配置

spring.datasource.url=jdbc:mariadb://localhost:3306/test
spring.datasource.driver-class-name=com.mariadb.jdbc.Driver
spring.datasource.username=root
spring.datasource.password=

添加 mybatis-plus

在 bulid.gradle 的 dependencies 中添加以下内容：

compile group:'com.baomidou', name: 'mybatis-plus-boot-starter', version: '3.4.2'

在项目的入口处添加以下注解：

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

在 test.mapper 下创建 ImagesMapper 文件

public interface ImageMapper extends BaseMapper<Images> {}

使用：

@Service
public class imageService {
    @Resource
    ImagesMapper imagesMapper
    public Images page() {
        List<Images> imagesList = imagesMapper.selectList(null);
    }
}

获取配置中的值

在Java使用SpringBoot开发的时候，我们有时候需要获取application.properties文件中的值。这个时候我们就需要使用一些方法了。话不多说，上代码：

import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PropertiesLoaderUtils;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;
public class Example {
    private static Map<String,String> getDatabaseSourceConfig() throws IOException {
        Map<String,String> map = new HashMap<>();
        Resource resource = new ClassPathResource("application.properties");
        Properties props = PropertiesLoaderUtils.loadProperties(resource);
        String url = props.getProperty("spring.datasource.url");
        String username = props.getProperty("spring.datasource.username");
        String password = props.getProperty("spring.datasource.password");
        map.put("url",url);
        map.put("username",username);
        map.put("password",password);
        return map;
    }
}

拦截器

在SpringBoot的开发过程中，我们难免会用到拦截器。我们要在SpringBoot中使用基本的拦截器一般只要实现两个类就行。废话少说，先上代码：
实现HandlerInterceptor:

@Component
public class WebInterceptor implements HandlerInterceptor {
  @Override
  public boolean preHandle(HttpSerletRequest request, HttpSerletResponse response, Object handler) throws Exception {
      return true;
  }
  @Override
  public void postHandle(HttpSerletRequest request, HttpSerletRespone response, Object handler,ModelAndView mv) throws Exception {}
  @Override
  public void afterCompeletion(HttpSerletRequest request, HttpSerletResponse response, Object handler, Exception exception) throws Exception {}
}

在`HandlerInterceptor`类中，`preHandle`在请求到达Controller之前拦截，`postHanlde`在Controller处理完成后，返回ModelView之前拦截，`afterCompeletion`在返回ModelView之后拦截。<br />preHandle的返回值，决定了是否要继续把请求向下传播，如果返回`false`，则请求在拦截器中中止，如果返回`true`,请求继续向下传播。<br />实现`WebMvcConfigurer`:

@Component
public class WebConfig implements WebMvcConfigurer {
    @Autowired
    WebInterceptor webInterceptor;
    @Override
    public void addInterceptor(InterceptorRegistry registry) {
        registry.add(webInterceptor);
    }
}

Mybatis-Plus

自动填充

在使用Mybatis-Plus的时候，有时我们需要使用自动填充的功能，比如自动更新创建时间和更新时间等。在使用Mybatis_Plug的自动填充的功能的时候，只要实现两个功能就好。1. 实现元对象处理器接口:com.baodidou.mybatisplus.core.handlers.MetaObjectHandler.2. 给指定的字段添加@TableField(.. fill = FieldFill.INSERT)注解。
示例代码：

实现接口

package com.silence.realworldspring.config;
import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;
import org.apache.ibatis.reflection.MetaObject;
import org.springframework.stereotype.Component;
import java.time.LocalDateTime;
@Component
public class MyMetaObjectHandler implements MetaObjectHandler {
    @Override
    public void insertFill(MetaObject metaObject) {
        final LocalDateTime now = LocalDateTime.now();
        this.fillStrategy(metaObject, "createdAt", now);
        this.fillStrategy(metaObject,"updatedAt", now);
    }
    @Override
    public void updateFill(MetaObject metaObject) {
        final LocalDateTime now = LocalDateTime.now();
        this.fillStrategy(metaObject, "updatedAt", now);
    }
}

添加注解

package com.silence.realworldspring.persistent.entity;
import com.baomidou.mybatisplus.annotation.*;
import java.io.Serializable;
import java.time.LocalDateTime;
import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.experimental.Accessors;
/**
 * <p>
 * 文章
 * </p>
 *
 * @author silence_zhpf
 * @since 2021-08-12
 */
@Data
@EqualsAndHashCode(callSuper = false)
@Accessors(chain = true)
@TableName("articles")
public class Articles implements Serializable {
    /**
     * 主键
     */
    @TableId(type = IdType.ASSIGN_UUID)
    private String slug;
    /**
     * 标题
     */
    private String title;
    /**
     * 描述
     */
    private String description;
    /**
     * 文章内容
     */
    private String body;
    /**
     * 创建时间
     */
    @TableField(value = "created_at",fill = FieldFill.INSERT)
    private LocalDateTime createdAt;
    /**
     * 更新时间
     */
    @TableField(value = "updated_at",fill = FieldFill.INSERT_UPDATE)
    private LocalDateTime updatedAt;
    public static final String SLUG = "slug";
    public static final String TITLE = "title";
    public static final String DESCRIPTION = "description";
    public static final String BODY = "body";
    public static final String CREATED_AT = "created_at";
    public static final String UPDATED_AT = "updated_at";
}