mybatis笔记01-mysql数据查询-java黑洞网

本站消息

站长简介/公众号

出租广告位,需要合作请联系站长

javagogogo

2598

文章

1324785

访问

+关注

分类

暂无分类

日期归档

2023-06(3)

mybatis笔记01-mysql数据查询

发布于2020-11-19 20:12 阅读(830) 评论(0) 点赞(15) 收藏(3)

最近开始学习ssm框架，用mybatis实现最简单的数据查询，数据库使用mysql数据库。mysql数据库建议使用5.1.x或者5.5.x版本，可自行下载。

1.数据准备

安装mysql数据库后，建立测试表user，自行插入几条测试数据


DROP TABLE IF EXISTS `user`;
 
CREATE TABLE `user` (
  `id` int(11) NOT NULL auto_increment,
  `username` varchar(32) NOT NULL COMMENT '用户名称',
  `birthday` datetime default NULL COMMENT '生日',
  `sex` char(1) default NULL COMMENT '性别',
  `address` varchar(256) default NULL COMMENT '地址',
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

2.工程结构

pom.xml中添加如下依赖：包括mybatis,mysql,日志，单元测试


    <packaging>jar</packaging>
 
    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.6</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.49</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.10</version>
        </dependency>
    </dependencies>

log4j.properties可直接放到resources目录下，指定下本地目录


# Set root category priority to INFO and its only appender to CONSOLE.
#log4j.rootCategory=INFO, CONSOLE            debug   info   warn error fatal
log4j.rootCategory=debug, CONSOLE, LOGFILE
 
# Set the enterprise logger category to FATAL and its only appender to CONSOLE.
log4j.logger.org.apache.axis.enterprise=FATAL, CONSOLE
 
# CONSOLE is set to be a ConsoleAppender using a PatternLayout.
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n
 
# LOGFILE is set to be a File appender using a PatternLayout.
log4j.appender.LOGFILE=org.apache.log4j.FileAppender
log4j.appender.LOGFILE.File=C:\\mybatis_day01\\first\\log4j.log
log4j.appender.LOGFILE.Append=true
log4j.appender.LOGFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.LOGFILE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n

User为实体类，与我们建的User表对应


package com.tjchy.domain;
 
import java.io.Serializable;
import java.util.Date;
 
public class User implements Serializable {
    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;
    }
 
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", birthday=" + birthday +
                ", sex='" + sex + '\'' +
                ", address='" + address + '\'' +
                '}';
    }

IUserDao为持久层接口，如下


package com.tjchy.dao;
import com.tjchy.domain.User;
import java.util.List;
 
/**
 * 持久层接口
 */
public interface IUserDao {
    /**
     * 查询所有用户接口
     */
    List<User> findAll();
}

IUserDao.xml为对象关系映射文件，在resources目录下，注意需与IUserDao.java文件的目录结构相同，都为com.tjchy.dao


<?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.tjchy.dao.IUserDao">
    <!--配置查询所有-->
    <select id="findAll" resultType="com.tjchy.domain.User">
        select * from user
    </select>
</mapper>

SqlMapConfig.xml


<?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">
 
<!--mybatis主配置文件-->
<configuration>
    <!--配置环境-->
    <environments default="mysql">
        <!--配置mysql环境-->
        <environment id="mysql">
            <!-- 配置事务的类型-->
            <transactionManager type="JDBC"></transactionManager>
            <!-- 配置数据源（连接池） -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/xxxx"/>
                <property name="username" value="xxxx"/>
                <property name="password" value="xxxx"/>
            </dataSource>
        </environment>
    </environments>
 
    <!-- 指定映射配置文件的位置，映射配置文件指的是每个dao独立的配置文件 -->
    <mappers>
        <mapper resource="com/tjchy/dao/IUserDao.xml"/>
    </mappers>
</configuration>

建立测试类，TestMain


package com.tjchy.test;
 
import com.tjchy.dao.IUserDao;
import com.tjchy.domain.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.InputStream;
import java.util.List;
 
public class TestMain {
 
    public static void main(String[] args) throws Exception {
        //1.读取配置文件
        InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.创建SqlSessionFactory工厂
        SqlSessionFactoryBuilder builder;
        builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory sessionFactory = builder.build(in);
        //3.使用工厂创建Sqlsession对象
        SqlSession session=sessionFactory.openSession();
        //4.使用session创建dao接口的代理对象
        IUserDao userDao = session.getMapper(IUserDao.class);
        //5.执行方法
        List<User> users = userDao.findAll();
 
        for(User user : users)
        {
            System.out.println(user);
        }
        //6.释放资源
        session.close();
        in.close();
 
 
    }
}