开发环境：
硬件环境：Windows10+JDK 1.8；
软件环境：Java+Eclipse+Mybatis+maven3.6+tomcat8.0+Postgresql 10.6；
用到的jar包：
asm-3.3.1.jar
cglib-2.2.2.jar
commons-logging-1.1.1.jar
javassist-3.17.1-GA.jar
log4j-1.2.17.jar
log4j-api-2.0-rc1.jar
log4j-core-2.0-rc1.jar
mybatis-3.2.7.jar
mybatis-spring-1.2.1.jar
mysql-connector-java-5.1.20.jar
postgresql-42.2.5.jre7.jar
slf4j-api-1.7.5.jar
slf4j-log4j12-1.7.5.jar其他：
postgreSQL中已经存在一张表表名use,Windows环境下可通过命令行模式登录，打开cmd输入：psql -U postgrese;
按回车键，键入密码（当初安装postgreSQL设置的root密码）；项目结构：
1.1 配置文件
创建Mybatis.conf.xml
<?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="db.properties"/><typeAliases><package name="com.ironxi.entity"/> </typeAliases><environments default="development"><environment id="development"><transactionManager type="JDBC" /><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="com/ironxi/entity/TeacherMapper.xml" /></mappers>
</configuration>设置数据库关管理文件：
db.properties
driver=org.postgresql.Driver
url=jdbc:postgresql://localhost:5432/postgres
username=postgres
password=Your.3341.2 设置MybtisUtils类（编写sqlsessionfactory，sqlsession）
package com.ironxi.util;import java.io.IOException;
import java.io.InputStream;import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;public class MybatisUtil {/**SqlSessionFactory* 通过配置文件创建SqlSessionFactory，是一个SqlSession工厂类*/public static SqlSessionFactory getSqlSessionFactory() throws IOException {String resource = "mybatis.conf.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);return sqlSessionFactory;}/**SqlSession* 通过id找到对应的sql语句并执行它*/public static SqlSession getSession() throws IOException {SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();return sqlSessionFactory.openSession();}
}
1.3 设置Student类，Teacher类
设置User类
package com.ironxi.entity;public class User {private int id;private String name;private String password;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;}@Overridepublic String toString() {return "User [id=" + id + ", name=" + name + ", password=" + password + "]";}}1.4 设置Mapper.xml文件
UserMapper.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="com.ironxi.entity.UserMapper">
<!-- 结果映射不能返回成一个类型时用resultTypt --><select id="getUserByCondition" parameterType="Map" resultType="User">select * from use<where><!-- 利用sql语句的传参函数模糊匹配 --><if test="name!=null">name like CONCAT('%',#{name},'%')</if></where></select>
</mapper> 1.5 创建查询方法
UserDao.java
package com.ironxi.dao;import java.io.IOException;
import java.util.List;
import java.util.Map;import org.apache.ibatis.session.SqlSession;import com.ironxi.entity.User;
import com.ironxi.util.MybatisUtil;public class UserDao {/**search all* @throws IOException */public List<User> getAll(Map<String,Object> map) throws IOException{SqlSession session = MybatisUtil.getSession();List<User> list= session.selectList("com.ironxi.entity.UserMapper.getUserByCondition",map);session.close();return list;}
}1.6 编写测试文件
package com.ironxi.test;import java.io.IOException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;import com.ironxi.dao.UserDao;
import com.ironxi.entity.User;public class Test {public static void main(String[] args) throws IOException {/** Select */UserDao userDao = new UserDao();Map<String,Object> map=new HashMap<String,Object>();map.put("name", "四");List<User> list=userDao.getAll(map);for(User u:list){System.out.println(u);}System.out.println("************");}
}
输出结果：
log4j:WARN No appenders could be found for logger (org.apache.ibatis.logging.LogFactory).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
User [id=23, name=四种, password=123455]
User [id=24, name=四狗, password=123455]
************
1.7 动态SQL语句
引入了<where></where>条件语句，同时在里面写if条件，若有多个if则除第一条语句外其余都需加and；
<where><!-- 利用sql语句的传参函数模糊匹配 --><if test="name!=null">name like CONCAT('%',#{name},'%')</if>
</where>
