MyBatis--HelloWorld

工具：MyEclipse

jar包：mybatis-3.4.4.jar,mysql-connector-java-5.1.7.bin.jar

项目目录：

步骤

一.新建数据源：jdbc.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/test
username=root
password=mysql

二.新建Mybatis配置文件：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>

  <properties resource="jdbc.properties"></properties>
  <typeAliases>
    <typeAlias alias="User" type="mybatis.model.User"/>
  </typeAliases>
  <environments default="development">
    <environment id="development">
      <transactionManager type="JDBC"/>
      <dataSource type="POOLED">
        <property name="driver" value="${driver}"/>
        <property name="url" value="${url}"/>
        <property name="username" value="${username}"/>
        <property name="password" value="${password}"/>
      </dataSource>
    </environment>
  </environments>
  <mappers>
    <mapper resource="mapper/UserMapper.xml"/>
  </mappers>
</configuration>

• typeAliases类型别名是Java 类型的简称。
  它仅仅只是关联到XML 配置，简写冗长的JAVA 类名。例如：

  
  
  
  
  

• mappers这里是告诉MyBatis 去哪寻找映射SQL 的语句。可以使用类路径中的资源引用，或者使用字符，输入确切的URL 引用，若不明白请继续看下文.

三.新建Model(POJO)(不必照搬，可自行对照数据库中的表)

package mybatis.model;

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;
    }

}

四.新建Dao

package mybaits.dao;

import mybatis.model.User;

public interface UserDao {
    public User getById(int id);
}

五.新建Mapper.xml

• 先在src目录中新建一个mapper文件夹

• 新建一个UserMapper.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="mybaits.dao.UserDao">
      <select id="getById" parameterType="int" resultType="User">
          select * from user where id=#{id}
      </select>
  </mapper>
  

• namesapce为mapper对应的类

• id为所调用的方法
• parameterType属性为传入的参数类型
• returnType为返回类型，如果前面mybatis-config.xml中的typeAliases没有写，就得写为 mybatis.model.User，这可以写User就是起别名的好处
• #{id}即读取传入的id值

六.创建SqlSessionFactoryUtil来读取配置文件和获取Session

package mybatis.util;

import java.io.IOException;
import java.io.InputStream;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

public class SqlSessionFactoryUtil {

    public static SqlSessionFactory sqlSessionFactory;

    public static SqlSessionFactory getSqlSessionFactory(){
        if(sqlSessionFactory==null){
            InputStream inputStream = null;
            try {
                //读取配置文件
                inputStream = Resources.getResourceAsStream("mybatis-config.xml");
                //创建SqlSessionFactory
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        return sqlSessionFactory;
    }

    public static SqlSession openSession(){
        return getSqlSessionFactory().openSession();
    }
}

七.运行

package mybatis.main;

import org.apache.ibatis.session.SqlSession;

import mybaits.dao.UserDao;
import mybatis.model.User;
import mybatis.util.SqlSessionFactoryUtil;

public class Main {
    public static void main(String[] args) {
        SqlSession session = SqlSessionFactoryUtil.openSession();
        UserDao userDao = session.getMapper(UserDao.class);
        User user = userDao.getById(1);
        System.out.println("Hello!"+user.getName());
    }
}