Spring Boot詳解各類請求和響應的處理方法

2022-07-18 22:01:37

1. HttpServletRequest與HttpServletResponse

瀏覽器輸入：http://localhost:8080/community/alpha/http?code=10

@RequestMapping("/http")
public void http(HttpServletRequest request, HttpServletResponse response) {
    // 獲取請求資料
    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"));
    // 返回響應資料
    response.setContentType("text/html;charset=utf-8");
    try {
        PrintWriter writer = response.getWriter();
        writer.write("<h1>nowcoder</h1>");
    } catch (IOException e) {
        e.printStackTrace();
    }
}

前端頁面顯示：nowcoder

同時，IDEA控制檯輸出：

GET
/alpha/http
host: localhost:8080
connection: keep-alive
sec-ch-ua: " Not;A Brand";v="99", "Google Chrome";v="97", "Chromium";v="97"
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: "Windows"
upgrade-insecure-requests: 1
user-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36
accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
sec-fetch-site: none
sec-fetch-mode: navigate
sec-fetch-user: ?1
sec-fetch-dest: document
accept-encoding: gzip, deflate, br
accept-language: zh-CN,zh;q=0.9
cookie: Idea-10659edd=72fa12c3-9b68-4da6-8b68-38a81c822aa0
10

2. GET型別的請求

在AlphaController中增加方法，處理GET型別的請求。

2.1 /students?current=1&limit=20

瀏覽器輸入：http://localhost:8080/community/alpha/students?current=1&limit=100

@GetMapping("/students")
@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";
}

前端頁面顯示：some students

同時，IDEA控制檯輸出：

1
100

2.2 /student/123

瀏覽器輸入：http://localhost:8080/community/alpha/student/123

@GetMapping("/student/{id}")
@ResponseBody
public String getStudent(@PathVariable("id") int id) {
    System.out.println(id);
    return "one student";
}

前端頁面顯示：one students

同時，IDEA控制檯輸出：

123

3. POST型別的請求

在AlphaController中增加方法，處理POST型別的請求。

瀏覽器輸入：http://localhost:8080/community/html/student.html

@PostMapping("/student")
@ResponseBody
public String saveStudent(String name, int age) {
    System.out.println(name);
    System.out.println(age);
    return "success";
}

resources/static/html/student.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>增加學生</title>
</head>
<body>
  <form method="post" action="/community/alpha/student">
    <p>
      姓名：<input type="text" name="name">
    </p>
    <p>
      年齡：<input type="text" name="age">
    </p>
    <p>
      <input type="submit" value="儲存">
    </p>
  </form>
</body>
</html>

前端頁面顯示一個表單，包含兩行：姓名、年齡，還有一個 “儲存” 按鈕。

輸入 “Lebron”、38 後，點選 “儲存” 後，顯示 “success”。

4. 響應HTML格式的資料

在AlphaController中增加方法，向瀏覽器響應HTML格式的資料。

4.1 使用ModelAndView

瀏覽器輸入：http://localhost:8080/community/alpha/teacher

@GetMapping("/teacher")
public ModelAndView getTeacher() {
    ModelAndView mav = new ModelAndView();
    mav.addObject("name", "Lebron");
    mav.addObject("age", 38);
    mav.setViewName("/demo/view");
    return mav;
}

前端頁面顯示：

Lebron
38

4.2 使用Model

瀏覽器輸入：http://localhost:8080/community/alpha/school

@GetMapping("/school")
public String getSchool(Model model) {
    model.addAttribute("name", "xx大學");
    model.addAttribute("age", 100);
    return "/demo/view";
}

resources/templates/demo/view.html

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Teacher</title>
</head>
<body>
    <p th:text="${name}"></p>
    <p th:text="${age}"></p>
</body>
</html>

前端頁面顯示：

xx大學
100

5. 響應JSON格式的資料

在AlphaController中增加方法，向瀏覽器響應JSON格式的資料。

5.1 單組資料

瀏覽器輸入：http://localhost:8080/community/alpha/emp

@GetMapping("/emp")
@ResponseBody
public Map<String, Object> getEmp() {
    Map<String, Object> emp = new HashMap<>();
    emp.put("name", "Kitty");
    emp.put("age", 20);
    emp.put("salary", 12000.00);
    return emp;
}

前端頁面顯示：

{"name":"Kitty","salary":12000.0,"age":20}

5.2 多組資料

瀏覽器輸入：http://localhost:8080/community/alpha/emps

@GetMapping("/emps")
@ResponseBody
public List<Map<String, Object>> getEmps() {
    List<Map<String, Object>> list = new ArrayList<>();
    Map<String, Object> emp = new HashMap<>();
    emp.put("name", "Tom");
    emp.put("age", 20);
    emp.put("salary", 12000.00);
    list.add(emp);
    emp = new HashMap<>();
    emp.put("name", "Jerry");
    emp.put("age", 18);
    emp.put("salary", 15000.00);
    list.add(emp);
    emp = new HashMap<>();
    emp.put("name", "Leo");
    emp.put("age", 25);
    emp.put("salary", 8000.00);
    list.add(emp);
    return list;
}

前端頁面顯示：