一、给Controller传值，值将显示在控制台
1.第一种：使用@RequestParam，改HelloController.java
//RequestMapping表示用哪一个url来对应
@RequestMapping({"/hello","/"})
public String hello(@RequestParam("username") String username){
System.out.println("hello");
System.out.println(username);
return "hello";
}
然后在浏览器中输入请求
http://localhost:8080/SpringMVC_hello/hello?username=123
控制台可以看到传的值
但是使用了RequestParam，如果在请求中不传值的话，会报400错误，因为默认把参数作为了地址的一部分
2.第二种，把RequestParam删除，直接String username
//RequestMapping表示用哪一个url来对应
@RequestMapping({"/hello","/"})
public String hello(String username){
System.out.println("hello");
System.out.println(username);
return "hello";
}
这种可以不传值，不传值时候为null
二、再从Controller给视图传值
1.用Map来传值
修改HelloController.java文件，用Map<String,Object> context，不过不太建议用Map
package org.common.controller;
import java.util.Map;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
@Controller
public class HelloController {
//RequestMapping表示用哪一个url来对应，从Controller给视图传值
@RequestMapping({"/hello","/"})
public String hello(String username,Map<String,Object> context){
context.put("username", username); //从Controller给视图传值
System.out.println(username);
System.out.println("hello");
return "hello";
}
}
hello.jsp文件
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>hello!! ${username}!!</h1>
</body>
</html>
输入
http://localhost:8080/SpringMVC_hello/hello?username=123
2.用Model来传值
HelloController.java文件改为
public String hello(String username,Model model){
model.addAttribute("String", username); //使用Model从Controller给视图传值
或者addAttribute只有一个参数，这时是默认使用username的类型（String）作为参数
//等于model.addAttribute("String",username);
model.addAttribute(username);
完整文件
package org.common.controller;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
@Controller
public class HelloController {
//RequestMapping表示用哪一个url来对应
@RequestMapping({"/hello","/"})
public String hello(String username,Model model){
System.out.println("hello");
model.addAttribute("username", username);
//等于model.addAttribute("String",username);
model.addAttribute(username);
//model.addAttribute(new User());等于model.addAttribute("user",new User());
System.out.println(username);
return "hello";
}
@RequestMapping("/welcome")
public String welcome(){
System.out.println("welcome");
return "welcome";
}
}
hello.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>hello!! ${username}!!</h1>
${string}
</body>
</html>