MyBatis入門示例

說明：

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

2， 以持久化一個簡單的User bean為例

User實體類的代碼如下：

1. package bean;
2.  
3. publicclass User {
4.     private String name;
5.     private Integer age;
6.    
7.     public String getName() {
8.       return name;
9.     }
10.     publicvoid setName(String name) {
11.       this.name = name;
12.     }
13.     public Integer getAge() {
14.       return age;
15.     }
16.     publicvoid 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.     }
24.    
25.     public User() {
26.       super();
27.     }  //必須要有這個無參構造方法，不然根據UserMapper.xml中的配置，在查詢數據庫時，將不能反射構造出User實例
28. }

User實體的映射器取名為UserMapper(接口)，其代碼如下

1. package Mapper;
2. import bean.User;
3. publicinterface UserMapper {
4. publicvoid insertUser(User user);
5. public User getUser(String name);
6. }

注意，該接口類似於Hibernate中的DAO層接口，唯一不同的是，MyBatis中，只聲明該接口就可以，不需要去實現.

UserMapper映射器對應的配置文件如下(相當於Hibernate中的User.hbm.xml,當然這裡面不是屬性映射字段，而是直接是映射器中各種方法對應的sql語句)：

1. <?xmlversion="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. <mappernamespace="Mapper.UserMapper">
6. <!-- 這裡namespace必須是UserMapper接口的路徑，不然要運行的時候要報錯 “is not known to the MapperRegistry”-->
7. <insertid="insertUser"parameterType="User">
8. insert into vincent_user(name,age) values(#{name},#{age})
9. <!-- 這裡sql結尾不能加分號，否則報“ORA-00911”的錯誤 -->
10. </insert>
11. <!-- 這裡的id必須和UserMapper接口中的接口方法名相同，不然運行的時候也要報錯 -->
12. <selectid="getUser"resultType="User"parameterType="java.lang.String">
13. select * from vincent_user where name=#{name}
14. </select>
15. </mapper>

MyBatis的配置文件這裡取名為mybatis-config.xml其配置代碼如下(相當與Hibernate的hibernate.cfg.xml):

1. <?xmlversion="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">
5. <configuration>
6. <settings>
7. <!-- changes from the defaults for testing -->
8. <settingname="cacheEnabled"value="false"/>
9. <settingname="useGeneratedKeys"value="true"/>
10. <settingname="defaultExecutorType"value="REUSE"/>
11. </settings>
12. <typeAliases>
13. <typeAliasalias="User"type="bean.User"/>
14. </typeAliases>
15. <environmentsdefault="development">
16. <environmentid="development">
17. <transactionManagertype="jdbc"/>
18. <dataSourcetype="POOLED">
19. <propertyname="driver"value="Oracle.jdbc.driver.OracleDriver"/>
20. <propertyname="url"value="jdbc:oracle:thin:@192.168.56.201:1521:system"/>
21. <propertyname="username"value="vincent"/>
22. <propertyname="password"value="1234"/>
23. </dataSource>
24. </environment>
25. </environments>
26. <mappers>
27. <mapperresource="resource/UserMapper.xml"/>
28. </mappers>
29. </configuration>

加載配置文件得到sqlSessionFactory的工具類

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

測試代碼如下：

1. package TestMapper;
2. import org.apache.ibatis.session.SqlSession;
3. import org.apache.ibatis.session.SqlSessionFactory;
4. import org.junit.Test;
5. publicclass TestMapper {
6. static SqlSessionFactory sqlSessionFactory = null;
7. static {
8. sqlSessionFactory = MyBatisUtil.getSqlSessionFactory();
9. }
10. @Test
11. publicvoid testAdd() {
12. SqlSession sqlSession = sqlSessionFactory.openSession();
13. try {
14. UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
15. User user = new User("tom",new Integer(5));
16. userMapper.insertUser(user);
17. sqlSession.commit();//這裡一定要提交，不然數據進不去數據庫中
18. } finally {
19. sqlSession.close();
20. }
21. }
22. @Test
23. publicvoid getUser() {
24. SqlSession sqlSession = sqlSessionFactory.openSession();
25. try {
26. UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
27. User user = userMapper.getUser("jun");
28. System.out.println("name: "+user.getName()+"|age: "+user.getAge());
29. } finally {
30. sqlSession.close();
31. }
32. }
33. }

MyBatis 的詳細介紹：請點這裡
MyBatis 的下載地址：請點這裡

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