get 方式的签名生产，困然了我2天，今天终于解决了，记录如下

var args = sampler.getArguments();
var size = args.getArgumentCount();

var argObj = {}
for(var i=0; i< size; i++) {
    var name = args.getArgument(i).getName();
    var value = args.getArgument(i).getValue();
    log.info(name);
    log.info(value);
    argObj[name] = value;   
}
var argsStr = JSON.stringify(argObj);
log.info(argsStr);

var s = doSign(argsStr)
log.info(s)
sampler.getArguments().removeArgument("sign");
sampler.addArgument("sign",s); 


function doSign(playload){
    return playload;    
}

下面的知识点是关键

import org.apache.jmeter.config.Argument;

sampler.getArguments().removeArgument("page_submission_id");
sampler.addArgument("page_submission_id","8743718386872"); 

参考： https://stackoverflow.com/questions/35793287/in-jmeter-java-api-how-to-set-post-form-values-in-a-preprocessor-sampler