java详解Spring接收web请求参数的方式

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1 查询参数

请求格式：url?参数1=值1&参数2=值2...
同时适用于GET和POST方式
spring处理查询参数的方法又有几种写法：

方法一：
方法参数名即为请求参数名

  // 查询参数1
  @RequestMapping(value = "/test/query1", method = RequestMethod.GET)  
  public String testQuery1(String username, String password) {
    System.out.println("username=" + username + ", password=" + password);    
    return "username=" + username + ", password=" + password;
  }

方法二：
从HttpServletRequest中提取参数

  // 查询参数2
  @RequestMapping(value = "/test/query2", method = RequestMethod.GET)  
  public String testQuery2(HttpServletRequest request) {
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    System.out.println("username=" + username + ", password=" + password);    
    return "username=" + username + ", password=" + password;
  }

方法三：
方法参数名和请求参数名可以不一样，通过@RequestParam注解来绑定参数

  // 查询参数3
  @RequestMapping(value = "/test/query3", method = RequestMethod.GET)  
  public String testQuery3(@RequestParam("username") String un, @RequestParam("password") String pw) {
    System.out.println("username=" + un + ", password=" + pw);    
    return "username=" + un + ", password=" + pw;
  }

方法四：
创建一个实体类对象作为参数承载体，spring会根据参数名称自动将参数绑定到实体类对象的属性上

  // 查询参数4
  @RequestMapping(value = "/test/query4", method = RequestMethod.GET)  
  public String testQuery4(User user) {
    String username = user.getUsername();
    String password = user.getPassword();
    System.out.println("username=" + username + ", password=" + password);    
    return "username=" + username + ", password=" + password;
  }

实体类定义如下：

@Data
@NoArgsConstructor
@AllArgsConstructor
@Builderpublic class User {  
   private String username;  
   private String password;
}

这里用到了第三方库lombok，这样就不需要在代码中手动添加get、set等方法，lombok会自动添加。

发送请求的curl命令如下：

curl -i 'http://192.168.1.14:8080/test/query1?username=aaa&password=bbb'

交互报文如下：

GET /test/query1?username=aaa&password=bbb HTTP/1.1
Host: 192.168.1.14:8080
User-Agent: curl/7.58.0
Accept: */*HTTP/1.1 200 
Content-Type: text/plain;charset=UTF-8
Content-Length: 26
Date: Thu, 25 Oct 2018 07:01:30 GMT

username=aaa, password=bbb

2 表单参数

请求参数不在url中，而是在Body体中，格式为：url?参数1=值1&参数2=值2...

适用于POST方式

表单参数处理方法和前面的请求参数处理方法几乎完全一样，只是RequestMethod注解中将method方法设置成POST方法

方法一：

  // 表单参数1
  @RequestMapping(value = "/test/form1", method = RequestMethod.POST)  
  public String testForm1(String username, String password) {
    System.out.println("username=" + username + ", password=" + password);    
    return "username=" + username + ", password=" + password;
  }

方法二：

  // 表单参数2
  @RequestMapping(value = "/test/form2", method = RequestMethod.POST)  
  public String testForm2(HttpServletRequest request) {
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    System.out.println("username=" + username + ", password=" + password);    
    return "username=" + username + ", password=" + password;
  }

方法三：

  // 表单参数3
  @RequestMapping(value = "/test/form3", method = RequestMethod.POST)  
  public String testForm3(@RequestParam("username") String un, @RequestParam("password") String pw) {
    System.out.println("username=" + un + ", password=" + pw);    
    return "username=" + un + ", password=" + pw;
  }

方法四：

  // 表单参数4
  @RequestMapping(value = "/test/form4", method = RequestMethod.POST)
  public String testForm4(User user) {
    String username = user.getUsername();
    String password = user.getPassword();
    System.out.println("username=" + username + ", password=" + password);    
    return "username=" + username + ", password=" + password;
  }

curl请求命令如下：

curl -X POST -i -d "username=aaa&password=bbb" http://192.168.1.14:8080/test/form1

请求和响应报文如下：

POST /test/form1 HTTP/1.1
Host: 192.168.1.14:8080
User-Agent: curl/7.58.0
Accept: */*
Content-Length: 25
Content-Type: application/x-www-form-urlencoded

username=aaa&password=bbbHTTP/1.1 200 
Content-Type: text/plain;charset=UTF-8
Content-Length: 26
Date: Thu, 25 Oct 2018 07:05:35 GMT

username=aaa, password=bbb

3 路径参数

请求参数为url中的一部分，格式为：url/参数1/参数2...
同时适用于GET和POST方式
代码如下：

  @RequestMapping(value = "/test/url/{username}/{password}", method = RequestMethod.GET)  
  public String testUrl(@PathVariable String username, @PathVariable String password) {
    System.out.println("username=" + username + ", password=" + password);    
    return "username=" + username + ", password=" + password;
  }

请求curl命令如下：

curl -i http://192.168.1.14:8080/test/url/aaa/bbb

请求和响应报文如下：

GET /test/url/aaa/bbb HTTP/1.1
Host: 192.168.1.14:8080
User-Agent: curl/7.58.0
Accept: */*HTTP/1.1 200 
Content-Type: text/plain;charset=UTF-8
Content-Length: 26
Date: Thu, 25 Oct 2018 07:07:44 GMT

username=aaa, password=bbb

4 json格式参数

请求参数在Body体中，并且为json格式。需要添加请求头：Content-Type: application/json;charset=UTF-8
适用于POST方式
方法一：
定义实体类，将json对象解析成实力类，需要添加RequestBody注解

  // json参数1
  @RequestMapping(value = "/test/json1", method = RequestMethod.POST)  
  public String testJson1(@RequestBody User user) {
    String username = user.getUsername();
    String password = user.getPassword();
    System.out.println("username=" + username + ", password=" + password);    
    return "username=" + username + ", password=" + password;
  }

方法二：

如果不像定义实体类，也可以将json请求直接解析成JSONObject类

  // json参数2
  @RequestMapping(value = "/test/json2", method = RequestMethod.POST)  
  public String testJson2(@RequestBody JSONObject json) {
    String username = json.getString("username");
    String password = json.getString("password");
    System.out.println("username=" + username + ", password=" + password);    
    return "username=" + username + ", password=" + password;
  }

方法三：

也可以将json对象直接解析成Map对象

  // json参数3
  @RequestMapping(value = "/test/json3", method = RequestMethod.POST)  
  public String testJson3(@RequestBody Map<String, String> userMap) {
    String username = userMap.get("username");
    String password = userMap.get("password");
    System.out.println("username=" + username + ", password=" + password);    
    return "username=" + username + ", password=" + password;
  }

请求curl命令如下：

curl -X POST -i -H 'Content-Type: application/json;charset=UTF-8' -d '{    
   "username" : "aaa",    
   "password" : "bbb"
} 
'http://192.168.1.14:8080/test/json1

请求和响应报文如下：

POST /test/json1 HTTP/1.1
Host: 192.168.1.14:8080
User-Agent: curl/7.58.0
Accept: */*
Content-Type: application/json;charset=UTF-8
Content-Length: 52


{
    "username" : "aaa",
    "password" : "bbb"
}HTTP/1.1 200 
Content-Type: text/plain;charset=UTF-8
Content-Length: 26
Date: Thu, 25 Oct 2018 07:09:06 GMT

username=aaa, password=bbb

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