瀏覽器總會向服務器傳遞一些參數，那么Spring MVC如何接收這些參數？
先寫個簡單的html，向服務器傳遞一些書籍信息，如下：
<!DOCTYPE html>
<html>
<head>
<title>Spring MVC如何接受瀏覽器傳遞來的參數</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
</head>
<body>
<form action="addbook" method="POST">
<fieldset>
<legend>要上傳的書籍信息</legend>
書名：<input name="bookname" /><br>
作者：<input name="author" /><br>
出版社：<input name="press" /><br>
ISBN：<input name="isbn" /><br>
豆瓣評分：<input name="douban" /><br>
<input type="submit" value="提交" />
</fieldset>
</form>
</body>
</html>
再寫個視圖result.jsp
<%@page pageEncoding="utf-8"
contentType="text/html;charset=utf-8" %>
<html>
<head>
<title>返回結果</title>
</head>
<body style="color:blue;font-size:18px">
您輸入的書籍信息為：<br>
書籍的名稱：${bookname }<br><br>
書籍的作者：${author }<br><br>
書籍的出版社：${press }<br><br>
書籍的ISBN：${isbn }<br><br>
書籍的豆瓣評分：${douban }<br><br>
</body>
</html>
1. 通過HttpServletRequest獲得請求參數和數據
tomcat類容器會自動將請求的參數封裝到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"); //將請求的編碼設為utf-8
String bookname=request.getParameter("bookname"); //從request中或參數值
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. 處理方法形參名==請求參數名
將處理方法的形參名設為跟傳遞來的參數名稱相同，Spring會自動將參數值傳遞進來
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){
//將形參名跟請求參數名設為相同，自動將值傳遞進來
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;
}
}
用這種方式可能導致編碼錯誤，這里沒有request參數，那就在web.xml中添加個過濾器
<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. 如果形參名跟請求參數名不一樣怎么辦呢？用@RequestParam注解
處理方法該成這樣：
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注解將請求參數值賦值給形參
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可以將指定的請求參數賦值給形參，該注解有4個參數
----name：指定請求參數名
----value：跟name屬性相同
----required：boolean類型，該參數是否必須綁定。注意這是指是否必須有這個參數，而不是參數的值是否為null。如果該屬性設置為true，但是又沒有對應的參數傳遞來，那么會拋出異常：Required String parameter '參數名' is not present
----defaultValue：如果沒有該參數，那么使用使用默認值
4. 用實體類接收
寫個實體類，其實例變量名稱跟傳遞來的參數名稱相同，並將該實體類作為處理方法的形參，Spring會自動將請求參數封裝到該實體類對象中
先寫個Book實體類，注意實例變量名跟傳遞的參數名相同
package net.sonng.mvcdemo.entity;
public class Book {
private String bookname; //實體類的形參名跟請求參數名相同
private String press;
private String author;
private String isbn;
private float douban;
//省略getter、setter、toString
}
處理方法寫成這樣：
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)
//用實體類封裝請求參數
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>返回結果</title>
</head>
<body style="color:blue;font-size:18px">
您輸入的書籍信息為：<br>
書籍的名稱：${book.bookname }<br><br> <!-- 從名為book的模型中拿到bookname數據 -->
書籍的作者：${book.author }<br><br>
書籍的出版社：${book.press }<br><br>
書籍的ISBN：${book.isbn }<br><br>
書籍的豆瓣評分：${book.douban }<br><br>
</body>
</html>
最后，如何選擇？
如果參數比較少，就用：形參名跟請求參數名相同的辦法
如果參數比較多，就用：實體類封裝
如果瀏覽器端沒有做參數檢查，那就從request拿值