Debugging AJAX to Spring Controller (count of variables and spelling) - ajax

Question

I am spending a lot of effort debugging ajax calls. The common issues are
number of parameters dont match from the ajax to the controller
spelling of the #RequestMapping parameter does not match
If the type does not match the call happens and it can be debugged. But the bigger issue is the above two. I have 88 parameters that I am passing and have a hell of a time trying to figure out what is missing or spelt incorrectly.
example
#RequestMapping("/saveClient")
public #ResponseBody String saveClientAJAXMethodView(#RequestParam(value = "clientName") String clientName,
.... 88 parameters more
$
.ajax({
type : "Post",
url : "saveClient",
data : {
clientName : clientName,
... 88 parameters more
I got this error
The request sent by the client was syntactically incorrect.
So I changed the signature of my controller to add , method = RequestMethod.POST).
Now I am getting
message Request method 'GET' not supported
description The specified HTTP method is not allowed for the requested resource.
Its clearly a "POST" and still it get a request method GET not supported.
The question is NOT how to solve this problem. The question is how to debug such issues easily. What errors map to what issues, how to debug the 88 parameter spellings and count ? There must be a easier way to do this debugging.
I use the following
Debugging Mode of the controller
Inspect on Chrome.

Answer 1

Since you are sending huge amount of parameter in URL for POST request. I would suggest you to send your data in body.
For example if you are sending parameters like clientId, clientName, clientEmail etc.. you have used #RequestParam annotation to get individual parameter data in your controller:
String saveClientAJAXMethodView( #RequestParam String clientId,
#RequestParam String clientName,
#RequestParam String clientEmail
.... more parameters)
Instead of using #RequestParam I would suggest you to use #RequestBody, For this you need to create a Data transfer object (DTO) like this:
class ClientInfo{
String clientId,
String clientName,
String clientEmail,
....
.... other variables
.... getters and setters of variables
}
And then use this DTO in your controller method like this:
String saveClientAJAXMethodView(#RequestBody ClientInfo clientInfo){
}
Using this approach you will not get any exception regarding spelling mistake or parameter missing .The value will be assigned to a DTO variable if you are sending value with right key as specified in DTO.
To count variables in ClientInfo object you will need to cast ClientInfo to JSONObject and use its size() method to get count of variables
String saveClientAJAXMethodView(#RequestBody ClientInfo clientInfo){
JSONObject json = new JSONObject(clientInfo);
System.out.println(json.keySet().size());
}
Your ajax call will look like this:
var clientInfo = {
'clientName': 'tom',
'clientId': '23AZ1',
'clientEmail': 'xyz#gmail.com',
...
};
$.ajax({
url: url,
type: "POST",
data: JSON.stringify(clientInfo),
contentType: "application/json",
complete: callback
});

Answer 2

I hope following steps would help you debug:
1- Use a filter to intercept request.
2- Create a custom annotation which would indicate that you want to debug this method.
3- Use the method defined in this post Can I get all of requestMapping URL with GET method in the Spring? and your custom annotation to store list of all methods which you want to debug in a singleton bean.
4- Now write some logic in filter which would print mismatch between the method parameters and request parameters.
CustomFilter:
public class CustomFilter extends GenericFilterBean {
#Autowired
#Qualifier("printMismatchMethods")
HashMap<String,Method> methodsToCheck;
#Override
public void doFilter(
ServletRequest request,
ServletResponse response,
FilterChain chain) throws IOException, ServletException {
SpringBeanAutowiringSupport.processInjectionBasedOnCurrentContext(this);
HttpServletRequest r = (HttpServletRequest) request;
String url = r.getRequestURI().substring(r.getContextPath().length());
//Remove extensions if present any
int index = url.indexOf('.');
if(index > 0)
url = url.substring(0,url.indexOf('.'));
/*Matching string this should be replaced by url pattern matching of spring.*/
if (methodsToCheck.containsKey(url)){
Method method = methodsToCheck.get(url);
Map<String, String[]> requestParameterMap = r.getParameterMap();
Map<String,Boolean> isParamPresent = new HashMap<String,Boolean>();
for (Parameter parameter : method.getParameters()){
RequestParam requestParam = parameter.getAnnotation(RequestParam.class);
if (requestParam != null && requestParam.required()){
if (!requestParam.name().isEmpty())
isParamPresent.put(requestParam.name(), false);
else
isParamPresent.put(requestParam.value(), false);
}
}
for (Parameter parameter : method.getParameters()){
RequestParam requestParam = parameter.getAnnotation(RequestParam.class);
if (requestParam != null && requestParam.required()){
String name = null;
if (!requestParam.name().isEmpty())
name=requestParam.name();
else
name=requestParam.value();
if (requestParameterMap.containsKey(name)){
isParamPresent.put(name, true);
}
}
}
for (Map.Entry<String, Boolean> entry : isParamPresent.entrySet()){
if (!entry.getValue()){
System.out.println(entry.getKey() + " is either missing or mis-spelled");
}
}
}
chain.doFilter(request, response);
}
}
configured as follows:
http.addFilterAfter(
new CustomFilter(), BasicAuthenticationFilter.class);
Declare following custom annotation.
#Target(ElementType.METHOD)
#Retention(RetentionPolicy.RUNTIME)
#Documented
public #interface PrintParamMismatch {
}
Define following bean which would populate on startup
#Bean(name="printMismatchMethods")
#Autowired
public HashMap<String,Method> printParamMismatchMethods(BeanFactory beanFactory){
HashMap<String,Method> methods = new HashMap<String,Method>();
Map<String, RequestMappingHandlerMapping> matchingBeans =
BeanFactoryUtils.beansOfTypeIncludingAncestors(
(ListableBeanFactory)beanFactory,
RequestMappingHandlerMapping.class, true, false);
if (!matchingBeans.isEmpty()) {
ArrayList<HandlerMapping> handlerMappings = new ArrayList<HandlerMapping>(matchingBeans.values());
AnnotationAwareOrderComparator.sort(handlerMappings);
RequestMappingHandlerMapping mappings = matchingBeans.get("requestMappingHandlerMapping");
Map<RequestMappingInfo, HandlerMethod> handlerMethods = mappings.getHandlerMethods();
for (Map.Entry<RequestMappingInfo, HandlerMethod> handlerMethod : handlerMethods.entrySet()){
RequestMappingInfo info = handlerMethod.getKey();
HandlerMethod hMethod = handlerMethod.getValue();
Method method = hMethod.getMethod();
if (method.getAnnotation(PrintParamMismatch.class) != null){
String path = info.getPatternsCondition().toString();
path = path.substring(1,path.length());
path = path.substring(0,path.length()-1);
methods.put(path, method);
}
}
}
return methods;
}
This, I think is generic enough to show debug information for now. However we need to store and match Patterns instead of url string.

Answer 3

So I used divide and rule and solved my issue. I commented top half of the parameters and ran, to check if my controller gets called. It did. then I added 1/4th, then 1/8th and found that I missed a parameter.
That along with #ArsianAnjum's answer is good for debugging. #Aji's answer is the long term solution. I should be using that.