Spring Boot项目搭建（Spring Boot 2.2.4 + MyBatis + MySql）

<plugin>
                <groupId>org.mybatis.generator</groupId>
                <artifactId>mybatis-generator-maven-plugin</artifactId>
                <version>1.3.2</version>
                <dependencies>
                    <dependency>
                        <groupId>mysql</groupId>
                        <artifactId>mysql-connector-java</artifactId>
                        <version>5.1.48</version>
                    </dependency>
                </dependencies>
            </plugin>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfiguration
        PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
        "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
 
<generatorConfiguration>
    <context id="testTables" targetRuntime="MyBatis3">
        <commentGenerator>
            <!-- 是否去除自动生成的注释 true：是 ： false:否 -->
            <property name="suppressAllComments" value="true"/>
        </commentGenerator>
        <!--数据库连接的信息：驱动类、连接地址、用户名、密码 -->
        <jdbcConnection driverClass="com.mysql.jdbc.Driver"
                        connectionURL="jdbc:mysql://localhost:3306/test?characterEncoding=utf8" userId="root"
                        password="123456">
        </jdbcConnection>
        <!-- 默认false，把JDBC DECIMAL 和 NUMERIC 类型解析为 Integer，为 true时把JDBC DECIMAL 和
            NUMERIC 类型解析为java.math.BigDecimal -->
        <javaTypeResolver>
            <property name="forceBigDecimals" value="false"/>
        </javaTypeResolver>
 
        <!-- targetProject:生成PO类的位置 -->
        <javaModelGenerator targetPackage="com.example.demo.bean"
                            targetProject="src/main/java">
            <!-- enableSubPackages:是否让schema作为包的后缀 -->
            <property name="enableSubPackages" value="false"/>
            <!-- 从数据库返回的值被清理前后的空格 -->
            <property name="trimStrings" value="true"/>
        </javaModelGenerator>
        <!-- targetProject:mapper映射文件生成的位置 -->
        <sqlMapGenerator targetPackage="mapper"
                         targetProject="src/main/resources">
            <!-- enableSubPackages:是否让schema作为包的后缀 -->
            <property name="enableSubPackages" value="false"/>
        </sqlMapGenerator>
        <!-- targetPackage：mapper接口生成的位置 -->
        <javaClientGenerator type="XMLMAPPER"
                             targetPackage="com.example.demo.mapper"
                             targetProject="src/main/java">
            <!-- enableSubPackages:是否让schema作为包的后缀 -->
            <property name="enableSubPackages" value="false"/>
        </javaClientGenerator>
        <!-- 指定数据库表 -->
        <table schema=""  tableName="test"></table>
 
    </context>
</generatorConfiguration>

server.port=8080
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.url=jdbc:mysql://localhost:3306/test
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
mybatis.mapper-locations=classpath:mapper/*.xml
mybatis.type-aliases-package=com.example.demo.bean
mybatis.configuration.map-underscore-to-camel-case=true

@SpringBootApplication
@MapperScan("com.example.demo.mapper")
public class Sb2Application {
 
    public static void main(String[] args) {
        SpringApplication.run(Sb2Application.class, args);
    }
 
}

@Component
public class DemoService
{
 
    @Autowired
    private TestMapper testMapper;
 
    public Test getTestInfoById(Integer id){
        return Optional.ofNullable(testMapper.selectByPrimaryKey(id)).orElse(null);
    }
 
}

@Controller
@RequestMapping("/demo")
public class DemoController {
 
    @Autowired
    private DemoService demoService;
 
 
    @RequestMapping("/hello/{id}")
    @ResponseBody
    public String hello(@PathVariable(value = "id") Integer id){
        return Optional.ofNullable(demoService.getTestInfoById(id)).map(Test::toString).orElse("empty String");
    }
 
}

public class Test {
    private Integer id;
 
    private String name;
 
    public Integer getId() {
        return id;
    }
 
    public void setId(Integer id) {
        this.id = id;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name == null ? null : name.trim();
    }
 
    @Override
    public String toString() {
        return "Test{" +
                "id=" + id +
                ", name=‘" + name + ‘\‘‘ +
                ‘}‘;
    }
}