MyBatis第一节

1. 简介

它是一款半自动的ORM持久层框架，具有较高的SQL灵活性，支持高级映射(一对一，一对多)，动态SQL，延迟加载和缓存等特性，但它的数据库无关性较低。

2. 配置

编写全局配置文件
编写mapper映射文件
加载全局配置文件，生成SqlSessionFactory
创建SqlSession，调用mapper映射文件中的SQL语句来执行CRUD操作

3. doing

3.1 创建一个表

这就不提了

3.2 打开IDEA，创建一个maven项目

maven

3.3 导入依赖的jar包

	<dependencies><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.10</version></dependency><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.4.6</version></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>1.18.12</version><scope>provided</scope></dependency><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.10</version><scope>test</scope></dependency><!-- 日志 --><dependency><groupId>log4j</groupId><artifactId>log4j</artifactId><version>1.2.17</version></dependency></dependencies>

3.4 创建entity

package com.qcby.entity;import java.io.Serializable;
import java.util.Date;public class User implements Serializable{private static final long serialVersionUID = 525400707336671154L;private Integer id;private String username;private Date birthday;private String sex;private String address;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 Date getBirthday() {return birthday;}public void setBirthday(Date birthday) {this.birthday = birthday;}public String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}@Overridepublic String toString() {return "User{" +"id=" + id +", username='" + username + '\'' +", birthday=" + birthday +", sex='" + sex + '\'' +", address='" + address + '\'' +'}';}
}

3.5 编写mapper映射文件(编写SQL)

<?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="com.qcby.dao.UserDao"><select id="findAll" resultType="user">select * from userx;</select><!--通过id查询SQL语句使用#{占位符的名称，名称可以任意}，仅限于基本数据类型和String类型--><select id="findById" resultType="com.qcby.entity.User" parameterType="int">select * from userx where id = #{id};</select><!--保存操作--><insert id="insert" parameterType="com.qcby.entity.User">/*keyProperty表示要返回的属性名称order取值AFTER表示插入数据后的行为resultType表示返回值的类型*/<selectKey keyProperty="id" order="AFTER" resultType="java.lang.Integer">select last_insert_id();</selectKey>insert into userx (username,birthday,sex,address) values (#{username},#{birthday},#{sex},#{address})</insert><!-- 修改 --><update id="update" parameterType="com.qcby.entity.User">update userx set username = #{username},birthday = #{birthday},sex = #{sex},address=#{address} where id = #{id}</update><!-- 删除 --><delete id="delete" parameterType="Integer">delete from userx where id = #{id}</delete><!-- 模糊查询 --><select id="findByName" resultType="com.qcby.entity.User" parameterType="string"><!-- 第一种方式的SQL语句select * from user where username  like #{username}--><!-- 第二章SQL语句的编写 强调：'%${value}%'不能修改，固定写法（不推荐使用）  -->select * from userx where username  like '%${value}%'</select><!-- 具体函数的查询 --><select id="findByCount" resultType="int">select count(*) from userx</select>
</mapper>

3.6 编写主配置文件

<?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><!-- 别名 注意位置--><typeAliases><!-- 把com.qcbyjy.domain.User使用user别名来显示，别名user User USER都可以，默认是忽略大写的<typeAlias type="com.qcbyjy.domain.User" alias="user"/>--><!-- 针对com.qcbyjy.domain包下的所有的类，都可以使用当前的类名做为别名 --><package name="com.qcby.entity"/></typeAliases><!-- 配置环境们 --><environments default="mysql"><!-- 配置具体的环境 --><environment id="mysql"><!-- 配置事务管理类型 --><transactionManager type="JDBC"/><!-- 配置是否需要使用连接池，POOLED使用，UNPOOLED不使用 --><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="root"/></dataSource></environment></environments><!-- 加载映射的配置文件 --><mappers><mapper resource="mapper/UserMapper.xml"/></mappers>
</configuration>

3.7 编写接口

package com.qcby.dao;import com.qcby.entity.User;import java.util.List;public interface UserDao {List<User> findAll();public User findById(Integer userId);public void insert(User user);public void update(User user);public void delete(Integer userId);public List<User> findByName(String username);public Integer findByCount();
}

3.8 测试

UserTest.java

package com.qcby.demo;import com.qcby.dao.UserDao;
import com.qcby.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 org.junit.Test;import java.io.InputStream;
import java.util.List;public class UserTest {@Testpublic void testFindAll() throws Exception {// 加载主配置文件，目的是构建SqlSessionFactory的对象InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");// 创建SqlSessionFactory对象SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);// 使用SqlSessionFactory工厂对象创建SqlSession对象SqlSession session = factory.openSession();// 通过session创建UserMapper接口的代理对象UserDao mapper = session.getMapper(UserDao.class);// 调用查询所有的方法List<User> list = mapper.findAll();// 遍历集合for (User user : list) {System.out.println(user);}// 释放资源session.close();in.close();}@Testpublic void run2() throws Exception {// 加载配置文件InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");// 构建SqlSessionFactory对象SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(inputStream);// 获取到session对象SqlSession session = factory.openSession();// 查询所有的数据List<User> list = session.selectList("com.qcby.dao.UserDao.findAll");// 变量集合for (User user : list) {System.out.println(user);}// 关闭资源session.close();inputStream.close();}
}

运行结果：

UserTest2.java

package com.qcby.demo;import com.qcby.dao.UserDao;
import com.qcby.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 org.junit.After;
import org.junit.Before;
import org.junit.Test;import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.List;public class UserTest2 {private InputStream in;private SqlSession session;private UserDao mapper;@Beforepublic void init() throws Exception {// 加载配置文件in = Resources.getResourceAsStream("SqlMapConfig.xml");// 创建工厂对象SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);// 创建Session对象session = factory.openSession();// 获取到代理对象mapper = session.getMapper(UserDao.class);}@Afterpublic void destory() throws IOException {in.close();session.close();}@Testpublic void testFindAll() throws Exception {List<User> list = mapper.findAll();// 遍历for (User user : list) {System.out.println(user);}in.close();}@Testpublic void testFindById() throws Exception {User user = mapper.findById(41);System.out.println(user);in.close();}@Testpublic void testInsert() throws Exception {User user = new User();user.setUsername("美美");user.setBirthday(new Date());user.setSex("男");user.setAddress("顺义");mapper.insert(user);session.commit();System.out.println(user.getId());}@Testpublic void testUpdate() throws Exception {User user = mapper.findById(41);user.setUsername("小凤");mapper.update(user);session.commit();}@Testpublic void testDelete() throws Exception {mapper.delete(48);session.commit();}// 第一种
/*    @Testpublic void testFindByName() throws Exception {List<User> list = mapper.findByName("%王%");for (User user : list) {System.out.println(user);}}*/// 第二种@Testpublic void testFindByName() throws Exception {List<User> list = mapper.findByName("王");for (User user : list) {System.out.println(user);}}@Testpublic void testFindByCount() throws Exception {Integer count = mapper.findByCount();System.out.println("总记录数：" + count);}
}