到了另一个事务已经提交的update的数据，导致多次查询的结果不一致。 虚读：一个事务读到了另一个事务已经提交的insert的数据，导致多次查询的结果不一致。 解决读问题：设置事务的隔离级别 未提交读：脏读、不可重复读和虚读都有可能发生。 已提交读：避免脏读，但是不可重复读和虚读有可能发生。 可重复读：避免脏读和不可重复读，但是虚读有可能发生。 串行化的：避免以上所有读问题。 Spring的声明式事务管理方式 Spring进行声明式事务配置的方式有两种： 基于xml配置文件方式 基于注解方式 但无论使用什么方式进行Spring的事务操作，首先要配置一个事务管理器。 搭建转账的环境 第一步，创建数据库表。 DROP TABLE IF EXISTS `account`; CREATE TABLE `account` ( `id` int(11) DEFAULT NULL, `username` varchar(100) DEFAULT NULL, `salary` int(11)

How do we determine an object's responsibility in OOP?

由 瘦欲@ 提交于 2019-12-21 23:19:34
问题 I just started learning OOP and I'm finding it really hard to decide where functionality belongs. Let's use a down vote in SO for our example: When we cast one, the following must happen in a transaction: Decrement the voter's rep and downVotes count. Decrement the recipient's rep . Decrement the post score . So... How do we determine which action belongs to which object? Where would such functionality live? In the DAO layer, services layer, or the actual objects themselves? It becomes

Spring的bean管理（注解）

由 雨燕双飞 提交于 2019-12-21 20:49:21
前端时间总是用配置文件 内容太多 下面认识一下注解 注解是什么？ 1代码里面的特殊标记，使用注解可以完成功能 2注解写法@XXX 3使用注解可以少些很多配置文件 Spring注解开发准备 注解创建准备 1导入Spring的jar包 2创建类 public class User{ 　　public void add(){ 　　　System.out.print("add")　 　　　　} } 3创建Spring配置文件 引入约束 开启注解扫描 到包里面扫描类 ，方法，属性上是否有注解 <context:component-scan base-package="com.bdqn.entity"> </context:component-scan> 如果是多个包 那么 可以在 com.bdqn.entity,com.bdqn.entity1,.... 注解创建对象 1在你创建对象的上面 使用注解实现 @Component(value="user")相当于<bean id="user" class="当前类"> 测试 ApplicationContext context=ClassPathXmlApplicationContext("Spring.xml"); User u=(User) context.getBean("user"); u.add(); 创建对象一共有四个注解 (1)

Transaction management with DAOs

由 爷，独闯天下 提交于 2019-12-21 19:48:03
问题 In my Java application's DAO layer I have two DAO classes EmployeeDAO and BankDAO . I need to control/handle their database transactions. I use connection pooling to get database connections. EmployeeDAO class: public class EmployeeDAO { String name; String empCode; int age; // Getters & Setters } BankDAO class: public class BankDAO { String bankName; String acNo; String empCode; // Getters & Setters } Let's say I am going to store an Employee and Bank account details related to that employee

Spring JDBC: How to create the tables?

由 女生的网名这么多〃 提交于 2019-12-21 17:37:11
问题 I am using Spring JdbcTemplate with the DAO pattern to access a database. Instead of creating the database tables manually, I am looking for a way to generate the tables in the DAO layer. I understand that I can use the JdbcTemplate to execute statements, I am only looking for the right place to do it. Is there a best practice for that? 回答1: Slightly offtopic: Is it absolutely necessary that you need to execute the DDL commands from within your code? In fact I do think it is a good idea to

easyui增删改查

由 僤鯓⒐⒋嵵緔 提交于 2019-12-21 16:47:54
easyui的crud（dialog，datagrid、form讲解） 1、datagrid布局 2、dialog布局 3、form布局 4、通用的JsonBaseDao增删改方法 5、dao层 6、web层 7、功能完善 导入jar包 MVC_Book_dao package com.hmc.dao; import java.util.List; import java.util.Map; import com.hmc.util.JsonBaseDao; import com.hmc.util.JsonUtils; import com.hmc.util.PageBean; import com.hmc.util.StringUtils; public class MVC_Book_dao extends JsonBaseDao{ /** * 查询分页 * @param paMap * @param pageBean * @return * @throws Exception */ public List<Map<String, Object>> list(Map<String, String[]> paMap,PageBean pageBean) throws Exception{ //String sql="SELECT * FROM t_book"; String sql=
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