前面章节介绍了使用xml方式编写sql映射语句，实现对数据库的增删改查操作。本章将介绍另外一种方式，使用Java注解编写sql映射语句。
准备数据
在MYBATIS教程 – 环境搭建中，我们创建好了数据库，数据库中包含了一个用户表。
CREATE DATABASE IF NOT EXISTS `qikegu_mybatis`
USE `qikegu_mybatis`;
CREATE TABLE IF NOT EXISTS `user` (
`id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(50) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8 COMMENT='用户表';
INSERT INTO `user` (`id`, `name`) VALUES
(1, 'user1'),
(2, 'user2'),
(3, 'user3'),
(4, 'user4'),
(5, 'user5');
User 类
创建一个对应的Java类：User.java
public class User {
private long id;
private String name;
public User(String name) {
super();
this.name = name;
}
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
UserMapper.java
在前面章节中，使用xml方式编写sql映射语句，映射文件是UserMapper.xml，类似的，使用注解方式，映射文件可命名为UserMapper.java。
UserMapper是一个接口，我们通过给接口函数加注解编写sql映射语句。
可比较一下注解方式与xml方式编写sql映射语句的异同
UserMapper.java
public interface UserMapper {
final String getAll = "SELECT * FROM User";
final String getById = "SELECT * FROM User WHERE id = #{id}";
final String deleteById = "DELETE from User WHERE id = #{id}";
final String insert = "INSERT INTO User (name) VALUES (#{name})";
final String update = "UPDATE User SET name = #{name} WHERE id = #{id}";
@Select(getAll)
@Results(value = {
@Result(property = "id", column = "id"),
@Result(property = "name", column = "name")
})
List<User> getAll();
@Select(getById)
@Results(value = {
@Result(property = "id", column = "ID"),
@Result(property = "name", column = "NAME")
})
User getById(long id);
@Update(update)
void update(User user);
@Delete(deleteById)
void delete(long id);
@Insert(insert)
@Options(useGeneratedKeys = true, keyProperty = "id")
void insert(User user);
}
修改MybatisConfig.xml中的mapper标签
MybatisConfig.xml中的<mapper>指向映射文件位置，按如下修改：
<mappers>
<mapper class = "com.qikegu.demo.mapper.UserMapper"/>
</mappers>
App.java
应用程序main类文件。
package com.qikegu.demo;
import java.io.IOException;
import java.io.Reader;
import java.util.List;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import com.qikegu.demo.mapper.UserMapper;
public class App {
public static void main(String args[]) throws IOException {
Reader reader = Resources.getResourceAsReader("MybatisConfig.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
SqlSession session = sqlSessionFactory.openSession();
UserMapper mapper = session.getMapper(UserMapper.class);
System.out.println("------------ 数据插入 -----------");
// 创建用户对象
User user = new User("newUser100");
// 插入新用户到数据库
mapper.insert(user);
session.commit();
System.out.println("数据插入成功");
System.out.println("------------ 读取用户列表 -----------");
List<User> userList = mapper.getAll();
for (User u : userList) {
System.out.println(u.getId());
System.out.println(u.getName());
}
System.out.println("读取用户列表成功");
System.out.println("------------ 读取用户详情 -----------");
User user1 = (User) mapper.getById(user.getId());
System.out.println(user1.getId());
System.out.println(user1.getName());
System.out.println("读取用户详情成功");
System.out.println("------------ 修改用户 -----------");
user1.setName("userNameUpdated");
mapper.update(user1);
session.commit();
// 查询修改后的用户详情
User user2 = (User) mapper.getById(user.getId());
System.out.println(user2.getId());
System.out.println(user2.getName());
System.out.println("修改用户成功");
System.out.println("------------ 删除用户 -----------");
mapper.delete(user.getId());
System.out.println("删除用户成功");
session.commit();
session.close();
}
}
运行
运行结果：
------------ 数据插入 -----------
数据插入成功
------------ 读取用户列表 -----------
1
user1
2
userNameUpdated
3
user3
4
user4
5
user5
6
newUser100
8
newUser100
9
newUser100
10
newUser100
11
newUser100
12
newUser100
13
newUser100
14
newUser100
读取用户列表成功
------------ 读取用户详情 -----------
14
newUser100
读取用户详情成功
------------ 修改用户 -----------
14
userNameUpdated
修改用户成功
------------ 删除用户 -----------
删除用户成功