Mybatis(一)--入门小demo

Love The Way You Lie 2022-06-01 22:58 242阅读 0赞

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# 简介 #

Mybatis的前身是iBATIS,是在2001年发起的一个开源项目,最初侧重于密码软件的开发,后来发展成为一款基于Java的持久层框架。

Mybatis是一款优秀的支持自定义SQL查询、存储过程和高级映射的持久层框架。Mybatis可以使用XML或注解进行配置和映射,Mybatis通过将参数映射到配置的SQL形成最终执行的SQL语句,最后将执行SQL的结果集映射成JAVA对象返回。与其他ORM框架不同,Mybatis并没有将java对象与数据库表关联起来,而是将java方法和sql语句关联起来,所以我们可以使用一些数据库的特性或者视图等等,极大的提高了开发的灵活性。

# 创建demo #

1.使用idea进行开发

2.创建一个maven工程,命名mybatis-zh

①新建工程

![20171227173528966][]

②设置坐标

groupId:zh.mybatis

artifactId:zh

version:1.0-SNAPSHOT

3.引入mybatis、mysql、日志相关的jar包

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    
      <modelVersion>4.0.0</modelVersion>
    
      <groupId>zh.mybatis</groupId>
      <artifactId>zh</artifactId>
      <version>1.0-SNAPSHOT</version>
      <packaging>jar</packaging>
    
      <name>zh</name>
      <url>http://maven.apache.org</url>
    
      <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      </properties>
    
      <dependencies>
        
        <dependency>
          <groupId>org.mybatis</groupId>
          <artifactId>mybatis</artifactId>
          <version>3.4.5</version>
        </dependency>
    
        
        <dependency>
          <groupId>mysql</groupId>
          <artifactId>mysql-connector-java</artifactId>
          <version>5.1.38</version>
        </dependency>
    
        
        <dependency>
          <groupId>org.slf4j</groupId>
          <artifactId>slf4j-api</artifactId>
          <version>1.7.25</version>
        </dependency>
        <dependency>
          <groupId>org.slf4j</groupId>
          <artifactId>slf4j-log4j12</artifactId>
          <version>1.7.25</version>
        </dependency>
        <dependency>
          <groupId>log4j</groupId>
          <artifactId>log4j</artifactId>
          <version>1.2.17</version>
        </dependency>
        
        <dependency>
          <groupId>junit</groupId>
          <artifactId>junit</artifactId>
          <version>4.12</version>
          <scope>test</scope>
        </dependency>
      </dependencies>
    </project>

4.在src/main/java下建立model,包名为zh.mybatis.simple.model,实体名称为Country

package zh.mybatis.simple.model;
    
    /**
     * Created by huan on 2017/12/26.
     */
    public class Country {
        private Long id;
        private String countryname;
        private String countrycode;
    
        public Long getId() {
            return id;
        }
    
        public void setId(Long id) {
            this.id = id;
        }
    
        public String getCountryname() {
            return countryname;
        }
    
        public void setCountryname(String countryname) {
            this.countryname = countryname;
        }
    
        public String getCountrycode() {
            return countrycode;
        }
    
        public void setCountrycode(String countrycode) {
            this.countrycode = countrycode;
        }
    }

5.在resources下创建mapper,包名为zh.mybatis.simple.mapper,mapper的名称为CountryMapper.xml

<?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="zh.mybatis.simple.mapper.CountryMapper">
        <select id="selectAll" resultType="Country">
            SELECT id,countryname,countrycode FROM country
        </select>
    </mapper>

6.在resources下创建mybatis的配置文件,名称为mybatis-config.xml

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE configuration
            PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-config.dtd">
    <configuration>
        <settings>
            <setting name="logImpl" value="LOG4J"/>
        </settings>
        
        <typeAliases>
            <package name="zh.mybatis.simple.model" />
        </typeAliases>
    
        <environments default="development">
            <environment id="development">
                <transactionManager type="JDBC">
                    <property name="" value=""/>
                </transactionManager>
                <dataSource type="UNPOOLED">
                    <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=""/>
                </dataSource>
            </environment>
        </environments>
        <mappers>
            <mapper resource="zh/mybatis/simple/mapper/CountryMapper.xml"/>
        </mappers>
    </configuration>

7.在resources下创建log4j.properties

#全局变量
    log4j.rootLogger = ERROR,stdout
    #Mybatis 日志配置
    log4j.logger.zh.mybatis.simple.mapper = TRACE
    #控制台输出配置
    log4j.appender.stdout = org.apache.log4j.ConsoleAppender
    log4j.appender.stdout.layout = org.apache.log4j.PatternLayout
    log4j.appender.stdout.layout.ConversionPattern = %5p [%t] - %m%n

8.最后写一个测试类在test/java下创建包名为zh.mybatis.simple.mapper,类名为CountryMapperTest

package zh.mybatis.simple.mapper;
    
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    import org.junit.BeforeClass;
    import org.junit.Test;
    import zh.mybatis.simple.model.Country;
    
    import java.io.IOException;
    import java.io.Reader;
    import java.util.List;
    
    /**
     * Created by huan on 2017/12/26.
     */
    public class CountryMapperTest {
        private static SqlSessionFactory sqlSessionFactory;
    
        @BeforeClass
        public static void init(){
            try{
                Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
                reader.close();
            }catch (IOException ignore){
                ignore.printStackTrace();
            }
        }
    
        @Test
        public void testSelectAll(){
            SqlSession sqlSession = sqlSessionFactory.openSession();
            try{
                List<Country> countryList = sqlSession.selectList("selectAll");
                
            }finally {
                //关闭sqlsession
                sqlSession.close();
            }
        }
        
        private void printCountryList(List<Country> countryList){
            for (Country country : countryList) {
                System.out.printf("%-4d%4s%4s\n", country.getId(),country.getCountryname(),country.getCountrycode());
            }
        }
    }

# 运行demo #

运行结果如下:

![20171227215134362][]

# 最终搭好的项目结构 #

![20171227215216113][]

# 遇到的问题 #

创建项目时idea会自动在pom中添加版本为3.8.1版本的junit引用,发现使用注解不管用,如@Before和@Test,最终发现junit3.x是基于继承的,junit4.x是基于注解的,在junit3.x的版本不支持注解,如果想要使用junit3.x实现测试需要让测试类继承TestCase ,详情可参考博客:[http://maxpin.iteye.com/blog/1184494][http_maxpin.iteye.com_blog_1184494]

[http_www.captainbed.net_zhanghan]: http://www.captainbed.net/zhanghan
[20171227173528966]: /images/20220602/b0aae37df4dd462fac30efa4b9438210.png
[20171227215134362]: /images/20220602/0c981ac804294f4d844f59fb1cc63059.png
[20171227215216113]: /images/20220602/292a9af44dd646028dd5ec73879a759d.png
[http_maxpin.iteye.com_blog_1184494]: http://maxpin.iteye.com/blog/1184494