Mybatis 基本使用

工程结构：

　　

1、在test库创建表student（MySql数据库）

2、创建实体类Student.java

package com.gdut.testMybatis.vo;

public class Student {
    private int id;
    private String name;
    
    public Student() {
        super();
    }
    public Student(int id, String name) {
        this.id = id;
        this.name = name;
    }
    
    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;
    }
    
    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + "]";
    }

}

3、写Dao接口

package com.gdut.testMybatis.dao;

import java.util.List;
import java.util.Map;

import com.gdut.testMybatis.vo.Student;

public interface IStudentDao {
    void insertStudent(Student student); //添加
     
    void insertStudentCacheId(Student student);//添加并返回此学生id
 
    void deleteStudentById(int id);//删除学生
 
    void updateStudentById(Student student);//修改学生
 
    List<Student> selectAllStudents();//查询所有学生，返回List
 
    Map<String, Object> selectAllStudentsMap();//查询所有学生，返回Map
 
    Student selectById(int id);//根据id查询
 
    List<Student> selectByName(String name);//根据name查询

}

4、配置studentMapper.xml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.gdut.testMybatis.dao.IStudentDao">
     <insert id="insertStudent" parameterType="Student"><!-- mapper动态代理。其底层自动实现Dao接口 -->
         insert into student(id,name) values(#{id}, #{name})
         <!-- name是表字段，#{name}这个name是属性，mybatis会自动添加get方法获取属性值，不是成员变量 -->
     </insert>
 
 
     <insert id="insertStudentCacheId" parameterType="Student">
         insert into student(id,name) values(#{id},#{name})
         <!-- mysql:AFTER  oracle：BEFORE  mysql是先插入后有id -->
         <selectKey resultType="int" keyProperty="id" order="AFTER"> 
             select @@identity
         </selectKey>
     </insert>
 
 
    <delete id="deleteStudentById">
        delete from student where id = #{xxx}   <!-- 这块的#{}仅仅是一个占位符，可以随便指定值 -->
    </delete>     
    
    <update id="updateStudentById" parameterType="Student">
        update student set name=#{name} where id=#{id}
    </update>
    
    <select id="selectAllStudents" resultType="Student">
        select id,name from student 
    </select>
    
    <select id="selectById" resultType="Student">
        select id,name from student where id=#{id}
    </select>
    
    <select id="selectByName" resultType="Student">
        <!-- 推荐使用这种 -->
         select id,name from student where name like '%' #{xxx} '%'    
         <!-- select id,name,age,score from student where name like concat('%',#{xxx},'%') -->
         <!-- 这种不建议使用，这种使用statement查询方式，有sql注入风险 -->
         <!-- select id,name,age,score from student where name like '%${value}%' --> 
    </select>
     
 </mapper>

5、mybatis.xml主配置文件

<?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>
    <!-- 别名 -->
    <typeAliases>
        <!-- <typeAlias type="com.gdut.testMybatis.vo.Student" alias="Student"/> -->
        <package name="com.gdut.testMybatis.vo"/>
    </typeAliases>
 
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <!-- 配置数据库连接信息 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/test" />
                <property name="username" value="数据库用户名" />
                <property name="password" value="数据库密码" />
            </dataSource>
        </environment>
    </environments>
    
    <!-- 配置映射文件 -->
    <mappers>
        <mapper resource="com/gdut/testMybatis/dao/studentMapper.xml"/>
    </mappers>
</configuration>

6、编写utils类，用于创建SqlSession

package com.gdut.testMybatis.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 MyBatisUtils {
     
    private static SqlSessionFactory sqlSessionFactory;
 
    public static SqlSession getSqlSession() {
        try {
            InputStream inputStream = Resources.getResourceAsStream("mybatis.xml");
            if (sqlSessionFactory == null) {
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); //build()方法会把inputStream关闭掉
            } else {
                inputStream.close();
            }
            return sqlSessionFactory.openSession();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }
}

7、测试类Test1.java

package com.gdut.testMybatis;

import java.util.List;

import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.gdut.testMybatis.dao.IStudentDao;
import com.gdut.testMybatis.util.MyBatisUtils;
import com.gdut.testMybatis.vo.Student;

public class Test1 {
    IStudentDao dao;
     
    SqlSession  sqlSession;
 
    @Before
    public void before() {
        sqlSession = MyBatisUtils.getSqlSession();
        dao = sqlSession.getMapper(IStudentDao.class);
    }
 
    @After
    public void after() {
        if (sqlSession != null) {
            sqlSession.close();
        }
    }
 
    @Test
    public void test01() {
        Student student = new Student(4, "学生4");
        dao.insertStudent(student);
        sqlSession.commit();
    }
 
    @Test
    public void test02() {
        Student student = new Student(5, "学生5");
        System.out.println("插入前：" + student);
        dao.insertStudentCacheId(student);
        sqlSession.commit();
        System.out.println("插入后：" + student);
    }
 
    @Test
    public void test03() {
        dao.deleteStudentById(13);
        sqlSession.commit();
    }
 
    @Test
    public void test04() {
        Student student = new Student(4, "学生4-1" );
        student.setId(19);
        dao.updateStudentById(student);
        sqlSession.commit();
    }
 
    @Test
    public void test05() {
        List<Student> students = dao.selectAllStudents();
        for (Student student : students) {
            System.out.println(student);
        }
    }
 
    /* @Test
     public void test06() {
         Map<String, Object> map = dao.selectAllStudentsMap();
         System.out.println(map.get("张三"));
     }*/
 
    @Test
    public void test07() {
        Student student = dao.selectById(7);
        System.out.println(student);
    }
 
    @Test
    public void test08() {
        List<Student> students = dao.selectByName("学生3");
        for (Student student : students) {
            System.out.println(student);
        }
    }
}

配置文件默认都在类路径下面，即src文件夹下。

mapper.xml则是与Dao放在相同位置