使用 SNS 通知触发 lambda 不起作用

Triggering a lambda using SNS notification not working

package example;
import java.io.*;
import com.amazonaws.services.lambda.runtime.Context; 
public class LambdaMethodHandler {
    public String handlerString(String input,Context context) {
    System.out.println(input.length());
        return input;
    }
}
// This is my function policy
{
    "Version": "2012-10-17",
    "Id": "default",
    "Statement": [
        {
            "Sid": "sns-xxxx-Sns_Lambda_test",
            "Effect": "Allow",
            "Principal": {
                "Service": "sns.amazonaws.com"
            },
            "Action": "lambda:invokeFunction",
            "Resource": "arn:aws:lambda:xxxxx:function:theSimplestLambda",
            "Condition": {
                "ArnLike": {
                    "AWS:SourceArn": "arn:aws:sns:eu-west-1:xxxx:Sns_Lambda_test"
                }
            }
        }
    ]
}

显然,aws lambda 被正确调用,我在处理程序中显示的字符串的长度没有显示的原因是因为我在 lambda 中使用的参数,为了处理作为来自 SNS 的输入,我必须在参数中获取一个 SNSevent 类型的事件,然后再对其进行处理。