What is `@RequestBody ` does?

@RequestBody 是SpringMVC框架中的注解，通常与POST、PUT等方法配合使用。当客户端发送包含JSON或XML格式数据的请求时，可以通过该注解将请求体内容绑定到Controller方法参数上

作用

自动反序列化：
SpringMVC会根据@RequestBody注解的参数类型，利用Jackson库（默认配置下）或其他MessageConverter将HTTP请求体中的JSON或XML数据转换成对应的Java对象。

支持复杂数据结构：
可以轻松处理嵌套对象、数组、集合等复杂数据结构，将其映射为Java实体类或自定义对象。

使用样例

部份参数

# 对应请求示例（假设User类有username和password属性）：POST /users HTTP/1.1Content-Type: application/json{"username": "john.doe","password": "secret"}@PostMapping("/users")
public User createUser(@RequestBody User user) {// 将请求体中的JSON或XML数据转换为User对象userService.save(user);return user;
}

接收并处理嵌套对象

# 对应请求示例：POST /users HTTP/1.1Content-Type: application/json{"username": "john.doe","password": "secret","address": {"street": "123 Main St.","city": "Springfield"}}@PostMapping("/users")
public User createUser(@RequestBody UserRequest userRequest) {User user = new User();user.setUsername(userRequest.getUsername());user.setPassword(userRequest.getPassword());user.setAddress(userRequest.getAddress());userService.save(user);return user;
}public class Address {private String street;private String city;// getters and setters...
}public class UserRequest {private String username;private String password;private Address address;// getters and setters...
}

处理数组或集合数据

# 对应请求示例（创建多个用户）：POST /batch/users HTTP/1.1Content-Type: application/json[{"username": "user1","password": "pass1"},{"username": "user2","password": "pass2"}]@PostMapping("/batch/users")
public List<User> createUsers(@RequestBody List<UserRequest> userRequests) {List<User> users = new ArrayList<>();for (UserRequest request : userRequests) {User user = new User();// map request properties to user object...users.add(user);}userService.saveAll(users);return users;
}

使用 @RequestBody 和自定义JSON属性名映射

# 对应请求示例（使用与Java字段不同的JSON属性名）：POST /users HTTP/1.1Content-Type: application/json{"user_name": "john.doe","pwd": "secret"}@PostMapping("/users")
public User createUser(@RequestBody UserRequest userRequest) {User user = new User();user.setUsername(userRequest.getUsername());user.setPassword(userRequest.getPassword());userService.save(user);return user;
}public class UserRequest {@JsonProperty("user_name")private String username;@JsonProperty("pwd")private String password;// getters and setters...
}