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>