springboot3

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {
    @RequestMapping("/helloworld")
    public String helloworld(){
        return "hello";
    }
}
maven下载地址Index of /dist/maven/maven-3/3.9.6/binaries

注意版本  jdk 17

下载地址Java Downloads | Oracle

Index of /spring-boot/docs/current/reference

Common Application Properties

#虚拟路径
server.servlet.context-path=/start

@Value注解

@ConfigurationProperties(prefix="前缀")

整合mybatis

实现第一个findbyid

实体类  pojo

public class User {
    private Integer id;
    private String name;
    private Integer age;
    private String phone;
    private String gender;
    public User(){

    }

接口mapper

@Mapper
public interface UserMapper {
    @Select("select * from user where id = #{id}")
    public  User findById(Integer id);
}

service

public interface UserService {
    public User findById(Integer id);
}

实现service

//将实现类交给容器
@Service
public class UserServiceImpl implements UserService {

    @Autowired
    UserMapper userMapper;
//调用usermapper需要注入usermapper
    @Override
    public User findById(Integer id) {
        return userMapper.findById(id);
    }
}

控制器

@RestController
public class UserController {
    @Autowired
    private UserService userService;

    @RequestMapping("/findById")
    public User findById(Integer id){
       return userService.findById(id);
    }
}

最新依赖

  <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>3.0.0</version>
        </dependency>

        <dependency>
            <groupId>com.mysql</groupId>
            <artifactId>mysql-connector-j</artifactId>
            <scope>runtime</scope>
        </dependency>

mybatis:
  mapper-locations: classpath:mappers/*xml
  type-aliases-package: com.example.demo.mybatis.entity

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/mybatis
    username: 
    password:

Bean扫描

<context:component-scan base-package="com.xxx"/>

@ComponentScan(basePackages="com.xxxx")

@SpringBootApplication(组合注解)  默认扫描启动类所在的包.

@ComponentScan(basePackages="com.xxxx") 指定扫描哪个包

Bean注册

@Component

@Controller  控制器

@Service    业务类

@Repository  数据访问类

第三方类包注册  (不是自定义的) 不能用@Component

下面两种可以访问第三方类包

@Bean

@Import

mvn install:file -Dfile = jar 包本地磁盘路径

-DgroupId = 组织名称

-Dartifactid = 项目名

-Dversion = 版本号

-Dpackaging 打包方式

nvm install:install-file -Dartifactid=xxxx -Dfile=C:\user\xx.jar -DgroupId=cn.xx.xx -Dversion=1.0 -Dpackaging=jar

<dependency>
    <groupId>cn.xx.xx DgroupId</groupId>
    <artifactId>xxxx Dartifactid</artifactId>
    <version>1.0</version>
</dependency>

@Bean
public Counter counter() {
    return  new Counter();
}

在启动类中接收

ApplicationContext context = SpringApplication.run(Demo1Application.class, args);


xx xx=context.getBean(xx.class)

不建议  ,建议在配置类中集中注册

config配置类

@Configuration

@Bean

导入 @import

如果不在同一个包里面找不到的情况下,可以使用这个@import

public class CommonImportSelector implements ImportSelector {
    @Override
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {
        return new String[]{"com.example.demo.config","com.example.demo.dao"};
    }
}

多个import

@Import(CommonImportSelector.class)

读取配置文件

public class CommonImportSelector implements ImportSelector {
    @Override
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {
        List<String> list = new ArrayList<String>();
        InputStream   is =  CommonImportSelector.class.getClassLoader().getResourceAsStream("common.imports");
        BufferedReader br = new BufferedReader(new InputStreamReader(is));
        String line = null;
        try {
            while ((line = br.readLine()) != null) {
                list.add(line);
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        } finally {
            try {
                if (is != null){
                    br.close();
                }
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return list.toArray(new String[0]);
    }
}

package com.example.demo.anno;

import com.example.demo.config.CommonImportSelector;
import org.springframework.context.annotation.Import;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Import(CommonImportSelector.class)
public @interface EnableCommonConfig {
}

注解

注册条件

@Value("${country.name}")
private  String name;

读取配置文件

配置文件不要忘记空格