三、Mybatis基本应用
1.快速入门
MyBatis官网地址： http://www.mybatis.org/mybatis-3/
1.1 开发步骤：
①添加MyBatis的坐标
②创建user数据表
③编写User实体类
④编写映射文件UserMapper.xml
⑤编写核心文件SqlMapConfig.xml
⑥编写测试类
1.2 环境搭建：
1)导入MyBatis的坐标和其他相关坐标
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.cookie</groupId>
<artifactId>mybatis-quickstart</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.encoding>UTF-8</maven.compiler.encoding>
<java.version>1.8</java.version>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
<dependencies>
<!--mybatis坐标-->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.4.5</version>
</dependency>
<!--mysql驱动坐标-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.6</version>
<scope>runtime</scope>
</dependency>
<!--单元测试坐标-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
<!--⽇志坐标-->
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.12</version>
</dependency>
</dependencies>
</project>
2)创建user数据表
CREATE TABLE `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(50) DEFAULT NULL,
`password` varchar(50) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;
3)编写User实体
package com.cookie.pojo;
public class User {
private Integer id;
private String username;
private String password;
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 String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
'}';
}
}
4)编写UserMapper映射文件
<?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="userMapper">
<!--namespace ：命名空间：与id组成sql的唯一标识-->
<!--resultType：表明返回值类型-->
<select id="findAll" resultType="com.cookie.pojo.User">
select * from user
</select>
</mapper>
5)编写MyBatis核心文件
<?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="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql:///test"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="UserMapper.xml"/>
</mappers>
</configuration>
6）编写测试代码
package com.cookie.test;
import com.cookie.pojo.User;
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 org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
public class MybatisTest {
@Test
public void test1() throws IOException {
//加载核⼼配置文件
InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
List<User> userList = sqlSession.selectList("userMapper.findAll");
System.out.println(userList);
sqlSession.close();
}
}
1.3 MyBatis的增删改查操作
MyBatis的插入数据操作：
1)编写UserMapper映射文件
<!--添加-->
<insert id="add" parameterType="com.cookie.pojo.User">
insert into user values(#{id},#{username},#{password})
</insert>
2)编写插入实体User的代码
@Test
public void test2() throws IOException {
InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
User user = new User();
user.setId(3);
user.setUsername("cookie");
user.setPassword("123456");
int insert = sqlSession.insert("userMapper.add", user);
System.out.println(insert);
//提交事务
sqlSession.commit();
sqlSession.close();
}
插入操作注意的问题：
- 插入语句使用insert标签
- 在映射文件中使用parameterType属性指定要插入的数据类型
- Sql语句中使用#{实体属性名}方式引用实体中的属性值
- 插入操作使用的API是sqlSession.insert(“命名空间.id”,实体对象);
- 插入操作涉及数据库数据变化，所以要使用sqlSession对象显示的提交事务，即sqlSession.commit()
MyBatis的修改数据操作
1)编写UserMapper映射文件
<!--修改-->
<update id="update" parameterType="com.cookie.pojo.User">
update user set username = #{username},password = #{password} where id = #{id}
</update>
2)编写修改实体User的代码
@Test
public void test3() throws IOException {
InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
User user = new User();
user.setId(3);
user.setUsername("cookies");
user.setPassword("1234567");
int update = sqlSession.update("userMapper.update", user);
System.out.println(update);
//提交事务
sqlSession.commit();
sqlSession.close();
}
3)修改操作注意问题
- 修改语句使用update标签
- **修改操作使用的API是sqlSession.update(“命名空间.id”,实体对象); **
MyBatis的删除数据操作：
1)编写UserMapper映射文件
<!--删除-->
<delete id="delete" parameterType="java.lang.Integer">
delete from user where id = #{id}
</delete>
2)编写删除数据的代码
@Test
public void test4() throws IOException {
InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
int delete = sqlSession.delete("userMapper.delete",3);
System.out.println(delete);
//提交事务
sqlSession.commit();
sqlSession.close();
}
3)删除操作注意问题
- 删除语句使用delete标签
- Sql语句中使用#{任意字符串}方式引用传递的单个参数
- 删除操作使用的API是sqlSession.delete(“命名空间.id”,Object);
- 删除操作使用的API是sqlSession.delete(“命名空间.id”,Object);
1.4 MyBatis相应API介绍
SqlSession工厂构建器SqlSessionFactoryBuilder：
常用API： SqlSessionFactory build(InputStream inputStream)
通过加载mybatis的核心文件的输入流的形式构建一个SqlSessionFactory对象
String resource = "org/mybatis/builder/mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
SqlSessionFactory factory = builder.build(inputStream);
其中， Resources 工具类，这个类在 org.apache.ibatis.io 包中。 Resources 类帮助从类路径下、文件系统或一个 web URL 中加载资源文件。
SqlSession工厂对象SqlSessionFactory：
SqlSessionFactory 有多个方法创建SqlSession 实例。常用的有如下两个：
SqlSession会话对象：
SqlSession 实例在 MyBatis 中是非常强大的一个类。会看到所有执行语句、提交或回滚事务和获取映射器实例的方法。执行语句的方法主要有：
<T> T selectOne(String statement, Object parameter)
<E> List<E> selectList(String statement, Object parameter)
int insert(String statement, Object parameter)
int update(String statement, Object parameter)
int delete(String statement, Object parameter)
操作事务的方法主要有：
void commit()
void rollback()
2.Mybatis的DAO层实现
2.1 传统开发方式
编写UserDao接口
package com.cookie.dao;
import com.cookie.pojo.User;
import java.io.IOException;
import java.util.List;
public interface UserDao {
//查询所有
List<User> findAll() throws IOException;
}
编写UserDaoImpl实现
package com.cookie.dao.impl;
import com.cookie.dao.UserDao;
import com.cookie.pojo.User;
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 java.io.IOException;
import java.io.InputStream;
import java.util.List;
public class UserDaoImpl implements UserDao {
@Override
public List<User> findAll() throws IOException {
InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
List<User> userList = sqlSession.selectList("userMapper.findAll");
sqlSession.close();
return userList;
}
}
测试传统方式：
@Test
public void test5() throws IOException {
UserDao userDao = new UserDaoImpl();
List<User> users = userDao.findAll();
for (User user : users) {
System.out.println(user);
}
}
2.2 代理开发方式
代理开发方式介绍：
采用Mybatis的代理开发方式实现 DAO 层的开发，这种方式是企业的主流开发方式。
Mapper 接口开发方法只需要程序员编写Mapper 接口（相当于Dao 接口），由Mybatis 框架根据接口定义创建接口的动态代理对象，代理对象的方法体同上边Dao接口实现类方法。
Mapper 接口开发需要遵循以下规范：
1) Mapper.xml文件中的namespace与mapper接口的全限定名相同
2) Mapper接口方法名和Mapper.xml中定义的每个statement的id相同
3) Mapper接口方法的输入参数类型和mapper.xml中定义的每个sql的parameterType的类型相同
4) Mapper接口方法的输出参数类型和mapper.xml中定义的每个sql的resultType的类型相同** **
编写UserMapper接口：
package com.cookie.mapper;
import com.cookie.pojo.User;
import java.util.List;
public interface UserMapper {
List<User> findAll();
}
Mapper配置文件：
<?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="com.cookie.mapper.UserMapper">
<!--namespace ：命名空间：与id组成sql的唯一标识-->
<!--resultType：表明返回值类型-->
<select id="findAll" resultType="com.cookie.pojo.User">
select * from user
</select>
<!--添加-->
<insert id="add" parameterType="com.cookie.pojo.User">
insert into user values(#{id},#{username},#{password})
</insert>
<!--修改-->
<update id="update" parameterType="com.cookie.pojo.User">
update user set username = #{username},password = #{password} where id = #{id}
</update>
<!--删除-->
<delete id="delete" parameterType="java.lang.Integer">
delete from user where id = #{id}
</delete>
</mapper>
<?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="development">
<environment id="development">
<!--当前事务交给JDBC处理-->
<transactionManager type="JDBC"/>
<!--当前使用mybatis提供的连接池-->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql:///test"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<!--引入映射配置文件-->
<mappers>
<mapper resource="UserMapper.xml"/>
<mapper resource="UserMapperProxy.xml"/>
</mappers>
</configuration>
测试代理方式：
@Test
public void testProxy() throws IOException {
InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> users = mapper.findAll();
for (User user : users) {
System.out.println(user);
}
}