Table of contents
Related readings of previous columns & articles
4. Spring MVC series of columns
一、@Controller、@RequestMapping
@Controller: Function: mark the controller and hand over the controller to the Spring container for management.
Location: Above Class
@RequestMapping: Function: Set the request path for the controller method
Location: Above the method or class. Used on a class, it means that all controller methods in the class use this address as the parent path.
Attributes:
- value/path: request path
- method: Specify the request method
- params: specifies the request parameters that must be sent
- headers: specifies the request headers that the request must contain
1.1 Sample program
package com.example.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;
@Controller
@RequestMapping("/c3")
public class MyController3 {
/**
* 访问路径为 /c3/annotation1
* 支持post和get请求
* 请求时必须带有age参数
* 请求时必须带有User-agent请求头
* @param username
* @return
*/
@RequestMapping(path = "/annotation1",method = {RequestMethod.GET,RequestMethod.POST},params = {"age"},headers = {"User-agent"})
public String annotation1(String username){
System.out.println("annotation1\t"+username);
return "lyl-HQX";
}
}Here it is stipulated that the request parameter must have age, but the method parameter list below does not have age, so let's test whether it has age or no age.
1.2 Test results
If the request path is: http://localhost:8080/c3/annotation1?age=10
The test results are:
But if the request path is: http://localhost:8080/c3/annotation1?username=10
You can report an error when you see it, so you really need to take the age parameter
So the request path should be written like this: http://localhost:8080/c3/annotation1?username=10&age=10
You can see that the username 10 is indeed printed.
2. @RequestParam
Function: Obtain request parameters in the controller method
Position: Before the method parameters
Attributes:
- name: Specify the name of the request parameter
- defaultValue: set the default value for the parameter
- required: Whether the setting is a parameter that must be passed in
2.1 Sample program
// 在控制器方法中获取请求参数
@RequestMapping("/annotation2")
public String annotation2(@RequestParam(name = "name",defaultValue = "HQX",required = false) String name){
System.out.println("annotation2\t"+name);
return "lyl-HQX";
}This annotation is a related attribute for modifying request parameters, so we should be able to have this name attribute or not.
2.2 Test results
When the request path is: http://localhost:8080/c3/annotation2
The request path does not have this parameter, and the default value of this parameter is HQX, which is output normally
When the request path is: http://localhost:8080/c3/annotation2?name=LYL
OK, when the request path has this parameter, it will be output according to the parameter value of the request path, and it can be seen that the test is indeed successful.
三、@RequestHeader、@CookieValue
@RequestHeader
- Role: Get the request header data in the controller method
- Position: Before the method parameter
@CookieValue
- Role: Get Cookie data in the controller method
- Position: Before the method parameter
3.1 Sample program
/**
* @RequestHeader
* 作用：在控制器方法中获取请求头数据
* 位置：方法参数前
* @CookieValue
* 作用：在控制器方法中获取Cookie数据
* 位置：方法参数前
*/
// 获取User-Agent请求头和JSESSIONID的Cookie值
@RequestMapping("/annotation3")
public String annotation3(@RequestHeader("User-Agent")String userAgent, @CookieValue("JSESSIONID") String jSessionId){
System.out.print("annotation3\t");
System.out.println("userAgent: "+userAgent);
System.out.print("jSessionId: " + jSessionId);
return "lyl-HQX";
}3.2 Test results
Request path: http://localhost:8080/c3/annotation3
It can be seen that the relevant data of the request header is indeed printed: for example, the windows system, how many bits, the version of the browser, etc. The sessionID is also obtained.
四、@SessionAttributes
Function: store the data in the Model model in the session domain
Location: above the class
4.1 Sample program
package com.example.controller;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.SessionAttributes;
import javax.servlet.http.HttpSession;
@Controller
@RequestMapping("/c4")
// 将Model模型中name的数据存到session域中
@SessionAttributes("name")
public class MyController4 {
@RequestMapping("/t1")
public String t1(Model model){
// model1中保存name数据
model.addAttribute("name","LYL");
return "lyl-HQX";
}
@RequestMapping("/t2")
public String t2(HttpSession session){
// 从session中获取name数据
System.out.println(session.getAttribute("name"));
return "lyl-HQX";
}
}
4.2 Test results
OK, from the above program we can know that the value of name can only be obtained by visiting /t1 first and then visiting /t2. Direct access to /t2 cannot print out the attribute value of name. Next we test it:
When we first visit /t2:: http://localhost:8080/c4/t2
OK, you can see that it is indeed printing out null,
And the browser has no corresponding value.
Next visit /t1, http://localhost:8080/c4/t1
After adding the value
Visit /t2 again, you can see that the console is indeed printed out.
5. @ModelAttribute
Function 1: Set the specified method to be executed before other methods of the controller
Position: above the methodFunction 2: Obtain data from the Model model and assign values to parameters
Position: Before the method parameters
5.1 Sample program
Function 1 sample program:
package com.example.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
@Controller
@RequestMapping("/c5")
public class MyController5 {
// @ModelAttribute作用1：设置指定方法在控制器其他方法前执行
@ModelAttribute
public void before(){
System.out.println("前置方法");
}
@RequestMapping("/t1")
public String t1(){
System.out.println("t1");
return "lyl-HQX";
}
}
Function 2 sample program:
package com.example.controller;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
@Controller
@RequestMapping("/c5")
public class MyController5 {
// @ModelAttribute作用1：设置指定方法在控制器其他方法前执行
@ModelAttribute
public void before(Model model){
System.out.println("前置方法");
model.addAttribute("name","LYL");
}
@RequestMapping("/t1")
public String t1(@ModelAttribute("name") String name){
System.out.println(name);
return "lyl-HQX";
}
}
5.2 Test results
Function 1 test result: http://localhost:8080/c5/t1
OK, it can be seen that the pre-method has indeed taken effect.
Function 2 test results: http://localhost:8080/c5/t1
OK, you can see that both functions have been successfully executed.
Related readings of previous columns & articles
If you don’t know anything about the content of this issue, you can also go to see the content of previous issues. The following is a series of column articles such as Maven and Mybatis carefully crafted by bloggers in the past. Don’t miss it when you pass by! If it is helpful to you, please like it and bookmark it. Among them, some of the Spring columns are being updated, so they cannot be viewed, but they can be viewed after the bloggers have completed all the updates.
1. Maven series of columns
| Maven Series Column | Maven project development |
| Maven aggregation development [example detailed explanation --- 5555 words] |