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1.新建SqlSessionUtils工具类

2.编写静态方法

SqlSessionUtils类：

package com.rqs.mybatis.utils;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;public class SqlSessionUtils {public static SqlSession getSqlSession() {SqlSession sqlSession = null;try {InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);sqlSession = sqlSessionFactory.openSession(true);} catch (IOException e) {e.printStackTrace();}return sqlSession;}
}

3.项目结构及代码

项目结构

数据库和表

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.rqs.mybatis</groupId><artifactId>MyBatis_demo2</artifactId><version>1.0-SNAPSHOT</version><packaging>jar</packaging><dependencies><!-- Mybatis核心 --><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.5.7</version></dependency><!-- junit测试 --><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.12</version><scope>test</scope></dependency><!-- MySQL驱动 --><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.3</version></dependency><!-- log4j日志 --><dependency><groupId>log4j</groupId><artifactId>log4j</artifactId><version>1.2.17</version></dependency></dependencies></project>

ParameterMapper接口：

package com.rqs.mybatis.mapper;import com.rqs.mybatis.pojo.User;import java.util.List;public interface ParameterMapper {/*** 查询所有员工信息*/List<User> getAllUser();
}

User类：

package com.rqs.mybatis.pojo;public class User {private Integer id;private String username;private String password;private Integer age;private String gender;private  String email;public User() {}public User(Integer id, String username, String password, Integer age, String gender, String email) {this.id = id;this.username = username;this.password = password;this.age = age;this.gender = gender;this.email = email;}@Overridepublic String toString() {return "User{" +"id=" + id +", username='" + username + '\'' +", password='" + password + '\'' +", age=" + age +", gender='" + gender + '\'' +", email='" + email + '\'' +'}';}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 String getPassword() {return password;}public void setPassword(String password) {this.password = password;}public Integer getAge() {return age;}public void setAge(Integer age) {this.age = age;}public String getGender() {return gender;}public void setGender(String gender) {this.gender = gender;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}
}

ParameterMapper.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.rqs.mybatis.mapper.ParameterMapper"><!--    List<User> getAllUser();--><select id="getAllUser" resultType="user">select * from t_user</select></mapper>

jdbc.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis
jdbc.username=root
jdbc.password=root

log4j.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/"><appender name="STDOUT" class="org.apache.log4j.ConsoleAppender"><param name="Encoding" value="UTF-8" /><layout class="org.apache.log4j.PatternLayout"><param name="ConversionPattern" value="%-5p %d{MM-dd HH:mm:ss,SSS}
%m  (%F:%L) \n" /></layout></appender><logger name="java.sql"><level value="debug" /></logger><logger name="org.apache.ibatis"><level value="info" /></logger><root><level value="debug" /><appender-ref ref="STDOUT" /></root>
</log4j:configuration>

mybatis-config.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><!--    MyBatis核心配置文件，标签的顺序properties?,settings?,typeAliases?,typeHandlers?,objectFactory?,objectWrapperFactory?,reflectorFactory?,plugins?,environments?,databaseIdProvider?,mappers?--><properties resource="jdbc.properties"></properties><!--设置类型别名，大小写不敏感。如果不设置alias，则默认为类名（大小写不敏感）--><typeAliases><!--typeAlias: 设置某个类型的别名属性：type 设置需要设置别名的类型alias 设置某个类型的别名，如果不设置该属性，那么该类型拥有默认的类名，且不区分大小写--><!--<typeAlias type="com.rqs.mybatis.pojo.User" alias="User"></typeAlias>--><!--推荐以包为单位，将包下所有的类型设置默认的类型别名且不区分大小写--><package name="com.rqs.mybatis.pojo"/></typeAliases><!--设置连接数据库的环境--><!--每一个environment都是具体连接数据库的环境--><!--一个项目中只会用一个环境，default用于使用默认使用的环境：id：表示连接数据库的环境的唯一标识 不能重复--><environments default="development"><!--transactionmanager:设置事务管理方式属性：type="JDBC/MANAGED"JDBC: 在当前环境中，执行sql时，使用的时jdbc原声的事务管理方式，需要手动的提交和回滚事务MANAGED：被管理，例如Spring--><environment id="development"><transactionManager type="JDBC"/><!--        dataSource：配置数据源属性"type：设置数据源的类型type=""POOLED:表示使用数据库连接池缓存数据库连接UNPOOLED：表示不使用数据库连接池JNDI：表示使用上下文中的数据源--><dataSource type="POOLED"><!--设置连接数据库的驱动--><property name="driver" value="${jdbc.driver}"/><!--设置连接地址--><property name="url" value="${jdbc.url}"/><!--注意：如果在建sql表单的时候选了字符集（如utf8），这里的value要改成：value="jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf8"--><!--用户名和密码--><property name="username" value="${jdbc.username}"/><property name="password" value="${jdbc.password}"/></dataSource></environment></environments><!--引入映射文件--><mappers><!--推荐以包为单位引入映射文件，要求：1。 mapper接口所在的包要和映射文件所在的包一致2。 mapper接口要和映射文件的名字一致--><!--        com.rqs.mybatis.mapper创建包时要用/分隔，这样才是目录，否则这整一个就只是文件夹名字而已--><package name="com.rqs.mybatis.mapper"/></mappers>
</configuration>

ParameterMapperTest测试类：

package com.rqs.mybatis.test;import com.rqs.mybatis.mapper.ParameterMapper;
import com.rqs.mybatis.pojo.User;
import com.rqs.mybatis.utils.SqlSessionUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;import java.util.List;public class ParameterMapperTest {@Testpublic void getAllUser() {SqlSession sqlSession = SqlSessionUtils.getSqlSession();ParameterMapper mapper = sqlSession.getMapper(ParameterMapper.class);List<User> allUser = mapper.getAllUser();for(int i=0; i<allUser.size(); i++){System.out.println(allUser.get(i));}}
}

测试结果