Mybatis-Plus从入门到入土

目录

一、介绍

二、特性

三、架构

四、 使用mybatis进行User查询

1.创建工程

2.配置pom.xml

3.创建子模块

4.编写mybatis-config.xml

5.编写User对象

6.编写UserMapper接口

7.编写UserMapper.xml

8.编写测试用例​​​​​​​

五、使用Mybatis+MybatisPlus查询User

1.UserMapper继承BaseMapper

2.User对象类加上对表的引用

3.使用MP中的MybatisSqlSessionFactoryBuilder进程构建

六、Spring+Mybatis+MP查询User

1.创建子模块

2.在子模块的pom.xml中导入依赖

3.编写jdbc.properties

4.编写applicationContext.xml

5.编写User对象

6.编写UserMapper接口

7.编写测试用例

七、SpringBoot+Mybatis+MP查询User

1.创建spring工程

2.导入依赖pom.xml

3.编写application.properties

4.编写pojo

5.编写mapper

6.编写启动类

7.编写测试用例

八、基于springboot的其余CRUD

1.插入

@TableId主键策略

@TableField

2.更新

3.删除

4.查询

九、Mybatis-Plus对Service的封装

1.创建service接口

2.实现service接口

3.调用

---

一、介绍

Mybatis-Plus是Mybatis的增强工具，只增强不改变，为简化开发，提高效率

二、特性

损耗小

强大的CRUD操作

支持lambda形式调用

支持多种数据库

支持主键自动生成

……

三、架构

四、 使用mybatis进行User查询

1.创建工程

2.配置pom.xml

"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>4.0.0modelVersion>
 
    <groupId>com.mpgroupId>
    <artifactId>mybatis_mpartifactId>
    <packaging>pompackaging>
    <version>1.0-SNAPSHOTversion>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.pluginsgroupId>
                <artifactId>maven-compiler-pluginartifactId>
                <version>3.8.1version>
                <configuration>
                    <source>1.8source>
                    <target>1.8target>
                configuration>
            plugin>
        plugins>
    build>
    <modules>
        <module>mybatismodule>
    modules>
 
    <properties>
        <maven.compiler.source>8maven.compiler.source>
        <maven.compiler.target>8maven.compiler.target>
        <project.build.sourceEncoding>UTF-8project.build.sourceEncoding>
    properties>
    <dependencies>
        <dependency>
            <groupId>com.baomidougroupId>
            <artifactId>mybatis-plusartifactId>
            <version>3.5.2version>
        dependency>
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <version>8.0.30version>
        dependency>
        <dependency>
            <groupId>com.alibabagroupId>
            <artifactId>druidartifactId>
            <version>1.2.15version>
        dependency>
        <dependency>
            <groupId>org.projectlombokgroupId>
            <artifactId>lombokartifactId>
            <version>1.18.24version>
        dependency>
        <dependency>
            <groupId>junitgroupId>
            <artifactId>junitartifactId>
            <version>4.13.2version>
        dependency>
        <dependency>
            <groupId>org.slf4jgroupId>
            <artifactId>slf4j-apiartifactId>
            <version>2.0.5version>
        dependency>
    dependencies>
 
project>

3.创建子模块

4.编写mybatis-config.xml

"1.0" encoding="UTF-8" ?>
configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://127.0.0.1:3306/zxkt?
                    useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQuerie
                    s=true&useSSL=false"/>
                <property name="username" value="root"/>
                <property name="password" value="1234"/>
            dataSource>
        environment>
    environments>
    <mappers>
        <mapper resource="UserMapper.xml"/>
    mappers>
configuration>

5.编写User对象

package com.mp.pojo;
 
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
 
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private long id;
    private String user_name;
    private String password;
    private String name;
    private Integer age;
    private String email;
 
}

6.编写UserMapper接口

package com.mp.mapper;
 
import com.mp.pojo.User;
 
import java.util.List;
 
public interface UserMapper {
    List findAll();
}

7.编写UserMapper.xml

"1.0" encoding="UTF-8" ?>
mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.mp.mapper.UserMapper">
    <select id="findAll" resultType="com.mp.pojo.User">
        select * from tb_user
    select>
mapper>

8.编写测试用例

import com.mp.mapper.UserMapper;
import com.mp.pojo.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;
 
public class test_mybatis {
 
    @Test
    public void testFindAll() throws IOException {
        String config = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(config);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
 
        List users = userMapper.findAll();
        for(User user : users) {
            System.out.println(user);
        }
    }
}

五、使用Mybatis+MybatisPlus查询User

在上述Mybatis的基础上做如下修改

1.UserMapper继承BaseMapper

public interface UserMapper extends BaseMapper{
    List findAll();
}

2.User对象类加上对表的引用

package com.mp.pojo;
 
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
 
@Data
@NoArgsConstructor
@AllArgsConstructor
@TableName("tb_user")    //这一行需要加上，否则会查不到表
public class User {
    private long id;
    private String userName;
    private String password;
    private String name;
    private Integer age;
    private String email;
 
}

3.使用MP中的MybatisSqlSessionFactoryBuilder进程构建

public class TestMybatisPlus {
    @Test
    public void testUserList() throws Exception{
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        //这里使用的是MP中的MybatisSqlSessionFactoryBuilder
        SqlSessionFactory sqlSessionFactory = new MybatisSqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        
        // 可以调用BaseMapper中定义的方法
        List list = userMapper.selectList(null);
        for (User user : list) {
            System.out.println(user);
        }
}

六、Spring+Mybatis+MP查询User

1.创建子模块

2.在子模块的pom.xml中导入依赖

"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">
    <parent>
        <artifactId>mybatis_mpartifactId>
        <groupId>com.mpgroupId>
        <version>1.0-SNAPSHOTversion>
    parent>
    <modelVersion>4.0.0modelVersion>
 
    <artifactId>mybatis_mp_springartifactId>
 
    <properties>
        <maven.compiler.source>8maven.compiler.source>
        <maven.compiler.target>8maven.compiler.target>
        <project.build.sourceEncoding>UTF-8project.build.sourceEncoding>
        <spring.version>5.1.6.RELEASEspring.version>
    properties>
 
    <dependencies>
        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-webmvcartifactId>
            <version>${spring.version}version>
        dependency>
        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-jdbcartifactId>
            <version>${spring.version}version>
        dependency>
        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-testartifactId>
            <version>${spring.version}version>
        dependency>
    dependencies>
 
project>

3.编写jdbc.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/tb_user?
useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=true&useSSL
=false
jdbc.username=root
jdbc.password=1234

4.编写applicationContext.xml

"1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
    <context:property-placeholder location="classpath:*.properties"/>
    
    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource"
          destroy-method="close">
        <property name="url" value="${jdbc.url}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
        <property name="driverClassName" value="${jdbc.driver}"/>
        <property name="maxActive" value="10"/>
        <property name="minIdle" value="5"/>
    bean>
    
    <bean id="sqlSessionFactory"
          class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
    bean>
    
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="cn.itcast.mp.simple.mapper"/>
    bean>
beans>

5.编写User对象

package com.mp.pojo;
 
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
 
@Data
@NoArgsConstructor
@AllArgsConstructor
@TableName("tb_user")
public class User {
    private long id;
    private String userName;
    private String password;
    private String name;
    private Integer age;
    private String email;
 
}

6.编写UserMapper接口

package com.mp.mapper;
 
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.mp.pojo.User;
 
import java.util.List;
 
public interface UserMapper extends BaseMapper {
    List findAll();
}

7.编写测试用例

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext.xml")
public class TestSpringMP {
    @Autowired
    private UserMapper userMapper;
    @Test
    public void testSelectList(){
        List users = this.userMapper.selectList(null);
        for (User user : users) {
            System.out.println(user);
        }
    }
}

七、SpringBoot+Mybatis+MP查询User

1.创建spring工程

2.导入依赖pom.xml

"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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0modelVersion>
 
    <parent>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-parentartifactId>
        <version>2.2.2.RELEASEversion>
        <relativePath/> 
    parent>
 
    <groupId>com.mpgroupId>
    <artifactId>SpringBoot_MPartifactId>
    <version>0.0.1-SNAPSHOTversion>
 
    <name>SpringBoot_MPname>
    <description>SpringBoot_MPdescription>
 
    <properties>
        <java.version>1.8java.version>
    properties>
 
    <dependencies>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starterartifactId>
        dependency>
 
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-testartifactId>
            <scope>testscope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintagegroupId>
                    <artifactId>junit-vintage-engineartifactId>
                exclusion>
            exclusions>
        dependency>
 
        
        <dependency>
            <groupId>org.projectlombokgroupId>
            <artifactId>lombokartifactId>
            <optional>trueoptional>
        dependency>
        
        <dependency>
            <groupId>com.baomidougroupId>
            <artifactId>mybatis-plus-boot-starterartifactId>
            <version>3.1.1version>
        dependency>
        
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <version>5.1.47version>
        dependency>
        <dependency>
            <groupId>org.slf4jgroupId>
            <artifactId>slf4j-log4j12artifactId>
        dependency>
        <dependency>
            <groupId>junitgroupId>
            <artifactId>junitartifactId>
            <scope>testscope>
        dependency>
 
    dependencies>
 
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.pluginsgroupId>
                <artifactId>maven-compiler-pluginartifactId>
                <version>3.8.1version>
                <configuration>
                    <source>1.8source>
                    <target>1.8target>
                    <encoding>UTF-8encoding>
                configuration>
            plugin>
            <plugin>
                <groupId>org.springframework.bootgroupId>
                <artifactId>spring-boot-maven-pluginartifactId>
            plugin>
        plugins>
    build>
 
project>

3.编写application.properties

spring.application.name = SpringBoot_MP
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://127.0.0.1:3306/zxkt?useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=true&useSSL=false
spring.datasource.username=root
spring.datasource.password=1234

4.编写pojo

package com.mp.pojo;
 
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@NoArgsConstructor
@AllArgsConstructor
@TableName("tb_user")
public class User {
    private Long id;
    private String userName;
    private String password;
    private String name;
    private Integer age;
    private String email;
}

5.编写mapper

package com.mp.mapper;
 
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.mp.pojo.User;
import org.springframework.stereotype.Repository;
 
@Repository
public interface UserMapper extends BaseMapper {
}

6.编写启动类

package com.mp;
 
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.WebApplicationType;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
@MapperScan("com.mp.mapper") //设置mapper接口的扫描包
@SpringBootApplication
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }
}

7.编写测试用例

package com.mp;
 
import com.mp.mapper.UserMapper;
import com.mp.pojo.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import java.util.List;
@RunWith(SpringRunner.class)
 
@SpringBootTest
public class UserMapperTest {
    @Autowired
    private UserMapper userMapper;
    @Test
    public void testSelect() {
        List userList = userMapper.selectList(null);
        for (User user : userList) {
            System.out.println(user);
        }
    }
}

八、基于springboot的其余CRUD

1.插入

//返回的result是受影响的行数
int result = usermapper.insert(user);

@TableId主键策略

放在对象类中，想设为主键的属性上方

AUTO是自增长（数据库中的表的对应id需要设为AUTO_INCREMENT）

NONE无策略

INPUT手动输入

 

@TableField

通过@TableField可以注解指定字段的一些属性

在对象类中进行注解

//解决字段名不一致
@TableField(value = "email")
private String mail;

//该字段在数据库表中不存在
@TableField(exist = false)
private String address;

//该字段不加入查询字段
@TableField(selece = false)
private String password;

2.更新

①根据id更新

public void testUpdateById() {
    User user = new User();
    user.setId(6L); //主键
    user.setAge(21); //更新的字段
    
    //根据id更新，更新不为null的字段
    this.userMapper.updateById(user);
}

②根据条件更新

public void testUpdate() {
    User user = new User();
    user.setAge(22); //更新的字段
 
    //更新的条件
    QueryWrapper wrapper = new QueryWrapper<>();
    wrapper.eq("id", 6);
 
    //执行更新操作
    int result = this.userMapper.update(user, wrapper);
    System.out.println("result = " + result);
}

3.删除

①deleteById

userMapper.deleteById(6L);

②deleteByMap

public void testDeleteByMap() {
    Map columnMap = new HashMap<>();
    columnMap.put("age",20);
    columnMap.put("name","张三");
 
    //将columnMap中的元素设置为删除的条件，多个之间为and关系
    int result = this.userMapper.deleteByMap(columnMap);
    System.out.println("result = " + result);
}

③delete

public void testDeleteByMap() {
    User user = new User();
    user.setAge(20);
    user.setName("张三");
 
    //将实体对象进行包装，包装为操作条件
    QueryWrapper wrapper = new QueryWrapper<>(user);
 
    int result = this.userMapper.delete(wrapper);
    System.out.println("result = " + result);
}

④批量删除

userMapper.deleteBatchIds(Arrays.asList(1L,10L,20L));

4.查询

①selectById

userMapper.selectById(2L);

②selectBatchlds

List users = this.userMapper.selectBatchIds(Arrays.asList(2L, 3L, 10L));
for (User user : users) {
    System.out.println(user);
}

③selectOne

QueryWrapper wrapper = new QueryWrapper();
wrapper.eq("name", "李四");
 
//根据条件查询一条数据，如果结果超过一条会报错
User user = this.userMapper.selectOne(wrapper);

④selectCount

QueryWrapper wrapper = new QueryWrapper();
wrapper.gt("age", 23); //年龄大于23岁
 
//根据条件查询数据条数
Integer count = this.userMapper.selectCount(wrapper);

⑤selectList

QueryWrapper wrapper = new QueryWrapper();
wrapper.gt("age", 23); //年龄大于23岁
 
//根据条件查询数据
List users = this.userMapper.selectList(wrapper);
for (User user : users) {
    System.out.println("user = " + user);
}

⑥selectPage

创建config包，在其中创建config对象如下

配置分页插件

@Configuration
@MapperScan("com.mp.mapper") //设置mapper接口的扫描包
public class MybatisPlusConfig {
    /**
    * 分页插件
    */
    @Bean
    public PaginationInterceptor paginationInterceptor() {
        return new PaginationInterceptor();
    }
}

QueryWrapper wrapper = new QueryWrapper();
wrapper.gt("age", 20); //年龄大于20岁
 
//第一个参数是当前页，第二个是每页显示记录数
Page page = new Page<>(1,1);
 
//根据条件查询数据
IPage iPage = this.userMapper.selectPage(page, wrapper);
System.out.println("数据总条数：" + iPage.getTotal());
System.out.println("总页数：" + iPage.getPages());
 
List users = iPage.getRecords();
for (User user : users) {
    System.out.println("user = " + user);
}

九、Mybatis-Plus对Service的封装

1.创建service接口

public interface UserService extends IService{
}

2.实现service接口

@Service
public UserServiceImpl extends ServiceImpl implements UserService{
}

3.调用

@AutoWored
private UserService userService;
 
@Test
public void testQuery() {
    List list = userService.list();
    System.out.prinlt(list);
}