spring中使用mybatis

June 30, 2023

mybatis 可以使我们方便地创建 mapper 层

实例

下面使用 mysql 作为数据源，并在 spring boot 项目下演示。

mysql 的 jdbc url 参见：
https://dev.mysql.com/doc/connectors/en/connector-j-reference-jdbc-url-format.html
https://dev.mysql.com/doc/connector-j/8.0/en/connector-j-reference-jdbc-url-format.html
添加 mysql 驱动 maven 依赖：
https://mvnrepository.com/artifact/com.mysql/mysql-connector-j
spring boot 项目添加 mybatis 依赖：
https://mvnrepository.com/artifact/tk.mybatis/mapper-spring-boot-starter
为了方便生成 getter 和 setter 安装 lombok 依赖：
https://mvnrepository.com/artifact/org.projectlombok/lombok
idea 使用 Free MyBatis Tool 插件自动生成 mybatis 的 mapper 的 xml 配置文件：
（注：可以将 model 创建在 entity 包下，将 dao 放在 dao 包下，将 mapper xml 放在 resources 的 mapper 包下）
https://plugins.jetbrains.com/plugin/18617-free-mybatis-tool

（自动生成的文件就不演示了）

application.yml 的内容例如：

yaml

spring:
    datasource:
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://[host][:port]/[db]?serverTimezone=GMT%2B8&useUnicode=true&characterEncodeing=UTF-8&useSSL=false
        username: root
        password: 123456
mybatis:
    mapper-locations: classpath:mapper/*.xml
    configuration:
        map-underscore-to-camel-case: true

我们创建（自动生成）的 mapper (即 DAO) 类置于 dao 包下，注意需要使用 @Repository 注解，
这样 mapper 类就可以被 spring 自动装配。
此时 srping boot 的启动类如下

java

@MapperScan("com.example.demo.dao")
@SpringBootApplication
public class DemoApplication {/* .. */}

注：此处 DAO 和 Service 是接口，mapper 和 ServiceImpl 是实现类
model 层存放 entity，service 层存放业务逻辑（但不直接访问数据库）并被 controller 层直接调用
mapper 和 DAO 直接对数据库操作并被 service 层直接调用

编写 service 实现类如下

java

@Service
public class OrderServiceImpl implements OrderService {

    // 这个 DAO 是由 Free MyBatis Tool 插件生动生成的，此处直接注入即可
    @Autowired
    private OrderDao orderDao;

    @Override
    public void add(Order order) {orderDao.insert(order);}

    @Override
    public void update(Order order) {orderDao.updateByPrimaryKey(order);}

    @Override
    public void delete(Integer id) {orderDao.deleteByPrimaryKey(id);}

    @Override
    public Order selectById(Integer id) {return orderDao.selectByPrimaryKey(id);}
}

在 controller 包内编写一个类来测试一下

java

@RestController
public class OrderController {
    @Autowired
    private OrderService orderService;

    @GetMapping("/selectById/{id}")
    public Result<Order> selectById(@PathVariable("id") Integer id) {
        Order order = orderService.selectById(id);
        return new Result(true, 200, "ok", order);
    }
}

// @Data 注解由 lombok 提供
// Result 工具类，可放在 common 包内
@Data
class Result<T> implements Serializable {
    private boolean success;
    private Integer code;
    private String message;
    private T data;
    public Result(boolean success, Integer code, String message, T data) {
        this.success = success;
        this.code = code;
        this.message = message;
        this.data = data;
    }
}

配置 (Servlet) Filter

FilterRegistrationBean 类由 spring 提供
配置类声明 @Configuration 注解就能被 spring 扫描和配置

java

@Configuration
public class FilterConfig {
    @Bean
    public FilterRegistrationBean<Filter> Filter01() {
        FilterRegistrationBean filter = new FilterRegistrationBean();
        filter.setFilter(new LogFilter1());
        List urls = new ArrayList();
        urls.add("/*");
        filter.setUrlPatterns(urls);
        filter.setOrder(1);
        return filter;
    }

    @Bean
    public FilterRegistrationBean Filter02() {
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
        filterRegistrationBean.setFilter(new LogFilter2());
        filterRegistrationBean.addUrlPatterns("/*");
        filterRegistrationBean.setOrder(2);
        return filterRegistrationBean;
    }

}


class LogFilter1 implements Filter {
    final Logger logger = LoggerFactory.getLogger(getClass());

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        logger.info("LogFilter1 before");
        filterChain.doFilter(servletRequest, servletResponse);
        logger.info("LogFilter1 after");
    }
}

class LogFilter2 implements Filter {
    final Logger logger = LoggerFactory.getLogger(getClass());

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        logger.info("LogFilter2 before");
        filterChain.doFilter(servletRequest, servletResponse);
        logger.info("LogFilter2 after");
    }
}

class CorsFilter implements Filter {
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletResponse res = (HttpServletResponse) response;
        res.setHeader("Access-Control-Allow-Origin", "*");

        HttpServletRequest req = (HttpServletRequest) request;
        if (req.getMethod().equals("OPTIONS")){
            res.setStatus(HttpServletResponse.SC_OK);
            return;
        }
        chain.doFilter(request, res);
    }
}

配置 (Spring) Interceptor

同上，@Configuration 注解表示通过 spring 扫描和配置

java

@Configuration
public class MyInterceptorConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new MyInterceptor())
                .addPathPatterns("/**")
                .excludePathPatterns("/static/**");
    }
}


class MyInterceptor implements HandlerInterceptor {
    final Logger logger = LoggerFactory.getLogger(getClass());

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        HandlerMethod handlerMethod = (HandlerMethod) handler;
        Method method = handlerMethod.getMethod();
        String methodName = method.getName();
        logger.debug("Method = " + methodName);
        return true; // 返回值表示是否放行
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        logger.info("postHandle");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        logger.info("afterCompletion");
    }
}

使用了上面的过滤器和拦截器后，访问 servlet 的日志效果如下

<time>  INFO <pid> --- [nio-8080-exec-1] com.example.demo.LogFilter1              : LogFilter1 before
<time>  INFO <pid> --- [nio-8080-exec-1] com.example.demo.LogFilter2              : LogFilter2 before
<time>  INFO <pid> --- [nio-8080-exec-1] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
<time>  INFO <pid> --- [nio-8080-exec-1] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
<time>  INFO <pid> --- [nio-8080-exec-1] com.example.demo.MyInterceptor           : postHandle
<time>  INFO <pid> --- [nio-8080-exec-1] com.example.demo.MyInterceptor           : afterCompletion
<time>  INFO <pid> --- [nio-8080-exec-1] com.example.demo.LogFilter2              : LogFilter2 after
<time>  INFO <pid> --- [nio-8080-exec-1] com.example.demo.LogFilter1              : LogFilter1 after

可以看到，是先进入 Filter 再进入 Interceptor

分页

使用pagehelper进行分页

在 mapper/OrderDao.xml <mapper/> 结束标签之前添加如下

xml

<select id="selectAllGoods" resultType="com.example.demo.entity.Order">
    select
    <include refid="Base_Column_List" />
    from tb_order
    <where>
        <if test="type!=null">
            and type=#{type}
        </if>
    </where>
</select>

OrderDao 接口中添加方法

java

List<Order> selectAllGoods(Order order);

OrderService 接口中添加方法

java

PageInfo<Order> selectAllGoods(Integer pageNum);

OrderServiceImpl 类中实现该方法

java


@Override
public PageInfo<Order> selectAllGoods(Integer pageNum) {
    Order order = new Order();
    order.setType("goods");

    Integer pageSize = 10;
    PageHelper.startPage(pageNum, pageSize);
    List<Order> goods = orderDao.selectAllGoods(order);
    return new PageInfo<>(goods);
}

OrderController 类中添加调用该 service 层的方法

java

@GetMapping("/goods/{pageNum}")
public Result<PageInfo> selectAllGoods(@PathVariable("pageNum") Integer pageNum) {
    PageInfo<Order> orders = orderService.selectAllGoods(pageNum);
    return new Result<PageInfo>(true, 200, "ok", orders);
}

参数校验

spring boot 可直接使用 spring-boot-starter-validation，实际上是依赖了 hibernate-validator。（具体使用方法可自行搜索，此处不展示）修改 Order 实体如下

java

@Data
public class Order implements Serializable {
    /* ... ... */

    @NotBlank(message = "标题不能为空")
    @Length(min = 2, max = 8, message = "标题长度在2-8之间")
    private String title;

    @NotBlank(message = "内容不能为空")
    private String content;

    /* ... ... */
}

在 controller 中可通过 BindingResult 参数获得校验结果

java

@PostMapping("/goods/add")
public Result<String> add(@Valid @RequestBody Order order, BindingResult bindingResult) {
    // 处理校验失败
    if (bindingResult.hasErrors()) {
        StringBuffer stringBuffer = new StringBuffer();
        List<ObjectError> allErrors = bindingResult.getAllErrors();
        for (ObjectError objectError : allErrors) {
            stringBuffer.append(objectError.getDefaultMessage()).append("; ");
        }
        return new Result<>(false, 400, "error", stringBuffer.toString());
    }

    // 处理校验成功，添加到数据库
    order.setCreateTime(new Date());
    order.setUpdateTime(new Date());
    order.setOrderStatus(0);
    order.setType("1");
    order.setOwnName("name");
    orderService.add(order);
    return new Result(true, 200, "ok", null);
}

# 测试一下
curl -H "Content-Type: application/json" \
     -d '{"title":"title", "content":"content"}' \
     http://127.0.0.1:8080/goods/add

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