MyBatisPlus学习笔记

Java Web

看完黑马的视频之后写的，应该不是很完整（后面如果发现不全的话再加？）

依赖

下面是mp、druid、lombok、代码生成器的依赖

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<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.2</version>
</dependency>

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.2.16</version>
</dependency>

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
</dependency>

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-generator</artifactId>
    <version>3.4.1</version>
</dependency>

<dependency>
    <groupId>org.apache.velocity</groupId>
    <artifactId>velocity-engine-core</artifactId>
    <version>2.3</version>
</dependency>

JDBC参数

在application.yml里添加

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spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://124.223.44.144:3306/mybatisplus?serverTimezone=UTC&useSSL=false
    username: root
    password: dong

标准数据层CRUD功能

在UserDao中继承BaseMapper<User>即可使用mp的接口

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@Mapper
public interface UserDao extends BaseMapper<User> {
}

对于一般的crud，mp给了非常多的接口可以使用，这里不多赘述

image-20230326202155372

lombok

引入lombok依赖（在文章开头）

然后实体类添加@Data注解即自动添加get/set等等方法，注意不包含有参无参构造！！！！

有参无参构造可以用@NoArgsConstructor、@AllArgsConstructor

如User实体类：

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@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private Long id;
    private String name;
    private String password;
    private Integer age;
    private String tel;
    private Integer deleted;
    @Version
    private Integer version;
}

mp标准日志输出

在yml里加入以下代码

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mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

分页功能

添加拦截器

下面的PaginationInnerInterceptor就是分页拦截器

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package top.zhengru.config;

@Configuration
public class MpConfig {
    @Bean
    public MybatisPlusInterceptor mpInterceptor(){
        MybatisPlusInterceptor mpInterceptor = new MybatisPlusInterceptor();
        mpInterceptor.addInnerInterceptor(new PaginationInnerInterceptor());
        return mpInterceptor;
    }
}

执行分页查询

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@Test
void testGetByPage(){
    IPage page = new Page(2,3);
    userDao.selectPage(page,null);
    System.out.println("当前页码："+page.getCurrent());
    System.out.println("每页显示数："+page.getSize());
    System.out.println("总页数："+page.getPages());
    System.out.println("总条数："+page.getTotal());
    System.out.println("数据："+page.getRecords());
}

条件查询

常规格式

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QueryWrapper qw = new QueryWrapper();
qw.lt("age",23);
List<User> userList = userDao.selectList(qw);
System.out.println(userList);

Lambda格式

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QueryWrapper<User> qw = new QueryWrapper<User>();
qw.lambda().lt(User::getAge,23);
List<User> userList = userDao.selectList(qw);
System.out.println(userList);

null值处理

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LambdaQueryWrapper<User> lqw =new LambdaQueryWrapper<User>();
lqw.lt(null != uq.getAge(),User::getAge,uq.getAge())
        .gt(null != uq.getAge2(),User::getAge,uq.getAge2());
List<User> userList = userDao.selectList(lqw);
System.out.println(userList);

查询投影

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LambdaQueryWrapper<User> lqw =new LambdaQueryWrapper<User>();
QueryWrapper<User> lqw =new QueryWrapper<User>();
lqw.select("id","name","age","tel");
lqw.select("count(*) as count,tel");
lqw.groupBy("tel");
List<Map<String, Object>> userList = userDao.selectMaps(lqw);
System.out.println(userList);

模糊查询

like还有likeLeft

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LambdaQueryWrapper<User> lqw =new LambdaQueryWrapper<>();
lqw.like(User::getName,"o");
List<User> users = userDao.selectList(lqw);
System.out.println(users);

还有很多就不列举了…

字段映射与表名映射

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@TableName("t_user")	//表名映射
@TableField(exist = false)		//是否存在
@TableField(value = "pwd")		//字段名映射
@TableField(select = false)		//是否查询

DML控制

id生成策略控制

如下图

image-20230326211821002

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mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  global-config:
    db-config:
      id-type: assign_id		#全局配置

表名前缀

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mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  global-config:
    db-config:
      table-prefix: t_		#全局配置

逻辑删除

用deleted标记0未删除，1删除

image-20230326212455123

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@TableLogic(value = "0",delval = "1")
private Integer deleted;

或者

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mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  global-config:
    db-config:
      logic-delete-field: deleted	#全局配置
      logic-not-delete-value: 0
      logic-delete-value: 1

乐观锁

用version标记

image-20230326212214171

用@Version注解标记实体类属性

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@Version
private Integer version;

添加OptimisticLockerInnerInterceptor拦截器拼接SQL

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@Configuration
public class MpConfig {
    @Bean
    public MybatisPlusInterceptor mpInterceptor(){
        MybatisPlusInterceptor mpInterceptor = new MybatisPlusInterceptor();
        mpInterceptor.addInnerInterceptor(new PaginationInnerInterceptor());
        mpInterceptor.addInnerInterceptor(new OptimisticLockerInnerInterceptor());	//拦截器
        return mpInterceptor;
    }
}

快速开发

同理依赖在文章开头

下面是创建对象的方法和代码生成器的配置文件

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AutoGenerator autoGenerator = new AutoGenerator();
autoGenerator.execute();
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public class CodeGenerator {
    public static void main(String[] args) {
        //1.获取代码生成器的对象
        AutoGenerator autoGenerator = new AutoGenerator();
 
        //设置数据库相关配置
        DataSourceConfig dataSource = new DataSourceConfig();
        dataSource.setDriverName("com.mysql.cj.jdbc.Driver");
        dataSource.setUrl("jdbc:mysql://localhost:3306/mybatisplus_db?serverTimezone=UTC");
        dataSource.setUsername("root");
        dataSource.setPassword("root");
        autoGenerator.setDataSource(dataSource);
 
        //设置全局配置
        GlobalConfig globalConfig = new GlobalConfig();
        globalConfig.setOutputDir(System.getProperty("user.dir")+"/mybatisplus_04_generator/src/main/java");    //设置代码生成位置
        globalConfig.setOpen(false);    //设置生成完毕后是否打开生成代码所在的目录
        globalConfig.setAuthor("黑马程序员");    //设置作者
        globalConfig.setFileOverride(true);     //设置是否覆盖原始生成的文件
        globalConfig.setMapperName("%sDao");    //设置数据层接口名，%s为占位符，指代模块名称
        globalConfig.setIdType(IdType.ASSIGN_ID);   //设置Id生成策略
        autoGenerator.setGlobalConfig(globalConfig);
 
        //设置包名相关配置
        PackageConfig packageInfo = new PackageConfig();
        packageInfo.setParent("com.aaa");   //设置生成的包名，与代码所在位置不冲突，二者叠加组成完整路径
        packageInfo.setEntity("domain");    //设置实体类包名
        packageInfo.setMapper("dao");   //设置数据层包名
        autoGenerator.setPackageInfo(packageInfo);
 
        //策略设置
        StrategyConfig strategyConfig = new StrategyConfig();
        strategyConfig.setInclude("tbl_user");  //设置当前参与生成的表名，参数为可变参数
        strategyConfig.setTablePrefix("tbl_");  //设置数据库表的前缀名称，模块名 = 数据库表名 - 前缀名  例如： User = tbl_user - tbl_
        strategyConfig.setRestControllerStyle(true);    //设置是否启用Rest风格
        strategyConfig.setVersionFieldName("version");  //设置乐观锁字段名
        strategyConfig.setLogicDeleteFieldName("deleted");  //设置逻辑删除字段名
        strategyConfig.setEntityLombokModel(true);  //设置是否启用lombok
        autoGenerator.setStrategy(strategyConfig);
        //2.执行生成操作
        autoGenerator.execute();
    }
}