java数据库访问（四）—Mybatis

前述的几种java访问数据库的方式：

• jdbc是最原始的方式，使用比较繁琐；
• JdbcTemplate方式相对方便性有一些提高，但在工程应用中仍然很不方便。

接下来继续记录使用持久化框架来进行数据库操作，本文记录使用Mybatis进行记录的的简单示例：

1、定义

官网的定义：

MyBatis is a first class persistence framework with support for custom SQL, stored procedures and advanced mappings. MyBatis eliminates almost all of the JDBC code and manual setting of parameters and retrieval of results. MyBatis can use simple XML or Annotations for configuration and map primitives, Map interfaces and Java POJOs (Plain Old Java Objects) to database records.

2、依赖

spring中使用mybatis需要添加如下依赖（pom.xml）：

  <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis-spring -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
            <version>1.3.3</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>

3、配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
     http://www.springframework.org/schema/context
     http://www.springframework.org/schema/context/spring-context-2.5.xsd  
     http://www.springframework.org/schema/beans
     https://www.springframework.org/schema/beans/spring-beans.xsd">
     <bean id="dataSource"
     class="org.apache.commons.dbcp2.BasicDataSource"
     destroy-method="close">
     <property name="url" value="jdbc:mysql://localhost:3306/test"/>
     <property name="username" value="root"/>
     <property name="password" value="root"/>
     <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
     </bean>
     <bean id="sqlSessionFactory"
     class="org.mybatis.spring.SqlSessionFactoryBean">
      <property name="dataSource" ref="dataSource"/>
      <property name="mapperLocations" value="classpath:mybatis/mapper/*.xml"/>
     </bean>
     <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
      <property name="basePackage" value="com.test.database.mybatis"/>
      <property name="sqlSessionFactory" ref="sqlSessionFactory"/>
     </bean>
</beans>

4、sql映射文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.test.database.mybatis.TestDao">
<select id="getAll" resultType="com.test.database.User">
select * from user
</select>
</mapper>

5、接口定义

package com.test.database.mybatis;

import java.util.List;

import com.test.database.User;

public interface TestDao {
    
    public List<User> getAll();

}

User定义

package com.test.database;

public class User {
    
    private int id;
    private String name;
    private String password;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", name=" + name + ", password=" + password + "]";
    }
    
    

}

6、测试类

package com.test;

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.test.database.mybatis.TestDao;

public class Main {

    public static void main(String[] args) throws BeansException, Exception {
        ApplicationContext context = new ClassPathXmlApplicationContext("spring-context*.xml");
        //测试mybatis
        System.out.println(context.getBean(TestDao.class).getAll());
    }
}

7、测试结果

[User [id=1, name=tim, password=tim], User [id=2, name=park, password=park]]