部署为AWS Lambda的Spring Boot应用GET请求多值Query参数丢失

向部署为AWS Lambda函数的Spring Boot应用发送以下GET请求：

GET https://my-dev-host.com/fdx/v6/accounts?accountIds=confUser_1&accountIds=confUser_2&accountIds=confUser_3&accountIds=confUser_4&offset=1&limit=3
Authorization: Bearer ....
Accept: application/json
Accept-Charset: UTF-8
Content-Type: application/json

但日志显示仅最后一个accountId到达控制器：

Modified request:
{
  "multiValueQueryStringParameters": {
    "accountIds": [
      "confUser_4"
    ],
    "limit": [
      "3"
    ],
    "offset": [
      "1"
    ]
  },
  "queryStringParameters": {
    "accountIds": "confUser_4",
    "limit": "3",
    "offset": "1"
  },
  "multiValueHeaders": {
    "accept": [
      "application/json"
    ],
    "accept-charset": [
      "UTF-8"
    ],
    "accept-encoding": [
      "br, deflate, gzip, x-gzip"
    ],
    "authorization": [
      "Bearer ..."
    ],
    "content-type": [
      "application/json"
    ],
    "host": [
      "my-dev-host.com"
    ]
  },
  "headers": {
    "accept": "application/json",
    "accept-charset": "UTF-8",
    "accept-encoding": "br, deflate, gzip, x-gzip",
    "authorization": "Bearer ...",
    "content-type": "application/json",
    "host": "my-dev-host.com"
  },
  "pathParameters": {},
  "httpMethod": "GET",
  "stageVariables": {},
  "path": "/fdx/v6/accounts",
  "isBase64Encoded": false,
  "requestSource": "ALB"
}

尝试改用逗号分隔的传参方式，问题依旧：

GET https://my-dev-host.com/fdx/v6/accounts?accountIds=confUser_1,confUser_2,confUser_3,confUser_4&offset=1&limit=3
Authorization: Bearer ....
Accept: application/json
Accept-Charset: UTF-8
Content-Type: application/json

控制器API定义如下：

@RequestMapping(
        method = RequestMethod.GET,
        value = "/accounts",
        produces = {"application/json"}
)
ResponseEntity<Object> searchForAccounts(
        @Parameter(name = "accountIds", description = "Comma separated list of account ids", in = ParameterIn.QUERY) @Valid @RequestParam(value = "accountIds", required = false) List<String> accountIds,       
        @Parameter(name = "offset", description = "Opaque cursor used by the provider to send the next set of records", in = ParameterIn.QUERY) @Valid @RequestParam(value = "offset", required = false) String offset,
        @Parameter(name = "limit", description = "Number of elements that the consumer wishes to receive. Providers should implement reasonable default and maximum values", in = ParameterIn.QUERY) @Valid @RequestParam(value = "limit", required = false) Integer limit
);

1. 开启ALB目标组多值查询参数支持 #

请求来源为ALB，默认情况下ALB会将重复的查询参数覆盖为最后一个值，需调整配置：

• 进入AWS控制台EC2服务，找到对应ALB的目标组
• 编辑目标组属性，将「多值查询字符串」设置为「启用」
• 保存配置后重新测试请求

2. 适配逗号分隔参数的解析逻辑 #

如果需要支持逗号分隔的传参方式，需在@RequestParam中指定分隔符：

@RequestParam(value = "accountIds", required = false, delimiter = ",") List<String> accountIds

配置后Spring会自动将逗号分隔的字符串拆分为List集合

3. 验证中间转发层的参数处理 #

如果ALB与Lambda之间存在API Gateway等转发层，需同步开启对应组件的多值查询参数支持，确保完整的参数列表能传递到Lambda函数中

内容的提问来源于stack exchange，提问作者Sergey Tsypanov