pom.xml依赖包引入

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
        <exclusions>
            <exclusion>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-logging</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
    </dependency>

    <dependency>
        <groupId>com.fasterxml.jackson.dataformat</groupId>
        <artifactId>jackson-dataformat-yaml</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <exclusions>
            <exclusion>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-logging</artifactId>
            </exclusion>
        </exclusions>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-log4j2</artifactId>
    </dependency>

    <!-- mybatis plus-->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.0.7.1</version>
    </dependency>
    <dependency>
        <groupId>com.h2database</groupId>
        <artifactId>h2</artifactId>
        <scope>runtime</scope>
    </dependency>
    <!-- 引入Druid依赖，阿里巴巴所提供的数据源 -->
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>druid</artifactId>
        <version>1.0.29</version>
    </dependency>
    <!-- 提供mysql驱动 -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.38</version>
    </dependency>

    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>fastjson</artifactId>
        <version>1.2.54</version>
    </dependency>
</dependencies>

属性配置（application.yml）

spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/ez-user?allowMultiQueries=true&useUnicode=true&characterEncoding=UTF-8
    username: root
    password: admin
    filters: stat
    maxActive: 20
    initialSize: 1
    maxWait: 60000
    minIdle: 1
    timeBetweenEvictionRunsMillis: 60000
    minEvictableIdleTimeMillis: 300000
    validationQuery: select 1 FROM DUAL
    testWhileIdle: true
    testOnBorrow: false
    testOnReturn: false
    poolPreparedStatements: true

示例entity

public class User {
    private Long id;
    private String name;
    private Integer age;
    private String email;
    private Integer isDel;
...
}

示例mapper

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.entity.User;

public interface UserMapper extends BaseMapper<User> {

}

示例测试

@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTests {
    Logger logger = LoggerFactory.getLogger(getClass());

    @Resource
    private UserMapper userMapper;

    @Test
    public void testSelectByCondition() {
        System.out.println("----- 普通查询 ------");
        List<User> plainUsers = userMapper.selectList(new QueryWrapper<User>().eq("name", "ydp"));
        List<User> lambdaUsers = userMapper.selectList(new QueryWrapper<User>().lambda().eq(User::getName, "ydp"));
        Assert.assertEquals(plainUsers.size(), lambdaUsers.size());
        logger.info("plainUsers:{},lambdaUsers:{}", plainUsers, lambdaUsers);

        System.out.println("----- 带子查询(sql注入) ------");
        List<User> plainUsers2 = userMapper.selectList(new QueryWrapper<User>().inSql("name", "select name from user where id = 1"));
        List<User> lambdaUsers2 = userMapper.selectList(new QueryWrapper<User>().lambda().inSql(User::getName, "select name from user where id = 1"));
        Assert.assertEquals(plainUsers2.size(), lambdaUsers2.size());
        logger.info("plainUsers2:{},lambdaUsers2:{}", plainUsers2, lambdaUsers2);

        System.out.println("----- 带嵌套查询 ------");
        List<User> plainUsers3 = userMapper.selectList(new QueryWrapper<User>()
                .nested(i -> i.eq("id", 1).or().eq("name", "ydp"))
                .and(i -> i.ge("age", 20)));
        List<User> lambdaUsers3 = userMapper.selectList(new QueryWrapper<User>().lambda()
                .nested(i -> i.eq(User::getId, 1).or().eq(User::getName, "ydp"))
                .and(i -> i.ge(User::getAge, 20)));
        Assert.assertEquals(plainUsers3.size(), lambdaUsers3.size());
        logger.info("plainUsers3:{},lambdaUsers3:{}", plainUsers3, lambdaUsers3);

        System.out.println("----- 自定义(sql注入) ------");
        List<User> plainUsers4 = userMapper.selectList(new QueryWrapper<User>()
                .apply("id = 2"));
        logger.info("plainUsers4:{}", plainUsers4);

        System.out.println("----- 更新数据 ------");
        UpdateWrapper<User> uw = new UpdateWrapper<>();
        uw.set("email", "");
        uw.eq("id", 4);
        userMapper.update(new User(), uw);
        User u4 = userMapper.selectById(4);
        Assert.assertEquals(u4.getEmail(),"");
        logger.info("u4:{}", u4);
    }
}

示例代码见

https://github.com/yedp/mybatis-plus-example/tree/dev_mysql_v1