初始代码准备

  1. 创建一个itheima_springboot的project

  2. 在pom.xml中导入相应的坐标

      <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>junit</groupId>
    	<artifactId>junit</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>3.4.2</version>
    </dependency>
    <dependency>
    	<groupId>mysql</groupId>
    	<artifactId>mysql-connector-java</artifactId>
    	<version>5.1.46</version>
    </dependency>
    <dependency>
    	<groupId>org.slf4j</groupId>
    	<artifactId>slf4j-log4j12</artifactId>
    </dependency>

  3. 在resources下新建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

  4. 在java下新建com.itheima.pojo.User实体类

    package com.itheima.pojo;
    import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.NoArgsConstructor;

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

  5. 在java下新建com.itheima.mapper.UserMapper.java

    package com.itheima.mapper;
    import com.baomidou.mybatisplus.core.mapper.BaseMapper;
    import com.itheima.pojo.User;
    public interface UserMapper extends BaseMapper<User> {
    }

  6. 在resources下新建mapper/UserMapper.xml

    <?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.itheima.mapper.UserMapper">

    </mapper>

  7. 在resources下修改application.yml

    spring:
      datasource:
        driver-class-name: com.mysql.jdbc.Driver
        url: jdbc:mysql://127.0.0.1:3306/mp?useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=true&useSSL=false
        username: root
        password: root
    mybatis-plus:
      # 指定Mapper.xml文件的路径
      mapper-locations: classpath:mapper/UserMapper.xml
      # 实体对象的扫描包
      type-aliases-package: com.itheima.pojo
      # 配置表名(tb_user)
      global-config:
        db-config:
          table-prefix: tb_

  8. 编写测试方法

    package com.itheima.test;
    import com.itheima.mapper.UserMapper;
    import com.itheima.pojo.User;
    import org.junit.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 java.util.List;
    @RunWith(SpringJUnit4ClassRunner.class)
    @SpringBootTest
    public class MyTest {
        @Autowired
        private UserMapper mapper;
        @Test
        public void selectMyList() {
            List<User> userList = mapper.selectList(null);
            for (User user : userList) {
                System.out.println(user);
            }
        }
    }

ActiveRecord

什么是ActiveRecord？
ActiveRecord也属于ORM（对象关系映射）层，由Rails最早提出，遵循标准的ORM模型：表映射到记录，记录映射到对象，字段映射到对象属性。配合遵循的命名和配置惯例，能够很大程度的快速实现模型的操作，而且简洁易懂。

ActiveRecord的主要思想是：

  1. 每一个数据库表对应创建一个类，类的每一个对象实例对应于数据库中表的一行记录；通常表的每个字段在类中都有相应的Field；
  2. ActiveRecord同时负责把自己持久化，在ActiveRecord中封装了对数据库的访问，即CURD;；
  3. ActiveRecord是一种领域模型(Domain Model)，封装了部分业务逻辑；

开启AR之旅

  • 在MP中，开启AR非常简单，只需要将实体对象继承Model即可。
    • 修改pojo.User实体类
      package com.itheima.pojo;
      import com.baomidou.mybatisplus.extension.activerecord.Model;
      import lombok.AllArgsConstructor;
      import lombok.Data;
      import lombok.NoArgsConstructor;
      @Data
      @NoArgsConstructor
      @AllArgsConstructor
      public class User extends Model<User> {
          private Long id;
          private String userName;
          private String password;
          private String name;
          private Integer age;
          private String email;
      }

根据主键查询

package com.itheima.test;
import com.itheima.pojo.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class MyTest2 {
    @Test
    public void selectMyList() {
        User user = new User();
        user.setId(2L);
        User user1 = user.selectById();
        System.out.println(user1);
    }
}

新增数据

package com.itheima.test;
import com.itheima.pojo.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class MyTestInsert {
    @Test
    public void insertMyList() {
        User user = new User();
        user.setEmail("dkdu477@qq.com");
        user.setPassword("123");
        user.setUserName("youzi");
        user.setAge(18);
        user.setName("柚子");
        boolean insert = user.insert();
        System.out.println(insert);
    }
}

更新操作

package com.itheima.test;
import com.itheima.pojo.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class MyTestUpdate {
    @Test
    public void updateMyList() {
        User user = new User();
        user.setName("刘璋");
        user.setAge(24);
        user.setId(10L);
        boolean updateById = user.updateById();
        System.out.println(updateById);
    }
}

删除操作

package com.itheima.test;
import com.itheima.pojo.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class MyTestDelete {
    @Test
    public void deleteMyList() {
        User user = new User();
        user.setId(10L);
        boolean updateById = user.deleteById();
        System.out.println(updateById);
    }
}

根据条件查询

package com.itheima.test;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.itheima.pojo.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import java.util.List;
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class MyTestCondition {
    @Test
    public void conditionMyList() {
        User user = new User();
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.gt("age", "20");
        List<User> userList = user.selectList(wrapper);
        for (User user1 : userList) {
            System.out.println(user1);
        }
    }
}

自动填充功能

  • 有些时候我们可能会有这样的需求，插入或者更新数据时，希望有些字段可以自动填充数据，比如密码、version等。在MP中提供了这样的功能，可以实现自动填充。

添加@TableField注解

  1. 在pojo.User.java实体类中添加@TableField注解
    package com.itheima.pojo;
    import com.baomidou.mybatisplus.annotation.FieldFill;
    import com.baomidou.mybatisplus.annotation.TableField;
    import com.baomidou.mybatisplus.extension.activerecord.Model;
    import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.NoArgsConstructor;
    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    public class User extends Model<User> {
        private Long id;
        private String userName;
        @TableField(fill = FieldFill.INSERT) // insert时自动填充
        private String password;
        private String name;
        private Integer age;
        private String email;
    }

编写MyMetaObjectHandler

  • 在java下新建com.itheima.handle.MyMetaObjectHandler.java，实现MetaObjectHandler的insertFill方法
    package com.itheima.handle;
    import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;
    import org.apache.ibatis.reflection.MetaObject;
    import org.springframework.stereotype.Component;
    @Component
    public class MyMetaObjectHandler implements MetaObjectHandler {
        /**
        * 插入数据时填充
        * @param metaObject
        */
        @Override
        public void insertFill(MetaObject metaObject) {
            // 先获取到password的值，再进行判断，如果为空，就进行填充，如果不为空，就不做处理
            Object password = getFieldValByName("password", metaObject);
            if(password == null) {
                setFieldValByName("password", "123", metaObject);
            }
        }
        /**
        * 更新数据时填充
        * @param metaObject
        */
        @Override
        public void updateFill(MetaObject metaObject) {
        }
    }

编写测试方法

package com.itheima.test;
import com.itheima.pojo.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class MyTestInsert2 {
    @Test
    public void insertMyList() {
        User user = new User();
        user.setEmail("555@qq.com");
        user.setUserName("baipiao");
        user.setAge(21);
        user.setName("白嫖");
        boolean insert = user.insert();
        System.out.println(insert);
    }
}

逻辑删除

  • 开发系统时，有时候在实现功能时，删除操作需要实现逻辑删除，所谓逻辑删除就是将数据标记为删除，而并非真正的物理删除（非DELETE操作），查询时需要携带状态条件，确保被标记的数据不被查询到。这样做的目的就是避免数据被真正的删除。

修改表结构

  1. 为tb_user表增加deleted字段，用于表示数据是否被删除，1代表删除，0代表未删除。
    ALTER TABLE `tb_user` ADD COLUMN `deleted` int(1) NULL DEFAULT 0 COMMENT '1代表删除，0代表未删除' AFTER `email`;
  2. 同时，也修改pojo.User实体，增加deleted属性并且添加@TableLogic注解：
    package com.itheima.pojo;
    import com.baomidou.mybatisplus.annotation.FieldFill;
    import com.baomidou.mybatisplus.annotation.TableField;
    import com.baomidou.mybatisplus.annotation.TableLogic;
    import com.baomidou.mybatisplus.extension.activerecord.Model;
    import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.NoArgsConstructor;
    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    public class User extends Model<User> {
        private Long id;
        private String userName;
        @TableField(fill = FieldFill.INSERT) // insert时自动填充
        private String password;
        private String name;
        private Integer age;
        private String email;
        @TableLogic
        private int deleted;
    }

配置

  • 在application.properties中
    # 逻辑已删除值(默认为 1)
    mybatis-plus.global-config.db-config.logic-delete-value=1
    # 逻辑未删除值(默认为 0)
    mybatis-plus.global-config.db-config.logic-not-delete-value=0

编写测试方法

package com.itheima.test;
import com.itheima.pojo.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class MyTestDelete2 {
    @Test
    public void deleteMyList() {
        User user = new User();
        user.setId(11L);
        boolean updateById = user.deleteById();
        System.out.println(updateById);
    }
}

测试结果

  • 结果

通用枚举

  • 解决了繁琐的配置，让 mybatis 优雅的使用枚举属性！

修改表结构

ALTER TABLE `tb_user` ADD COLUMN `sex` int(1) NULL DEFAULT 1 COMMENT '1-男，2-女' AFTER `deleted`;

定义枚举

  • 在java下新建com.itheima.enums.SexEnum.java的枚举类，去实现IEnum方法
    package com.itheima.enums;
    import com.baomidou.mybatisplus.core.enums.IEnum;
    public enum SexEnum implements IEnum<Integer> {
        MAN(1,"男"),
        WOMAN(2,"女");
        private int value;
        private String desc;
        SexEnum(int value, String desc) {
            this.value = value;
            this.desc = desc;
        }
        @Override
        public Integer getValue() {
            return this.value;
        }
        @Override
        public String toString() {
            return this.desc;
        }
    }

配置

  • 在application.properties中
    # 枚举包扫描
    mybatis-plus.type-enums-package=cn.itcast.mp.enums

修改实体

  • 在pojo.User.java实体类中
    package com.itheima.pojo;
    import com.baomidou.mybatisplus.annotation.FieldFill;
    import com.baomidou.mybatisplus.annotation.TableField;
    import com.baomidou.mybatisplus.annotation.TableLogic;
    import com.baomidou.mybatisplus.extension.activerecord.Model;
    import com.itheima.enums.SexEnum;
    import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.NoArgsConstructor;
    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    public class User extends Model<User> {
        private Long id;
        private String userName;
        @TableField(fill = FieldFill.INSERT) // insert时自动填充
        private String password;
        private String name;
        private Integer age;
        private String email;
        @TableLogic
        private int deleted;
        private SexEnum sex;
    }

编写测试方法

package com.itheima.test;
import com.itheima.enums.SexEnum;
import com.itheima.pojo.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class MyTestInsert3 {
    @Test
    public void insertEnumMyList() {
        User user = new User();
        user.setEmail("888@qq.com");
        user.setUserName("yaosheng");
        user.setAge(23);
        user.setName("药神");
        user.setSex(SexEnum.WOMAN);
        boolean insert = user.insert();
        System.out.println(insert);
    }
}

代码生成器

  • AutoGenerator 是 MyBatis-Plus 的代码生成器，通过 AutoGenerator 可以快速生成 Entity、Mapper、Mapper、XML、Service、Controller 等各个模块的代码，极大的提升了开发效率。

创建工程

  • 新建itheima_my_boot3的springboot project
  • 在pom.xml中导入相应的坐标
    <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>
    <!--mybatis-plus的springboot支持-->
    <dependency>
      <groupId>com.baomidou</groupId>
      <artifactId>mybatis-plus-boot-starter</artifactId>
      <version>3.4.2</version>
    </dependency>
    <dependency>
      <groupId>com.baomidou</groupId>
      <artifactId>mybatis-plus-generator</artifactId>
      <version>3.1.1</version>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-freemarker</artifactId>
    </dependency>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.46</version>
    </dependency>
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-log4j12</artifactId>
    </dependency>
    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
    </dependency>

在java下新建com.itheima.generator.MyGenerator.java

package com.itheima.generator;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import com.baomidou.mybatisplus.core.exceptions.MybatisPlusException;
import com.baomidou.mybatisplus.core.toolkit.StringPool;
import com.baomidou.mybatisplus.core.toolkit.StringUtils;
import com.baomidou.mybatisplus.generator.AutoGenerator;
import com.baomidou.mybatisplus.generator.InjectionConfig;
import com.baomidou.mybatisplus.generator.config.DataSourceConfig;
import com.baomidou.mybatisplus.generator.config.FileOutConfig;
import com.baomidou.mybatisplus.generator.config.GlobalConfig;
import com.baomidou.mybatisplus.generator.config.PackageConfig;
import com.baomidou.mybatisplus.generator.config.StrategyConfig;
import com.baomidou.mybatisplus.generator.config.TemplateConfig;
import com.baomidou.mybatisplus.generator.config.po.TableInfo;
import com.baomidou.mybatisplus.generator.config.rules.NamingStrategy;
import com.baomidou.mybatisplus.generator.engine.FreemarkerTemplateEngine;
/**
* <p>
* mysql 代码生成器演示例子
* </p>
*/
public class MysqlGenerator {

    /**
    * <p>
    * 读取控制台内容
    * </p>
    */
    public static String scanner(String tip) {
        Scanner scanner = new Scanner(System.in);
        StringBuilder help = new StringBuilder();
        help.append("请输入" + tip + "：");
        System.out.println(help.toString());
        if (scanner.hasNext()) {
            String ipt = scanner.next();
            if (StringUtils.isNotEmpty(ipt)) {
                return ipt;
            }
        }
        throw new MybatisPlusException("请输入正确的" + tip + "！");
    }

    /**
    * RUN THIS
    */
    public static void main(String[] args) {
        // 代码生成器
        AutoGenerator mpg = new AutoGenerator();

        // 全局配置
        GlobalConfig gc = new GlobalConfig();
        String projectPath = System.getProperty("user.dir");
        gc.setOutputDir(projectPath + "/src/main/java");
        gc.setAuthor("itcast");
        gc.setOpen(false);
        mpg.setGlobalConfig(gc);

        // 数据源配置
        DataSourceConfig dsc = new DataSourceConfig();
        dsc.setUrl("jdbc:mysql://127.0.0.1:3306/mp?useUnicode=true&useSSL=false&characterEncoding=utf8");
        // dsc.setSchemaName("public");
        dsc.setDriverName("com.mysql.jdbc.Driver");
        dsc.setUsername("root");
        dsc.setPassword("root");
        mpg.setDataSource(dsc);

        // 包配置
        PackageConfig pc = new PackageConfig();
        pc.setModuleName(scanner("模块名"));
        pc.setParent("com.itheima.generator");
        mpg.setPackageInfo(pc);

        // 自定义配置
        InjectionConfig cfg = new InjectionConfig() {
            @Override
            public void initMap() {
                // to do nothing
            }
        };
        List<FileOutConfig> focList = new ArrayList<>();
        focList.add(new FileOutConfig("/templates/mapper.xml.ftl") {
            @Override
            public String outputFile(TableInfo tableInfo) {
                // 自定义输入文件名称
                return projectPath + "/itheima-generator/src/main/resources/mapper/" + pc.getModuleName()
                        + "/" + tableInfo.getEntityName() + "Mapper" + StringPool.DOT_XML;
            }
        });
        cfg.setFileOutConfigList(focList);
        mpg.setCfg(cfg);
        mpg.setTemplate(new TemplateConfig().setXml(null));

        // 策略配置
        StrategyConfig strategy = new StrategyConfig();
        strategy.setNaming(NamingStrategy.underline_to_camel);
        strategy.setColumnNaming(NamingStrategy.underline_to_camel);
//        strategy.setSuperEntityClass("com.baomidou.mybatisplus.samples.generator.common.BaseEntity");
        strategy.setEntityLombokModel(true);
//        strategy.setSuperControllerClass("com.baomidou.mybatisplus.samples.generator.common.BaseController");
        strategy.setInclude(scanner("表名"));
        strategy.setSuperEntityColumns("id");
        strategy.setControllerMappingHyphenStyle(true);
        strategy.setTablePrefix(pc.getModuleName() + "_");
        mpg.setStrategy(strategy);
        // 选择 freemarker 引擎需要指定如下加，注意 pom 依赖必须有！
        mpg.setTemplateEngine(new FreemarkerTemplateEngine());
        mpg.execute();
    }
}

测试

  • 执行MyGenerator.java里面的方法 结果
  • 生成代码 结果

MybatisX 快速开发插件

  • MybatisX 是一款基于 IDEA 的快速开发插件，为效率而生。
  • 安装方法：打开 IDEA，进入 File -> Settings -> Plugins -> Browse Repositories，输入 mybatisx 搜索并安装。
  • 功能：
    • Java 与 XML 调回跳转
    • Mapper 方法自动生成 XML