MyBatis入门示例

说明：

1，本文采用的Mybatis框架版本为： mybatis-3.0.4.jar

2， 以持久化一个简单的User bean为例

User实体类的代码如下：

1. package bean;
3. public class User {
4. private String name;
5. private Integer age;
7. public String getName() {
8. return name;
9. }
10. public void setName(String name) {
11. this.name = name;
12. }
13. public Integer getAge() {
14. return age;
15. }
16. public void setAge(Integer age) {
17. this.age = age;
18. }
19. public User(String name, Integer age) {
20. super();
21. this.name = name;
22. this.age = age;
23. }
25. public User() {
26. super();
27. } //必须要有这个无参构造方法，不然根据UserMapper.xml中的配置，在查询数据库时，将不能反射构造出User实例
28. }

User实体的映射器取名为UserMapper(接口)，其代码如下

1. package Mapper;
2. import bean.User;
4. public interface UserMapper {
5. public void insertUser(User user);
6. public User getUser(String name);
7. }

注意，该接口类似于Hibernate中的DAO层接口，唯一不同的是，MyBatis中，只声明该接口就可以，不需要去实现.

UserMapper映射器对应的配置文件如下(相当于Hibernate中的User.hbm.xml,当然这里面不是属性映射字段，而是直接是映射器中各种方法对应的sql语句)：

1. <?xml version="1.0" encoding="UTF-8" ?>
2. <!DOCTYPE mapper
3. PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
4. "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
5. <mapper namespace="Mapper.UserMapper">
6. <!-- 这里namespace必须是UserMapper接口的路径，不然要运行的时候要报错 “is not known to the MapperRegistry”-->
7. <insert id="insertUser" parameterType="User">
8. insert into vincent_user(name,age) values(#{name},#{age})
9. <!-- 这里sql结尾不能加分号，否则报“ORA-00911”的错误 -->
10. </insert>
11.  
12. <!-- 这里的id必须和UserMapper接口中的接口方法名相同，不然运行的时候也要报错 -->
13. <select id="getUser" resultType="User" parameterType="java.lang.String">
14. select * from vincent_user where name=#{name}
15. </select>
16. </mapper>

MyBatis的配置文件这里取名为mybatis-config.xml其配置代码如下(相当与Hibernate的hibernate.cfg.xml):

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE configuration
3. PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
4. "http://mybatis.org/dtd/mybatis-3-config.dtd">
6. <configuration>
7. <settings>
8. <!-- changes from the defaults for testing -->
9. <setting name="cacheEnabled" value="false" />
10. <setting name="useGeneratedKeys" value="true" />
11. <setting name="defaultExecutorType" value="REUSE" />
12. </settings>
13. <typeAliases>
14. <typeAlias alias="User" type="bean.User"/>
15. </typeAliases>
16. <environments default="development">
17. <environment id="development">
18. <transactionManager type="jdbc"/>
19. <dataSource type="POOLED">
20. <property name="driver" value="oracle.jdbc.driver.OracleDriver"/>
21. <property name="url" value="jdbc:oracle:thin:@192.168.56.201:1521:system"/>
22. <property name="username" value="vincent"/>
23. <property name="password" value="1234"/>
24. </dataSource>
25. </environment>
26. </environments>
27. <mappers>
28. <mapper resource="resource/UserMapper.xml" />
29. </mappers>
30. </configuration>

加载配置文件得到sqlSessionFactory的工具类

1. package Util;
3. import java.io.IOException;
4. import java.io.Reader;
6. import org.apache.ibatis.io.Resources;
7. import org.apache.ibatis.session.SqlSessionFactory;
8. import org.apache.ibatis.session.SqlSessionFactoryBuilder;
10. public class MyBatisUtil {
11. private final static SqlSessionFactory sqlSessionFactory;
12. static {
13. String resource = "resource/mybatis-config.xml";
14. Reader reader = null;
15. try {
16. reader = Resources.getResourceAsReader(resource);
17. } catch (IOException e) {
18. System.out.println(e.getMessage());
20. }
21. sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
22. }
24. public static SqlSessionFactory getSqlSessionFactory() {
25. return sqlSessionFactory;
26. }
27. }

测试代码如下：

1. package TestMapper;
2. import org.apache.ibatis.session.SqlSession;
3. import org.apache.ibatis.session.SqlSessionFactory;
4. import org.junit.Test;
6. public class TestMapper {
7. static SqlSessionFactory sqlSessionFactory = null;
8. static {
9. sqlSessionFactory = MyBatisUtil.getSqlSessionFactory();
10. }
12. @Test
13. public void testAdd() {
14. SqlSession sqlSession = sqlSessionFactory.openSession();
15. try {
16. UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
17. User user = new User("tom",new Integer(5));
18. userMapper.insertUser(user);
19. sqlSession.commit();//这里一定要提交，不然数据进不去数据库中
20. } finally {
21. sqlSession.close();
22. }
23. }
25. @Test
26. public void getUser() {
27. SqlSession sqlSession = sqlSessionFactory.openSession();
28. try {
29. UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
30. User user = userMapper.getUser("jun");
31. System.out.println("name: "+user.getName()+"|age: "+user.getAge());
32. } finally {
33. sqlSession.close();
34. }
35. }
37. }