Spring MVC 入門配置與工作流程詳解

Spring MVC 入門配置與工作流程詳解

Spring MVC 是基於 Servlet API 的請求驅動型 Web 框架，核心是 DispatcherServlet 前端控制器模式。本文梳理核心流程與最小化配置步驟。

核心處理流程

1. 請求攔截：DispatcherServlet 接收所有匹配的 HTTP 請求
2. HandlerMapping：根據 URL 映射查找對應的 Controller（處理器）
3. Controller 執行：調用業務邏輯，處理請求參數，調用 Service 層
4. 返回 ModelAndView：封裝模型數據與視圖邏輯名
5. ViewResolver 解析：將邏輯視圖名解析為具體 View 實例（JSP/Thymeleaf/FreeMarker 等）
6. 視圖渲染：View 結合模型數據生成響應，返回給 DispatcherServlet 輸出

最小化配置步驟

1. 依賴引入 (Maven)

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>5.3.x</version>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>4.0.1</version>
        <scope>provided</scope>
    </dependency>
</dependencies>

2. web.xml 配置 DispatcherServlet

<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>
<servlet-mapping>
    <servlet-name>dispatcher</servlet-name>
    <url-pattern>/</url-pattern>
</servlet-mapping>

3. spring-mvc.xml 核心配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="https://www.springframework.org/schema/beans"
       xmlns:context="https://www.springframework.org/schema/context"
       xmlns:mvc="https://www.springframework.org/schema/mvc"
       xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="
           https://www.springframework.org/schema/beans https://www.springframework.org/schema/beans/spring-beans.xsd
           https://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd
           https://www.springframework.org/schema/mvc https://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <!-- 掃描 Controller -->
    <context:component-scan base-package="com.example.controller" />

    <!-- 啟用註解驅動：@RequestMapping, @RequestBody, @ResponseBody 等 -->
    <mvc:annotation-driven />

    <!-- 靜態資源映射 -->
    <mvc:resources mapping="/static/**" location="/static/" />

    <!-- 視圖解析器：JSP 為例 -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/views/" />
        <property name="suffix" value=".jsp" />
    </bean>
</beans>

4. 編寫 Controller

@Controller
@RequestMapping("/user")
public class UserController {
    
    @Autowired
    private UserService userService;
    
    @GetMapping("/{id}")
    public String detail(@PathVariable Long id, Model model) {
        User user = userService.findById(id);
        model.addAttribute("user", user);
        return "user/detail";  // 邏輯視圖名 -> /WEB-INF/views/user/detail.jsp
    }
    
    @PostMapping
    @ResponseBody
    public Result<User> create(@RequestBody UserDTO dto) {
        User user = userService.create(dto);
        return Result.success(user);
    }
}

關鍵組件說明

• HandlerMapping：默認 RequestMappingHandlerMapping 掃描 @RequestMapping
• HandlerAdapter：RequestMappingHandlerAdapter 支持方法參數綁定、返回值處理
• ViewResolver：解耦 Controller 與具體視圖技術，支持鏈式解析
• Interceptor：mvc:interceptors 配置攔截器，實現權限、日誌、國際化等橫切關注點

現代化改進：Java Config 替代 XML

@Configuration
@EnableWebMvc
@ComponentScan("com.example")
public class WebConfig implements WebMvcConfigurer {
    
    @Override
    public void configureViewResolvers(ViewResolverRegistry registry) {
        registry.jsp("/WEB-INF/views/", ".jsp");
    }
    
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/static/**").addResourceLocations("/static/");
    }
}

Spring Boot 進一步簡化為自動配置，只需 @SpringBootApplication 即可啟動，但理解原生配置有助於排查問題與定制擴展。