Mybatis的Dao层实现-代理开发方式

你的UserMapper.xml有多个sql（比如有增删改）语句，但是你对应的接口写不全（只写了对应xml的增方法）这些sql的方法时也不会报错啊。

重点：接口的参数名无论parameterType是对象还是基本都是随便写。xml才要求对象要写属性名，基本才随便写（接口不管参数名的，只管参数的类型要跟xml的parameterType一样就行）：

下面的mapper就是之前的dao，只不过叫法不一样而已

Sys_user：

package com.itheima.domain;

/**
 * @author QLBF
 * @version 1.0
 * @date 2021/1/28 12:18
 */
public class Sys_user {
    
    
    private int id;
    private String username;
    private String email;
    private String password;
    private String phoneNum;

    @Override
    public String toString() {
    
    
        return "Sys_user{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", email='" + email + '\'' +
                ", password='" + password + '\'' +
                ", phoneNum='" + phoneNum + '\'' +
                '}';
    }

    public int getId() {
    
    
        return id;
    }

    public void setId(int id) {
    
    
        this.id = id;
    }

    public String getUsername() {
    
    
        return username;
    }

    public void setUsername(String username) {
    
    
        this.username = username;
    }

    public String getEmail() {
    
    
        return email;
    }

    public void setEmail(String email) {
    
    
        this.email = email;
    }

    public String getPassword() {
    
    
        return password;
    }

    public void setPassword(String password) {
    
    
        this.password = password;
    }

    public String getPhoneNum() {
    
    
        return phoneNum;
    }

    public void setPhoneNum(String phoneNum) {
    
    
        this.phoneNum = phoneNum;
    }
}

UserMapper：

package com.itheima.mapper;

import com.itheima.domain.Sys_user;

import java.util.List;

/**
 * @author QLBF
 * @version 1.0
 * @date 2021/1/30 11:06
 */
public interface UserMapper {
    
    
    public List<Sys_user> findAll();
    public Sys_user findone(int id2);  //由于parameterType是基本类型，那么参数名在接口和.xml都是随便写

    public int save(Sys_user user1);
}

ServiceDemo：

package com.itheima.service;

import com.itheima.domain.Sys_user;
import com.itheima.mapper.UserMapper;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import org.apache.ibatis.io.Resources;

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

/**
 * @author QLBF
 * @version 1.0
 * @date 2021/1/30 11:07
 */
public class ServiceDemo {
    
    

    @Test
    //查全部
    public void test1() throws IOException {
    
    
        InputStream resourceAsStream= Resources.getResourceAsStream("sqlMapConfig.xml");
        SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession=sqlSessionFactory.openSession(true);

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<Sys_user> sys_userList = mapper.findAll();
        System.out.println(sys_userList);
    }


    @Test
    //测试查一条
    public void test2() throws IOException {
    
    
        InputStream resourceAsStream= Resources.getResourceAsStream("sqlMapConfig.xml");
        SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession=sqlSessionFactory.openSession(true);

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        Sys_user sys_use = mapper.findone(7);
        System.out.println(sys_use);
    }

    @Test
    //增
    public void test3() throws IOException {
    
    
        Sys_user sys_user=new Sys_user();
        sys_user.setUsername("喜洋洋");
        sys_user.setPhoneNum("555522");
        InputStream resourceAsStream= Resources.getResourceAsStream("sqlMapConfig.xml");
        SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession=sqlSessionFactory.openSession(true);

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int count = mapper.save(sys_user);
        System.out.println(count);
    }
}

测试成功，演示test3：

UserMapper.xml：

<?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.mapper.UserMapper">
    <!--查询数据表封装成集合输出-->
    <select id="findAll" resultType="com.itheima.domain.Sys_user">   /*Sys_user是数据库对应的实体类*/
        SELECT * FROM sys_user  /*这里是sys_user是数据库真实的表*/
    </select>

    <!--查询一个对象数据-->
    <select id="findone" resultType="com.itheima.domain.Sys_user" parameterType="int">   /*Sys_user是数据库对应的实体类*/
        SELECT * FROM sys_user WHERE id=#{id1}/*这里是sys_user是数据库真实的表*/
    </select>

    <!--插入操作,save是随便起的,parameterType后面都是写对象类型进行传递的哦，这里的user是对应sqlMapConfig的别名-->
    <insert id="save" parameterType="user">
        /*这里#后的{}写的是对应上面parameterType对象里面的属性，而不是对应数据库表的哦
        （虽然一般数据库表跟实体类设置成一样，但有时不一样，这里要写的是实体类的哦）*/
        INSERT INTO sys_user VALUES(#{id},#{username},#{email},#{password},#{phoneNum})
    </insert>



</mapper>

jdbc.properties:

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

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">
<configuration>

    <!--通过properties标签加载外部properties文件-->
    <properties resource="jdbc.properties"></properties>

    <!--自定义别名-->
    <typeAliases>
        <typeAlias type="com.itheima.domain.Sys_user" alias="user"></typeAlias>
        <!--这里还可以配多个-->
    </typeAliases>

    <!--数据源环境-->
    <environments default="developement">
        <environment id="developement">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"></property>
                <property name="url" value="${jdbc.url}"></property>
                <property name="username" value="${jdbc.username}"></property>
                <property name="password" value="${jdbc.password}"></property>

            </dataSource>
        </environment>
    </environments>

    <!--加载映射文件-->
    <mappers>
        <mapper resource="com.itheima.mapper/UserMapper.xml"></mapper>
    </mappers>
</configuration>

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>cn.itcast</groupId>
    <artifactId>Mybatis_day2_dao</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>war</packaging>

    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.32</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
    </dependencies>
    
</project>