mybatis-plus插件

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分页插件

• MyBatis Plus自带分页插件，只要简单的配置即可实现分页功能

配置并使用自带分页插件

@Configuration
@MapperScan("com.itzhh.mapper")//可以将主类中的注解移到此处
public class MybatisPlusConfig {

    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor(){
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        return interceptor;
    }
}

 @Test
    public void testPage(){
        //设置分页参数
        Page<User> page = new Page<>(2, 3);
        //Preparing: SELECT uid AS id,username AS name,
        //age,email,is_deleted FROM t_user WHERE is_deleted=0 LIMIT ?,?
        userMapper.selectPage(page,null);
        //获取分页数据
        List<User> list = page.getRecords();
        list.forEach(System.out::println);
        System.out.println();System.out.println("当前页："+page.getCurrent());
        System.out.println("每页显示的条数："+page.getSize());
        System.out.println("总记录数："+page.getTotal());
        System.out.println("总页数："+page.getPages());
        System.out.println("是否有上一页："+page.hasPrevious());
        System.out.println("是否有下一页："+page.hasNext());
    }

使用自定义分页插件

• 创建接口（注意，第一个参数一定要是Page）

@Repository
public interface UserMapper extends BaseMapper<User> {
    Page<User> selectPageVo(@Param("page")Page<User> page,@Param("age")Integer age);
}

• UserMapper.xml中编写SQL

<?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.itzhh.mapper.UserMapper">

    <sql id="BaseColumns" >uid,username,age,email</sql>

    <select id="selectPageVo" resultType="com.itzhh.pojo.User">
     select <include refid="BaseColumns"></include>
     from t_user where  age>#{age}

    </select>
</mapper>

• 测试

 @Test
    public void testSelectPageVo(){
        //设置分页参数
        Page<User> page = new Page<>(1, 2);
        userMapper.selectPageVo(page, 20);
        //获取分页数据
        List<User> list = page.getRecords();
        list.forEach(System.out::println);
        System.out.println("当前页："+page.getCurrent());
        System.out.println("每页显示的条数："+page.getSize());
        System.out.println("总记录数："+page.getTotal());
        System.out.println("总页数："+page.getPages());
        System.out.println("是否有上一页："+page.hasPrevious());
        System.out.println("是否有下一页："+page.hasNext());
    }

Mybatis-Plus实现乐观锁

• 添加version字段
  
• 添加乐观锁插件配置

 @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor(){
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        //添加分页插件
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        //添加乐观锁配置
        interceptor.addInnerInterceptor(new OptimisticLockerInnerInterceptor());
        return interceptor;
    }

• 测试

 @Test
    public void testConcurrentVersionUpdate() {
        //小李取数据
        Product p1 = productMapper.selectById(00000000000000000001L);
        //小王取数据
        Product p2 = productMapper.selectById(00000000000000000001L);
        //小李修改 + 50
        p1.setPrice(p1.getPrice() + 50);
        int result1 = productMapper.updateById(p1);
        System.out.println("小李修改的结果：" + result1);
        //小王修改 - 30
        p2.setPrice(p2.getPrice() - 30);
        int result2 = productMapper.updateById(p2);
        System.out.println("小王修改的结果：" + result2);
        if(result2 == 0){
        //失败重试，重新获取version并更新
            p2 = productMapper.selectById(00000000000000000001L);
            p2.setPrice(p2.getPrice() - 30);
            result2 = productMapper.updateById(p2);
        }
        System.out.println("小王修改重试的结果：" + result2);
        //老板看价格
        Product p3 = productMapper.selectById(00000000000000000001L);
        System.out.println("老板看价格：" + p3.getPrice());
    }

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@15dc339f] was not registered for synchronization because synchronization is not active
2023-02-14 09:42:36.662  INFO 21336 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2023-02-14 09:42:36.842  INFO 21336 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@695085082 wrapping com.mysql.cj.jdbc.ConnectionImpl@59cda16e] will not be managed by Spring
==>  Preparing: SELECT id,name,price,version FROM t_product WHERE id=?
==> Parameters: 1(Long)
<==    Columns: id, name, price, version
<==        Row: 1, 新华字典, 100, 1
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@15dc339f]
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@10b1a751] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@1406114969 wrapping com.mysql.cj.jdbc.ConnectionImpl@59cda16e] will not be managed by Spring
==>  Preparing: SELECT id,name,price,version FROM t_product WHERE id=?
==> Parameters: 1(Long)
<==    Columns: id, name, price, version
<==        Row: 1, 新华字典, 100, 1
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@10b1a751]
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5a1c3cb4] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@709841971 wrapping com.mysql.cj.jdbc.ConnectionImpl@59cda16e] will not be managed by Spring
==>  Preparing: UPDATE t_product SET name=?, price=?, version=? WHERE id=? AND version=?
==> Parameters: 新华字典(String), 150(Integer), 2(Integer), 1(Long), 1(Integer)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5a1c3cb4]
小李修改的结果：1
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7f5538a1] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@1929218620 wrapping com.mysql.cj.jdbc.ConnectionImpl@59cda16e] will not be managed by Spring
==>  Preparing: UPDATE t_product SET name=?, price=?, version=? WHERE id=? AND version=?
==> Parameters: 新华字典(String), 70(Integer), 2(Integer), 1(Long), 1(Integer)
<==    Updates: 0
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7f5538a1]
小王修改的结果：0
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@34780cd9] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@1648278215 wrapping com.mysql.cj.jdbc.ConnectionImpl@59cda16e] will not be managed by Spring
==>  Preparing: SELECT id,name,price,version FROM t_product WHERE id=?
==> Parameters: 1(Long)
<==    Columns: id, name, price, version
<==        Row: 1, 新华字典, 150, 2
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@34780cd9]
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@1ab5f08a] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@1860118977 wrapping com.mysql.cj.jdbc.ConnectionImpl@59cda16e] will not be managed by Spring
==>  Preparing: UPDATE t_product SET name=?, price=?, version=? WHERE id=? AND version=?
==> Parameters: 新华字典(String), 120(Integer), 3(Integer), 1(Long), 2(Integer)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@1ab5f08a]
小王修改重试的结果：1
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@66b59b7d] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@1395725953 wrapping com.mysql.cj.jdbc.ConnectionImpl@59cda16e] will not be managed by Spring
==>  Preparing: SELECT id,name,price,version FROM t_product WHERE id=?
==> Parameters: 1(Long)
<==    Columns: id, name, price, version
<==        Row: 1, 新华字典, 120, 3
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@66b59b7d]
老板看价格：120

通用枚举

• 表中的有些字段值是固定的，例如性别（男或女），此时我们可以使用MyBatis-Plus的通用枚举来实现
• 创建枚举类（如果不加 @EnumValue，会报如下错误）

package com.itzhh.enums;

import com.baomidou.mybatisplus.annotation.EnumValue;
import lombok.Getter;

/**
 * Author: zhh
 * Date: 2023-02-14 10:11
 * Description: <描述>
 */
@Getter
public enum  SexEnum {
    MALE(1,"男"),
    FEMALE(0,"女");

    @EnumValue
    private Integer sex;
    private String sexName;



    SexEnum(Integer sex, String sexName) {
        this.sex = sex;
        this.sexName = sexName;
    }
}

• 添加枚举字段
  
• 配置扫描通用枚举

#    配置mybatis日志
mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  global-config:
    db-config:
      # 配置MyBatis-Plus操作表的默认前缀
      table-prefix: t_
      #配置mybatis-plus的主键策略
      id-type: auto
      # 配置扫描通用枚举
  type-enums-package: com.itzhh.enums

• 测试

@Test
    public void testSexEnum(){
        User user = new User();
        user.setName("Enum");
        user.setAge(20);
        //设置性别信息为枚举项，会将@EnumValue注解所标识的属性值存储到数据库
        user.setSex(SexEnum.MALE);

        userMapper.insert(user);
    }

代码生成器

• 引入依赖

<dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-generator</artifactId>
            <version>3.5.1</version>
        </dependency>
        <dependency>
            <groupId>org.freemarker</groupId>
            <artifactId>freemarker</artifactId>
            <version>2.3.31</version>
        </dependency>

@Test
    void contextLoads() {
        FastAutoGenerator.create("jdbc:mysql://localhost:3306/mybatis_plus?serverTimezone=GMT%2B8&characterEncoding=utf-8&useSSL=false", "root", "123456")
                .globalConfig(builder -> {
                    builder.author("zhh") // 设置作者
                            //.enableSwagger() // 开启 swagger 模式
                            .fileOverride() // 覆盖已生成文件
                            .outputDir("E:\\IDEA\\IDEAProjects\\mybatis_plus_auto"); // 指定输出目录
                })
                .packageConfig(builder -> {
                    builder.parent("com.itzhh") // 设置父包名
                            .moduleName("mybatisplus") // 设置父包模块名
                            .pathInfo(Collections.singletonMap(OutputFile.mapperXml, "E:\\IDEA\\IDEAProjects\\mybatis_plus_auto"));// 设置mapperXml生成路径
                })
                .strategyConfig(builder -> {
                    builder.addInclude("t_user") // 设置需要生成的表名
                            .addTablePrefix("t_", "c_"); // 设置过滤表前缀
                })
                .templateEngine(new FreemarkerTemplateEngine()) // 使用Freemarker 引擎模板，默认的是Velocity引擎模板
                .execute();
    }

多数据源

• 模拟场景
  我们创建两个库，分别为：mybatis_plus（以前的库不动）与mybatis_plus_1（新建），将mybatis_plus库的product表移动到mybatis_plus_1库，这样每个库一张表，通过一个测试用例分别获取用户数据与商品数据，如果获取到说明多库模拟成功
• 添加依赖

<dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>dynamic-datasource-spring-boot-starter</artifactId>
            <version>3.5.0</version>
        </dependency>

• 配置多数据源

spring:
  datasource:
    dynamic:
      strict: false
      datasource:
        master:
          driver-class-name: com.mysql.cj.jdbc.Driver
          url: jdbc:mysql://localhost:3306/mybatis_plus?serverTimezone=GMT%2B8&characterEncoding=utf-8&useSSL=false
          username: root
          password: 123456
        slave_1:
          driver-class-name: com.mysql.cj.jdbc.Driver
          url: jdbc:mysql://localhost:3306/mybatis_plus_1?serverTimezone=GMT%2B8&characterEncoding=utf-8&useSSL=false
          username: root
          password: 123456
#    配置mybatis日志
mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

• 创建用户service

public interface UserService extends IService<User> {
}

@DS("master") //指定所操作的数据源
@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {
}

• 创建商品service

public interface ProductService extends IService<Product> {
}

@DS("slave_1") //指定所操作的数据源
@Service
public class ProductServiceImpl extends ServiceImpl<ProductMapper, Product> implements ProductService {
}

• 测试

 @Autowired
    private UserService userService;

    @Autowired
    private ProductService productService;

    @Test
    void contextLoads() {
        System.out.println(userService.getById(1L));
        System.out.println(productService.getById(1L));
    }

安装MybatisX插件并使用其简化开发

• 这个我一直再用，就不记录了