MyBatis笔记之环境配置以及入门案例

（1）创建一个maven工程，其pom.xml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>4.0.0modelVersion>

  <groupId>com.ahu.csgroupId>
  <artifactId>mybatis01artifactId>
  <version>1.0-SNAPSHOTversion>
  <packaging>jarpackaging>

  <name>mybatis01name>
  
  <url>http://www.example.comurl>

  <properties>
    <project.build.sourceEncoding>UTF-8project.build.sourceEncoding>
    <maven.compiler.source>1.7maven.compiler.source>
    <maven.compiler.target>1.7maven.compiler.target>
  properties>

  <dependencies>
    
    <dependency>
      <groupId>junitgroupId>
      <artifactId>junitartifactId>
      <version>4.11version>
      <scope>testscope>
    dependency>
    
    <dependency>
      <groupId>mysqlgroupId>
      <artifactId>mysql-connector-javaartifactId>
      <version>5.1.6version>
    dependency>
    
    <dependency>
      <groupId>org.mybatisgroupId>
      <artifactId>mybatisartifactId>
      <version>3.4.5version>
    dependency>
    <dependency>
      <groupId>log4jgroupId>
      <artifactId>log4jartifactId>
      <version>1.2.17version>
    dependency>
  dependencies>

  <build>
    <pluginManagement>
      <plugins>
        
        <plugin>
          <artifactId>maven-clean-pluginartifactId>
          <version>3.1.0version>
        plugin>
        
        <plugin>
          <artifactId>maven-resources-pluginartifactId>
          <version>3.0.2version>
        plugin>
        <plugin>
          <artifactId>maven-compiler-pluginartifactId>
          <version>3.8.0version>
        plugin>
        <plugin>
          <artifactId>maven-surefire-pluginartifactId>
          <version>2.22.1version>
        plugin>
        <plugin>
          <artifactId>maven-jar-pluginartifactId>
          <version>3.0.2version>
        plugin>
        <plugin>
          <artifactId>maven-install-pluginartifactId>
          <version>2.5.2version>
        plugin>
        <plugin>
          <artifactId>maven-deploy-pluginartifactId>
          <version>2.8.2version>
        plugin>
        
        <plugin>
          <artifactId>maven-site-pluginartifactId>
          <version>3.7.1version>
        plugin>
        <plugin>
          <artifactId>maven-project-info-reports-pluginartifactId>
          <version>3.0.0version>
        plugin>
      plugins>
    pluginManagement>
  build>
project>

主要是dependences，导入junit，mysql，mybatis以及log4j的jar包。

（2）编写domain和dao代码，注意mysql中必须有对应的表：

package com.ahu.cs.domain;

import java.io.Serializable;
import java.util.Date;

public class User implements Serializable {

    private Integer id;
    private String userName;
    private Date birthday;
    private String sex;
    private String address;

    public Integer getId() {
        return id;
    }

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

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", userName='" + userName + '\'' +
                ", birthday=" + birthday +
                ", sex='" + sex + '\'' +
                ", address='" + address + '\'' +
                '}';
    }
}

package com.ahu.cs.dao;

import com.ahu.cs.domain.User;

import java.util.List;

public interface UserDao {

    List findAll();
}

（3）在resources目录下创建SqlMapConfig.xml，编写mybatis的连接配置文件：

<?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>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC">transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis01" />
                <property name="username" value="root" />
                <property name="password" value="123456" />
            dataSource>
        environment>
    environments>
    <mappers>
        <mapper resource="com/ahu/cs/dao/UserDao.xml" />
    mappers>
configuration>

其中default可以随便起，但是必须和下面的environment的id相同。标签配置映射器，其中resource属性配置该映射文件的位置。

（4）配置映射器文件：

<?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.ahu.cs.dao.UserDao">
    <select id="findAll" resultType="com.ahu.cs.domain.User">
        select * from user
    select>
mapper>

其中namespace写dao接口的全限定名，id属性是接口中的方法名，resultType是结果集类型。

（5）测试代码：

package com.ahu.cs;

import com.ahu.cs.dao.UserDao;
import com.ahu.cs.domain.User;
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.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

/**
 * Unit test for simple App.
 */
public class AppTest 
{
    public static void main(String[] args) throws IOException {
        // 读取配置文件
        InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
        // 获取工厂
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(in);
        // 获取SqlSession
        SqlSession session = factory.openSession();
        // 获取dao接口的实例对象
        UserDao dao = session.getMapper(UserDao.class);
        // 调用方法
        List users = dao.findAll();
        for(User u: users) {
            System.out.println(u);
        }

    }
}

最后配上一张目录结构图：