Spring Boot系列九 spring mvc的@RequestMapping支持的方法参数类型和返回类型
1. 概述
本文介绍了spring mvc中使用@RequestMapping时，支持常用方法参数类型和返回类型。
常用的方法参数类型有：
- 1 PathVariable
- 2 RequestParam
- 3 RequestBody
- 4 HttpEntity
- 5 CookieValue
- 6 RequestHeader
- 7 自动封装form表单请求到对象中
- 8 HttpServletRequest HttpServletResponse
- 9 RequestMapping 参数配置params headers
常用的返回类型有：
- 1 返回一个页面的地址
- 2 ResponseBody
- 3 ResponseEntity
- 4 ModelAndView
2. 前提条件
代码工程名称：mvc
测试PO类
ModelAttributeVO
public class ModelAttributeVO {
private String name;
private String value;
private Date date;
// set/get方法略
}VO
public class VO {
private String name;
private String value;
private Date date;
// set/get方法略
}3. @RequestMapping支持的方法参数类型
3.1. RequestParameterController
以下代码都在RequestParameterController类中
@Controller: 表示此类对外提供url服务
@RequestMapping：此注解不仅可以作用在方法上，也可以作用在类上。如果作用在类上，则表示此值是类中的所有@RequestMapping方法的URL的前缀
@Controller
@RequestMapping(value = "/request") // 全局URL
public class RequestParameterController {
....
}3.2. 使用的jsp
下面用到jsp的页面如下，都在META-INF\resources\WEB-INF\page\reqparameter目录下：
showInput.jsp
打印内容
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Request Parametertitle>
head>
<body>
${map}
body>
html>formModel.jsp
测试form表单
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title heretitle>
head>
<body>
<form name="myform" method="post" action="formModel">
<table>
<tr>
<td>First Name:td>
<td><input type="text" name="name" value="fisr name" />td>
tr>
<tr>
<td>Last Name:td>
<td><input type="text" name="value" value="lastName" />td>
tr>
<tr>
<td colspan="2">
<input type="submit" value="Save Changes" />
td>
tr>
table>
form>
body>
html>httpEntityForm.jsp
测试form表单
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title heretitle>
head>
<body>
<form name="myform" method="post" action="httpEntity">
<table>
<tr>
<td>First Name:td>
<td><input type="text" value="name" />td>
tr>
<tr>
<td>Last Name:td>
<td><input type="text" value="lastName" />td>
tr>
<tr>
<td colspan="2">
<input type="submit" value="Save Changes" />
td>
tr>
table>
form>
body>
html>3.3. @PathVariable
作用：可以注入URL中的变量值，可以注入一个或者多个
单个 @PathVariable值
代码：
@RequestMapping(value="/path/{ownerId}")
public String pathVariable(@PathVariable String ownerId, Model model){
Map<String,Object> map = new HashMap<String,Object>();
map.put("ownerId", ownerId);
model.addAttribute("map", map);
return "reqparameter/showInput";
}访问URL:
http://127.0.0.1:8080/request/path/1
返回结果：
{ownerId=1}多个 @PathVariable值
作用： 可以注入URL中的变量值，可以注入一个或者多个
代码：
@RequestMapping(value="/path/{ownerId}/pet/{petId}")
public String pathVariable2(@PathVariable String ownerId, @PathVariable String petId, Model model){
Map<String,Object> map = new HashMap<String,Object>();
map.put("ownerId", ownerId);
map.put("petId", petId);
model.addAttribute("map", map);
return "reqparameter/showInput";
}访问URL:
http://127.0.0.1:8080/request/path/1/pet/1234
返回结果：
{petId=1234, ownerId=1}3.4. @RequestParam
通过@RequestParam注入单个值
作用：可以从请求参数中获取参数值
代码：
@RequestMapping(value="/requestParam", method = RequestMethod.GET)
public String requestParam(@RequestParam("ownerId") int ownerId, ModelMap model) {
Map<String,Object> map = new HashMap<String,Object>();
map.put("ownerId", ownerId);
model.addAttribute("map", map);
return "reqparameter/showInput";
}访问URL:
http://127.0.0.1:8080/request/requestParam?ownerId=223
返回结果：
{ownerId=223}通过@RequestParam注入多个值
作用： 可以从请求参数中获取多个参数值
代码：
@RequestMapping(value="/requestParam2", method = RequestMethod.GET)
public String requestParam2(@RequestParam Map<String,Object> map, ModelMap model) {
// Map map = new HashMap();
// map.put("ownerId", ownerId);
model.addAttribute("map", map);
return "reqparameter/showInput";
}访问URL:
http://127.0.0.1:8080/request/requestParam2?ownerId=223&a=4&c=5
返回结果：
{ownerId=223, a=4, c=5}@RequestParam： required、defaultValue
作用：设置@RequestParam自定义参数：如设置默认值(defaultValue)，是否必须（required）等等
代码：
@RequestMapping("/requestParam3")
public String requestParam3(@RequestParam(value="inputStr", required=true, defaultValue="noInput") String inputStr,
ModelMap model) {
Map<String,Object> map = new HashMap<String,Object>();
map.put("inputStr",inputStr );
model.addAttribute("map",map);
return "reqparameter/showInput";
}访问URL:
http://127.0.0.1:8080/request/requestParam3?inputStr=myInput
此URL有inputStr值，则其值为myInput值
{inputStr=myInput}访问URL:
http://127.0.0.1:8080/request/requestParam3
此URL没有inputStr值，则其值为默认值，即noInput
返回结果：
{inputStr=noInput}3.5. @RequestBody
作用：@RequestBody: 获取请求的内容。请求内容为JSON，因为本工程设置请求为json，所以demo为：{“a”:1}
代码：
@RequestMapping(value = "/requestBody", method = RequestMethod.POST)
public String requestBody(@RequestBody String body, ModelMap model){
Map<String,Object> map = new HashMap<String,Object>();
map.put("body",body );
model.addAttribute("map",map);
return "reqparameter/showInput";
}访问URL：
http://127.0.0.1:8080/request/requestBody
内容为{“a”:1}
此请求为POST，需要使用postman等模拟POST请求
返回结果：
{body={"a":1}}3.6. HttpEntity
作用：HttpEntity，可以操作更原始的请求方法
代码：
@RequestMapping(value="/httpEntity", method = RequestMethod.GET)
public String httpEntity(ModelMap model){
return "reqparameter/httpEntityForm";
}
@RequestMapping("/httpEntity")
public String httpEntity2(HttpEntity<byte[]> requestEntity, ModelMap model){
// 获取header
String acceptLanguage = requestEntity.getHeaders().getFirst("Accept-Language");
// 获取内容：获取body的内容为空，暂时不知道原因
byte[] requestBody = requestEntity.getBody();
Map map = new HashMap();
map.put("acceptLanguage", acceptLanguage);
// map.put("content", new String(requestBody));
model.addAttribute("map", map);
return "reqparameter/showInput";
} 访问URL:
http://127.0.0.1:8080/request/httpEntity
返回结果：
输入上面URL，进入form表单，填写内容后，会转到新的页面如下
{acceptLanguage=zh-CN,zh;q=0.9,zh-TW;q=0.8}3.7. @CookieValue
作用：获取cookie里的值
代码：
@RequestMapping("/cookieValue")
public String cookieValue(@CookieValue("JSESSIONID") String cookie,ModelMap model) {
Map<String,Object> map = new HashMap<String,Object>();
map.put("cookie", cookie);
model.addAttribute("map", map);
return "reqparameter/showInput";
}访问URL:
http://127.0.0.1:8080/request/cookieValue
返回结果：
{cookie=38EDB55B71BB4CCA6EF1A2CDA7F1BCC0}3.8. @RequestHeader
作用：操作http header的值
获取指定header里的值
代码：
@RequestMapping("/requestHeader")
public String requestHeader (
@RequestHeader ("User-Agent") String userAgent,
@RequestHeader ("Host") String host,
@RequestHeader ("Cache-Control") String cacheControl,
ModelMap model) {
Map<String,Object> map = new HashMap<String,Object>();
map.put("User-Agent", userAgent);
map.put("Host", host);
map.put("Cache-Control", cacheControl);
model.addAttribute("map", map);
return "reqparameter/showInput";
}访问URL:
http://127.0.0.1:8080/request/requestHeader
此请求刷新需求刷新多次
返回结果：
{Cache-Control=max-age=0, User-Agent=Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.62 Safari/537.36, Host=127.0.0.1:8080}获取所有header封装到Map
代码：
@RequestMapping("/requestHeaderMap")
public String requestHeaderMap (@RequestHeader Map<String,String> map,
ModelMap model) {
model.addAttribute("map", map);
return "reqparameter/showInput";
}访问URL:
http://127.0.0.1:8080/request/requestHeaderMap
返回结果：
{host=127.0.0.1:8080, connection=keep-alive, user-agent=Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.62 Safari/537.36, upgrade-insecure-requests=1, accept=text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8, accept-encoding=gzip, deflate, br, accept-language=zh-CN,zh;q=0.9,zh-TW;q=0.8, cookie=JSESSIONID=38EDB55B71BB4CCA6EF1A2CDA7F1BCC0}3.9. 自动封装form表单请求到对象中
作用：
代码：
@RequestMapping(value="/formModel", method = RequestMethod.GET)
public String form(){
return "reqparameter/formModel";
}
@RequestMapping("/formModel")
public String formPost(VO vo, ModelMap model){
Map<String,Object> map = new HashMap<String,Object>();
map.put("name", vo.getName());
map.put("value", vo.getValue());
map.put("date", vo.getDate());
model.addAttribute("map", map);
return "reqparameter/showInput";
}访问URL:
http://127.0.0.1:8080/request/formModel
此URL进入form表单，我们填写内容后，会提交到formPost方法，此时时会自动封装值到VO对象中，打印内容如下
返回结果：
{date=Sun Nov 12 22:11:22 CST 2017, name=fisr name, value=lastName}3.10. HttpServletRequest + HttpServletResponse
作用：直接操作原始的HttpServletRequest 和 HttpServletResponse
代码：
@RequestMapping("/httpServlet")
public void formPost(HttpServletRequest request, HttpServletResponse response) throws IOException{
String userAgent = request.getHeader("User-Agent");
String host = request.getHeader("Host");
String cacheControl = request.getHeader("Cache-Control");
PrintWriter pw = response.getWriter();
pw.println("User-Agent :"+ userAgent);
pw.println("Host :" + host);
pw.println("Cache-Control :" + cacheControl);
}访问URL:
http://127.0.0.1:8080/request/httpServlet
返回结果：
User-Agent :Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.62 Safari/537.36
Host :127.0.0.1:8080
Cache-Control :null3.11. @RequestMapping 参数配置params、headers
@RequestMapping 参数配置params
作用：通过params过滤请求，如下面的代码，只有URL带上myParam=myValue才能进入
代码：
@RequestMapping(value="/reqparameters/{ownerId}", method = RequestMethod.GET, params="myParam=myValue")
public String reqParameters(@PathVariable String ownerId, Model model){
Map<String,Object> map = new HashMap<String,Object>();
map.put("ownerId", ownerId);
model.addAttribute("map", map);
return "reqparameter/showInput";
t";
}访问URL:http://127.0.0.1:8080/request/reqparameters/1?myParam=myValue 可以进入到这个方法，
但是以下URL无法进入这个方法：http://127.0.0.1:8080/request/reqparameters/1
备注： 其他条件，也可以这样： “myParam”, “!myParam”, or “myParam=myValue”
@RequestMapping 参数配置headers
作用：通过headers过滤请求，请求头里必须带上myParam，且值为myValue
代码：
@RequestMapping(value="/reqparameters/{ownerId}", method = RequestMethod.GET, headers="myParam=myValue")
public String headerParameters(@PathVariable String ownerId, Model model){
Map<String,Object> map = new HashMap<String,Object>();
map.put("ownerId", ownerId);
model.addAttribute("map", map);
return "reqparameter/showInput";
}访问URL:
http://127.0.0.1:8080/reqparameters/1
如果使用POST请求，请使用postman，并在请求头里必须带上myParam，且值为myValue
4. @RequestMapping支持的返回类型
4.1. ResponseParameterController
以下代码都在此类中
@Controller
@RequestMapping(value = "/response")
public class ResponseParameterController {
...
}4.2. 使用到JSP
下面用到jsp的页面如下，都在META-INF\resources\WEB-INF\page\resparameter目录下：
showInput.jsp
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Request Parametertitle>
head>
<body>
${map}
body>
html>4.3. 返回一个页面的地址
默认情况下，返回一个字符串，表示转到一个指定页面，上面的demo都是这个模式
@RequestMapping(value="/path/{ownerId}")
public String pathVariable(@PathVariable String ownerId, Model model){
Map<String,Object> map = new HashMap<String,Object>();
map.put("ownerId", ownerId);
model.addAttribute("map", map);
return "reqparameter/showInput";
}4.4. @ResponseBody
@ResponseBody： 直接返回字符串内容
作用：此注解注解的方法返回字符串
代码：
@RequestMapping(value = "/responseBody", method = RequestMethod.GET)
@ResponseBody
public String responseBodyString() {
return "Hello World";
}访问URL:
http://127.0.0.1:8080/response/responseBody
返回结果：
"Hello World"@ResponseBody：方法返回对象，系统自动转化为json
作用：方法返回对象，返回客户端时系统自动转化为json
代码：
@RequestMapping(value = "/responseBodyMode", method = RequestMethod.GET)
@ResponseBody
public VO responseBodyMode() {
return new VO();
}访问URL:
http://127.0.0.1:8080/response/responseBodyMode
返回结果：
{ "date":1510497345620, "name":"name", "value":"value" }4.5. ResponseEntity
作用：返回一个ResponseEntity
代码：
@RequestMapping("/responseEntity")
public ResponseEntity responseEntity(){
// do something with request header and body
HttpHeaders responseHeaders = new HttpHeaders();
responseHeaders.set("MyResponseHeader", "MyValue");
return new ResponseEntity("Hello World", responseHeaders, HttpStatus.CREATED);
} 访问URL:
http://127.0.0.1:8080/response/responseEntity
返回结果：
"Hello World"4.6. ModelAndView
作用：返回ModelAndView
代码：
public ModelAndView modelAndView(){
Map<String,Object> map = new HashMap<String,Object>();
map.put("ownerId", "1");
map.put("petId", "23");
ModelAndView modelAndView = new ModelAndView();
modelAndView.setViewName("resparameter/showInput");
modelAndView.addObject("map", map);
return modelAndView;
}访问URL:
http://127.0.0.1:8080/response/modelAndView
返回结果：
{petId=23, ownerId=1}5. 代码
上文的详细代码见github代码，请尽量使用tag v0.4，不要使用master，因为master一直在变，不能保证文章中代码和github上的代码一直相同