IDEA创建MyBatis项目--实现简单的查操作

IDEA创建MyBatis项目--实现简单的查操作

1.创建一个maven工程，不使用模板

2.通过maven加载Mybatis依赖包

在pom文件中导入maven坐标

<dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.3.0</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.29</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.12</version>
        </dependency>
    </dependencies>

3.新建config.properties配置文件

填写内容

4.新建Mybatis配置文件

在以下位置创建

命名为mybatis-config.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">
<configuration>
    <properties resource="config.properties"/>
    <typeAliases>

        <package name=""/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${database.driver}"/>
                <property name="url" value="${database.url}"/>
                <property name="username" value="${database.username}"/>
                <property name="password" value="${database.password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="mapper/StudentMapper.xml"/>
    </mappers>

</configuration>

5.编写SqlSessionFactoryUtils工具类

在以下位置创建



没有的包右击创建package

package com.Utils;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.apache.ibatis.io.Resources;

import java.io.IOException;
import java.io.InputStream;

public class SqlSessionFactoryUtils {

    private final static Class<SqlSessionFactoryUtils> lock=SqlSessionFactoryUtils.class;

    private static SqlSessionFactory sqlSessionFactory=null;

    private SqlSessionFactoryUtils(){};

    public static SqlSessionFactory getSqlSessionFactory(){
        synchronized (lock){
            if (sqlSessionFactory!=null){
                return sqlSessionFactory;
            }

            String resource="mybatis-config.xml";
            InputStream inputStream;
            try {
                inputStream=Resources.getResourceAsStream(resource);
                sqlSessionFactory =new SqlSessionFactoryBuilder().build(inputStream);
            }catch (IOException e){
                e.printStackTrace();
                return null;
            }

            return sqlSessionFactory;
        }
    }

    public static SqlSession openSqlSession(){
        if (sqlSessionFactory==null){
            getSqlSessionFactory();
        }
        return  sqlSessionFactory.openSession();
    }

}

6.编写Student实体类

package com.entity;

public class Student {

    private int id;
    private String name;
    private int age;

    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 int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

7.编写StudentMapper接口

package com.mapper;

import com.entity.Student;

public interface StudentMapper {
    public Student getStudent(long id);
}

8.编写StudentMapper.xml映射器

<?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.mapper.StudentMapper">

    <select id="getStudent" parameterType="long" resultType="com.entity.Student">
        select id,name,age from student where id=#{id}
    </select>

</mapper>

9.与数据库表结构对应

10.编写Main类（或测试类test）

package com;

import com.entity.Student;
import com.mapper.StudentMapper;
import com.utils.SqlSessionFactoryUtils;
import org.apache.ibatis.session.SqlSession;

public class Main {

    public static void main(String[] args){
        SqlSession sqlSession=SqlSessionFactoryUtils.openSqlSession();
        StudentMapper studentMapper=sqlSession.getMapper(StudentMapper.class);
        System.out.println(studentMapper.getStudent(1).toString());
    }
}

注意点

1.Mapper.xml的namespace与Mapper.java类的包名要一致

2.Mapper.xml中select元素的id属性值必须跟Mapper.java中方法名要一致

3.把xml文件放在resources目录下