SpringMVC——接收请求参数和数据回显

SpringMVC——接收请求参数和数据回显

1、接收参数为属性

@Controller
@RequestMapping("/user")
public class UserController {
    @GetMapping("/t1")
    public String test1(@RequestParam("username") String name, Model model){
        //1.接收前端参数
        System.out.println("参数为"+name);
        //2.将返回的结果传递给前端
        model.addAttribute("msg",name);
        //3.视图跳转
        return "hello";
    }
}

前端提交的域名为：http://localhost:8080/user?name=wanli

@RequestParam()可以解决提交的域名称和处理方法参数名不一致问题，在参数前加@RequestParam("username")

我们前端可提交的域名就只能为：http://localhost:8080/user?username=wanli

2、接收参数为对象

实体类User

package com.cheng.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private int id;
    private String name;
    private int age;
}

    @GetMapping("/t2")
    public String test2(User user,Model model){
        System.out.println(user); //User(id=1, name=null, age=3)
        model.addAttribute("msg",user);        
        return "hello";
    }

提交数据 : http://localhost:8080/s2/user/t2?username=wanli&id=1&age=3

前端传递的参数名和对象名必须一致，否则接收到的就是null。

3、数据回显

3.1、通过ModelAndView

public class ControllerTest1 implements Controller {

   public ModelAndView handleRequest(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws Exception {
       //返回一个模型视图对象
       ModelAndView mv = new ModelAndView();
       mv.addObject("msg","ControllerTest1");
       mv.setViewName("test");
       return mv;
  }
}

3.2、通过ModelMap

@RequestMapping("/hello")
public String hello(@RequestParam("username") String name, ModelMap model){
   //封装要显示到视图中的数据
   //相当于req.setAttribute("name",name);
   model.addAttribute("name",name);
   System.out.println(name);
   return "hello";
}

3.3、通过Model

@RequestMapping("/ct2/hello")
public String hello(@RequestParam("username") String name, Model model){
   //封装要显示到视图中的数据
   //相当于req.setAttribute("name",name);
   model.addAttribute("msg",name);
   System.out.println(name);
   return "test";
}

三种回显方式的区别：

• Model 只有寥寥几个方法只适合用于储存数据，简化了新手对于Model对象的操作和理解；
• ModelMap 继承了 LinkedMap ，除了实现了自身的一些方法，同样的继承 LinkedMap 的方法和特性；
• ModelAndView 可以在储存数据的同时，可以进行设置返回的逻辑视图，进行控制展示层的跳转。

4、处理乱码问题

使用SpringMVC的过滤器

<!--配置SpringMVC的乱码过滤-->
    <filter>
        <filter-name>encoding</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>utf-8</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>encoding</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

如果上面的配置还不能解决乱码问题，就在Tomcat配置文件中设置编码apache-tomcat-9.0.41\conf\server.xml

<Connector URIEncoding="utf-8" port="8080" protocol="HTTP/1.1"
          connectionTimeout="20000"
          redirectPort="8443" />

终极乱码解决方法：自定义过滤器，通用，但记得在web.xml注册（网上大神写的，来源不明）

package com.cheng.filter;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Map;

/**
* 解决get和post请求 全部乱码的过滤器
*/
public class GenericEncodingFilter implements Filter {

   public void destroy() {
  }
  
   public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
       //处理response的字符编码
       HttpServletResponse myResponse=(HttpServletResponse) response;
       myResponse.setContentType("text/html;charset=UTF-8");

       // 转型为与协议相关对象
       HttpServletRequest httpServletRequest = (HttpServletRequest) request;
       // 对request包装增强
       HttpServletRequest myrequest = new MyRequest(httpServletRequest);
       chain.doFilter(myrequest, response);
  }

   public void init(FilterConfig filterConfig) throws ServletException {
  }

}

//自定义request对象，HttpServletRequest的包装类
class MyRequest extends HttpServletRequestWrapper {

   private HttpServletRequest request;
   //是否编码的标记
   private boolean hasEncode;
   //定义一个可以传入HttpServletRequest对象的构造函数，以便对其进行装饰
   public MyRequest(HttpServletRequest request) {
       super(request);// super必须写
       this.request = request;
  }

   // 对需要增强方法 进行覆盖
   public Map getParameterMap() {
       // 先获得请求方式
       String method = request.getMethod();
       if (method.equalsIgnoreCase("post")) {
           // post请求
           try {
               // 处理post乱码
               request.setCharacterEncoding("utf-8");
               return request.getParameterMap();
          } catch (UnsupportedEncodingException e) {
               e.printStackTrace();
          }
      } else if (method.equalsIgnoreCase("get")) {
           // get请求
           Map<String, String[]> parameterMap = request.getParameterMap();
           if (!hasEncode) { // 确保get手动编码逻辑只运行一次
               for (String parameterName : parameterMap.keySet()) {
                   String[] values = parameterMap.get(parameterName);
                   if (values != null) {
                       for (int i = 0; i < values.length; i++) {
                           try {
                               // 处理get乱码
                               values[i] = new String(values[i]
                                      .getBytes("ISO-8859-1"), "utf-8");
                          } catch (UnsupportedEncodingException e) {
                               e.printStackTrace();
                          }
                      }
                  }
              }
               hasEncode = true;
          }
           return parameterMap;
      }
       return super.getParameterMap();
  }

   //取一个值
   public String getParameter(String name) {
       Map<String, String[]> parameterMap = getParameterMap();
       String[] values = parameterMap.get(name);
       if (values == null) {
           return null;
      }
       return values[0]; // 取回参数的第一个值
  }

   //取所有值
   public String[] getParameterValues(String name) {
       Map<String, String[]> parameterMap = getParameterMap();
       String[] values = parameterMap.get(name);
       return values;
  }
}

    <filter>
        <filter-name>GenericEncodingFilter</filter-name>
        <filter-class>com.cheng.filter.GenericEncodingFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>GenericEncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>