详解springMVC获取前端请求的数据与三个作用域

// 处理注册请求
@PostMapping("/register/user")
public String register(HttpServletRequest request, HttpSession session, HttpServletResponse resp) {
    // 获取请求参数
    // HttpServletRequest\HttpSession\HttpServletResponse 都属于Servlet API，Spring MVC会自动将它们注入到方法参数中
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    return "success";
}

@PostMapping("/register/user/2")
public String register2(
        // @RequestParam注解用于将请求参数绑定到方法参数上，value属性指定请求参数的名称,参数名可以和请求参数名不同
        // 可以自动将请求参数转换为方法参数的类型，例如将字符串转换为整数、日期等
        @RequestParam("username") String username,
        @RequestParam("password") String password) {
    return "success";
}

@PostMapping("/register/user/2")
public String register2(
        // @RequestParam注解用于将请求参数绑定到方法参数上，value属性指定请求参数的名称,参数名可以和请求参数名不同
        // 可以自动将请求参数转换为方法参数的类型，例如将字符串转换为整数、日期等
        @RequestParam("username") String username,
        @RequestParam("password") String password,
        @RequestParam(value = "age",required = false,defaultValue = "20") Integer age) {
    return "success";
}

@PostMapping("/register/user/3")
public String register3(String username, String password) {
    // 这种方式要求请求参数的名称必须与方法参数的名称一致，Spring MVC会自动将请求参数绑定到方法参数上
    return "success";
}

@PostMapping("/register/user/4")
public String register4(User user) {
    // 这种方式要求请求参数的名称必须与User类的属性名称一致，Spring MVC会自动将请求参数绑定到User对象的属性上
    return "success";
}

@PostMapping("/register/user/4")
public String register4(User user, @RequestHeader(value = "Referer",required = false,defaultValue = "") String referer) {
    return "success";
}

@PostMapping("/register/user/4")
public String register4(User user,
                        @RequestHeader(value = "Referer",required = false,defaultValue = "") String referer,
                        @CookieValue(value = "JSESSIONID",required = false,defaultValue = "") String jsessionId) {
    // 这种方式要求请求参数的名称必须与User对象的属性名称一致，Spring MVC会自动将请求参数绑定到User对象的属性上
    // @RequestHeader注解用于将请求头信息绑定到方法参数上，value属性指定请求头的名称
    // @CookieValue注解用于将Cookie信息绑定到方法参数上，value属性指定Cookie的名称
    return "success";
}

// 这行代码必须在获取参数的代码之前执行，不能写在下面
request.setCharacterEncoding("UTF-8");
String username = request.getParameter("username");

public class CharacterEncodingFilter implements Filter {
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        // 设置请求和响应的字符编码为UTF-8，解决中文乱码问题
        servletRequest.setCharacterEncoding("UTF-8");
        servletResponse.setContentType("text/html;charset=UTF-8");
        // 将请求和响应对象传递给下一个过滤器或目标资源
        filterChain.doFilter(servletRequest, servletResponse);
    }
}

<!--    设置字符编码过滤器，解决post请求中文乱码问题-->
    <filter>
        <filter-name>characterEncodingFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>characterEncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

<!--    使用springmvc提供的字符编码过滤器，解决post请求中文乱码问题-->
    <filter>
        <filter-name>characterEncodingFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
<!--        设置字符集为UTF-8-->
        <init-param>
            <param-name>encoding</param-name>
            <param-value>UTF-8</param-value>
        </init-param>
<!--        请求体和响应体都使用UTF-8字符集-->
        <init-param>
            <param-name>forceRequestEncoding</param-name>
            <param-value>true</param-value>
        </init-param>
        <init-param>
            <param-name>forceResponseEncoding</param-name>
            <param-value>true</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>characterEncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

@RequestMapping("/testServletAPI")
public String testServletAPI(HttpServletRequest request) {
    // 将共享数据存入request域对象中
    request.setAttribute("testRequestScope", "hello,servletAPI");
    // 这个跳转视图默认是forward方式，request域对象中的数据可以共享到目标资源中
    return "ok";
}

<body>
<div th:text="${testRequestScope}"></div>
</body>

@RequestMapping("/testModel")
public String testModel(Model model) {
    // 将共享数据存入model中
    model.addAttribute("testRequestScope", "hello,Model");
    return "ok";
}

@RequestMapping("/testMap")
public String testMap(Map<String, Object> map) {
    // 将共享数据存入map中
    map.put("testRequestScope", "hello,Map");
    return "ok";
}

@RequestMapping("/testModelMap")
public String testModelMap(ModelMap modelMap) {
    // 将共享数据存入modelMap中
    modelMap.addAttribute("testRequestScope", "hello,ModelMap");
    return "ok";
}

@RequestMapping("/testModelAndView")
public ModelAndView testModelAndView(ModelAndView modelAndView) {
    // 将共享数据存入modelAndView中
    modelAndView.addObject("testRequestScope", "hello,ModelAndView");
    // 设置视图名称
    modelAndView.setViewName("ok");
    return modelAndView;
}

@RequestMapping("/testSessionScope")
public String test(HttpSession session) {
    // 将共享数据存入session域对象中
    session.setAttribute("testSessionScope", "hello,Session");
    return "ok";
}

<body>
<div th:text="${session.testSessionScope}"></div>
</body>

@Controller
// @SessionAttributes注解：将指定的属性存储到session域对象中
// 表示 将modelMap中key为"x"和"y"的属性存储到session域对象中
@SessionAttributes(value = {"x", "y"})
public class SessionScopeTestController {
    @RequestMapping("/testSessionAttribute")
    public String testSessionAttribute(ModelMap modelMap) {
        // 将共享数据存入session域对象中
        modelMap.addAttribute("x", "hello,x");
        modelMap.addAttribute("y", "hello,y");
        return "ok";
    }
}

@RequestMapping("/testApplicationScope")
public String test(HttpServletRequest request) {
    // 将共享数据存入application域对象中
    ServletContext servletContext = request.getServletContext();
    servletContext.setAttribute("testApplicationScope", "hello,Application");
    return "ok";
}

<body>
<div th:text="${application.testApplicationScope}"></div>
</body>