0056 Spring MVC如何接收浏览器传递来的请求参数--request--形参--实体类封装

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浏览器总会向服务器传递一些参数，那么Spring MVC如何接收这些参数？

先写个简单的html，向服务器传递一些书籍信息，如下：

<!DOCTYPE html> <html> <head> <title>Spring MVC如何接受浏览器传递来的参数</title> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> </head> <body> <form action="addbook" method="POST"> <fieldset> <legend>要上传的书籍信息</legend> 书名：<input name="bookname" /><br> 作者：<input name="author" /><br> 出版社：<input name="press" /><br> ISBN：<input name="isbn" /><br> 豆瓣评分：<input name="douban" /><br> <input type="submit" value="提交" /> </fieldset> </form> </body> </html>

再写个视图result.jsp

<%@page pageEncoding="utf-8" contentType="text/html;charset=utf-8" %> <html> <head> <title>返回结果</title> </head> <body style="color:blue;font-size:18px"> 您输入的书籍信息为：<br> 书籍的名称：${bookname }<br><br> 书籍的作者：${author }<br><br> 书籍的出版社：${press }<br><br> 书籍的ISBN：${isbn }<br><br> 书籍的豆瓣评分：${douban }<br><br> </body> </html>

1. 通过HttpServletRequest获得请求参数和数据

tomcat类容器会自动将请求的参数封装到HttpServletRequest中

package net.sonng.mvcdemo.controller;import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestMethod; import org.springframework.web.servlet.ModelAndView;@Controller public class BookController { @RequestMapping(value="/addbook",method=RequestMethod.POST) public ModelAndView addbook(HttpServletRequest request,HttpServletResponse response) throws Exception{ request.setCharacterEncoding("utf-8"); //将请求的编码设为utf-8 String bookname=request.getParameter("bookname"); //从request中或参数值 String author=request.getParameter("author"); String press=request.getParameter("press"); String isbn=request.getParameter("isbn"); float douban=Float.parseFloat(request.getParameter("douban")); ModelAndView mav=new ModelAndView(); mav.addObject("bookname",bookname); mav.addObject("author",author); mav.addObject("press",press); mav.addObject("isbn",isbn); mav.addObject("douban", douban); mav.setViewName("result"); return mav; } }

2. 处理方法形参名==请求参数名

将处理方法的形参名设为跟传递来的参数名称相同，Spring会自动将参数值传递进来

package net.sonng.mvcdemo.controller;import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestMethod; import org.springframework.web.servlet.ModelAndView;@Controller public class BookController { @RequestMapping(value="/addbook",method=RequestMethod.POST) public ModelAndView addBook(String bookname,String author,String press,String isbn,float douban){ //将形参名跟请求参数名设为相同，自动将值传递进来 ModelAndView mav=new ModelAndView(); mav.addObject("bookname",bookname); mav.addObject("author",author); mav.addObject("press",press); mav.addObject("isbn",isbn); mav.addObject("douban", douban); mav.setViewName("result"); return mav; } }

用这种方式可能导致编码错误，这里没有request参数，那就在web.xml中添加个过滤器

<filter> <filter-name>utf8Filter</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>utf8Filter</filter-name> <servlet-name>springmvc</servlet-name> </filter-mapping>

3. 如果形参名跟请求参数名不一样怎么办呢？用@RequestParam注解

处理方法该成这样：

package net.sonng.mvcdemo.controller;import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;import net.sonng.mvcdemo.entity.Book;import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestMethod; import org.springframework.web.bind.annotation.RequestParam; import org.springframework.web.servlet.ModelAndView;@Controller public class BookController { @RequestMapping(value="/addbook",method=RequestMethod.POST) public ModelAndView addBook( @RequestParam(name="bookname",required=true) String b, @RequestParam(value="author") String a, @RequestParam("press") String p, @RequestParam("isbn") String i, @RequestParam(value="douban",defaultValue="0.0") float d){ //用@RequestParam注解将请求参数值赋值给形参 ModelAndView mav=new ModelAndView(); mav.addObject("bookname",b); mav.addObject("author",a); mav.addObject("press",p); mav.addObject("isbn",i); mav.addObject("douban", d); mav.setViewName("result"); return mav; } }

@RequestParam可以将指定的请求参数赋值给形参，该注解有4个参数

----name：指定请求参数名

----value：跟name属性相同

----required：boolean类型，该参数是否必须绑定。注意这是指是否必须有这个参数，而不是参数的值是否为null。如果该属性设置为true，但是又没有对应的参数传递来，那么会抛出异常：Required String parameter '参数名' is not present

----defaultValue：如果没有该参数，那么使用使用默认值

4. 用实体类接收

写个实体类，其实例变量名称跟传递来的参数名称相同，并将该实体类作为处理方法的形参，Spring会自动将请求参数封装到该实体类对象中

先写个Book实体类，注意实例变量名跟传递的参数名相同

package net.sonng.mvcdemo.entity;public class Book { private String bookname; //实体类的形参名跟请求参数名相同 private String press; private String author; private String isbn; private float douban; //省略getter、setter、toString }

处理方法写成这样：

result.jsp改一改

<%@page pageEncoding="utf-8" contentType="text/html;charset=utf-8" %> <html> <head> <title>返回结果</title> </head> <body style="color:blue;font-size:18px"> 您输入的书籍信息为：<br> 书籍的名称：${book.bookname }<br><br>  书籍的作者：${book.author }<br><br> 书籍的出版社：${book.press }<br><br> 书籍的ISBN：${book.isbn }<br><br> 书籍的豆瓣评分：${book.douban }<br><br> </body> </html>