spring-mvc

接收参数的方式

参数格式是 k=v [常见于get请求 或者 文件上传等请求], 直接接收或者 pojo实体接收

• 直接接收或者@RequestParam重命名接收

// 前端请求格式为
/user?id=1&name=bwf&age=88

// 当k与变量名一致时，可以不用@RequestParam，同名变量接收
@GetMapping("/user")
public String getUser(
    @RequestParam("id") Long userId,           // 必须参数 取出id赋值给变量 userId
    @RequestParam(value = "name", required = false) String name, // 可选参数
    @RequestParam(value = "age", defaultValue = "18") int age    // 默认值
) {
    return "user";
}

• 封装为POJO对象接收

// 前端请求格式为
/user?username=bwf&email=163@qq.com&age=88

@GetMapping("/register")
public String register(UserForm form) {
    // Spring 自动将参数绑定到对象的同名属性
    return "success";
}

// 表单对象
@Data
public class UserForm {
    private String username;
    private String email;
    private Integer age;
}

参数格式请求体json格式 [常见于post等请求]

• @RequestBody

@PostMapping("/order")
public void createOrder(@RequestBody OrderRequest request) {
   
}

@Data
public class OrderRequest {
    private Long userId;
    private List items;
    private AddressDTO shippingAddress;
    private String paymentMethod;
}

文件上传 MultipartFile类接收

/**
 * 前端上传图片
 * h5请求方式
 *     post
 * h5 入参
 *    let formData = new FormData();
 *    formData.append("file", file.raw);
 *    formData.append("file", file.raw);
 *    formData.append("attach", file.raw);
 *    formData.append(其他字段名， 字段对应的值)
 * h5 请求头
 *    {headers:{"Content-Type":"multipart/form-data"}}
 * h5发送
 *    {headers:{"Content-Type":"multipart/form-data"}}
 *    data:formData
 */

@PostMapping("/upload")
public void upload(User user, @RequestParam("file")MultipartFile[] files, @RequestParam("attach") MultipartFile attach){
    log.info("upload---user:{}", user); // 其他字段名映射到User实体类中
}

文件下载

• 图片/excel下载 (前端get/post请求均可)

/**
 * 下载图片等文件
 * @param httpServletResponse
 */
public void downLoadFile(HttpServletResponse httpServletResponse) {
    //模拟读取 resources目录下的资源
    String filePath = this.getClass().getResource("/static/pic/1.jpg").getPath();
    File file = new File(filePath);
    String fileName = filePath.substring(filePath.lastIndexOf("/")+1);
    try {
        InputStream inputStream = Files.newInputStream(file.toPath());
        //响应头需要设置内容的处理方式：下载文件需要指定为文件
        httpServletResponse.setHeader("Content-Disposition", "attachment;filename=" + fileName);
        httpServletResponse.setHeader("Content-type","blob");
        cn.hutool.core.io.IoUtil.copy(inputStream, httpServletResponse.getOutputStream());
    } catch (IOException e) {
        e.printStackTrace();
    }
}

//excel下载
public void exportExcel(HttpServletResponse httpServletResponse){
    List list = "下载的集合"
    httpServletResponse.setContentType("application/vnd.ms-excel");
        httpServletResponse.setHeader("Content-Disposition", "attachment;filename=" + fileName + ".xlsx");
    httpServletResponse.setCharacterEncoding("UTF-8");
    com.alibaba.excel.EasyExcel.write(httpServletResponse.getOutputStream, User.class).sheet("sheet1").doWrite(list)
}

@Data
@AllArgsConstructor
public class User{
    /**
     * value={"一级表头","二级表头","三级表头"}
     * index=0 排序从左到右
     */
    @ExcelProperty(value={"用户信息","姓名"},index=0)
    private String userName;

    @ExcelProperty(value={"用户信息","性别"},index=1)
    private String sex;

    /**
     * 不要在excel中展示
     */
    @ExcelIgnore
    private String score

}

封装响应统一结果类

import lombok.AllArgsConstructor;
import lombok.Data;

@AllArgsConstructor
@Data
public class Result{
    private String code;
    private String msg;
    private T data;

    public Result(String code, String msg) {
        this.code = code;
        this.msg = msg;
    }

    public static Result ok(){
        return new Result("200", "OK");
    }

    public static Result ok(T data){
        return new Result<>("200", "ok", data);
    }

}

取前端路径参数

• @PathVariable

@GetMapping("/users/{id}")
public void getUserById(@PathVariable Long id) {
    // 访问: GET /users/123
    // id = 123

}


@GetMapping("/products/{productId}")
public void getProduct(
    @PathVariable("productId") Long id  // 参数名与路径变量名不同
) {
    // 访问: GET /products/789
    // id = 789

}

springmvc 拦截器

• 1. 实现HandlerInterceptor接口生成一个拦截器
• 2. 实现WebMvcConfigurer接口addInterceptors方法添加上述拦截器

@Slf4j
@Component
public class AuthInterceptor implements HandlerInterceptor {

    /**
     * @return boolean true-放行请求  false-拦截请求
     */
    @Override
    public boolean preHandle(HttpServletRequest request,
                             HttpServletResponse response,
                             Object handler) throws Exception {
        log.info("AuthInterceptor.preHandle---start");
        return true;
    }

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

    @Override
    public void afterCompletion(HttpServletRequest request,
                                HttpServletResponse response,
                                Object handler,
                                Exception ex) throws Exception {
    }
}


@Configuration
public class MySpringConfig implements WebMvcConfigurer {

    @Autowired
    private AuthInterceptor authInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(authInterceptor).addPathPatterns("/**");
    }
}

拦截器执行顺序

• 正常执行顺序

请求进入 →
    拦截器1.preHandle()  (放行)
    拦截器2.preHandle()  (放行)
    拦截器3.preHandle()  (放行)
    ↓
    Controller执行
    ↓
    拦截器3.postHandle() ← (逆序)
    拦截器2.postHandle() ← (逆序)
    拦截器1.postHandle() ← (逆序)
    ↓
    视图渲染
    ↓
    拦截器3.afterCompletion() ← (逆序)
    拦截器2.afterCompletion() ← (逆序)
    拦截器1.afterCompletion() ← (逆序)
    ↓
响应返回

• 中断执行顺序（拦截器2不放行）

请求进入 →
    拦截器1.preHandle()  (放行)
    拦截器2.preHandle()  (返回false，拦截！)
    ↓
    【中断！】后续拦截器3和Controller不会执行
    ↓
    拦截器1.afterCompletion() ← (只有放行的才执行)
    ↓
    直接返回响应给客户端

Spring MVC 拦截器 vs 过滤器（Filter）