SpringMVC中@RequestMapping处理请求参数的@RequestParam注解

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首先在页面添加一个带有参数的请求，分别是username和age

<a href="springmvc/testRequestParam?username=yoni&age=20">Test RequestParam</a>

然后在类中添加方法

	@RequestMapping("/testRequestParam")
	public String testRequestParam(@RequestParam(value="username") String username,
			@RequestParam(value="age") int age ){
		System.out.println("Test RequestParam UserName:" + username + ",age:"+ age);
		return SUCCESS;
	}

运行页面，后台会显示

Test RequestParam UserName:yoni,age:20

如果将请求修改为

<a href="springmvc/testRequestParam?username=yoni">Test RequestParam</a>

会出现报错，

HTTP Status [400] – [Bad Request]

Type Status Report

Message Required Integer parameter 'age' is not present

Description The server cannot or will not process the request due to something that is perceived to be a client error (e.g., malformed request syntax, invalid request message framing, or deceptive request routing).

因为类中的age定义的是int类型，不能为空值。

可以在注解中添加required = false，并将age定义为Integer，问题解决。

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	@RequestMapping("/testRequestParam")
	public String testRequestParam(@RequestParam(value="username") String username,
			@RequestParam(value="age",required = false) Integer age ){
		System.out.println("Test RequestParam UserName:" + username + ",age:"+ age);
		return SUCCESS;
	}

但如果非要设置成int，那需要给age参数附一个默认值，修改代码如下

	@RequestMapping("/testRequestParam")
	public String testRequestParam(@RequestParam(value="username") String username,
			@RequestParam(value="age",required = false，defaultValue="0") Integer age ){
		System.out.println("Test RequestParam UserName:" + username + ",age:"+ age);
		return SUCCESS;
	}

@RequestParam注解中，value对应的是请求参数中的参数名，requirde是设置该参数是否必须存在，defaultValue是设置该参数的默认值。