因为学校的要求,无奈学习java,本来是学前端的,今天学了mybatis,写篇博客加深印象
首先要下载mybatis,配置maven的pom.xml文件
<?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>Day5</groupId>
<artifactId>Day5</artifactId>
<version>1.0-SNAPSHOT</version>
<build>
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>false</filtering>
</resource>
</resources>
</build>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.2</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.15</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
</dependencies>
</project>
然后是配置mybatis.config.xml资源文件
<?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">
<!-- XML 配置文件包含对 MyBatis 系统的核心设置 -->
<configuration>
<environments default="mysql">
<!-- 环境配置,即连接的数据库。 -->
<environment id="mysql">
<!-- 指定事务管理类型,type="JDBC"指直接简单使用了JDBC的提交和回滚设置 -->
<transactionManager type="JDBC" />
<!-- dataSource指数据源配置,POOLED是JDBC连接对象的数据源连接池的实现。 -->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.cj.jdbc.Driver" />
<property name="url" value="jdbc:mysql://localhost:3306/db?serverTimezone=UTC" />
<property name="username" value="root" />
<property name="password" value="123456" />
</dataSource>
</environment>
</environments>
<!-- mappers告诉了MyBatis去哪里找持久化类的映射文件 -->
<mappers>
<mapper resource="Dao/UserMapper.xml" />
</mappers>
</configuration>
然后新建一个实体类User
public class User {
public String username;
public String password;
public void setUsername(String username) {
this.username = username;
}
public String getUsername() {
return username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public User(){
}
public User(String username,String password){
this.username=username;
this.password=password;
}
}
新建一个mybatisUtil工具类
public class mybatisUtil {
private static SqlSessionFactory sqlSessionFactory;
static {
try{
String resource="mybatis.config.xml";
InputStream inputStream= Resources.getResourceAsStream(resource);
sqlSessionFactory=new SqlSessionFactoryBuilder().build(inputStream);
}catch (Exception e){
e.printStackTrace();
}
}
public static SqlSession getSession(){
SqlSession sqlSession=sqlSessionFactory.openSession();
return sqlSession;
}
}
然后是新建一个UserDao接口
public interface UserDao {
//查找
public List<User> find();
public List<User> findByName(String username);
//新增
public void add(User user);
//删除
public void delete(String username);
//修改
public void update(User user);
}
以前的开发是再new一个接口的实现类,而mybatis则不用,新建一个xml文件即可在这个文件写sql语句
UserMapper.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="Dao.UserDao">
<select id="find" resultType="POJO.User">
select * from User;
</select>
<select id="findByName" parameterType="string" resultType="POJO.User">
select * from User where username=#{username}
</select>
<update id="add" parameterType="POJO.User">
insert into User values (#{username},#{password})
</update>
<delete id="delete" parameterType="string">
delete from user where username=#{username}
</delete>
<update id="update" parameterType="POJO.User">
update User set password=#{password} where username=#{username}
</update>
</mapper>
然后就可以测试
public class Tests {
@Test
public void test(){
SqlSession session= mybatisUtil.getSession();
UserDao dao=session.getMapper(UserDao.class);
System.out.println(dao.find());
System.out.println(dao.findByName("xx"));
session.close();
}
@Test
public void add(){
SqlSession session=mybatisUtil.getSession();
UserDao dao=session.getMapper(UserDao.class);
User u=new User("LL","435454");
dao.add(u);
session.commit();
session.close();
}
@Test
public void delete(){
SqlSession session=mybatisUtil.getSession();
UserDao dao=session.getMapper(UserDao.class);
dao.delete("xx");
session.commit();
session.close();
}
@Test
public void update(){
SqlSession session=mybatisUtil.getSession();
User u=new User("yy","087766");
UserDao dao=session.getMapper(UserDao.class);
dao.update(u);
session.commit();
session.close();
}
}
在mybatis中进行增加,修改和删除操作都要提交事务才能执行,查找不用