Spring全家桶笔记九：Web层与RESTful

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Spring全家桶笔记九：Web层与RESTful

Spring MVC概述

Spring MVC是Spring框架的Web层模块，基于Servlet API构建，实现了MVC设计模式。

请求处理流程

  1. 请求 → DispatcherServlet
  2. HandlerMapping查找处理器
  3. HandlerAdapter执行处理器
  4. Controller处理业务逻辑
  5. ViewResolver解析视图
  6. 渲染视图 → 响应

核心组件

DispatcherServlet

前端控制器，统一处理请求和响应。

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// web.xml配置
<servlet>
    <servlet-name>dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:spring-mvc.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>

@Controller vs @RestController

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// 返回视图
@Controller
public class UserController {
    @GetMapping("/user/{id}")
    public String getUser(Model model) {
        model.addAttribute("user", userService.findById(id));
        return "userDetail";
    }
}

// 返回JSON
@RestController
public class UserController {
    @GetMapping("/user/{id}")
    public User getUser(@PathVariable Long id) {
        return userService.findById(id);
    }
}

请求参数绑定

路径参数

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@GetMapping("/user/{id}")
public User getUser(@PathVariable Long id) {
    return userService.findById(id);
}

请求参数

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@GetMapping("/user/list")
public List<User> list(
    @RequestParam(defaultValue = "1") int page,
    @RequestParam(defaultValue = "10") int size,
    @RequestParam(required = false) String name
) {
    return userService.list(page, size, name);
}

请求体

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@PostMapping("/user")
public User create(@RequestBody User user) {
    return userService.save(user);
}

表单提交

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@PostMapping("/user/save")
public String save(@ModelAttribute User user, BindingResult result) {
    if (result.hasErrors()) {
        return "userForm";
    }
    userService.save(user);
    return "redirect:/user/list";
}

RESTful API设计

规范

方法 用途 示例
GET 查询 GET /users
POST 创建 POST /users
PUT 更新 PUT /users/1
DELETE 删除 DELETE /users/1

响应结构

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public class ApiResponse<T> {
    private int code;
    private String message;
    private T data;
    
    public static <T> ApiResponse<T> success(T data) {
        return new ApiResponse<>(200, "success", data);
    }
    
    public static <T> ApiResponse<T> error(String message) {
        return new ApiResponse<>(500, message, null);
    }
}

统一异常处理

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@RestControllerAdvice
public class GlobalExceptionHandler {
    
    @ExceptionHandler(BusinessException.class)
    public ApiResponse<Void> handleBusinessException(BusinessException e) {
        return ApiResponse.error(e.getMessage());
    }
    
    @ExceptionHandler(Exception.class)
    public ApiResponse<Void> handleException(Exception e) {
        return ApiResponse.error("系统错误");
    }
}

文件上传

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@PostMapping("/upload")
public ApiResponse<String> upload(@RequestParam("file") MultipartFile file) {
    if (file.isEmpty()) {
        return ApiResponse.error("文件为空");
    }
    String filename = file.getOriginalFilename();
    // 保存文件
    return ApiResponse.success(filename);
}

跨域处理

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@CrossOrigin(origins = "*")
@RestController
public class UserController {}

// 或全局配置
@Configuration
public class WebConfig implements WebMvcConfigurer {
    @Override
    public void addCorsMappings(CorsRegistry registry) {
        registry.addMapping("/api/**")
            .allowedOrigins("*")
            .allowedMethods("GET", "POST", "PUT", "DELETE");
    }
}

拦截器

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@Component
public class AuthInterceptor implements HandlerInterceptor {
    
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
        String token = request.getHeader("Authorization");
        if (token == null) {
            response.setStatus(401);
            return false;
        }
        return true;
    }
}

@Configuration
public class WebConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new AuthInterceptor())
            .addPathPatterns("/api/**");
    }
}

总结

Spring MVC提供了强大的Web开发能力，RESTful风格的API设计已成为现代Web服务的主流选择。掌握请求参数绑定、异常处理、拦截器等核心功能是开发高效Web应用的基础。