mybatis学习之入门实例

测试版本

mybatis：3.2.8

数据库：mysql

项目结构





jar包准备

mybatis-3.2.8.jar

mysql-connector-java-5.1.39-bin.jar

junit-4.4.jar

log4j-1.2.17.jar

配置文件

1、jdbc.properties配置文件：

jdbc.driverClassName = com.mysql.jdbc.Driver
jdbc.url = jdbc:mysql://127.1.0.1:3306/db_mybatis
jdbc.username=root
jdbc.password=root

2、mybatis主要配置文件，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 type="com.cz.model.Student" alias="Student"/>        <!-- 类型别名 -->
</typeAliases>

<environments default="development">        <!-- 默认开发环境 -->
<environment id="development">
<transactionManager type="JDBC"></transactionManager>
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driverClassName}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</dataSource>
</environment>
</environments>

<mappers>
<mapper resource="com/cz/mappers/StudentMapper.xml"/>
</mappers>

</configuration>

其中typeAliases是为了指定类型别名，这样使用到com.cz.model.Student类时直接使用Student代替即可。

创建SqlSessionFactoryUtil工具类

该工具类主要是加载mybatis配置文件并通过相应的builder生成session工厂，再从工厂产生sql session对象，这里使用到了单例设计模式（懒汉式）：

package com.cz.utill;

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 {

private static SqlSessionFactory sqlSessionFactory;

private SqlSessionFactoryUtil() {}

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

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

创建实体映射类

实体类Student.java，这里只有三个属性：

package com.cz.model;

public class Student {

private Integer id;
private String name;
private int age;

public Student(String name, int age) {
super();
this.name = name;
this.age = age;
}

public Student() {
super();
}

public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}

}

编写Dao接口

mybatis支持传统的类似hibernate的Dao层封装数据库操作，也支持面向mapper.xml映射文件的动态sql类型，如果使用传统的Dao数据库编程模型的话，需要在相应的Dao类中注入sql session工厂对象（一般通过构造注入），这里使用后一种方式即mapper配置：

package com.cz.mappers;

import java.util.List;

import com.cz.model.Student;

public interface StudentDao {
/**
* 新增
* @param student
* @return
*/
public int add(Student student);
/**
* 修改
* @param student
* @return
*/
public int update(Student student);
/**
* 删除
* @param student
* @return
*/
public int delete(Integer id);
/**
* 根据id查找
* @param id
* @return
*/
public Student findById(Integer id);
/**
* 查找
* @param id
* @return
*/
public List<Student> find();
}

mapper.xml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">
<mapper namespace="com.cz.mappers.StudentDao">

<resultMap type="Student" id="StudentResult">
<result property="id" column="id"/>
<result property="name" column="name"/>
<result property="age" column="age"/>
</resultMap>

<!-- 插入 -->
<insert id="add" parameterType="Student">
insert into t_student values(null,#{name},#{age})
</insert>

<update id="update" parameterType="Student">
update t_student set name = #{name},age = #{age} where id = #{id}
</update>

<delete id="delete" parameterType="Integer">
delete from t_student where id = #{id}
</delete>

<select id="findById" resultMap="StudentResult" parameterType="Integer">
select * from t_student where id = #{id}
</select>

<select id="find" resultMap="StudentResult">
select * from t_student
</select>
</mapper>

dao接口跟mapper文件的对应关系如下：



添加log4j日志记录

添加jar包：log4j-1.2.17.jar

编写测试类StudentServiceTest.java：

package com.cz.service;

import org.apache.ibatis.session.SqlSession;
import org.apache.log4j.Logger;

import com.cz.mappers.StudentDao;
import com.cz.model.Student;
import com.cz.utill.SqlSessionFactoryUtil;

public class StudentServiceTest {

public static Logger logger = Logger.getLogger(StudentServiceTest.class);

public static void main(String[] args) {

SqlSession sqlSession = SqlSessionFactoryUtil.openSession();
StudentDao studentDao = sqlSession.getMapper(StudentDao.class);        //返回student dao接口
int result = studentDao.add(new Student("张三", 20));
sqlSession.commit();
if (result > 0) {
logger.info("测试成功");
}
}

}

使用junit单元测试

添加junit-4.4.jar，单元测试代码：

package com.cz.test;

import java.util.Iterator;
import java.util.List;

import org.apache.ibatis.session.SqlSession;
import org.apache.log4j.Logger;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.cz.mappers.StudentDao;
import com.cz.model.Student;
import com.cz.utill.SqlSessionFactoryUtil;

public class StudentTest {

public static Logger logger = Logger.getLogger(StudentTest.class);
SqlSession sqlSession = null;
StudentDao studentDao = null; // 返回student dao接口

@Before
public void setUp() throws Exception {
sqlSession = SqlSessionFactoryUtil.openSession();
studentDao = sqlSession.getMapper(StudentDao.class);
logger.info("开始执行了");
}

@After
public void tearDown() throws Exception {
sqlSession.close();
logger.info("执行结束了");
}

@Test
public void testAdd() throws Exception {
Student student = new Student("admin", 22);
int result = studentDao.add(student);
sqlSession.commit();
if (result > 0) {
logger.info("添加成功了");
}
}

@Test
public void testUpdate() throws Exception {
Student student = new Student(24, "xxxxxxx", 21);
int result = studentDao.update(student);
sqlSession.commit();
if (result > 0) {
logger.info("修改成功了");
}
}

@Test
public void testDelete() throws Exception {
int result = studentDao.delete(26);
sqlSession.commit();
if (result > 0) {
logger.info("删除成功了");
}
}

@Test
public void testFindById() throws Exception {
Student student = studentDao.findById(25);
System.out.println(student.toString());
sqlSession.commit();
}

@Test
public void testFind() throws Exception {
List<Student> students = studentDao.find();
// Iterator<Student> iterator = students.iterator();
// while (iterator.hasNext()) {
// System.out.println(iterator.next());
// }
// for(Student s:students){
// System.out.println(s.toString());
// }
Student student = null;
for (int i = 0; i < students.size(); i++) {
student = students.get(i);
System.out.println(student.toString());
}
sqlSession.commit();
}
}

测试结果：