SpringMVC@RequestMapping详解

Java Spring 项目中用到了REST风格来开发程序，但是当用POST、PUT模式提交数据时，发现服务器端接受不到提交的数据（服务器端参数绑定没有加任何注解），查看了提交方式为application/json，而且服务器端通过request.getReader() 打出的数据里确实存在浏览器提交的数据。为了找出原因，便对参数绑定（@RequestParam、 @RequestBody、 @RequestHeader 、 @PathVariable）进行了研究，同时也看了一下HttpMessageConverter的相关内容，在此一并总结。

简介

@RequestMapping

RequestMapping是一个用来处理请求地址映射的注解，可用于类或方法上。

用于类上，表示类中的所有响应请求的方法都是以该地址作为父路径。

RequestMapping注解有六个属性，下面我们把她分成三类进行说明。

1、 value， method

value：指定请求的实际地址，指定的地址可以是URI Template 模式（后面将会说明）；

method：指定请求的method类型， GET、POST、PUT、DELETE 等；

2、 consumes，produces

consumes：指定处理请求的提交内容类型（Content-Type），例如application/json, text/html;

produces: 指定返回的内容类型，仅当request请求头中的(Accept)类型中包含该指定类型才返回；

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

Request Headers

Request Headers
:authority: blog.mimvp.com
:method: GET
:path: /article/15995.html
:scheme: https
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
accept-encoding: gzip, deflate, br
accept-language: zh-CN,zh;q=0.9,en;q=0.8,ja;q=0.7,pt;q=0.6
cache-control: no-cache
cookie: bdshare_firstime=1596590319506; wordpress_logged_in_f7ff243f355b=sadmin%7C1611ee6cbc9; Hm_lvt_2470f08b0a4e8514a3d12a641ddcb46d=1608200301,1610549732,1610678829; Hm_lpvt_2470f08b0a4e8514a3d12a641ddcb46d=1610678829; Hm_lvt_7d76d7c38895953b30e22cd22efc2720=1609247588,1609247661,1610549749,1610681239; wp-settings-1=editor%3Dtinymce%26libraryContent%3Dbrowse%26imgsize%3Dfull%26mfold%3Do; Hm_lpvt_7d76d7c38895953b30e22cd22efc2720=1610875143; wp-settings-time-1=1610881055
dnt: 1
pragma: no-cache
referer: https://blog.mimvp.com/article/46174.html
sec-fetch-dest: document
sec-fetch-mode: navigate
sec-fetch-site: same-origin
sec-fetch-user: ?1
upgrade-insecure-requests: 1
user-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36

3、 params，headers

params：指定request中必须包含某些参数值是，才让该方法处理。

headers：指定request中必须包含某些指定的header值，才能让该方法处理请求。

示例：

1、value / method 示例

默认RequestMapping("....str...")即为value的值；

@Controller  
@RequestMapping("/appointments")  
public class AppointmentsController {  
  
    private final AppointmentBook appointmentBook;  
      
    @Autowired  
    public AppointmentsController(AppointmentBook appointmentBook) {  
        this.appointmentBook = appointmentBook;  
    }  
  
    @RequestMapping(method = RequestMethod.GET)  
    public Map<String, Appointment> get() {  
        return appointmentBook.getAppointmentsForToday();  
    }  
  
    @RequestMapping(value="/{day}", method = RequestMethod.GET)  
    public Map<String, Appointment> getForDay(@PathVariable @DateTimeFormat(iso=ISO.DATE) Date day, Model model) {  
        return appointmentBook.getAppointmentsForDay(day);  
    }  
  
    @RequestMapping(value="/new", method = RequestMethod.GET)  
    public AppointmentForm getNewForm() {  
        return new AppointmentForm();  
    }  
  
    @RequestMapping(method = RequestMethod.POST)  
    public String add(@Valid AppointmentForm appointment, BindingResult result) {  
        if (result.hasErrors()) {  
            return "appointments/new";  
        }  
        appointmentBook.addAppointment(appointment);  
        return "redirect:/appointments";  
    }  
}

value的 uri 值为以下三类：

A）可以指定为普通的具体值；

B) 可以指定为含有某变量的一类值(URI Template Patterns with Path Variables)；

C) 可以指定为含正则表达式的一类值( URI Template Patterns with Regular Expressions);

example A)

@ResponseBody
@RequestMapping(value = "/saveComment.htm", method = { RequestMethod.POST,RequestMethod.GET })
@ActionAccess({ "df_report_write" })
public CommonResponse saveComment(
		@RequestParam(required = true, value = "statDate") String month,
		@RequestParam(required = true, value = "factoryName") String factoryName,
		@RequestParam(required = false, value = "content") String content) throws Exception {
	DfMonthDO report = new DfMonthDO();
	report.setTheday(month);
	report.setFactoryName(factoryName);
	report.setContent(content);
	report.setUser(this.getUserNick());
	DFResultDTO<Boolean> result = dfMonthAnalyseService.saveComment(report);
	return responseTo(result.getValue(), result.isSuccess() ? "更新成功" : "更新失败", result.getValue());
}

example B)

@RequestMapping(value="/owners/{ownerId}", method=RequestMethod.GET)  
public String findOwner(@PathVariable String ownerId, Model model) {  
  Owner owner = ownerService.findOwner(ownerId);    
  model.addAttribute("owner", owner);    
  return "displayOwner";   
}

example C)

@RequestMapping("/spring-web/{symbolicName:[a-z-]+}-{version:\d\.\d\.\d}.{extension:\.[a-z]}")  
  public void handle(@PathVariable String version, @PathVariable String extension) {      
    // ...  
  }  
}

2 consumes、produces 示例

cousumes 样例：

@Controller  
@RequestMapping(value = "/pets", method = RequestMethod.POST, consumes="application/json")  
public void addPet(@RequestBody Pet pet, Model model) {      
    // implementation omitted  
}

方法仅处理request Content-Type为“application/json”类型的请求。

produces 样例：

@Controller  
@RequestMapping(value = "/pets/{petId}", method = RequestMethod.GET, produces="application/json")  
@ResponseBody  
public Pet getPet(@PathVariable String petId, Model model) {      
    // implementation omitted  
}

方法仅处理request请求中Accept头中包含了"application/json"的请求，同时暗示了返回的内容类型为application/json;

3 params、headers 示例

params 样例：

@Controller  
@RequestMapping("/owners/{ownerId}")  
public class RelativePathUriTemplateController {  
  
  @RequestMapping(value = "/pets/{petId}", method = RequestMethod.GET, params="myParam=myValue")  
  public void findPet(@PathVariable String ownerId, @PathVariable String petId, Model model) {      
    // implementation omitted  
  }  
}

仅处理请求中包含了名为“myParam”，值为“myValue”的请求；

headers 样例：

@Controller  
@RequestMapping("/owners/{ownerId}")  
public class RelativePathUriTemplateController {  
  
@RequestMapping(value = "/pets", method = RequestMethod.GET, headers="Referer=http://www.mimvp.com/")  
  public void findPet(@PathVariable String ownerId, @PathVariable String petId, Model model) {      
    // implementation omitted  
  }  
}

仅处理request的header中包含了指定“Refer”请求头和对应值为“http://www.mimvp.com/”的请求；

上面仅仅介绍了，RequestMapping指定的方法处理哪些请求，

下面一篇将讲解怎样处理request提交的数据（数据绑定）和返回的数据。

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