SpringMVC - 请求处理

@RequestMapping

@RequestMapping 用于映射请求 URL 到处理方法。

基本使用

@Controller
@RequestMapping("/user")  // 类级别，设置基础路径
public class UserController {
    
    // 访问路径：/user/list
    @RequestMapping("/list")
    public String list() {
        return "user/list";
    }
    
    // 访问路径：/user/detail
    @RequestMapping("/detail")
    public String detail() {
        return "user/detail";
    }
}

请求方法限定

// 限定 GET 请求
@RequestMapping(value = "/get", method = RequestMethod.GET)

// 限定 POST 请求
@RequestMapping(value = "/post", method = RequestMethod.POST)

// 多种请求方法
@RequestMapping(value = "/multi", method = {RequestMethod.GET, RequestMethod.POST})

快捷注解

注解	等价于
@GetMapping	@RequestMapping(method = RequestMethod.GET)
@PostMapping	@RequestMapping(method = RequestMethod.POST)
@PutMapping	@RequestMapping(method = RequestMethod.PUT)
@DeleteMapping	@RequestMapping(method = RequestMethod.DELETE)
@PatchMapping	@RequestMapping(method = RequestMethod.PATCH)

@RestController
@RequestMapping("/api/users")
public class UserApiController {
    
    @GetMapping
    public List<User> list() { ... }
    
    @GetMapping("/{id}")
    public User getById(@PathVariable Long id) { ... }
    
    @PostMapping
    public User create(@RequestBody User user) { ... }
    
    @PutMapping("/{id}")
    public User update(@PathVariable Long id, @RequestBody User user) { ... }
    
    @DeleteMapping("/{id}")
    public void delete(@PathVariable Long id) { ... }
}

其他属性

@RequestMapping(
    value = "/test",           // 请求路径
    method = RequestMethod.GET, // 请求方法
    params = "id",              // 必须包含参数 id
    headers = "Content-Type=application/json",  // 请求头
    consumes = "application/json",  // 请求内容类型
    produces = "application/json"   // 响应内容类型
)

参数绑定

基本类型参数

// URL: /user?id=1&name=张三
@GetMapping("/user")
public String getUser(Integer id, String name) {
    // id = 1, name = "张三"
    return "user";
}

@RequestParam

@GetMapping("/user")
public String getUser(
    @RequestParam("userId") Integer id,           // 参数名映射
    @RequestParam(required = false) String name,  // 非必须
    @RequestParam(defaultValue = "1") Integer page // 默认值
) {
    return "user";
}

@PathVariable 路径变量

// URL: /user/1
@GetMapping("/user/{id}")
public String getUser(@PathVariable("id") Integer userId) {
    return "user";
}

// URL: /user/1/order/100
@GetMapping("/user/{userId}/order/{orderId}")
public String getOrder(
    @PathVariable Integer userId,
    @PathVariable Integer orderId
) {
    return "order";
}

POJO 对象绑定

public class User {
    private Long id;
    private String name;
    private Integer age;
    // getter/setter
}

// URL: /user?id=1&name=张三&age=25
@PostMapping("/user")
public String saveUser(User user) {
    // 自动绑定到 User 对象
    return "success";
}

嵌套对象绑定

public class User {
    private String name;
    private Address address;  // 嵌套对象
}

public class Address {
    private String city;
    private String street;
}

// URL: /user?name=张三&address.city=北京&address.street=长安街
@PostMapping("/user")
public String saveUser(User user) {
    // user.getAddress().getCity() = "北京"
    return "success";
}

数组和集合

// URL: /delete?ids=1&ids=2&ids=3
@PostMapping("/delete")
public String delete(Integer[] ids) {
    // ids = [1, 2, 3]
    return "success";
}

// List 需要 @RequestParam
@PostMapping("/delete")
public String delete(@RequestParam List<Integer> ids) {
    return "success";
}

@RequestBody

接收 JSON 请求体：

@PostMapping("/user")
public String saveUser(@RequestBody User user) {
    // JSON 自动转为 User 对象
    return "success";
}

@PostMapping("/users")
public String saveUsers(@RequestBody List<User> users) {
    // JSON 数组转为 List
    return "success";
}

@RequestHeader

获取请求头：

@GetMapping("/header")
public String getHeader(
    @RequestHeader("User-Agent") String userAgent,
    @RequestHeader("Accept") String accept
) {
    return "header";
}

@CookieValue

获取 Cookie：

@GetMapping("/cookie")
public String getCookie(
    @CookieValue("JSESSIONID") String sessionId,
    @CookieValue(value = "token", required = false) String token
) {
    return "cookie";
}

HttpServletRequest/HttpServletResponse

@GetMapping("/servlet")
public String servlet(HttpServletRequest request, HttpServletResponse response) {
    String param = request.getParameter("param");
    HttpSession session = request.getSession();
    return "servlet";
}

RESTful 风格

REST（Representational State Transfer）是一种软件架构风格，使用 URL 定位资源，用 HTTP 方法描述操作。

传统 vs RESTful

操作	传统方式	RESTful 方式
查询所有	/user/list	GET /users
查询单个	/user/detail?id=1	GET /users/1
新增	/user/add	POST /users
修改	/user/update?id=1	PUT /users/1
删除	/user/delete?id=1	DELETE /users/1

RESTful API 示例

@RestController
@RequestMapping("/api/users")
public class UserRestController {
    
    @Autowired
    private UserService userService;
    
    // GET /api/users - 查询所有
    @GetMapping
    public List<User> list() {
        return userService.findAll();
    }
    
    // GET /api/users/1 - 查询单个
    @GetMapping("/{id}")
    public User getById(@PathVariable Long id) {
        return userService.findById(id);
    }
    
    // POST /api/users - 新增
    @PostMapping
    public User create(@RequestBody User user) {
        return userService.save(user);
    }
    
    // PUT /api/users/1 - 修改
    @PutMapping("/{id}")
    public User update(@PathVariable Long id, @RequestBody User user) {
        user.setId(id);
        return userService.update(user);
    }
    
    // DELETE /api/users/1 - 删除
    @DeleteMapping("/{id}")
    public void delete(@PathVariable Long id) {
        userService.deleteById(id);
    }
    
    // GET /api/users?page=1&size=10 - 分页查询
    @GetMapping(params = {"page", "size"})
    public Page<User> page(
        @RequestParam(defaultValue = "1") Integer page,
        @RequestParam(defaultValue = "10") Integer size
    ) {
        return userService.findPage(page, size);
    }
}

HiddenHttpMethodFilter

浏览器表单只支持 GET 和 POST，可以通过隐藏域模拟 PUT/DELETE：

<!-- web.xml -->
<filter>
    <filter-name>hiddenHttpMethodFilter</filter-name>
    <filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>hiddenHttpMethodFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

<!-- 模拟 PUT 请求 -->
<form action="/users/1" method="post">
    <input type="hidden" name="_method" value="PUT">
    <input type="text" name="name">
    <button type="submit">提交</button>
</form>

<!-- 模拟 DELETE 请求 -->
<form action="/users/1" method="post">
    <input type="hidden" name="_method" value="DELETE">
    <button type="submit">删除</button>
</form>