Mybatis环境搭建-实现查询所有的功能

Posted 2021-03-08 遍唱阳春

1.在数据库中新建一个表与java中的实体类对应，我这里新建一个mybatis数据库，在数据库中新建一个user表：

 

2.打开IDEA，新建一个maven项目，可以什么都不选直接创建：

 

 

3.创建好maven项目之后，在pom.xml中引入需要的依赖：

 <groupId>com.itheima</groupId>
    <artifactId>day02_mybatis</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.15</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

 

4.在src-main-resources里面加入log4j.properties:

 

 

 

5.在src-main-java下新建类com.itheima.domain.User类并实现Serializable：

 

6.在User类中建立与数据库mybatis中的user表对应的属性，生成getter and setter方法和toString()方法：

package com.itheima.domain;

import java.io.Serializable;
import java.util.Date;

public class User implements Serializable {
    private Integer id;
    private String username;
    private String address;
    private String sex;
    private Date birthday;

    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 getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username=\'" + username + \'\\\'\' +
                ", address=\'" + address + \'\\\'\' +
                ", sex=\'" + sex + \'\\\'\' +
                ", birthday=" + birthday +
                \'}\';
    }
}

 

 7.在src-main-java-com-itheima下新建一个dao包，并且新建接口IUserDao:

 

 

 8.在IUserDao中写查询所有的方法：

package com.itheima.dao;

import com.itheima.domain.User;

import java.util.List;

public interface IUserDao {
    //查询所有
    List<User> findAll();
}

 

9.在src-main-resources里面新建file，命名为SqlMapConfig.xml,并且加入配置信息：

<?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">
<configuration>
<!--    配置mysql信息-->
    <environments default="mysql">
        <environment id="mysql">
<!--            配置事务-->
            <transactionManager type="JDBC"/>
<!--            配置资源（连接池）-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
<!--    配置mapper信息-->
    <mappers>
        <mapper resource="com/itheima/dao/IUserDao.xml"/>
    </mappers>
</configuration>

注意：因为我的数据库是8.0版本，所以pom.xml中引入的jar包也是mysql-connector-java 8.0.15版本，所以这里的driver里面有一个"cj",而且我的数据库会报TimeZone异常，所以我在url后面加上了参数“?serverTimezone=UTC"，其实可以不加。

 

10.在resources下面按照java里面的dao路径，新建IUserDao.xml文件：

 

 

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

 

11.在test目录下编写测试类：

 

 

package com.itheima.test;

import com.itheima.dao.IUserDao;
import com.itheima.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 org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

//测试mybatis的crud
public class MybatisTest {
    @Test
    public void testFindAll() throws IOException {
        //1.读取配置文件，生成字节输入流
        InputStream in= Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.获取SqlSessionFactory
        SqlSessionFactory factory=new SqlSessionFactoryBuilder().build(in);
        //3.获取SqlSession对象
        SqlSession session=factory.openSession();
        //4.获取dao的代理对象
        IUserDao userDao=session.getMapper(IUserDao.class);
        //5.执行查询所有对象
        List<User> users = userDao.findAll();
        for (User user:users){
            System.out.println(user);
        }
        //6.释放资源
        session.close();
        in.close();

    }
}

 

12.运行测试方法testFindAll(),结果如下：