public class HelloController implements Controller {
    @Override
    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception{
        //ModelAndView 模型和视图
        ModelAndView mv = new ModelAndView();
        //封装对象，放在ModelAndView中
        mv.addObject("msg","HelloSpringMVC!");
        //封装要跳转的视图，放在ModelAndView中
        mv.setViewName("hello"); // 跳转到/WEB-INF/jsp/hello.jsp
        return mv;
    }
}

@Controller // 让Spring IOC容器初始化时自动扫描到
public class HelloController {
    @RequestMapping("/hello")
    public String sayHello(Model model){
        //向模型中添加属性msg与值，可以在JSP页面中取出并渲染
        model.addAttribute("msg","hello,SpringMVC");
        // 跳转到 /WEB-INF/jsp/hello.jsp
        return "hello";
    }
}

@RequestMapping("/forward")
public String forwardExample() {
    return "forward:/target"; // 转发到"/target"处理器或视图
}

@RequestMapping("/forward")
public String forwardExample() {
    return "forward:/target.jsp"; // 转发到"/target"处理器或视图
}

@RequestMapping("/redirect")
public String redirectExample() {
    return "redirect:/target"; // 重定向到"/target" URL
}

@RequestMapping("/redirect")
public String redirectExample() {
    return "redirect:/target.jsp"; // 重定向到"/target" URL
}

@Controller
public class LoginController {
    // 访问登录页
    @RequestMapping("/toLogin")
    public String toLogin(){
        // 跳转到登录界面
        return "forward:/login.jsp";
    }
    // 处理登录页接收到的参数
    @RequestMapping(value = "login",method = RequestMethod.POST)
    public String doLogin(String username,String password){
        /* 验证参数，验证登录
            验证成功，则记录session信息，同时重定向到首页
            验证失败，则执行 return toLogin();
         */
        return toLogin();
    }
    // 用户退出登录
    @RequestMapping(value = "/logout",method = RequestMethod.GET)
    public String doLogout(HttpServletRequest request){
        // 销毁session对象
        request.getSession().invalidate();
        // 重定向到登录页面
        return "redirect:toLogin";
    }
}

@RequestMapping("/hello")
public String hello(String name){
    System.out.println(name);
    return "hello";
}

@RequestMapping("/hello")
public String hello(@RequestParam("username") String name){
    System.out.println(name);
    return "hello";
}

@Controller
public class TestController {
    @RequestMapping(value = "/test",method = RequestMethod.GET)
    // 接收User对象
    public String test1(User user){
        //转发
        return "/WEB-INF/jsp/test.jsp";
    }
}

@Controller
public class RestFulController {
    //映射访问路径
    @RequestMapping("/commit/{p1}/{p2}")
    public String index(@PathVariable int p1, @PathVariable int p2, Model model){
        int result = p1+p2;
        //Spring MVC会自动实例化一个Model对象用于向视图中传值
        model.addAttribute("msg", "结果："+result);
        //返回视图位置
        return "test";
    }
}

@RestController
public class MyController {
    @PostMapping("/data")
    public void processData(@RequestBody MyData data) {
        // 处理接收到的JSON数据
        System.out.println(data);
    }
}

@RequestMapping("/hello")
public String hello(@RequestParam("username") String name, ModelMap model){
    //封装要显示到视图中的数据
    model.addAttribute("name",name);
    return "hello";
}

@RequestMapping("/hello")
public String hello(@RequestParam("username") String name, Model model){
    //封装要显示到视图中的数据
    model.addAttribute("msg",name);
    return "hello";
}

ObjectMapper mapper = new ObjectMapper();

String str = mapper.writeValueAsString(...);

public class HelloInterceptor implements HandlerInterceptor {

    // preHandle() 方法在请求处理之前调用，可以用于进行一些预处理操作
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("处理前");
        return true;
    }
	// postHandle() 方法在请求处理之后调用，在视图渲染之前调用，可以用于修改 ModelAndView 对象
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("处理后");
    }
	// afterCompletion() 方法在请求处理完成之后调用，可以用于进行一些资源清理操作，也可以用来统计请求耗时
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("清理");
    }
}

/*
addPathPatterns方法定义拦截的地址

excludePathPatterns定义排除某些地址不被拦截

添加的一个拦截器没有addPathPattern任何一个ur则默认拦截所有请求

如果没有excludePathPatterns任何一个请求，则默认不放过任何一个请求
*/
@Configuration
public class WebConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors (InterceptorRegistry registry) {
        registry.addInterceptor( new LoginInterceptor()).addPathPatterns ("/user/**");
    }
}

@Controller
public class LoginController {
    // 首页
    @RequestMapping(value = "/main",method = RequestMethod.GET)
    public String main(){
        return "main";
    }
    // 登录页
    @RequestMapping(value = "/doLogin",method = RequestMethod.GET)
    public String doLogin(){
        return "login";
    }
    // 处理登录信息
    @RequestMapping(value = "/login",method = RequestMethod.POST)
    public String hello(Model model,HttpSession session, @RequestParam("username") String username, @RequestParam("password") String password){
        // 接收登录信息，把用户信息存在session中
        session.setAttribute("userLoinInfo",username);
        // 传递信息到视图
        model.addAttribute("name",username);
        return "hello";
    }
    // 欢迎页面
    @RequestMapping(value = "/hello",method = RequestMethod.GET)
    public String doHello(){
        return "hello";
    }
    // 注销功能，将用户信息从session中删除
    @RequestMapping(value = "/logout",method = RequestMethod.GET)
    public String doLogout(HttpSession session){
        session.removeAttribute("userLoinInfo");
        return "login";
    }
}

public class LoginInterceptor implements HandlerInterceptor {
    /* 判断是否登录
       判断依据：session中是否有用户信息
    */
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        HttpSession session = request.getSession();
        // 访问 /hello时，若已经登录，则放行，否则拦截
        if (session.getAttribute("userLoinInfo") != null && request.getRequestURI().contains("/hello")) {
            System.out.println("已放行");
            return true;
        }
        // 访问 /doLogin 则放行
        if (request.getRequestURI().contains("/doLogin")) {
            System.out.println("已放行");
            return true;
        }
        // 访问 /main 则放行
        if (request.getRequestURI().contains("/main")){
            System.out.println("已放行");
            return true;
        }
        // 访问 /login 则放行
        if (request.getRequestURI().contains("/login")){
            System.out.println("已放行");
            return true;
        }
        // 访问 /logout 则放行
        if (request.getRequestURI().contains("/logout")){
            System.out.println("已放行");
            return true;
        } else {
            System.out.println("已拦截");
            return false;
        }
    }
}

@Controller
public class UploadController {
    // 文件上传页面
    @RequestMapping(value = "/file",method = RequestMethod.GET)
    public String file(){
        return "file";
    }
    // 处理上传的文件
    @ResponseBody
    @RequestMapping(value = "/upload",method = RequestMethod.POST)
    public String fileUpload(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws Exception{
        // 设置上传路径
        String path = request.getSession().getServletContext().getRealPath("/upload");
        // 创建上传路径的文件夹
        File realPath = new File(path);
        if (!realPath.exists()) {
            realPath.mkdir();
        }
        // 打印上传文件地址
        System.out.println("fileSavePath:\t" + realPath);
        // 通过CommonsMultipartFile的方法直接写文件
        file.transferTo(new File(realPath + "/" +file.getOriginalFilename()));
        return "success";
    }
}

@Controller
public class DownController {
    @RequestMapping(value = "/getDown",method = RequestMethod.GET)
    public String getDown(){
        return "down";
    }
    @RequestMapping(value = "/down",method = RequestMethod.GET)
    public String down(HttpServletResponse response, HttpServletRequest request) throws Exception{
        // 要下载的图片的地址
        String path = request.getServletContext().getRealPath("/static");
        // 图片名字
        String filename = "15.jpg";
        //设置response响应头
        response.reset(); // 设置页面不缓存
        response.setCharacterEncoding("UTF-8");
        response.setContentType("multype/form-data");
        // 设置响应头
        response.setHeader("Content-Disposition", "attachment;filename=" + filename);
        response.setContentType("image/jpeg");
        // 以流的形式下载文件
        File file = new File(path,filename);
        // 读取文件：输入流
        InputStream input = new FileInputStream(file);
        // 写出文件：输出流
        OutputStream out = response.getOutputStream();
        byte[] body = new byte[1024];
        int index=0;
        // 执行写出操作
        while ((index=input.read(body))!=-1){
            out.write(body,0,index);
            out.flush();
        }
        out.close();
        input.close();
        return null;
    }
}

public class ViewConfig implements ViewResolver {

    @Override
    public View resolveViewName(String viewName, Locale locale) throws Exception {
        if (viewName.startsWith("myview:")) {
            String viewPath = viewName.substring("myview:".length());
            MyView view = new MyView();
            view.setUrl(viewPath);
            return view;
        } else {
            return null; // 返回 null 表示无法解析视图名称
        }
    }
}

@Configuration
public class MyWebConfig implements WebMvcConfigurer {

    @Override
    public void configureViewResolvers(ViewResolverRegistry registry) {
        registry.viewResolver(new ViewConfig());
    }
}