关于@RequestParam注解的使用(简单易懂)

package com.day01springmvc.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.servlet.ModelAndView;
 
/**
 * @ Author     ：ShaoWei Sun.
 * @ Date       ：Created in 20:58 2018/11/16
 */
@Controller
@RequestMapping("hello")
public class HelloController2 {
 
    /**
     * 接收普通请求参数
     * http://localhost:8080/hello/show16?name=linuxsir
     * url参数中的name必须要和@RequestParam("name")一致
     * @return
     */
    @RequestMapping("show16")
    public ModelAndView test16(@RequestParam("name")String name){
        ModelAndView mv = new ModelAndView();
        mv.setViewName("hello2");
        mv.addObject("msg", "接收普通的请求参数：" + name);
        return mv;
    }
 
    /**
     * 接收普通请求参数
     * http://localhost:8080/hello/show17
     * url中没有name参数不会报错、有就显示出来
     * @return
     */
    @RequestMapping("show17")
    public ModelAndView test17(@RequestParam(value="name",required=false)String name){
        ModelAndView mv = new ModelAndView();
        mv.setViewName("hello2");
        mv.addObject("msg", "接收普通请求参数：" + name);
        return mv;
    }
 
    /**
     * 接收普通请求参数
     * http://localhost:8080/hello/show18?name=998 显示为998
     * http://localhost:8080/hello/show18?name 显示为hello
     * @return
     */
    @RequestMapping("show18")
    public ModelAndView test18(@RequestParam(value="name",required=true,defaultValue="hello")String name){
        ModelAndView mv = new ModelAndView();
        mv.setViewName("hello2");
        mv.addObject("msg", "接收普通请求参数：" + name);
        return mv;
    } 
}

    @ResponseBody
    @RequestMapping("login")
    public String login(@RequestParam(value = "username") final String username,
                        @RequestParam(value = "password",required = false) final String password,
                        @RequestParam(value = "valcode",required = false) final String valcode) {
                        }    

public interface Mapper {    
@Select("select s_id id,s_name name,class_id classid"+ 
        "from student where  s_name= #{aaaa} and class_id = #{bbbb}") 
 public Student select(@Param("aaaa") String name,@Param("bbbb")int class_id);  
   
@Delete......        
@Insert......     
} 

 List<Employee> getAllEmployeeByPage(@Param("page") Integer page, 
                                      @Param("size") Integer size);