springMVC的注解@RequestParam与@RequestBody

水深无声 2023-02-08 12:41 114阅读 0赞

### @RequestParam ###

简介

> You can use the @RequestParam annotation to bind Servlet request parameters (that is, query parameters or form data) to a method argument in a controller.
> 
> 可以使用@RequestParam注释将Servlet请求参数(即查询参数或表单数据)绑定到控制器中的方法参数。

#### `@RequestParam`注释简单类型 ####

官方解释：

> By default, any argument that is a simple value type (as determined by BeanUtils\#isSimpleProperty) and is not resolved by any other argument resolver, is treated as if it were annotated with @RequestParam.
> 
> 默认情况下，任何简单值类型的参数(由BeanUtils\#isSimpleProperty确定)，且不由任何其他参数解析器解析，将被视为使用@RequestParam注释。

BeanUtils\#isSimpleProperty的源码如下：

public static boolean isSimpleProperty(Class<?> type) {
        
    	Assert.notNull(type, "'type' must not be null");
    	return isSimpleValueType(type) || type.isArray() && isSimpleValueType(type.getComponentType());
    }
    
    public static boolean isSimpleValueType(Class<?> type) {
        
    	return Void.class != type && Void.TYPE != type && (ClassUtils.isPrimitiveOrWrapper(type) || Enum.class.isAssignableFrom(type) || CharSequence.class.isAssignableFrom(type) || Number.class.isAssignableFrom(type) || Date.class.isAssignableFrom(type) || Temporal.class.isAssignableFrom(type) || URI.class == type || URL.class == type || Locale.class == type || Class.class == type);
    }

结论：在使用springMVC的时候，参数的类型为BeanUtils\#isSimpleProperty认定为简单类型的，且不由任何其他参数解析器解析，都可以省略@RequestParam，示例1如下：

// 示例1
    @Controller
    public class TestController {
        
        @GetMapping("test/get")
        @ResponseBody
        public Object methodGet(Integer id, String name) {
        
            return "{\"id\": " + id + ", \"name\": " + name + "}";
        }
    }
    
    /*
        测试1
        http://localhost:8080/test/get?id=1&name=name01
        返回：
        {"id": 1, "name": name01}
    
        测试2
        http://localhost:8080/test/get?id=1
        返回：
        {"id": 1, "name": null}
    */

#### `@RequestParam`的required参数 ####

官方解释：

> By default, method parameters that use this annotation are required, but you can specify that a method parameter is optional by setting the @RequestParam annotation’s required flag to false or by declaring the argument with an java.util.Optional wrapper.  
> 默认情况下，使用此注释的方法参数是必需的，但是您可以通过将@RequestParam注释的required标志设置为false或使用java.util.Optional包装器声明参数来指定方法参数是可选的。

示例如下

// 示例2
    @Controller
    public class TestController {
        
        @GetMapping("test/get")
        @ResponseBody
        public Object methodGet(@RequestParam Integer id, @RequestParam String name) {
        
            return "{\"id\": " + id + ", \"name\": " + name + "}";
        }
    }
    
    /*
        测试
        http://localhost:8080/test/get?id=1
        返回：
        {   
            "status": 400,
            "error": "Bad Request",
            "trace": "org.springframework.web.bind.MissingServletRequestParameterException: Required request parameter 'name' for method parameter type String is not present....."
            "message": "Required request parameter 'name' for method parameter type String is not present"
            "path": "/test/get"
        }
    */
    
    // 示例3
    @Controller
    public class TestController {
        
        @GetMapping("test/get")
        @ResponseBody
        public Object methodGet(@RequestParam Integer id, @RequestParam(required = false) String name) {
        
            return "{\"id\": " + id + ", \"name\": " + name + "}";
        }
    }
    
    /*
        测试
        http://localhost:8080/test/get?id=1
        返回：
        {"id": 1, "name": null}
    */

#### `@RequestParam`的接收数组, 列表参数 ####

官方解释：

> Declaring the argument type as an array or list allows for resolving multiple parameter values for the same parameter name.  
> 将参数类型声明为数组或列表，允许为相同的参数名称解析多个参数值。

示例如下：

// 示例4
    @Controller
    public class TestController {
        
        @GetMapping("test/get")
        @ResponseBody
        public Object methodGet(@RequestParam Integer[] arr) {
        
            return arr;
        }
    }    
        
    /*
        测试1
        http://localhost:8080/test/get?arr=1&arr=2
        返回：
        [
            1,
            2
        ]
    
        测试2
        http://localhost:8080/test/get?arr=1,2,3
        返回
        [
            1,
            2,
            3
        ]
    */
    
    // 示例5
    @Controller
    public class TestController {
        
        @GetMapping("test/get")
        @ResponseBody
        public Object methodGet(@RequestParam List<Integer> list) {
        
            return list;
        }
    } 
    
    /*
        测试
        http://localhost:8080/test/get/8?list=11,22,33
        返回：
        [
            11,
            22,
            33
        ]
    */

#### `@RequestParam`的接收Map, MultiValueMap参数 ####

官方解释：

> When an @RequestParam annotation is declared as a Map<String, String> or MultiValueMap<String, String>, without a parameter name specified in the annotation, then the map is populated with the request parameter values for each given parameter name.
> 
> 当@RequestParam注释声明为Map<String, String>或MultiValueMap<String, String>，而没有在注释中指定参数名时，那么映射将使用每个给定参数名的请求参数值填充。

示例如下：

// 示例4
    @Controller
    public class TestController {
        
        @GetMapping("test/get")
        @ResponseBody
        public Object methodGet(@RequestParam Map<String, Object> params) {
        
            return params;
        }
    }  
    
    /*
        测试
        http://localhost:8080/test/get/5?id=1&name=01&age=22&date=2001-01-01
        返回：
        {
            "id": "1",
            "name": "01",
            "age": "22",
            "date": "2001-01-01"
        }
    */

#### `@RequestParam`处理POST请求表单application/x-www-form-urlencoded类型 ####

示例如下：

// 示例
    @Controller
    public class TestController {
        
    	/**
         * 测试@RequestParam 接收表单数据 application/x-www-form-urlencoded类型
         */
        @PostMapping("test/form/1")
        @ResponseBody
        public Object methodForm1(@RequestParam Map<String, Object> params) {
        
            return params;
        }
    }

测试1，使用postman 构造一个表单请求如下：  
![请添加图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA5L2g5oC75piv5oOz55-l6YGT_size_20_color_FFFFFF_t_70_g_se_x_16]  
测试2，使用`@RequestParam`可以同时接收url路径以及请求body中的参数  
![请添加图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA5L2g5oC75piv5oOz55-l6YGT_size_20_color_FFFFFF_t_70_g_se_x_16 1]

#### @RequestParam处理POST请求表单multipart/form-data类型 ####

示例如下：

// 示例
    @Controller
    public class TestController {
        
        /**
         * 测试@RequestParam 接收表单数据 multipart/form-data类型
         */
        @PostMapping("test/form/2")
        @ResponseBody
        public Object methodForm2(@RequestParam MultipartFile file, @RequestParam String name) {
        
            return name + "-------" + file.getOriginalFilename();
        }
    }

测试：  
![请添加图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA5L2g5oC75piv5oOz55-l6YGT_size_20_color_FFFFFF_t_70_g_se_x_16 2]

### @RequestBody ###

简介：

> You can use the @RequestBody annotation to have the request body read and deserialized into an Object through an HttpMessageConverter
> 
> 您可以使用@RequestBody注释通过HttpMessageConverter将请求体读取并反序列化为一个Object

#### @RequestBody与@Validated/@Valid 组合使用 ####

官方解释：

> You can use @RequestBody in combination with javax.validation.Valid or Spring’s @Validated annotation, both of which cause Standard Bean Validation to be applied.
> 
> 您可以将@RequestBody与javax. validate .valid或Spring的@Validated注释结合使用，这两者都会应用标准Bean验证。
> 
> By default, validation errors cause a MethodArgumentNotValidException, which is turned into a 400 (BAD\_REQUEST) response.
> 
> 默认情况下，验证错误会导致MethodArgumentNotValidException，该异常将转换为400 (BAD\_REQUEST)响应。
> 
> Alternatively, you can handle validation errors locally within the controller through an Errors or BindingResult argument, as the following example shows
> 
> 或者，您可以通过errors或BindingResult参数在控制器内部本地处理验证错误，

注意：如果要与使用@Validated需要引入`hibernate-validator`或者`validation-api`

<dependency>
    	<groupId>org.hibernate</groupId>
    	<artifactId>hibernate-validator</artifactId>
    	<version>5.3.6.Final</version>
    </dependency>

示例如下:

// 实体类 
    @Data
    @Accessors(chain = true)
    public class User {
        
        @Max(Integer.MAX_VALUE)
        private Integer id;
    
        @NotBlank // @NotBlank 验证元素不为空（不为null或者去除首尾空格后长度为0，用于字符串会去除首尾空格）
        @Size(max = 16, min = 1) // 验证数据的长度必须是在1~16
        private String name;
        
        @Max(200) // 验证最大的数值为200
        @Min(0) // 验证最小数值为0
        private Integer age;
    }
    
    @Controller
    public class TestController {
        
        @PostMapping("test/post/1")
        @ResponseBody
        public Object methodPost1(@RequestBody @Validated User user) {
        
            return user;
        }
    }
    
    /*
    测试(使用 application/json)

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