Spring MVC入门教程 - 从零开始学习Spring MVC框架

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Spring MVC入门教程 - 从零开始学习Spring MVC框架

1. Spring MVC简介

1.1 什么是Spring MVC

Spring MVC是Spring框架提供的用于构建Web应用程序的模块，它基于经典的MVC（Model-View-Controller）设计模式，提供了灵活、强大的Web开发能力。

MVC模式：

Model（模型）：数据和业务逻辑
View（视图）：用户界面展示
Controller（控制器）：处理用户请求，协调Model和View

1.2 Spring MVC的特点

✅ 松耦合：各个组件之间松耦合，易于测试和维护
✅ 灵活配置：支持XML配置和注解配置
✅ 强大的功能：请求映射、参数绑定、数据验证、文件上传等
✅ 与Spring集成：无缝集成Spring IoC和AOP
✅ RESTful支持：原生支持RESTful API开发
✅ 国际化支持：内置国际化功能
✅ 主题支持：支持主题切换

1.3 Spring MVC工作流程

1. 用户发送请求 → DispatcherServlet（前端控制器）
2. DispatcherServlet → HandlerMapping（处理器映射器）
3. HandlerMapping → Handler（处理器/Controller）
4. Handler → ModelAndView（模型和视图）
5. DispatcherServlet → ViewResolver（视图解析器）
6. ViewResolver → View（视图）
7. View → 响应返回给用户

1.4 Spring MVC核心组件

DispatcherServlet：前端控制器，统一处理请求
HandlerMapping：处理器映射器，映射请求到处理器
HandlerAdapter：处理器适配器，执行处理器
Controller：处理器，处理业务逻辑
ViewResolver：视图解析器，解析视图名称
View：视图，渲染响应

2. 环境搭建

2.1 前置要求

JDK 8或更高版本
Maven 3.6+ 或 Gradle
IDE（IntelliJ IDEA、Eclipse等）
Tomcat服务器（或使用Spring Boot内嵌Tomcat）

2.2 创建Maven项目

使用IDE创建

打开IntelliJ IDEA
File → New → Project
选择Maven，点击Next
填写GroupId和ArtifactId
点击Finish

使用命令行创建

mvn archetype:generate -DgroupId=com.example -DartifactId=springmvc-demo -DarchetypeArtifactId=maven-archetype-webapp -DinteractiveMode=false

2.3 添加依赖

在pom.xml中添加Spring MVC相关依赖：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
         http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>springmvc-demo</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>war</packaging>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <spring.version>5.3.23</spring.version>
        <servlet.version>4.0.1</servlet.version>
        <jsp.version>2.3.3</jsp.version>
        <jstl.version>1.2</jstl.version>
    </properties>

    <dependencies>
        <!-- Spring MVC核心依赖 -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <!-- Spring Context -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <!-- Servlet API -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>${servlet.version}</version>
            <scope>provided</scope>
        </dependency>

        <!-- JSP API -->
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>javax.servlet.jsp-api</artifactId>
            <version>${jsp.version}</version>
            <scope>provided</scope>
        </dependency>

        <!-- JSTL -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>${jstl.version}</version>
        </dependency>

        <!-- JSON支持 -->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.13.5</version>
        </dependency>

        <!-- 日志 -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.36</version>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.2.12</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <source>8</source>
                    <target>8</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>3.2.3</version>
            </plugin>
        </plugins>
    </build>
</project>

2.4 项目目录结构

springmvc-demo/
├── src/
│   ├── main/
│   │   ├── java/
│   │   │   └── com/
│   │   │       └── example/
│   │   │           ├── controller/
│   │   │           │   └── HelloController.java
│   │   │           ├── service/
│   │   │           │   └── UserService.java
│   │   │           ├── model/
│   │   │           │   └── User.java
│   │   │           └── config/
│   │   │               └── WebConfig.java
│   │   ├── resources/
│   │   │   └── springmvc-servlet.xml
│   │   └── webapp/
│   │       ├── WEB-INF/
│   │       │   ├── web.xml
│   │       │   └── views/
│   │       │       └── hello.jsp
│   │       └── index.jsp
└── pom.xml

3. 第一个Spring MVC程序

3.1 配置web.xml

创建src/main/webapp/WEB-INF/web.xml：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">

    <display-name>Spring MVC Demo</display-name>

    <!-- 配置DispatcherServlet -->
    <servlet>
        <servlet-name>springmvc</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>/WEB-INF/springmvc-servlet.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <!-- 映射所有请求到DispatcherServlet -->
    <servlet-mapping>
        <servlet-name>springmvc</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

    <!-- 字符编码过滤器 -->
    <filter>
        <filter-name>characterEncodingFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>UTF-8</param-value>
        </init-param>
        <init-param>
            <param-name>forceEncoding</param-name>
            <param-value>true</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>characterEncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>

3.2 配置Spring MVC

创建src/main/webapp/WEB-INF/springmvc-servlet.xml：

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

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

    <!-- 启用注解驱动 -->
    <mvc:annotation-driven/>

    <!-- 配置视图解析器 -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/views/"/>
        <property name="suffix" value=".jsp"/>
    </bean>

    <!-- 静态资源处理 -->
    <mvc:resources mapping="/static/**" location="/static/"/>
</beans>

3.3 创建Controller

创建src/main/java/com/example/controller/HelloController.java：

package com.example.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.ui.Model;

@Controller
public class HelloController {

    @RequestMapping(value = "/hello", method = RequestMethod.GET)
    public String hello(Model model) {
        model.addAttribute("message", "Hello, Spring MVC!");
        return "hello";
    }
}

3.4 创建视图

创建src/main/webapp/WEB-INF/views/hello.jsp：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Hello Spring MVC</title>
</head>
<body>
    <h1>${message}</h1>
</body>
</html>

3.5 部署和运行

使用Maven打包
```
mvn clean package
```
部署到Tomcat
- 将生成的war文件复制到Tomcat的webapps目录
- 启动Tomcat

访问应用

http://localhost:8080/springmvc-demo/hello

4. Spring MVC核心概念

4.1 DispatcherServlet

DispatcherServlet是Spring MVC的前端控制器，所有请求都经过它处理。

工作流程：

接收HTTP请求
查找HandlerMapping，确定处理请求的Controller
调用HandlerAdapter执行Controller
处理返回的ModelAndView
通过ViewResolver解析视图
渲染视图并返回响应

4.2 HandlerMapping

HandlerMapping负责将请求映射到对应的处理器。

类型：

BeanNameUrlHandlerMapping：根据Bean名称映射
SimpleUrlHandlerMapping：URL模式映射
RequestMappingHandlerMapping：注解方式映射（最常用）

4.3 HandlerAdapter

HandlerAdapter负责执行处理器。

类型：

SimpleControllerHandlerAdapter：执行Controller接口实现
HttpRequestHandlerAdapter：执行HttpRequestHandler
RequestMappingHandlerAdapter：执行@Controller注解的处理器

4.4 ViewResolver

ViewResolver负责将逻辑视图名解析为实际视图。

常用实现：

InternalResourceViewResolver：JSP视图
FreeMarkerViewResolver：FreeMarker模板
ThymeleafViewResolver：Thymeleaf模板
ContentNegotiatingViewResolver：内容协商视图解析器

4.5 Model和ModelAndView

Model：用于向视图传递数据

@Controller
public class UserController {
    @RequestMapping("/user")
    public String getUser(Model model) {
        model.addAttribute("name", "Alice");
        model.addAttribute("age", 25);
        return "user";
    }
}

ModelAndView：同时包含模型数据和视图信息

@RequestMapping("/user")
public ModelAndView getUser() {
    ModelAndView mav = new ModelAndView("user");
    mav.addObject("name", "Alice");
    mav.addObject("age", 25);
    return mav;
}

5. 控制器开发

5.1 @Controller注解

@Controller注解标识一个类为Spring MVC控制器。

@Controller
public class UserController {
    // 控制器方法
}

5.2 @RequestMapping注解

@RequestMapping用于映射请求到处理方法。

基本用法

@Controller
public class UserController {
    
    // 映射GET请求到/user
    @RequestMapping(value = "/user", method = RequestMethod.GET)
    public String getUser() {
        return "user";
    }
    
    // 映射POST请求到/user
    @RequestMapping(value = "/user", method = RequestMethod.POST)
    public String createUser() {
        return "success";
    }
    
    // 映射多个URL
    @RequestMapping(value = {"/user", "/users"}, method = RequestMethod.GET)
    public String listUsers() {
        return "users";
    }
}

简化注解

@Controller
public class UserController {
    
    // @GetMapping等价于@RequestMapping(method = RequestMethod.GET)
    @GetMapping("/user")
    public String getUser() {
        return "user";
    }
    
    // @PostMapping等价于@RequestMapping(method = RequestMethod.POST)
    @PostMapping("/user")
    public String createUser() {
        return "success";
    }
    
    // @PutMapping
    @PutMapping("/user/{id}")
    public String updateUser(@PathVariable Long id) {
        return "success";
    }
    
    // @DeleteMapping
    @DeleteMapping("/user/{id}")
    public String deleteUser(@PathVariable Long id) {
        return "success";
    }
}

类级别和方法级别

@Controller
@RequestMapping("/user")  // 类级别，所有方法都以此开头
public class UserController {
    
    @GetMapping("/list")  // 实际路径：/user/list
    public String list() {
        return "user/list";
    }
    
    @GetMapping("/detail")  // 实际路径：/user/detail
    public String detail() {
        return "user/detail";
    }
}

5.3 返回值类型

返回String（视图名）

@GetMapping("/user")
public String getUser() {
    return "user";  // 返回视图名
}

返回ModelAndView

@GetMapping("/user")
public ModelAndView getUser() {
    ModelAndView mav = new ModelAndView("user");
    mav.addObject("name", "Alice");
    return mav;
}

返回void（使用HttpServletResponse）

@GetMapping("/user")
public void getUser(HttpServletResponse response) throws IOException {
    response.getWriter().write("User Info");
}

返回ResponseEntity（RESTful）

@GetMapping("/user")
public ResponseEntity<User> getUser() {
    User user = new User("Alice", 25);
    return ResponseEntity.ok(user);
}

返回@ResponseBody

@GetMapping("/user")
@ResponseBody
public User getUser() {
    return new User("Alice", 25);
}

6. 请求映射

6.1 URL路径映射

精确匹配

@GetMapping("/user/detail")
public String detail() {
    return "user/detail";
}

路径变量

@GetMapping("/user/{id}")
public String getUser(@PathVariable Long id) {
    // 访问 /user/123，id = 123
    return "user/detail";
}

// 多个路径变量
@GetMapping("/user/{userId}/order/{orderId}")
public String getOrder(@PathVariable Long userId, 
                       @PathVariable Long orderId) {
    return "order/detail";
}

// 指定路径变量名
@GetMapping("/user/{id}")
public String getUser(@PathVariable("id") Long userId) {
    return "user/detail";
}

通配符匹配

// 匹配 /user/任意内容
@GetMapping("/user/*")
public String getUser() {
    return "user";
}

// 匹配 /user/任意多级路径
@GetMapping("/user/**")
public String getUserAll() {
    return "user";
}

6.2 请求参数映射

@RequestParam

// 必需参数
@GetMapping("/user")
public String getUser(@RequestParam String name) {
    // 访问 /user?name=Alice
    return "user";
}

// 可选参数
@GetMapping("/user")
public String getUser(@RequestParam(required = false) String name) {
    return "user";
}

// 默认值
@GetMapping("/user")
public String getUser(@RequestParam(defaultValue = "Guest") String name) {
    return "user";
}

// 多个参数
@GetMapping("/user")
public String getUser(@RequestParam String name,
                      @RequestParam int age) {
    // 访问 /user?name=Alice&age=25
    return "user";
}

参数绑定到对象

public class UserQuery {
    private String name;
    private Integer age;
    // getter/setter...
}

@GetMapping("/user")
public String getUser(UserQuery query) {
    // 自动绑定 /user?name=Alice&age=25
    return "user";
}

6.3 请求头映射

// 要求特定的请求头
@GetMapping(value = "/user", headers = "X-Requested-With=XMLHttpRequest")
public String getUserAjax() {
    return "user";
}

// 获取请求头值
@GetMapping("/user")
public String getUser(@RequestHeader("User-Agent") String userAgent) {
    return "user";
}

6.4 Content-Type映射

// 只接受JSON请求
@PostMapping(value = "/user", consumes = "application/json")
public String createUser(@RequestBody User user) {
    return "success";
}

// 返回JSON响应
@GetMapping(value = "/user", produces = "application/json")
@ResponseBody
public User getUser() {
    return new User("Alice", 25);
}

7. 参数绑定

7.1 基本类型绑定

@GetMapping("/user")
public String getUser(@RequestParam int id,
                      @RequestParam String name,
                      @RequestParam boolean active) {
    return "user";
}

7.2 对象绑定

public class User {
    private String name;
    private Integer age;
    private String email;
    // getter/setter...
}

@PostMapping("/user")
public String createUser(User user) {
    // 自动绑定表单数据到User对象
    return "success";
}

7.3 集合绑定

// List绑定
@PostMapping("/user")
public String createUsers(@RequestParam List<String> names) {
    // 表单：names=Alice&names=Bob
    return "success";
}

// Map绑定
@PostMapping("/user")
public String createUser(@RequestParam Map<String, String> params) {
    return "success";
}

7.4 日期绑定

@GetMapping("/user")
public String getUser(@RequestParam @DateTimeFormat(pattern = "yyyy-MM-dd") Date birthDate) {
    return "user";
}

7.5 @RequestBody（JSON绑定）

@PostMapping("/user")
public String createUser(@RequestBody User user) {
    // 自动将JSON转换为User对象
    return "success";
}

7.6 文件上传绑定

@PostMapping("/upload")
public String upload(@RequestParam("file") MultipartFile file) {
    if (!file.isEmpty()) {
        // 处理文件
        String fileName = file.getOriginalFilename();
        // 保存文件...
    }
    return "success";
}

8. 视图和视图解析器

8.1 JSP视图

配置InternalResourceViewResolver

<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="prefix" value="/WEB-INF/views/"/>
    <property name="suffix" value=".jsp"/>
</bean>

JSP中使用EL表达式

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>User Info</title>
</head>
<body>
    <h1>用户信息</h1>
    <p>姓名：${user.name}</p>
    <p>年龄：${user.age}</p>
</body>
</html>

JSP中使用JSTL

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<body>
    <c:forEach items="${users}" var="user">
        <p>${user.name}</p>
    </c:forEach>
</body>
</html>

8.2 JSON视图

使用@ResponseBody

@GetMapping("/user")
@ResponseBody
public User getUser() {
    return new User("Alice", 25);
}

使用ResponseEntity

@GetMapping("/user")
public ResponseEntity<User> getUser() {
    User user = new User("Alice", 25);
    return ResponseEntity.ok(user);
}

8.3 重定向和转发

@Controller
public class UserController {
    
    // 转发（默认）
    @GetMapping("/user")
    public String getUser() {
        return "user";  // 转发到user视图
    }
    
    // 重定向
    @PostMapping("/user")
    public String createUser() {
        return "redirect:/user/list";  // 重定向到/user/list
    }
    
    // 转发到另一个Controller
    @GetMapping("/user")
    public String getUser() {
        return "forward:/other/action";  // 转发到/other/action
    }
}

9. 数据绑定和验证

9.1 数据绑定

Spring MVC自动将请求参数绑定到方法参数或对象属性。

public class User {
    @NotNull
    @Size(min = 2, max = 50)
    private String name;
    
    @Min(18)
    @Max(100)
    private Integer age;
    
    @Email
    private String email;
    // getter/setter...
}

9.2 数据验证

添加验证依赖

<dependency>
    <groupId>org.hibernate.validator</groupId>
    <artifactId>hibernate-validator</artifactId>
    <version>6.2.3.Final</version>
</dependency>

使用@Valid注解

@PostMapping("/user")
public String createUser(@Valid User user, BindingResult result) {
    if (result.hasErrors()) {
        return "user/form";  // 返回表单页面
    }
    // 保存用户
    return "redirect:/user/list";
}

常用验证注解

@NotNull：不能为null
@NotEmpty：不能为空
@NotBlank：不能为空白
@Size(min=, max=)：长度限制
@Min、@Max：数值范围
@Email：邮箱格式
@Pattern：正则表达式
@Past、@Future：日期验证

9.3 自定义验证器

public class PhoneValidator implements ConstraintValidator<Phone, String> {
    @Override
    public boolean isValid(String value, ConstraintValidatorContext context) {
        return value != null && value.matches("^1[3-9]\\d{9}$");
    }
}

@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = PhoneValidator.class)
public @interface Phone {
    String message() default "Invalid phone number";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

10. 文件上传和下载

10.1 文件上传

配置MultipartResolver

<bean id="multipartResolver" 
      class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <property name="maxUploadSize" value="10485760"/>  <!-- 10MB -->
    <property name="maxInMemorySize" value="4096"/>
</bean>

添加依赖：

<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.4</version>
</dependency>

处理文件上传

@PostMapping("/upload")
public String upload(@RequestParam("file") MultipartFile file) {
    if (!file.isEmpty()) {
        try {
            byte[] bytes = file.getBytes();
            String fileName = file.getOriginalFilename();
            // 保存文件
            Path path = Paths.get("uploads/" + fileName);
            Files.write(path, bytes);
            return "redirect:/success";
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    return "redirect:/error";
}

多文件上传

@PostMapping("/upload")
public String upload(@RequestParam("files") MultipartFile[] files) {
    for (MultipartFile file : files) {
        if (!file.isEmpty()) {
            // 处理每个文件
        }
    }
    return "redirect:/success";
}

10.2 文件下载

@GetMapping("/download")
public ResponseEntity<Resource> download(@RequestParam String fileName) {
    try {
        Path filePath = Paths.get("uploads/" + fileName);
        Resource resource = new UrlResource(filePath.toUri());
        
        return ResponseEntity.ok()
            .header(HttpHeaders.CONTENT_DISPOSITION, 
                   "attachment; filename=\"" + resource.getFilename() + "\"")
            .body(resource);
    } catch (Exception e) {
        return ResponseEntity.notFound().build();
    }
}

11. 拦截器

11.1 创建拦截器

public class LoggingInterceptor implements HandlerInterceptor {
    
    @Override
    public boolean preHandle(HttpServletRequest request, 
                           HttpServletResponse response, 
                           Object handler) throws Exception {
        System.out.println("Before handling request: " + request.getRequestURI());
        return true;  // 返回true继续处理，false中断
    }
    
    @Override
    public void postHandle(HttpServletRequest request, 
                          HttpServletResponse response, 
                          Object handler, 
                          ModelAndView modelAndView) throws Exception {
        System.out.println("After handling request");
    }
    
    @Override
    public void afterCompletion(HttpServletRequest request, 
                               HttpServletResponse response, 
                               Object handler, 
                               Exception ex) throws Exception {
        System.out.println("Request completed");
    }
}

11.2 配置拦截器

<mvc:interceptors>
    <mvc:interceptor>
        <mvc:mapping path="/user/**"/>
        <bean class="com.example.interceptor.LoggingInterceptor"/>
    </mvc:interceptor>
</mvc:interceptors>

使用Java配置

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

11.3 实际应用：登录拦截器

public class LoginInterceptor implements HandlerInterceptor {
    
    @Override
    public boolean preHandle(HttpServletRequest request, 
                           HttpServletResponse response, 
                           Object handler) throws Exception {
        HttpSession session = request.getSession();
        Object user = session.getAttribute("user");
        
        if (user == null) {
            response.sendRedirect("/login");
            return false;
        }
        return true;
    }
}

12. 异常处理

12.1 @ExceptionHandler

@Controller
public class UserController {
    
    @ExceptionHandler(UserNotFoundException.class)
    public String handleUserNotFound(UserNotFoundException e, Model model) {
        model.addAttribute("error", e.getMessage());
        return "error";
    }
    
    @GetMapping("/user/{id}")
    public String getUser(@PathVariable Long id) {
        User user = userService.findById(id);
        if (user == null) {
            throw new UserNotFoundException("User not found: " + id);
        }
        return "user";
    }
}

12.2 @ControllerAdvice

@ControllerAdvice
public class GlobalExceptionHandler {
    
    @ExceptionHandler(Exception.class)
    public String handleException(Exception e, Model model) {
        model.addAttribute("error", e.getMessage());
        return "error";
    }
    
    @ExceptionHandler(UserNotFoundException.class)
    public ResponseEntity<String> handleUserNotFound(UserNotFoundException e) {
        return ResponseEntity.status(HttpStatus.NOT_FOUND)
            .body(e.getMessage());
    }
}

12.3 @ResponseStatus

@ResponseStatus(value = HttpStatus.NOT_FOUND, reason = "User not found")
public class UserNotFoundException extends RuntimeException {
    public UserNotFoundException(String message) {
        super(message);
    }
}

13. RESTful API开发

13.1 RESTful设计原则

使用HTTP动词（GET、POST、PUT、DELETE）
使用名词表示资源
使用JSON格式
使用HTTP状态码

13.2 RESTful Controller

@RestController  // 等价于@Controller + @ResponseBody
@RequestMapping("/api/users")
public class UserRestController {
    
    @Autowired
    private UserService userService;
    
    // GET /api/users - 获取所有用户
    @GetMapping
    public List<User> getAllUsers() {
        return userService.findAll();
    }
    
    // GET /api/users/{id} - 获取单个用户
    @GetMapping("/{id}")
    public ResponseEntity<User> getUser(@PathVariable Long id) {
        User user = userService.findById(id);
        if (user == null) {
            return ResponseEntity.notFound().build();
        }
        return ResponseEntity.ok(user);
    }
    
    // POST /api/users - 创建用户
    @PostMapping
    public ResponseEntity<User> createUser(@RequestBody User user) {
        User saved = userService.save(user);
        return ResponseEntity.status(HttpStatus.CREATED).body(saved);
    }
    
    // PUT /api/users/{id} - 更新用户
    @PutMapping("/{id}")
    public ResponseEntity<User> updateUser(@PathVariable Long id, 
                                          @RequestBody User user) {
        User updated = userService.update(id, user);
        return ResponseEntity.ok(updated);
    }
    
    // DELETE /api/users/{id} - 删除用户
    @DeleteMapping("/{id}")
    public ResponseEntity<Void> deleteUser(@PathVariable Long id) {
        userService.delete(id);
        return ResponseEntity.noContent().build();
    }
}

13.3 内容协商

@GetMapping(value = "/user/{id}", produces = {MediaType.APPLICATION_JSON_VALUE, 
                                               MediaType.APPLICATION_XML_VALUE})
public User getUser(@PathVariable Long id) {
    return userService.findById(id);
}

14. Spring MVC与Spring Boot集成

14.1 创建Spring Boot项目

使用Spring Initializr创建项目，选择：

Spring Web
Thymeleaf（可选）

14.2 配置Spring MVC

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {
    
    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
        registry.addViewController("/").setViewName("index");
    }
    
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LoggingInterceptor());
    }
}

14.3 application.properties配置

# 视图配置
spring.mvc.view.prefix=/WEB-INF/views/
spring.mvc.view.suffix=.jsp

# 静态资源
spring.web.resources.static-locations=classpath:/static/
spring.web.resources.cache.period=3600

# 文件上传
spring.servlet.multipart.max-file-size=10MB
spring.servlet.multipart.max-request-size=10MB