Mybatis-Plus介绍
Mybatis-Plus介绍
Mybatis-Plus概念
Mybatis-Plus介绍
官网https://mybatis-plus/或https://mp.baomidou.com/
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;
特性:
无侵入：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
损耗小：启动即会自动注入基本 CURD，性能基本无损耗，直接面向对象操作
强大的 CRUD 操作：内置通用 Mapper、通用 Service，仅仅通过少量配置即可实现单表大部分 CRUD 操作，更有强大的条件构造器，满足各类使用需求
支持 Lambda 形式调用：通过 Lambda 表达式，方便的编写各类查询条件，无需再担心字段写错
支持主键自动生成：支持多达 4 种主键策略（内含分布式唯一 ID 生成器 - Sequence），可自由配置，完美解决主键问题
支持 ActiveRecord 模式：支持 ActiveRecord 形式调用，实体类只需继承 Model 类即可进行强大的 CRUD 操作
支持自定义全局通用操作：支持全局通用方法注入（ Write once, use anywhere ）
内置代码生成器：采用代码或者 Maven 插件可快速生成 Mapper 、 Model 、 Service 、 Controller 层代码，支持模板引擎，更有超多自定义配置等您来使用
内置分页插件：基于 MyBatis 物理分页，开发者无需关心具体操作，配置好插件之后，写分页等同于普通 List 查询
分页插件支持多种数据库：支持 MySQL、MariaDB、Oracle、DB2、H2、HSQL、SQLite、Postgre、SQLServer 等多种数据库
内置性能分析插件：可输出 SQL 语句以及其执行时间，建议开发测试时启用该功能，能快速揪出慢查询
内置全局拦截插件：提供全表 delete 、 update 操作智能分析阻断，也可自定义拦截规则，预防误操作
Mybatis-Plus快速入门
JDK:1.8
Maven
Mybatis-Plus:3.0
WARNING:引入Mybatis-plus之后,请不要再此引入Mybatis以及Mybatis-Spring,以避免因版本差异导致的问题!
数据库脚本
DROP TABLE IF EXISTS user;
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)
);数据库 Data 脚本:
DELETE FROM user;
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');maven依赖
<dependencies>
<!--mybatis-plus插件依赖-->
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.4.0</version>
</dependency>
<!--mysql-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.47</version>
</dependency>
<!--数据库连接池-->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.1.20</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.22</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13.2</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.7.30</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-site-plugin</artifactId>
</plugin>
</plugins>
</build>创建Model子模块
<?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">
<parent>
<artifactId>Wsy-Mybatis-Plus</artifactId>
<groupId>com.yun</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>Wsy-Mybatis-Plus-simple</artifactId>
<properties>
<maven.compiler.source>15</maven.compiler.source>
<maven.compiler.target>15</maven.compiler.target>
</properties>
</project>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.ConversionPatten=[%t] [%c]-[%p] %m%n原生Mybatis实现查询User
1,编写文件
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>
<properties resource="jdbc.properties"></properties>
<!--environments:运行环境-->
<environments default="development">
<environment id="development">
<!--当前事务交由JDBC进行管理-->
<transactionManager type="JDBC"></transactionManager>
<!--当前使用mybatis提供的连接池-->
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</dataSource>
</environment>
</environments>
<!--引入映射配置文件-->
<mappers>
<mapper resource="mapper/UserMapper.xml"></mapper>
</mappers>
</configuration>jdbc.properties
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1/zdy_mybatis
jdbc.username=root
jdbc.password=1234562,User实体
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
/** id */
private Long id;
/** name */
private String name;
/** age */
private Integer age;
/** email */
private String email;
}3,编写UserMapper接口
public interface UserMapper {
/**
* 查询所有用户
* @return
*/
List<User> getAll();
}4,编写UserMapper.xml文件
<?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.yun.mapper.UserMapper">
<!--select-->
<select id="getAll" resultType="com.yun.pojo.User">
select * from user
</select>
</mapper>5,测试
public static void main(String[] args) throws IOException {
InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> userList = mapper.getAll();
userList.forEach(item -> {
System.out.println(item);
});
}运行结果报错!!!
Cause: java.io.IOException: Could not find resource mapper/UserMapper.xml提示找不到xml配置文件,我们在sqlMapConfig.xml中修改一下引入映射配置文件
<mappers>
<package name="com.yun.mapper"/>
</mappers>然后在运行一下,运行结果如下
Created connection 895599632.
Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@3561c410]
==> Preparing: select * from user
==> Parameters:
<== Total: 5
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)Mybatis+MP实现查询User
1,承接上面的代码,将UserMapper继承BaseMapper,将拥有了BaseMapper中的所有方法;
public interface UserMapper extends BaseMapper<User> {
}2,使用MP中的MybatisSqlSessionFactoryBuilder进程构建;
public static void main(String[] args) throws IOException {
InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new MybatisSqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> userList = mapper.getAll();
userList.forEach(item -> {
System.out.println(item);
});
}运行结果报错,提示java.lang.ClassNotFoundException: org.springframework.core.GenericTypeResolver经排查发现是jar包冲突了,然后检查pom依赖,发现mybatis-plusjar包引入依赖有误 这边修改一下为
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.4.0</version>
</dependency>重新运行代码.运行结果如下:
17:17:32.986 [main] DEBUG com.yun.mapper.UserMapper.getAll - ==> Preparing: select * from user
17:17:33.040 [main] DEBUG com.yun.mapper.UserMapper.getAll - ==> Parameters:
17:17:33.134 [main] DEBUG com.yun.mapper.UserMapper.getAll - <== Total: 5
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)现在我们换成Mybatsi-Plus内嵌的方法:
public static void main(String[] args) throws IOException {
InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new MybatisSqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> userList = mapper.selectList(null);
userList.forEach(item -> {
System.out.println(item);
});运行结果
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)发现是正常,展示Mybatis-Plus强大的特性!
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