前台请求：
Request URL:http://localhost:8080/testweb/UserDefined/downloadFile?userName=lijing&localPath=e:\download&fileName=BcaApiX.jar
Request Method:GET
Status Code:400 Bad Request

后台异常：
java.lang.IllegalArgumentException: Invalid character found in the request target. The valid characters are defined in RFC 7230 and RFC 3986

localPath=e:\download这里“\”的问题,\是路径分隔符

解决：

Request URL:http://localhost:8080/testweb/UserDefined/downloadFile?userName=lijing&localPath=e://download&fileName=BcaApiX.jar
Request Method:GET
Status Code:200 OK