Mybatis:
一种简化sql操作的长久层框架,开发只须要关注具体的sql语句即可
传统的JDBC: 1.操作sql 2.操作 Connection、Statment(向数据库发送sql的一个对象)、ResultSet等
ORM框架: 对象关系匹配,把关系数据库中的数据转换成面向对象程序中的对象
hibernate(全自动sql)和mybatis(自定义sql)
1.pom中引入依赖
mybais只有这一个依赖就实现了
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.4.6</version>
</dependency>
然而须要操作数据库,因而引入连贯数据库驱动
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.26</version>
</dependency>
再加一个测试类的依赖用于测试
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>2.mybatis.xml
编写myBatis外围配置文件(放在resource目录下)
<?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 core file-->
<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://localhost:3306/hualian?useSSL=false&characterEncoding=UTF-8&serverTimezone=UTC"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
<!--将Mapper.xml注册到Mybatis的外围配置文件中 重要!!-->
<mappers>
<mapper resource="com/gxa/hualian/mapper/UserMapper.xml"/>
</mappers>
</configuration>3.pom中引入mapper.xml
为了可能加载到java文件夹下的mapper的xml文件
<build>
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.xml</include>
</includes>
</resource>
</resources>
</build>4.写java代码
pojo/mapper/test
User
public class User implements Serializable {
private Long id;
private String name;
private Integer points;
private String phone;
private Timestamp regTime;
public User(Long id, String name, Integer points, String phone, Timestamp regTime) {
this.id = id;
this.name = name;
this.points = points;
this.phone = phone;
this.regTime = regTime;
}
public User() {
}
}UserMapper
public interface UserMapper {
void add(User user);
void deleteById(Long id);
void update(User user);
List<Map> selectAll();
}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="com.gxa.hualian.mapper.UserMapper">
<!--增删改查sql-->
<insert id="add" parameterType="com.gxa.hualian.pojo.User">
insert into `user` (`name`,`phone`,`regTime`) values (#{name},#{phone},#{regTime})
</insert>
<delete id="deleteById" parameterType="long">
delete from `user` where id=#{id}
</delete>
<update id="update" parameterType="com.gxa.hualian.pojo.User">
update `user` set `name`=#{name},`phone`=#{phone},`regTime`=#{regTime}
</update>
<select id="selectAll" resultType="java.util.Map">
select * from `user`
</select>Test
public class TestUser {
UserMapper mapper=null;
SqlSession sqlSession = null;
@Before
//为了获取sqlSession
public void init() throws IOException {
//Resources：mybatis提供的一个文件流读取工具
InputStream resourceAsStream = Resources.getResourceAsStream("mybatis.xml");
//实例化一个构建器
SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
//通过builder失去一个工厂对象
SqlSessionFactory factory = builder.build(resourceAsStream);
//通过openSession失去会话对象，默认为手动提交事务
//SqlSession 提供了在数据库执行 SQL 命令所需的所有办法
sqlSession= factory.openSession();
//取得mapper接口的代理对象
mapper= sqlSession.getMapper(UserMapper.class);
}
@Test
public void add(){
Timestamp timestamp = new Timestamp(System.currentTimeMillis());
User user = new User("测试",0,"7898",timestamp);
//取得代理对象再调办法
mapper.add(user);
//sqlSession自带的办法,同样有增删改查,statement参数(第一个参数)要与接口中的办法名统一
sqlSession.insert("add", user);
sqlSession.commit();
}
@Test
public void deleteById(){
mapper.deleteById(37L);
sqlSession.commit();
}
@Test
public void update(){
Timestamp timestamp1 = new Timestamp(System.currentTimeMillis());
User user1 = new User(44L,"测试4",0,"+65+6565+",timestamp1);
sqlSession.update("update", user1);
sqlSession.commit();
}
@Test
public void selectAll(){
List<Map> maps = mapper.selectAll();
System.out.println(maps.size());
for (Map map : maps) {
System.out.println(map);
}
}
}遇到的坑:
1.没有spring治理的时候,想要mapper对象须要本人创立sqlSession
2.没有在pom中引入xml文件,报找不到UserMapper.xml的错
标签配置解析:
mappers: 映射器 , UserMapper.xml文件中配置 映射到具体的Mapper.xml文件
<!--将Mapper.xml注册到Mybatis的外围配置文件中 -->
<mappers>
<mapper resource="com/gxa/hualian/mapper/UserMapper.xml"/>
</mappers>namespace:用于绑定Dao接口
<mapper namespace="com.xxx.hualian.mapper.UserMapper">
...
</mappe>environments:环境配置汇合 能够配置多种数据库
environment:环境配置 具体的实现
连接池:服务器端一次性向数据库创立多个连贯,并将多个连贯保留在一个连接池对象当中,下次有申请操作数据库时,间接从连接池取得一个连贯,应用完后不敞开而是持续放回连接池当中 ,可节俭创立连贯/开释连贯的资源
//default: development开发模式 work工作模式
<environments default="development">
//id: 指定以后环境的惟一标识
<environment id="development">
//transactionManager:事务管理器 type: JDBC-应用JDBC原生的事务管理形式,提交和回滚都须要手动
<transactionManager type="JDBC"/>
//datasource: 数据源 type: POOLED-应用连接池
<dataSource type="POOLED">
//property:属性, 连贯四大件 连贯驱动,url,用户名,明码
<property name="driver" value="com.mysql.jdbc.Driver"/>
//useSSL:SSL协定用于保障数据安全和正确,默认true
<property name="url" value="jdbc:mysql://localhost:3306/hualian?useSSL=false&characterEncoding=UTF-8&serverTimezone=UTC"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
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