mybatis基础入门
一.Mybatis介绍
Mybatis是一个优秀的基于java的持久层框架，它内部封装了jdbc，使开发者只需要关注sql语句本身，而不需要花费精力去处理加载驱动、创建连接、创建statement等繁杂的过程。
mybatis通过xml或注解的方式将要执行的各种statement配置起来，并通过java对象和statement中sql的动态参数进行映射生成最终执行的sql语句，最后由mybatis框架执行sql并将结果映射为java对象并返回。
采用ORM思想解决了实体和数据库映射的问题，对jdbc进行了封装，屏蔽了jdbc api底层访问细节，使我们不用和jdbc api打交道就可以完成对数据库的持久化操作。
二.mybatis环境搭建
第一步：创建maven工程，导入坐标
<dependencies>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.32</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.2.8</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.6.4</version>
</dependency>
</dependencies>
第二步：创建实体类和dao层接口
实体类:
public class User implements Serializable {
private Integer id;
private String username;
private Date birthday;
private String sex;
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", birthday=" + birthday +
", sex='" + sex + '\'' +
", address='" + address + '\'' +
'}';
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
private String address;
}
dao层接口
public interface IUserMapper {
//查询所有操作
List<User> findAll();
}
第三步：创建mybatis配置文件
SqlMapConfig.xml
<?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>
<environments default="mysql">
<environment id="mysql">
<transactionManager type="JDBC"></transactionManager>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/user "/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
<!-- 指定映射文件的位置 -->
<mappers>
<mapper resource="cn/fzkj/mapper/IUserMapper.xml"></mapper>
</mappers>
</configuration>
第四步：创建映射配置文件
IUserMapper.xml
<?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="cn.fzkj.mapper.IUserMapper">
<select id="findAll">
select * from user
</select>
</mapper>
注：1.映射配置文件的位置必须和dao接口的包结构相同，所以一般配置文件和dao层接口放在一个包下
2.xml中标签的id属性必须和dao层接口的方法名一致。
三.mybatis的CRUD操作
测试类中重复代码的抽取
private InputStream in;
private SqlSession session;
private IUserMapper userMapper;
@Before
public void init()throws Exception{
//1.读取配置文件
in = Resources.getResourceAsStream("mybatis/SqlMapConfig.xml");
//2.创建SqlSessionFactory工厂
SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
SqlSessionFactory factory = builder.build(in);
//3.使用工厂生产一个SqlSession对象
session = factory.openSession();
//4.使用sqlSession创建dao接口的代理对象
userMapper = session.getMapper(IUserMapper.class);
}
@After
public void destory()throws Exception{
//5.提交事务
session.commit();
//6.释放资源
session.close();
in.close();
}
1.保存操作
测试类
@Test
public void saveUser(){
User user = new User("ll",new Date(),"女","省");
userMapper.saveUser(user);
}
dao层接口
//插入用户
void saveUser(User user);
xml配置
<insert id="saveUser" parameterType="cn.fzkj.domain.User">//指明参数类型
insert into user (username,sex,birthday,address)
values(
#{username},
#{sex},
#{birthday},
#{address}
)
</insert>
用于获取保存操作之后的id值
<insert id="saveUser" parameterType="cn.fzkj.domain.User">
<!-- 获取新增返回的id -->
<selectKey keyProperty="id" keyColumn="id" resultType="java.lang.Integer" order="AFTER">
select last_insert_id();
</selectKey>
insert into user (username,sex,birthday,address)
values(
#{username},
#{sex},
#{birthday},
#{address}
)
</insert>
2.修改操作
测试类
@Test
public void updateUser(){
User user = new User("nh",new Date(),"女","dsaf");
user.setId(000);
userMapper.updateUser(user);
}
dao层接口
//修改用户
void updateUser(User user);
xml配置
<update id="updateUser" parameterType="cn.fzkj.domain.User">
update user set username=#{username},sex=#{sex},address=#{address},birthday=#{birthday} where id=#{id}
</update>
3.删除操作
测试类
@Test
public void delUser(){
userMapper.delUser(1111);
System.out.println("删除用户成功");
}
dao层接口
//删除用户
void delUser(Integer id);
xml配置
<delete id="delUser" parameterType="java.lang.Integer">
delete from user where id=#{id}
</delete>
4.查询操作
1.查询一个
测试类
@Test
public void findUserById(){
User user = userMapper.findUserById(1111);
System.out.println(user);
}
dao层接口
//按id查询
User findUserById(Integer id);
xml配置
<select id="findUserById" parameterType="java.lang.Integer" resultType="cn.fzkj.domain.User">//指明参数类型和返回值类型
select * from user where id=#{id}
</select>
2.模糊查询
测试类
@Test
public void findUserByName(){
List<User> users = userMapper.findUserByName("%m%");
for(User user : users){
System.out.println(user);
}
}
dao层接口
//按用户名模糊查询
List<User> findUserByName(String username);
xml配置
<select id="findUserByName" resultType="cn.fzkj.domain.User" parameterType="String">
select * from user where username like #{username}
</select>
查询操作的可扩展性很强，这里只举例，有待深入学习。
持续更新~~~
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