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Mybatis入门

栏目:数据库应用时间:2015-04-23 08:24:26

1、MyBatis介绍

MyBatis是支持普通SQL查询,存储进程和高级映照的优秀持久层框架。MyBatis消除几近所有的JDBC代码和参数的手工设置和对结果集的检索封装。MyBatis可使用简单的XML或注解用于配置和原始映照,将接口和Java的POJO(Plain Old Java Objects,普通的Java对象)映照成数据库中的记录。


Mybatis⑶.1.1下载地址:http://download.csdn.net/detail/huhui_bj/8575253


2、快速入门

2.1 准备

首先需要添加两个jar包,1个是mybatis⑶.1.1.jar,1个是mysql-connector-java⑸.1.7-bin.jar。然后在MySQL中建立数据库和数据表:

create database mybatis; use mybatis; CREATE TABLE users(id INT PRIMARY KEY AUTO_INCREMENT, NAME VARCHAR(20), age INT); INSERT INTO users(NAME, age) VALUES('Tom', 12); INSERT INTO users(NAME, age) VALUES('Jack', 11);

2.2 添加Mybatis的配置文件conf.xml

<?xml version="1.0" encoding="UTF⑻"?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis⑶-config.dtd"> <configuration> <environments default="development"> <environment id="development"> <transactionManager type="JDBC" /> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver" /> <property name="url" value="jdbc:mysql://localhost:3306/mybatis" /> <property name="username" value="root" /> <property name="password" value="root" /> </dataSource> </environment> </environments> </configuration>

2.3 定义表所对应的实体类

public class User { private int id; private String name; private int age; //get,set方法 }

2.4 定义操作users表的SQL映照文件userMapper.xml

<?xml version="1.0" encoding="UTF⑻" ?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis⑶-mapper.dtd"> <mapper namespace="com.atguigu.mybatis_test.test1.userMapper"> <select id="getUser" parameterType="int" resultType="com.atguigu.mybatis_test.test1.User"> select * from users where id=#{id} </select> </mapper>

2.5 在conf.xml文件中注册userMapper.xml文件

<mappers> <mapper resource="com/atguigu/mybatis_test/test1/userMapper.xml"/> </mappers>

2.6 编写测试代码

String resource = "conf.xml"; //加载mybatis的配置文件(它也加载关联的映照文件) Reader reader = Resources.getResourceAsReader(resource); //构建sqlSession的工厂 SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader); //创建能履行映照文件中sql的sqlSession SqlSession session = sessionFactory.openSession(); //映照sql的标识字符串 String statement = "com.atguigu.mybatis.bean.userMapper"+".selectUser"; //履行查询返回1个唯1user对象的sql User user = session.selectOne(statement, 1); System.out.println(user);

3、数据表的CRUD操作

3.1 XML的实现

<insert id="insertUser" parameterType="com.atguigu.ibatis.bean.User"> insert into users(name, age) values(#{name}, #{age}); </insert> <delete id="deleteUser" parameterType="int"> delete from users where id=#{id} </delete> <update id="updateUser" parameterType="com.atguigu.ibatis.bean.User"> update users set name=#{name},age=#{age} where id=#{id} </update> <select id="selectUser" parameterType="int" resultType="com.atguigu.ibatis.bean.User"> select * from users where id=#{id} </select> <select id="selectAllUsers" resultType="com.atguigu.ibatis.bean.User"> select * from users </select>

3.2 注解的实现

public interface UserMapper { @Insert("insert into users(name, age) values(#{name}, #{age})") public int insertUser(User user); @Delete("delete from users where id=#{id}") public int deleteUserById(int id); @Update("update users set name=#{name},age=#{age} where id=#{id}") public int updateUser(User user); @Select("select * from users where id=#{id}") public User getUserById(int id); @Select("select * from users") public List<User> getAllUser(); }

在conf.xml中注册这个映照接口:

<mapper class="com.atguigu.ibatis.crud.ano.UserMapper"/>

在DAO类中调用:

public User getUserById(int id) { SqlSession session = sessionFactory.openSession(); UserMapper mapper = session.getMapper(UserMapper.class); User user = mapper.getUserById(id); return user; }

4、几个可以优化的地方

4.1 建立数据库配置文件

## db.properties <properties resource="db.properties"/> <property name="driver" value="${driver}" /> <property name="url" value="${url}" /> <property name="username" value="${username}" /> <property name="password" value="${password}" />

然后在Mybatis的配置文件conf.xml中加入读取db.properties的配置:

<!-- 引入资源文件 --> <properties resource="db.properties"/>

4.2 为实体类定义别名

<!-- 配置实体类的别名 --> <typeAliases> <!-- <typeAlias type="com.mybatis.test1.User" alias="_User"/> --> <package name="com.mybatis.bean"/> <!-- 扫描这个包 --> </typeAliases>
上面的配置可以简化SQL映照xml文件中的援用,不再需要每次都要写类的全路径。


4.3 添加log4j配置文件,打印日志信息

#log4j.properties log4j.rootLogger=DEBUG, Console #Console log4j.appender.Console=org.apache.log4j.ConsoleAppender log4j.appender.Console.layout=org.apache.log4j.PatternLayout log4j.appender.Console.layout.ConversionPattern=%d [%t] %⑸p [%c] - %m%n log4j.logger.java.sql.ResultSet=INFO log4j.logger.org.apache=INFO log4j.logger.java.sql.Connection=DEBUG log4j.logger.java.sql.Statement=DEBUG log4j.logger.java.sql.PreparedStatement=DEBUG



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