实验内容
在上一章中，实现了基于XML文件的方式对数据库表进行增删查改操作。
本次实验将使用基于注解的方式实现对数据库表的增删查改操作。
操作步骤
一、安装
添加Maven依赖（本文使用版本为3.4.6）
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>x.x.x</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.42</version>
</dependency>
二、创建数据库及表结构
CREATE TABLE `user` (
`id` bigint(11) unsigned NOT NULL AUTO_INCREMENT COMMENT '主键',
`username` varchar(32) NOT NULL COMMENT '用户名',
`password` varchar(64) NOT NULL COMMENT '密码',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
三、创建 Mybatis 配置文件
在 src/main/resources 目录下创建 mybatis-config.xml 文件，内容如下
与上一章不同的地方：可以注释掉对XML文件的注册
<configuration>
<properties resource="jdbc.properties"></properties>
<environments default="development">
<environment id="development">
<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>
<!-- 加载XML，同时加载接口类 -->
<mappers>
<mapper class="tutorial.mybatis.mapper.UserMapper"></mapper>
<!-- 可以注释掉，不使用XML文件，也可以两者混用 -->
<!-- <mapper resource="mybatis/User.xml"></mapper> -->
</mappers>
</configuration>
在 src/main/resources 目录下创建 jdbc.properties 文件，内容如下
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/tutorial_mybatis?characterEncoding=utf-8&useSSL=true
jdbc.username=root
jdbc.password=
四、创建实体类
创建包 tutorial.mybatis.model，并在该包下创建 User 类，内容如下
与上一章不同的地方：可以删除掉 Mapper.xml 文件
public class User {
private Long id;
private String username;
private String password;
// 省略 get / set 方法
}
五、创建接口类
创建包 tutorial.mybatis.mapper，并在该包下创建接口 UserMapper，内容如下
与上一章不同的地方：在接口类中使用注解的方式代替了XML文件中的SQL语句
public interface UserMapper {
@Results({
@Result(id = true, column = "id", property = "id", javaType = Long.class, jdbcType = JdbcType.BIGINT),
@Result(column = "username", property = "username", javaType = String.class, jdbcType = JdbcType.VARCHAR),
@Result(column = "password", property = "password", javaType = String.class, jdbcType = JdbcType.VARCHAR)
})
@Select("SELECT * FROM `user` WHERE id = #{id}")
User getUserById(Long id);
@Results({
@Result(id = true, column = "id", property = "id", javaType = Long.class, jdbcType = JdbcType.BIGINT),
@Result(column = "username", property = "username", javaType = String.class, jdbcType = JdbcType.VARCHAR),
@Result(column = "password", property = "password", javaType = String.class, jdbcType = JdbcType.VARCHAR)
})
@Select("SELECT * FROM `user`")
List<User> listAll();
@Insert("INSERT INTO `user` VALUES (#{id}, #{username}, #{username})")
int save(User user);
@Update("UPDATE `user` SET `username` = #{username}, `password` = #{password} where `id` = #{id}")
int updateById(User user);
@Delete("DELETE FROM `user` WHERE id = #{id}")
int deleteById(Long id);
@Delete("DELETE FROM `user`")
int deleteAll();
}
六、构建
准备工作就绪，开始最终章，创建启动类 MybatisConfig，内容如下：
public class MybatisConfig {
private static SqlSessionFactory sqlSessionFactory;
private static Reader reader;
static {
try {
reader = Resources.getResourceAsReader("mybatis-config.xml");
sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
} catch (Exception e) {
e.printStackTrace();
}
}
public static SqlSessionFactory getSession() {
return sqlSessionFactory;
}
public static void main(String[] args) throws IOException {
SqlSession session = sqlSessionFactory.openSession();
try {
init(session);
testInsert(session);
User user1 = testGet(session, 1L);
testUpdate(session, user1);
User user2 = testGet(session, 2L);
testDelete(session, user2);
} finally {
session.close();
}
}
private static void init(SqlSession session) {
UserMapper userMapper = session.getMapper(UserMapper.class);
userMapper.deleteAll();
}
public static void testInsert(SqlSession session) {
UserMapper userMapper = session.getMapper(UserMapper.class);
User user1 = new User() {{
setId(1L);
setUsername("admin");
setPassword("admin");
}};
User user2 = new User() {{
setId(2L);
setUsername("user");
setPassword("user");
}};
userMapper.save(user1);
userMapper.save(user2);
System.out.println("------- 数据添加完成，现有数据 --------");
testList(session);
}
public static void testUpdate(SqlSession session, User user) {
UserMapper userMapper = session.getMapper(UserMapper.class);
user.setPassword("12345678");
userMapper.updateById(user);
System.out.println("------- 修改ID为" + user.getId() + "的用户密码为12345678 --------");
testList(session);
}
public static void testDelete(SqlSession session, User user) {
UserMapper userMapper = session.getMapper(UserMapper.class);
userMapper.deleteById(user.getId());
System.out.println("------- 删除ID为" + user.getId() + "的用户 --------");
testList(session);
}
public static User testGet(SqlSession session, Long id) {
UserMapper userMapper = session.getMapper(UserMapper.class);
return userMapper.getUserById(id);
}
private static void testList(SqlSession session) {
UserMapper userMapper = session.getMapper(UserMapper.class);
List<User> list = userMapper.listAll();
if (list != null && !list.isEmpty()) {
for (User user : list) {
printUser(user);
}
}
}
private static void printUser(User user) {
String userInfo = "ID：" + user.getId() + "名字：" + user.getUsername()+", 密码：" + user.getPassword();
System.out.println(userInfo);
}
}
打印结果为：
------- 数据添加完成，现有数据 --------
ID：1名字：admin, 密码：admin
ID：2名字：user, 密码：user
------- 修改ID为1的用户密码为12345678 --------
ID：1名字：admin, 密码：12345678
ID：2名字：user, 密码：user
------- 删除ID为2的用户 --------
ID：1名字：admin, 密码：12345678
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