目錄

• • 1、mybatis環(huán)境搭建
  • 2、mybatis dao接口實(shí)現(xiàn)
  • 3、動(dòng)態(tài)代理方式，只實(shí)現(xiàn)Mapper接口

• mybatis入門==單表操作demo

mybatis dao層實(shí)現(xiàn)1. 實(shí)現(xiàn)dao層接口 2. 接口代理方式實(shí)現(xiàn)dao代理開發(fā)要求：? Mapper接口開發(fā)方法只需要編寫Mapper接口（相當(dāng)于dao接口），由mybatis框架根據(jù)接口定義創(chuàng)建接口的動(dòng)態(tài)代理對(duì)象，代理對(duì)象的方法體和dao方式實(shí)現(xiàn)的接口一樣。1. mapper.xml 中namespace與mapper接口中全限定名相同 2. mapper接口方法名和mapper.xml中定義的每個(gè)statement的id相同 3. mapper接口方法入?yún)㈩愋?#xff0c;和 statement的paramType相同 4. mapper接口返回值類型，和statement的resultType相同

1、mybatis環(huán)境搭建

• user-mapper.xml

<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="cn.bitqian.dao.UserMapper"><!-- resultType 引用別名user --><select id="queryAllUser" resultType="user">select * from users1</select><select id="queryUserByUserId" parameterType="int" resultType="user">select * from users1 where userid = #{id}</select></mapper>

• mybatis-config.xml 核心配置文件

<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd"><configuration><properties resource="jdbc.properties"></properties><!-- user別名 --><typeAliases><typeAlias type="cn.bitqian.entity.User" alias="user"></typeAlias></typeAliases><environments default="development"><environment id="development"><transactionManager type="JDBC"></transactionManager><dataSource type="POOLED"><property name="driver" value="${driver}"/><property name="url" value="${url}"/><property name="username" value="${username}"/><property name="password" value="${password}"/></dataSource></environment></environments><mappers><mapper resource="cn\bitqian\mapper\user-mapper.xml"></mapper></mappers></configuration>

2、mybatis dao接口實(shí)現(xiàn)

• 編寫dao接口，同下面mapper接口

package cn.bitqian.dao;import cn.bitqian.entity.User;import java.io.IOException; import java.util.List;/*** 注意 接口代理開發(fā)* 1. 接口類名與mapper中namespace對(duì)應(yīng)* 2. 接口中方法名與statement中的id對(duì)應(yīng)* 3. 接口中方法參數(shù)與statement中的parameterType對(duì)應(yīng)* 4. 接口中方法返回值與statement中的resultType類型對(duì)應(yīng)*/ public interface UserMapper {public List<User> queryAllUser() throws IOException;public User queryUserByUserId(int userId);}

• dao接口實(shí)現(xiàn)

package cn.bitqian.dao.impl;import cn.bitqian.dao.UserMapper; import cn.bitqian.entity.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;/*** 傳統(tǒng)實(shí)現(xiàn)dao層接口 模板api* @author echo lovely* @date 2020/9/11 9:23*/ public class UserMapperImpl implements UserMapper {@Overridepublic List<User> queryAllUser() throws IOException {InputStream resourceAsStream = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);SqlSession sqlSession = sqlSessionFactory.openSession();// namespace.idList<User> userList = sqlSession.selectList("cn.bitqian.dao.UserMapper.queryAllUser");sqlSession.close();return userList;}@Overridepublic User queryUserByUserId(int userId) {return null;} }

3、動(dòng)態(tài)代理方式，只實(shí)現(xiàn)Mapper接口

• UserMapper 接口同上

優(yōu)點(diǎn)分析：1. 只需實(shí)現(xiàn)mapper接口，定義對(duì)應(yīng)的業(yè)務(wù)方法，注意接口名， 方法名，入?yún)?#xff0c;返回的參數(shù)和mappers的配置一致2. 無需實(shí)現(xiàn)mapper接口，mybatis通過動(dòng)態(tài)代理的方式進(jìn)行實(shí)現(xiàn)了 只需用UserMapper userMapper = sqlSession.getMapper(UserMapper.class); getMapper api 來創(chuàng)建對(duì)象，進(jìn)行數(shù)據(jù)庫操作 package cn.bitqian.service;import cn.bitqian.dao.UserMapper; import cn.bitqian.dao.impl.UserMapperImpl; import cn.bitqian.entity.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;/*** @author echo lovely* @date 2020/9/11 9:29*/ public class DemoTest {public static void main(String[] args) {// 通過實(shí)現(xiàn)dao層接口UserMapper userMapper = new UserMapperImpl();try {System.out.println(userMapper.queryAllUser());} catch (IOException e) {e.printStackTrace();}// 編寫mapper接口實(shí)現(xiàn)查詢所有test1();// 根據(jù)id查詢user對(duì)象test2();}private static UserMapper userMapper;static {try {InputStream resourceAsStream = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory build = new SqlSessionFactoryBuilder().build(resourceAsStream);SqlSession sqlSession = build.openSession();// 使用getMapper api拿到接口對(duì)象，mybatis會(huì)通過動(dòng)態(tài)代理進(jìn)行底層實(shí)現(xiàn)userMapper = sqlSession.getMapper(UserMapper.class);} catch (IOException e) {e.printStackTrace();}}// 通過編寫mapper接口實(shí)現(xiàn)查詢static void test1() {try {List<User> userList = userMapper.queryAllUser();System.out.println(userList);} catch (IOException e) {e.printStackTrace();}}static void test2() {User user = userMapper.queryUserByUserId(1);System.out.println(user);}}

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