问答平台（1），SpringMVC入门

HTTP

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- HyperText Transfer Protocol 
- 用于传输 HTML 等内容的应用层协议
- 规定了浏览器和服务器之间如何通信，以及通信时的数据格式。

Spring MVC

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- 三层架构
    - 表现层、业务层、数据访问层
    - 分层目的：解耦
- MVC
    - Model：模型层
    - View：视图层
    - Controller：控制层
- 核心组件
    - 前端控制器：DispatcherServlet

示意图

三层架构-图示

Thymeleaf

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- 模板引擎
    - 生成动态的 HTML。
- Thymeleaf
    - 倡导自然模板，即以 HTML 文件为模板。
- 常用语法
    - 标准表达式、判断与循环、模板的布局。

配置

  • application-develop.properties
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    # ThymeleafProperties
    spring.thymeleaf.cache=false

示意图

模板引擎-图示

示例

理解 MVC: 处理请求与响应

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// AlphaController.java
@Controller
@RequestMapping("/alpha")
public class AlphaController {

    @Autowired
    private AlphaService alphaService;

    @RequestMapping("/http")
    public void http(HttpServletRequest request, HttpServletResponse response) {
        // 获取请求数据
        System.out.println(request.getMethod());
        System.out.println(request.getServletPath());
        Enumeration<String> enumeration = request.getHeaderNames();
        while (enumeration.hasMoreElements()) {
            String name = enumeration.nextElement();
            String value = request.getHeader(name);
            System.out.println(name + ":" + value);
        }
        System.out.println(request.getParameter("code"));

        // 返回响应数据
        response.setContentType("text/html;charset=utf-8");
        try (
                PrintWriter writer = response.getWriter();
        ) {
            writer.write("<h1>牛客网</h1>");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // GET请求
    // /students?current=1&limit=20
    @RequestMapping(path = "/students", method = RequestMethod.GET)
    @ResponseBody
    public String getStudents(@RequestParam(name = "current", required = false, defaultValue = "1") int current,
                              @RequestParam(name = "limit", required = false, defaultValue = "10") int limit) {
        System.out.println(current);
        System.out.println(limit);
        return "some students";
    }

    // /student/123
    @RequestMapping(path = "/student/{id}", method = RequestMethod.GET)
    @ResponseBody
    public String getStudent(@PathVariable("id") int id) {
        System.out.println(id);
        return "a student";
    }

    // POST请求（static, 静态模板）
    @RequestMapping(path = "/student", method = RequestMethod.POST)
    @ResponseBody
    public String saveStudent(String name, int age) {
        System.out.println(name);
        System.out.println(age);
        return "success";
    }

    // 响应HTML数据
    @RequestMapping(path = "/teacher", method = RequestMethod.GET)
    public ModelAndView getTeacher() {
        ModelAndView mav = new ModelAndView();
        mav.addObject("name", "字节跳动");
        mav.addObject("age", 8);
        mav.setViewName("/demo/view");
        return mav;
    }

    @RequestMapping(path = "/school", method = RequestMethod.GET)
    public String getSchool(Model model) {
        model.addAttribute("name", "北京大学");
        model.addAttribute("age", 100);
        return "/demo/view";
    }

    // 响应JSON数据（异步请求）
    // Java对象 -> JSON字符串 -> JS对象（等其他语言的对象）
    @RequestMapping(path = "/emp", method = RequestMethod.GET)
    @ResponseBody
    public Map<String, Object> getEmp() {
        Map<String, Object> emp = new HashMap<>();
        emp.put("name", "李成风");
        emp.put("age", 23);
        emp.put("salary", 8000.00);
        return emp;
    }

    @RequestMapping(path = "/emps", method = RequestMethod.GET)
    @ResponseBody
    public List<Map<String, Object>> getEmps() {
        List<Map<String, Object>> list = new ArrayList<>();

        Map<String, Object> emp = new HashMap<>();
        emp.put("name", "李成风");
        emp.put("age", 23);
        emp.put("salary", 8000.00);
        list.add(emp);

        emp = new HashMap<>();
        emp.put("name", "刘毅");
        emp.put("age", 22);
        emp.put("salary", 9000.00);
        list.add(emp);

        emp = new HashMap<>();
        emp.put("name", "章七");
        emp.put("age", 22);
        emp.put("salary", 7000.00);
        list.add(emp);

        return list;
    }
}

参考资料

#问答平台
问答平台（1），SpringMVC入门
https://lcf163.github.io/2020/04/12/问答平台（1），SpringMVC入门/
作者
乘风的小站
发布于
2020年4月12日
许可协议