一个简单的MyBatis程序实例

1、在test库创建表student（MySql数据库）

CREATE TABLE `student` (

  `id` int(5) NOT NULL AUTO_INCREMENT,

  `name` varchar(10) DEFAULT NULL,

  `age` int(3) DEFAULT NULL,

  `score` double DEFAULT NULL,

  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=gbk;

2、创建实体类Student.java

public class Student {
private Integer id;   //成员变量【私有的，不暴露给外面】
private String  name;
private int     age;
private double  score;

public Student() {
super();
}

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

public Integer getId() {//属性【暴露给外面的】，方法名可以是getXxx等
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;
}

public double getScore() {
return score;
}

public void setScore(double score) {
this.score = score;
}

@Override
public String toString() {
return "Student [id=" + id + ", name=" + name + ", age=" + age + ", score=" + score + "]";
}

}

3、写Dao接口

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mapper.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.xin.mybatis.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(name,age,score) values(#{name}, #{age}, #{score})
<!-- 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(name,age,score) values(#{name}, #{age}, #{score})
<!-- 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},age=#{age},score=#{score} where id=#{id}
</update>

<select id="selectAllStudents" resultType="Student">
select id,name,age,score from student
</select>

<select id="selectById" resultType="Student">
select id,name,age,score from student where id=#{id}
</select>

<select id="selectByName" resultType="Student">
<!-- 推荐使用这种 -->
select id,name,age,score 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>
<!-- 读取加载配置文件信息 -->
<properties resource="jdbc.properties"/>

<!-- 别名 -->
<typeAliases>
<!-- <typeAlias type="com.xin.mybatis.beans.Student" alias="Student"/> -->
<package name="com.xin.mybatis.beans"/>
</typeAliases>

<!-- 配置环境变量，可以配置多个，有默认值 -->
<environments default="local">
<environment id="local">
<transactionManager type="JDBC" />	<!-- 事务 -->
<dataSource type="POOLED">			<!-- 数据源  连接池POOLED -->
<property name="driver" value="${jdbc.driver.local}"/>
<property name="url" value="${jdbc.url.local}"/>
<property name="username" value="${jdbc.username.local}"/>
<property name="password" value="${jdbc.password.local}"/>
</dataSource>
</environment>
<environment id="online">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</dataSource>
</environment>
</environments>

<!-- 配置映射文件 -->
<mappers>
<mapper resource="com/xin/mybatis/dao/mapper.xml"/>
</mappers>
</configuration>

6、编写jdbc.properties文件

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

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://192.168.1.10/online
jdbc.username=query
jdbc.password=xxx

7、编写utils类，用于创建SqlSession

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;
}
}

8、测试类MyTest.java

public class MyTest {
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("张三", 23, 93.5);
dao.insertStudent(student);
sqlSession.commit();
}

@Test
public void test02() {
Student student = new Student("张三", 23, 93.5);
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("王五", 25, 95.5);
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("张");
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