Mybatis（二）：怎样使用Mybatis

一、创建项目（本文以Idea基于Maven构建的项目为例）

• New——>Project

• 笔者这里是选择自己本地的Maven及配置

• 最后点击Finish即可

二、在配置文件中添加依赖包

• pom.xml配置文件中添加Mybatis、JDBC驱动、log4j日志管理的包依赖
• 完整代码如下：

<?xml version="1.0" encoding="UTF-8"?>

<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>com.zhurouwangzi</groupId>
  <artifactId>MybatisDemo</artifactId>
  <version>1.0-SNAPSHOT</version>

  <name>MybatisDemo</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
    <!--mybatis版本-->
    <mybatis.version>3.2.7</mybatis.version>
    <!--log4j版本-->
    <slf4j.version>1.6.6</slf4j.version>
    <log4j.version>1.2.12</log4j.version>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>

    <!-- mybatis核心包 -->
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>${mybatis.version}</version>
    </dependency>
    <!-- mysql驱动包 -->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.29</version>
    </dependency>

    <!-- 日志文件管理包 -->
    <!-- log start -->
    <dependency>
      <groupId>log4j</groupId>
      <artifactId>log4j</artifactId>
      <version>${log4j.version}</version>
    </dependency>
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-api</artifactId>
      <version>${slf4j.version}</version>
    </dependency>
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-log4j12</artifactId>
      <version>${slf4j.version}</version>
    </dependency>
    <dependency>
      <groupId>org.junit.jupiter</groupId>
      <artifactId>junit-jupiter-api</artifactId>
      <version>RELEASE</version>
      <scope>compile</scope>
    </dependency>
  </dependencies>

  <build>
    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
      <plugins>
        <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
        <plugin>
          <artifactId>maven-clean-plugin</artifactId>
          <version>3.1.0</version>
        </plugin>
        <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
        <plugin>
          <artifactId>maven-resources-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.8.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-surefire-plugin</artifactId>
          <version>2.22.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-jar-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-install-plugin</artifactId>
          <version>2.5.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-deploy-plugin</artifactId>
          <version>2.8.2</version>
        </plugin>
        <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
        <plugin>
          <artifactId>maven-site-plugin</artifactId>
          <version>3.7.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-project-info-reports-plugin</artifactId>
          <version>3.0.0</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>

• 等依赖包下载完了之后我们在项目这里可以看到：

•  在src下添加一个resource文件夹，然后鼠标右键Mark Directory As Resources Root

•  在src/resource文件夹下创建SqlMapConfig.xml作为Mybatis的全局配置文件
• 在src/resource然后再创建一个log4j.properties文件用来配置日志文件的配置
• 在src/resource再创建一个sqlmap文件夹用来存放Mybatis的映射文件
• 创建好的项目结构如下：

三、设置Mybatis相关配置文件

• log4j.properties配置文件的内容如下：

# Global logging configuration
log4j.rootLogger=DEBUG, stdout
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

• SqlMapConfig.xml配置文件内容如下：

<?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>
    <!-- 和spring整合后 environments配置将废除-->
    <environments default="development">
        <environment id="development">
            <!-- 使用jdbc事务管理-->
            <transactionManager type="JDBC" />
            <!-- 数据库连接池-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/web_test3?characterEncoding=utf-8" />
                <property name="username" value="root" />
                <property name="password" value="root" />
            </dataSource>
        </environment>
    </environments>

</configuration>

四、创建实体类

package com.zhurouwangzi.entity;

public class UserBaseInfo {
    private int id;
    private String username;

    @Override
    public String toString(){
        return "User [id=" + id + ", username=" + username+ "]";
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }
}

• 在src/resource/sqlmap文件夹下添加user.xml作为UserBaseInfo的映射文件

<?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">
<!-- namespace是命名空间，作用sql语句的隔离，后面还有重要作用
#{}作用就是占位符，相当于jdbc的“?”
parameterType：查询的参数类型
resultType：查询结果的数据类型，如果时候pojo应该给全路径。
-->
<mapper namespace="test">
    <select id="getUserById" parameterType="int" resultType="com.zhurouwangzi.entity.UserBaseInfo">
        select * from user_baseinfo where id = #{id}
    </select>
</mapper>

• 在SqlMapConfig.xml配置文件中添加<Mappers>配置：

 

五、用测试方法区测试

• 代码如下：

package com.zhurouwangzi.service;

import com.zhurouwangzi.entity.UserBaseInfo;
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.jupiter.api.Test;

import java.io.InputStream;

public class MybatisTest {

    @Test
    public void test() throws Exception{
        //1.创建一个SqlSessionFactoryBuilder对象
        SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
        //2.加载配置文件
        InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
        //3.创建SqlSessionFactory工厂对象
        SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream);
        //4.获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //5.执行sql语句
        UserBaseInfo userBaseInfo = sqlSession.selectOne("getUserById", 16);
        System.out.println(userBaseInfo);
        //关闭资源
        sqlSession.close();
    }
}

运行结果如下：