Spring MVC 的@RequestParam注解和request.getParameter("XXX")

在SpringMVC后台控制层获取参数的方式主要有两种，一种是request.getParameter("name")，另外一种是用注解@RequestParam直接获取。这里主要讲这个注解 

一、基本使用，获取提交的参数 
后端代码： 

@RequestMapping("testRequestParam")
   public String filesUpload(@RequestParam String inputStr, HttpServletRequest request) {
    System.out.println(inputStr);

    int inputInt = Integer.valueOf(request.getParameter("inputInt"));
    System.out.println(inputInt);

    // ......省略
    return "index";
   }

前端代码： 

<form action="/gadget/testRequestParam" method="post">
     参数inputStr:<input type="text" name="inputStr">
     参数intputInt:<input type="text" name="inputInt">
</form>

前端界面： 
 

执行结果： 
test1 
123 

可以看到spring会自动根据参数名字封装进入，我们可以直接拿这个参数名来用 

二、各种异常情况处理 
1、可以对传入参数指定参数名 

@RequestParam String inputStr
// 下面的对传入参数指定为aa，如果前端不传aa参数名，会报错
@RequestParam(value="aa") String inputStr

错误信息： 
HTTP Status 400 - Required String parameter 'aa' is not present 

2、可以通过required=false或者true来要求@RequestParam配置的前端参数是否一定要传 

// required=false表示不传的话，会给参数赋值为null，required=true就是必须要有
@RequestMapping("testRequestParam")
    public String filesUpload(@RequestParam(value="aa", required=true) String inputStr, HttpServletRequest request)

3、如果用@RequestMapping注解的参数是int基本类型，但是required=false，这时如果不传参数值会报错，因为不传值，会赋值为null给int，这个不可以 

@RequestMapping("testRequestParam")
   public String filesUpload(@RequestParam(value="aa", required=true) String inputStr,
        @RequestParam(value="inputInt", required=false) int inputInt
        ,HttpServletRequest request) {

    // ......省略
    return "index";
   }

解决方法： 
    “Consider declaring it as object wrapper for the corresponding primitive type.”建议使用包装类型代替基本类型，如使用“Integer”代替“int”

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AfrikaansAlbanianArabicArmenianAzerbaijaniBasqueBelarusianBengaliBosnianBulgarianCatalanCebuanoChichewaChinese (Simplified)Chinese (Traditional)CroatianCzechDanishDutchEnglishEsperantoEstonianFilipinoFinnishFrenchGalicianGeorgianGermanGreekGujaratiHaitian CreoleHausaHebrewHindiHmongHungarianIcelandicIgboIndonesianIrishItalianJapaneseJavaneseKannadaKazakhKhmerKoreanLaoLatinLatvianLithuanianMacedonianMalagasyMalayMalayalamMalteseMaoriMarathiMongolianMyanmar (Burmese)NepaliNorwegianPersianPolishPortuguesePunjabiRomanianRussianSerbianSesothoSinhalaSlovakSlovenianSomaliSpanishSundaneseSwahiliSwedishTajikTamilTeluguThaiTurkishUkrainianUrduUzbekVietnameseWelshYiddishYorubaZulu

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