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
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：
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.servlet.ModelAndView;
@Controller
public class BookController {
@RequestMapping(value="/addbook",method=RequestMethod.POST)
//用实体类封装请求参数
public ModelAndView addBook(Book book){
ModelAndView mav=new ModelAndView();
mav.addObject("book", book);
mav.setViewName("result");
return mav;
}
}
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> <!-- 从名为book的模型中拿到bookname数据 -->
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>
最后，如何选择？
如果参数比较少，就用：形参名跟请求参数名相同的办法
如果参数比较多，就用：实体类封装
如果浏览器端没有做参数检查，那就从request拿值
