MybatisPlus|整合SpringBoot

1. 基礎知識介紹

1.1 MP概要

MyBatis-Plus（簡稱 MP）是一個 MyBatis 的增強工具，在 MyBatis 的基礎上只做增強不做改變，爲簡化開發、提高效率而生。

1.2 MP特性

• 無侵入：只做增強不做改變，引入它不會對現有工程產生影響，如絲般順滑
• 損耗小：啓動即會自動注入基本 CURD，性能基本無損耗，直接面向對象操作
• 強大的 CRUD 操作：內置通用 Mapper、通用 Service，僅僅通過少量配置即可實現單表大部分 CRUD 操作，更有強大的條件構造器，滿足各類使用需求
• 支持 Lambda 形式調用：通過 Lambda 表達式，方便的編寫各類查詢條件，無需再擔心字段寫錯
• 支持主鍵自動生成：支持多達 4 種主鍵策略（內含分佈式唯一 ID 生成器 - Sequence），可自由配置，完美解決主鍵問題
• 支持 ActiveRecord 模式：支持 ActiveRecord 形式調用，實體類只需繼承 Model 類即可進行強大的 CRUD 操作
• 支持自定義全局通用操作：支持全局通用方法注入（ Write once, use anywhere ）
• 內置代碼生成器：採用代碼或者 Maven 插件可快速生成 Mapper 、 Model 、 Service 、 Controller 層代碼，支持模板引擎，更有超多自定義配置等您來使用
• 內置分頁插件：基於 MyBatis 物理分頁，開發者無需關心具體操作，配置好插件之後，寫分頁等同於普通 List 查詢
• 分頁插件支持多種數據庫：支持 MySQL、MariaDB、Oracle、DB2、H2、HSQL、SQLite、Postgre、SQLServer 等多種數據庫
• 內置性能分析插件：可輸出 Sql 語句以及其執行時間，建議開發測試時啓用該功能，能快速揪出慢查詢
• 內置全局攔截插件：提供全表 delete 、 update 操作智能分析阻斷，也可自定義攔截規則，預防誤操作

2. 環境準備

• 操作系統：macOS Catalina 10.15.3
• IDEA：IntelliJ IDEA 2019.1 (Ultimate Edition)
• JDK：1.8
• SpringBoot：2.3.1
• MybatisPlus：3.3.2
• Mysql：8.0.19

3. 項目結構

4. 基本操作過程

4.1 創建測試表

CREATE DATABASE mp;
USE mp;

DROP TABLE IF EXISTS `tbl_employee`;

CREATE TABLE `tbl_employee` (
  `id` int NOT NULL AUTO_INCREMENT,
  `last_name` varchar(45) DEFAULT NULL,
  `email` varchar(45) DEFAULT NULL,
  `gender` char(1) DEFAULT NULL,
  `age` int DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;


LOCK TABLES `tbl_employee` WRITE;

INSERT INTO `tbl_employee` VALUES (1,'Tom','[email protected]','1',22),(2,'Hedon','Hedon@hedon,com','1',21),(3,'Jerry','[email protected]','2',18),(4,'White','[email protected]','2',30);

UNLOCK TABLES;

4.2 創建 SpringBoot 的 Web 項目

4.3 編寫 pom.xml 文件，加入依賴座標

重點：

• mybatis-plus
• lombok

<dependency>
  <groupId>org.projectlombok</groupId>
  <artifactId>lombok</artifactId>
  <optional>true</optional>
</dependency>
<dependency>
  <groupId>com.baomidou</groupId>
  <artifactId>mybatis-plus-boot-starter</artifactId>
  <version>3.3.2</version>
</dependency>

4.4 編寫配置文件 application.properties，配置數據庫連接信息

spring.application.name=itcast-mp-springboot

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/mp
spring.datasource.username=root
spring.datasource.password=root

在 Spring Boot 啓動類中添加 @MapperScan 註解，掃描 Mapper 文件夾

4.6 編寫實體類 Employee

package it.cast.mp.itcastmpspringboot.pojo;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;

/**
 * @author Hedon Wang
 * @create 2020-06-24 22:53
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
@ToString
@TableName(value = "tbl_employee")
public class Employee {

    @TableId(value = "id",type = IdType.AUTO)
    private Integer id ;   //  int
    private String  lastName;
    private String  email ;
    private Integer gender;
    private Integer age ;
    private Double  salary ;

}

4.7 編寫Mapper接口，並繼承MP提供的BaseMapper

package it.cast.mp.itcastmpspringboot.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import it.cast.mp.itcastmpspringboot.pojo.Employee;

/**
 * @author Hedon Wang
 * @create 2020-06-25 00:25
 */
public interface EmployeeMapper extends BaseMapper<Employee> {

}

4.8 測試 selectList()

@RunWith(SpringRunner.class)
@SpringBootTest
class ItcastMpSpringbootApplicationTests {

    @Autowired
    EmployeeMapper employeeMapper;

    @Test
    public void testSearchList(){
        List<Employee> employees = employeeMapper.selectList(null);
        for (Employee employee:employees){
            System.out.println(employee);
        }
    }
}

• 測試結果

5. 項目源碼

5.1 ItcastMpSpringbootApplication.java

package it.cast.mp.itcastmpspringboot;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;


@MapperScan("it.cast.mp.itcastmpspringboot.mapper")
@SpringBootApplication
public class ItcastMpSpringbootApplication {

    public static void main(String[] args) {
        SpringApplication.run(ItcastMpSpringbootApplication.class, args);
    }

}

5.2 Employee.java

package it.cast.mp.itcastmpspringboot.pojo;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;

/**
 * @author Hedon Wang
 * @create 2020-06-24 22:53
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
@ToString
@TableName(value = "tbl_employee")
public class Employee {

    @TableId(value = "id",type = IdType.AUTO)
    private Integer id ;   //  int
    private String  lastName;
    private String  email ;
    private Integer gender;
    private Integer age ;
    private Double  salary ;

}

5.3 EmployeeMapper.java

package it.cast.mp.itcastmpspringboot.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import it.cast.mp.itcastmpspringboot.pojo.Employee;

/**
 * @author Hedon Wang
 * @create 2020-06-25 00:25
 */
public interface EmployeeMapper extends BaseMapper<Employee> {

}

5.4 application.properties

spring.application.name=itcast-mp-springboot

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/mp
spring.datasource.username=root
spring.datasource.password=root

5.5 log4j.properties

log4j.rootLogger=DEBUG,A1

log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout = org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=[%t]  [%c]-[%p]  %m%n

5.6 ItcastMpSpringbootApplicationTests.java

package it.cast.mp.itcastmpspringboot;

import it.cast.mp.itcastmpspringboot.mapper.EmployeeMapper;
import it.cast.mp.itcastmpspringboot.pojo.Employee;
import org.junit.jupiter.api.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.SpringJUnit4ClassRunner;
import org.springframework.test.context.junit4.SpringRunner;

import java.util.List;

@RunWith(SpringRunner.class)
@SpringBootTest
class ItcastMpSpringbootApplicationTests {


    @Autowired
    EmployeeMapper employeeMapper;

    @Test
    void contextLoads() {
    }


    @Test
    public void testSearchList(){
        List<Employee> employees = employeeMapper.selectList(null);
        for (Employee employee:employees){
            System.out.println(employee);
        }
    }

}

5.7 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 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>2.3.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>it.cast.mp</groupId>
    <artifactId>itcast-mp-springboot</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>itcast-mp-springboot</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>
            </dependency>
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <optional>true</optional>
            </dependency>
            <dependency>
                <groupId>com.baomidou</groupId>
                <artifactId>mybatis-plus-boot-starter</artifactId>
                <version>3.3.2</version>
            </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>