MyBatis-Plus 基础环境搭建

短命女 2022-09-13 11:26 200阅读 0赞

# 一 简介 #

MyBatis-Plus（简称 MP）是一个 MyBatis 的增强工具，在 MyBatis 的基础上只做增强不做改变，为简化开发、提高效率而生。

*  润物无声  
 *  只做增强不做改变，引入它不会对现有工程产生影响，如丝般顺滑。
 *  效率至上
 *  只需简单配置，即可快速进行 CRUD 操作，从而节省大量时间。
 *  丰富功能
 *  热加载、代码生成、分页、性能分析等功能一应俱全。

# 二 脚本 #

CREATE TABLE USER
    (
        id BIGINT(20)NOT NULL COMMENT '主键ID',
        NAME VARCHAR(30)NULL DEFAULT NULL COMMENT '姓名',
        age INT(11)NULL DEFAULT NULL COMMENT '年龄',
        email VARCHAR(50)NULL DEFAULT NULL COMMENT '邮箱',
        PRIMARY KEY (id)
    );
    INSERT INTO user (id, name, age, email)VALUES
    (1, 'Jone', 18, 'test1@baomidou.com'),
    (2, 'Jack', 20, 'test2@baomidou.com'),
    (3, 'Tom', 28, 'test3@baomidou.com'),
    (4, 'Sandy', 21, 'test4@baomidou.com'),
    (5, 'Billie', 24, 'test5@baomidou.com');

# 三 项目 #

### 1 初始化工程 ###

使用 Spring Initializr 快速初始化一个 Spring Boot 工程。

### 2 pom文件 ###

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.2.1.RELEASE</version>
            <relativePath/> 
        </parent>
        <groupId>com.cakin</groupId>
        <artifactId>demomptest</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <name>demomptest</name>
        <description>Demo project for Spring Boot</description>
        <properties>
            <java.version>1.8</java.version>
        </properties>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
                <exclusions>
                    <exclusion>
                        <groupId>org.junit.vintage</groupId>
                        <artifactId>junit-vintage-engine</artifactId>
                    </exclusion>
                </exclusions>
            </dependency>
    
            
            <dependency>
                <groupId>com.baomidou</groupId>
                <artifactId>mybatis-plus-boot-starter</artifactId>
                <version>3.3.1</version>
            </dependency>
    
            
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
            </dependency>
            
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <optional>true</optional>
            </dependency>
        </dependencies>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
                
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-surefire-plugin</artifactId>
                    <version>2.22.1</version>
                    <configuration>
                        <skipTests>true</skipTests>
                    </configuration>
                </plugin>
                
            </plugins>
        </build>
    </project>

### 3 插件安装 ###

安装 lombok

# 四 代码 #

### 1 配置 ###

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
    spring.datasource.url=jdbc:mysql://192.168.0.174:3306/mybatis_plus?serverTimezone=GMT%2B8
    spring.datasource.username=root
    spring.datasource.password=Mima123456
    
    # mybatis日志
    mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

### 2 启动类 ###

package com.cakin.demomptest;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    
    @SpringBootApplication
    public class DemomptestApplication {
        public static void main(String[] args) {
            SpringApplication.run(DemomptestApplication.class, args);
        }
    }

### 3 实体类 ###

@Data
    public class User {
        private Long id;
        private String name;
        private Integer age;
        private String email;
    }

### 4 添加mapper ###

package com.cakin.demomptest.mapper;
    
    import com.cakin.demomptest.entity.User;
    import com.baomidou.mybatisplus.core.mapper.BaseMapper;
    import org.springframework.stereotype.Repository;
    
    @Repository
    public interface UserMapper extends BaseMapper<User> {
    }

### 5 测试 ###

package com.cakin.demomptest;
    
    import com.cakin.demomptest.entity.User;
    import com.cakin.demomptest.mapper.UserMapper;
    import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
    import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
    import org.junit.jupiter.api.Test;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.test.context.SpringBootTest;
    
    
    import java.util.Arrays;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    
    
    @SpringBootTest
    class DemomptestApplicationTests {
        @Autowired
        private UserMapper userMapper;
    
        @Test
        public void findAll() {
            List<User> users = userMapper.selectList(null);
            System.out.println(users);
        }
    }

注意：

为了避免报错，可以在 dao 层 的接口上添加 @Repository 注解。

如果不加，IDEA 在 userMapper 处报错，因为找不到注入的对象，因为类是动态创建的，但是程序可以正确的执行。

通过以上几个简单的步骤，我们就实现了 User 表的 CRUD 功能，甚至连 XML 文件都不用编写！

# 五 测试结果 #

Creating a new SqlSession
    SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@1d25c1c] was not registered for synchronization because synchronization is not active
    2021-09-28 18:49:08.792  INFO 21380 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
    2021-09-28 18:49:09.992  INFO 21380 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
    JDBC Connection [HikariProxyConnection@1825662118 wrapping com.mysql.cj.jdbc.ConnectionImpl@242a209e] will not be managed by Spring
    ==>  Preparing: SELECT id,name,age,email FROM user
    ==> Parameters:
    <==    Columns: id, name, age, email
    <==        Row: 1, Jone, 18, test1@baomidou.com
    <==        Row: 2, Jack, 20, test2@baomidou.com
    <==        Row: 3, Tom, 28, test3@baomidou.com
    <==        Row: 4, Sandy, 21, test4@baomidou.com
    <==        Row: 5, Billie, 24, test5@baomidou.com
    <==      Total: 5
    Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@1d25c1c]
    [User(id=1, name=Jone, age=18, email=test1@baomidou.com), User(id=2, name=Jack, age=20, email=test2@baomidou.com), User(id=3, name=Tom, age=28, email=test3@baomidou.com), User(id=4, name=Sandy, age=21, email=test4@baomidou.com), User(id=5, name=Billie, age=24, email=test5@baomidou.com)]
    
    2021-09-28 18:49:10.194  INFO 21380 --- [extShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
    2021-09-28 18:49:10.219  INFO 21380 --- [extShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.
    
    Process finished with exit code 0