java.lang.NullPointerException尝试从哈希图中获取特定值

Question

I've spent several frustrating days on this now and would appreciate some help. I have a Java agent in Lotus Domino 8.5.3 which is activated by a cgi:POST from my Lotusscript validation agent which is checking that customer has filled in the Billing and delivery address form. This is the code that parses the incoming data into a HashMap where field names are mapped to their respective values.

HashMap hmParam = new HashMap(); //Our Hashmap for request_content data

//Grab transaction parameters from form that called agent (CGI: request_content)
if (contentDecoded != null) {
    String[] arrParam = contentDecoded.split("&");                  
    for(int i=0; i < arrParam.length; i++) {
        int n = arrParam[i].indexOf("=");
        String paramName = arrParam[i].substring(0, n);
        String paramValue = arrParam[i].substring(n + 1, arrParam[i].length());

        hmParam.put(paramName, paramValue); //Old HashMap
        if (paramName.equalsIgnoreCase("transaction_id")) {
          transactionID = paramValue;
          description = "Order " + transactionID + " from Fareham Wine Cellar";
          //System.out.println("OrderID = " + transactionID);
        }

        if (paramName.equalsIgnoreCase("amount")) {
            orderTotal = paramValue;
        }
        if (paramName.equalsIgnoreCase("deliveryCharge")) {
            shipping = paramValue;
        }
    }   
}

The block of code above dates back over a year to my original integration of shopping cart to Barclays EPDQ payment gateway. In that agent I recover the specific values and build a form that is then submitted to EPDQ CPI later on in the agent like this;

out.print("<input type=\"hidden\" name=\"shipping\" value=\"");
out.println(hmParam.get("shipping") + "\">");

I want to do exactly the same thing here, except when I try the agent crashes with a null pointer exception. I can successfully iterate through the hashMap with the snippet below, so I know the data is present, but I can't understand why I can't use myHashMap.Get(key) to get each field value in the order I want them for the html form. The original agent in another application is still in use so what is going on? The data too is essentially unchanged String fieldnames mapped to String values.

Iterator it = cgiData.entrySet().iterator();
while (it.hasNext()) {
    Map.Entry pairs = (Map.Entry)it.next();
    out.println("<br />" + pairs.getKey() + " = " + pairs.getValue());
    //System.out.println(pairs.getKey() + " = " + pairs.getValue());
}

Answer 1

I did two things that may have had an impact, in the process of trying to debug what was going on I needed these further imports;

import java.util.Iterator;
import java.util.Map;

Although I'm not iterating over the hashMap, I've left them in in case which gives me the option of dumping the hashMap out to my system audit trail when application is in production. In variations of the snippet below after it started working I was able to get to any of the data I needed, even if the value was Null, and toString() also seemed to be optional again, as it made no difference to the output.

String cgiValue = "";
cgiValue = hmParam.get("ship_to_lastname").toString();
out.println("<br />Lastname: " + cgiValue);
out.println("<br />Company name: " + hmParam.get("bill_to_company"));
out.println("<br />First name: " + hmParam.get("ship_to_firstname"));

The second thing I did, while trying to get code to work was I enabled the option "Compile Java code with debugging information" for the agent, this may have done something to the way the project was built within the Domino Developer client.

I think I have to put this down to some sort of internal error created when Domino Designer compiled the code. I had a major crash last night while working on this which necessitated a cold boot of my laptop. You also may find that when using Domino Designer 8.5.x that strange things can happen if you don't completely close down all the tasks from time to time with KillNotes