dao | 易学教程

How to create database from Assets in Android using GreenDao ORM library

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问题 I am using GreenDao orm library for creating database, it works good with the First sample for Creating Database, from within the code. Now the problem is I can't find any documentation or anything related to the Database copying from Assets Folder to the databases inside memory. 回答1: The accepted answer provides a solution but it's only partially correct. Check out the class I posted below. This is an extension of greenDao's OpenHelper class. Below that is an example of it's use and how you

Multiple Entity Manager issue in Spring when using more than one datasource

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问题 I have two entity managers in my applicationContext.xml which corresponds to two different databases. I can easily query database1 with entityManager1 , but when I try to access database2 with entityManager2 , I am not getting any results. I am using Spring+Hibernate+JPA. Here is my ApplicationContext.xml <?xml version="1.0" encoding="UTF-8"?> <beans default-autowire="byName" xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx=

Android Room使用详解

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使用Room将数据保存在本地数据库 Room提供了SQLite之上的一层抽象, 既允许流畅地访问数据库, 也充分利用了SQLite. 处理大量结构化数据的应用, 能从在本地持久化数据中极大受益. 最常见的用例是缓存有关联的数据碎片. 以这种方式, 在设备不能访问网络的时候, 用户依然能够浏览离线内容. 任何用户发起的改变, 都应该在设备重新在线之后同步到服务器. 因为Room为你充分消除了这些顾虑, 使用Room而非SQLite是高度推荐的. 添加依赖 Room的依赖添加方式如下: 1 dependencies { 2 def room_version = "1.1.1" 3 4 implementation "android.arch.persistence.room:runtime:$room_version" 5 annotationProcessor "android.arch.persistence.room:compiler:$room_version" 6 7 // optional - RxJava support for Room 8 implementation "android.arch.persistence.room:rxjava2:$room_version" 9 10 // optional - Guava support for Room,

Single DAO & generic CRUD methods (JPA/Hibernate + Spring)

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Following my previous question, DAO and Service layers (JPA/Hibernate + Spring) , I decided to use just a single DAO for my data layer (at least at the beginning) in an application using JPA/Hibernate, Spring and Wicket. The use of generic CRUD methods was proposed, but I'm not very sure how to implement this using JPA. Could you please give me an example or share a link regarding this? Here is an example interface: public interface GenericDao<T, PK extends Serializable> { T create(T t); T read(PK id); T update(T t); void delete(T t); } And an implementation: public class GenericDaoJpaImpl<T,

Hibernate or JPA or JDBC or? [closed]

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问题 Closed . This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed 6 years ago . I am developing a Java Desktop Application but have some confusions in choosing a technology for my persistence layer. Till now, I have been using JDBC for DB operations. Now, Recently I learnt Hibernate and JPA but still I am a novice on these technologies. Now my question

VBA - Run Time Error 3271 using DAO object

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问题 I'm trying to update a SQL server database using DAO.QueryDef and a local Append query in Microsoft Access. Some of my fields that are being updated contain very long strings (anywhere from 0 to upwards of 700 characters). When the string length is in the range from 0 to 255 characters, I have no problem passing it into my query and updating the respective tables. However when they exceed 255 characters, I receive the following run-time error: I have been using a random string generator

Get actual type of generic type argument on abstract superclass

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I have a class like: public abstract class BaseDao<T extends PersistentObject> { protected Class<T> getClazz() { return T.class; } // ... } But the compiler says to T.class; : Illegal class literal for the type parameter T . How can I get the class of T ? It's definitely possible to extract it from Class#getGenericSuperclass() because it's not defined during runtime, but during compiletime by FooDao extends BaseDao<Foo> . Here's a kickoff example how you could extract the desired generic super type in the constructor of the abstract class, taking a hierarchy of subclasses into account (along

Mybatis学习笔记之---环境搭建

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Mybatis环境搭建（一）环境搭建（1）第一步：创建maven工程并导入jar包 <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.11</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.41</version> </dependency> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.4.6</version> </dependency> </dependencies> （2）第二步：创建实体类和dao的接口（3）第三步：创建Mybatis的主配置文件SqlMapperConfig.xml <?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPEconfiguration PUBLIC"-//mybatis.org//DTD Config 3.0//EN" "http:/

Hibernate using multiple databases

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问题 Someone know how to add a another datasource in hibernate configuration and how to configure Spring to that datasource its autoinject in my respective DAO? This is my code with one datasource, that run perfectly, but i don't know how add another datasource. I want to add another data source that is a database with different tables than the actual database. HIBERNATE CONF <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"> <property name="driverClassName"

Hibernate Delete Error: Batch Update Returned Unexpected Row Count

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问题 I wrote this method below that is suppose to delete a member record from the database. But when I use it in my servlet it returns an error. MemberDao Class public static void deleteMember(Member member) { Session hibernateSession = HibernateUtil.getSessionFactory().getCurrentSession(); Transaction tx = hibernateSession.beginTransaction(); hibernateSession.delete(member); tx.commit(); } Controller Part if(delete != null) { HttpSession httpSession = request.getSession(); Member member = (Member