I have the following code in the Controller class and for some reason although i have exception handling implemented as well as a try.....catch block i am still unable to capture my exceptions.
I am just executing a test, in the DAO class i change the sql string that inserts into the database to leave out a column just so the DAO will fail. The DAO class fails and the error is written to the logs however even thou the officerManager.RegisterOfficer(officer) was not successful the code goes on to return the model.addAttribute("results","Record Was Saved").
This is not accurate and i would like for the controller to throw an error. Under is the code.
Controller
#RequestMapping(value="officer_registration.htm", method=RequestMethod.POST)
public ModelAndView handleRequest(#Valid #ModelAttribute Officers officer,BindingResult result,ModelMap m,Model model,HttpServletRequest request,HttpServletResponse response)throws Exception{
try{
if(result.hasErrors()){
model.addAttribute("division", myDivision);
model.addAttribute("position", myPosition);
model.addAttribute("gender", myGender);
return new ModelAndView("officer_registration");
}else{
//check the request if its an update or an insert
String user_request = request.getParameter("user_request");
logger.info("The Users Request Was " + user_request);
if (user_request.equals("Save")){
officerManager.RegisterOfficer(officer);
model.addAttribute("results","Record Was Saved");
}else{
officerManager.UpdateOfficer(officer);
model.addAttribute("results","Record Was Updated");
}
model.addAttribute("division", myDivision);
model.addAttribute("position", myPosition);
model.addAttribute("gender", myGender);
return new ModelAndView("officer_registration");
}
}catch(Exception e ){
model.addAttribute("division", myDivision);
model.addAttribute("position", myPosition);
model.addAttribute("gender", myGender);
model.addAttribute("results","Error: Unable to Save Record!");
return new ModelAndView("officer_registration");
}
}
DAO
public void saveOfficer(Officers officer) {
logger.info("In saveOfficer");
//SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
try{
int count = getJdbcTemplate().update("INSERT INTO crimetrack.tblofficers (userName,password, fName, lName, oName, divisionNo, positionId, emailAdd, startDate, endDate, genderId,phoneNo, dob,badgeNo) "+
"VALUES(?,?,?,?,?,?,?,?,?,?,?,?,?,?)"
, new Object[]{officer.getUserName(),StringSecurity.EncryptString(officer.getPassword()),officer.getfName(),
officer.getlName(),officer.getoName(),officer.getDivisionNo(),officer.getPositionId(),
officer.getEmailAdd(),officer.getStartDate(),officer.getEndDate(),officer.getGenderId(),
officer.getPhoneNo(),officer.getDob(),officer.getBadgeNo()});
logger.info(count +" Rows affected in tblOfficers");
}catch(Exception e){
logger.error("Could not save officer ", e);
}
}
You're not allowing the error to bubble up back to the controller.
You're handling the exception within the DAO, in which case the method exits normally, and no exception is caught within the Controller.
Either don't surround the DAO with a try catch and let the exception bubble back to the controller (recommended), or catch and rethrow the exception (if you follow this route, throw as a RuntimeException, either create your own, or rethrow as a RuntimeException, that way you won't have to catch all the way through the call stack.)
Also, it's generally frowned upon to catch generic exception as it is tougher to nail down exactly what caused it unless you look within the logs. Knowing which exceptions to handle ahead of time is usually better practice.
Related
After searching for days now and reading pretty much everything related to that, I'm finally posting my question here, since I couldn't find a solution for my specific problem.
I want my REST WebServices to return the original Exception, that has been thrown or at least the correct StackTrace. To test this, I'm using JUnit integrationtests and Wildfly 13 as app-server. After researching I found 2 possible solutions.
1.Using Exception Mappers
While this magical thing catches all of my Exceptions and allows me to return a Response, I've noticed that my StackTrace is changed if I use it like in the example. For example, "com.test.TestClass" is turned into "null.thread" or "null.interceptor". It seems like somehow the exception is changed on the way and the paths to the class are lost or censored, but I can't make sense of it.
Also I couldn't find any restrictions for the Response.entity, be it size, datatype or security.
As far as I understand, you can catch the ExceptionMapper Response OR a WebApplicationException, which contains the response. In my case, the response in the WebApplicationException contains all the relevant data except the (correct) StackTrace.
2.Using WebApplicationException
Another Solution would be to simply throw WebApplicationException instead of ECEException and not using a mapper. If I do that and catch it, the Exception is empty though. It doesn't contain any of the data set, it's always 500 - InternalServerError (I guess, Wildfly couldn't handle it then and threw an exception itself).
Or is it not supposed to be catched/thrown like that? Do I need to convert it to JSon or can I expect it to simply work out of the box with my annotations in the WebServiceInterface and the Response MediaType? Does it even make sense to put a full Response within a WebApplicationException? I mean, both contain fields for the ErrorCode, which seems redundand, even though there is a constructor for that approach.
Long story short:
What's the best approach to catch all possible exceptions and retrieve the full stack trace? Reading this post, I guess catching all "Exception"s is fine and they are always returned as WebApplicationExceptions, but the stack trace is still gone/malformed... your thoughts?
**JUnitTest**
#Test
public void testCreateTask_ClusterInvalid() throws IOException {
final RPETask taskToCreate = new RPETask();;
try
{
final long tid = taskManagerWebService.createTask(taskToCreate);
}
catch (WebApplicationException e) //Responses are ALWAYS catched as WebApplicationException
{
Response response = e.getResponse();
String emString = response.readEntity(String.class);
Gson gson = new Gson();
ECEWebErrorMessage errorMessage = gson.fromJson(emString, ECEWebErrorMessage.class);
errorMessage.displayErrorInformationOnConsole();
}
}
**WebServiceInterface**
#POST
#Path(URI_CREATE_TASK)
#Consumes(WebServiceNames.JSON)
#Produces(WebServiceNames.JSON)
long createTask(final RPETask task) throws ECEException;
**WebService**
#Override
public long createTask(final RPETask task) throws ECEException {
if (LOGGER.isTraceEnabled()) {
LOGGER.trace("createTask(" + task + ")");
}
return taskManager.createTask(task);
}
**ManagerBeanInterface**
long createTask(RPETask task) throws ECEException;
**ManagerBean**
#Override
public long createTask(final RPETask task) throws ECEException {
final ClusterEngineBean cluster = find(ClusterEngineBean.class, task.getCluster());
if (cluster == null) {
throw new ECEObjectNotFoundException(ClusterEngineBean.class, task.getCluster());
}
}
**ExceptionMapper**
#Provider
public class GenericWebExceptionMapper implements ExceptionMapper<Exception> {
final Log logger = LogFactory.getLog(getClass());
#Override
public Response toResponse(Exception ex) {
//At this point, the Exception is fully available -> Sending it as Response breaks it!
logger.error("GenericWebExceptionMapper -> toResponse(Throwable ex)", ex);
ECEWebErrorMessage errorMessage = new ECEWebErrorMessage(500,
ex.getMessage(),
ex.getClass().getCanonicalName(),
ex.getStackTrace());
return Response.status(Status.INTERNAL_SERVER_ERROR)
.entity(errorMessage)
.type(MediaType.APPLICATION_JSON)
.build();
}
}
After more research I've finally found a solution for myself.
Why is the StackTrace gone/malformed?
It's for security reasons. Wildfly automatically detects outgoing StackTraces and censors them, using interceptors. Im not sure if you can do anything about that, but I guess you shouldn't do that anyway.
What is the best approach?
Using Exception Mappers worked for me. Instead of catching them as WebApplicationException, you can always expect a response with the appropriote error code and handle them that way. For example error code 200 = OK, do this... error code 404 = NOTFOUND, do that...I that case your WebServices should always return Responses and contain the object you want to retreive in the entity field of the Response.
Feel free to add additional information to this solution.
I have a service method which does some operation inside a transaction.
public User method1() {
// some code...
Vehicle.withTransaction { status ->
// some collection loop
// some other delete
vehicle.delete(failOnError:true)
}
if (checkSomething outside transaction) {
return throw some user defined exception
}
return user
}
If there is a runtime exception we dont have to catch that exception and the transaction will be rolled back automatically. But how to determine that transaction rolled back due to some exception and I want to throw some user friendly error message. delete() call also wont return anything.
If I add try/catch block inside the transaction by catching the Exception (super class) it is not getting into that exception block. But i was expecting it to go into that block and throw user friendly exception.
EDIT 1: Is it a good idea to add try/catch arround withTransaction
Any idea how to solver this?? Thanks in advance.
If I understand you question correctly, you want to know how to catch an exception, determine what the exception is, and return a message to the user. There are a few ways to do this. I will show you how I do it.
Before I get to the code there are a few things I might suggest. First, you don't need to explicitly declare the transaction in a service (I'm using v2.2.5). Services are transactional by default (not a big deal).
Second, the transaction will automatically roll back if any exception occurs while executing the service method.
Third, I would recommend removing failOnError:true from save() (I don't think it works on delete()... I may be wrong?). I find it is easier to run validate() or save() in the service then return the model instance to the controller where the objects errors can be used in a flash message.
The following is a sample of how I like to handle exceptions and saves using a service method and try/catch in the controller:
class FooService {
def saveFoo(Foo fooInstance) {
return fooInstance.save()
}
def anotherSaveFoo(Foo fooInstance) {
if(fooInstance.validate()){
fooInstance.save()
}else{
do something else or
throw new CustomException()
}
return fooInstance
}
}
class FooController {
def save = {
def newFoo = new Foo(params)
try{
returnedFoo = fooService.saveFoo(newFoo)
}catch(CustomException | Exception e){
flash.warning = [message(code: 'foo.validation.error.message',
args: [org.apache.commons.lang.exception.ExceptionUtils.getRootCauseMessage(e)],
default: "The foo changes did not pass validation.<br/>{0}")]
redirect('to where ever you need to go')
return
}
if(returnedFoo.hasErrors()){
def fooErrors = returnedFoo.errors.getAllErrors()
flash.warning = [message(code: 'foo.validation.error.message',
args: [fooErrors],
default: "The foo changes did not pass validation.<br/>${fooErrors}")]
redirect('to where ever you need to go')
return
}else {
flash.success = [message(code: 'foo.saved.successfully.message',
default: "The foo was saved successfully")]
redirect('to where ever you need to go')
}
}
}
Hope this helps, or gets some other input from more experienced Grails developers.
Here are a few other ways I've found to get exception info to pass along to your user:
request.exception.cause
request.exception.cause.message
response.status
A few links to other relevant questions that may help:
Exception handling in Grails controllers
Exception handling in Grails controllers with ExceptionMapper in Grails 2.2.4 best practice
https://commons.apache.org/proper/commons-lang/javadocs/api-2.6/org/apache/commons/lang/exception/ExceptionUtils.html
When saving an object to database using hibernate, it sometimes fails because of certain fields in the object exceeding the maximum varchar length defined in the database.
Therefore I am using the following approach:
Attempt to save
If getting an DataException, I then truncate the fields in the object to the max length specified in the db definition, then try to save again.
However, in the second save after truncation, I'm getting the following exception:
hibernate: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails
Here's the relevant code, do you notice anything wrong with it?
public static void saveLenientObject(Object obj){
try {
save2(rec);
} catch (org.hibernate.exception.DataException e) {
// TODO Auto-generated catch block
e.printStackTrace();
saveLenientObject(rec, e);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private static void saveLenientObject(Object rec, DataException e) {
Util.truncateObject(rec);
System.out.println("after truncation ");
save2(rec);
}
public static void save2(Object obj) throws Exception{
try{
beginTransaction();
getSession().save(obj);
commitTransaction();
}catch(Exception e){
e.printStackTrace();
rollbackTransaction();
//closeSession();
throw e;
}finally{
closeSession();
}
}
All Hibernate exceptions (except for NonUniqueResultException) are irrecoverable. If you get an exception you should close the session and open another one for further operations.
See also:
13.2.3. Exception handling
The hibernate documentaiton is quite clear that once an exception is thrown the session will be left in an inconsistent state so is not safe to use for further operations. I suspect that what you're getting here is that the session is left half saving your first attempt so bad things happen.
Fundamentally you should not rely on database errors to check the length of your fields, instead you should pre-validate this in java code. If you know the lengths enough to truncate, then I suggest you simply call your trucate util every time.
Alternatively use Hibernate Validator to declaratively validate the objects before saving.
My struts2 webapp makes use of a SQL database. Within the DB access code, I've written a basic try/catch handler that catches SQL or general exceptions, writes the detail to a log file, and then continues. The hierarchy of classes is as follows:
Action method -> get or set method on Model -> DB access.
//Action method in action class
public string doActionMethod() throws Exception
{
String results = SampleModel.getResults();
}
//Model method in model class
public string getResults() throws Exception
{
String results = DBLayer.runQuery("SELECT Results FROM SampleTable WHERE Value='1');
}
//Method that queries database in DB access class
public string runQuery() throws Exception
{
ResultSet rs = null;
Connection dbConnection = null;
PreparedStatement preparedStatement = null;
dbConnection = MSSQLConnection.getConnection();
preparedStatement = dbConnection.prepareStatement(sqlQuery);
//run SQL statements
return String(rs.get(0));
}
I'd like caught exceptions to bubble up to the Action level, so that I can forward them to an appropriate error page. Is there a better way to do this than adding a "throws Exception" to the method signature?
Since you have no hope of recovery, throw an application-specific RuntimeException.
Use standard Struts 2 declarative exception handling to get your app to the appropriate error page.
Let's assume we have the following method in the business layer. What's the best practice to tell the UI layer that something went wrong and give also the error message? Should the method return an empty String when it was OK, otherwise the error message, or should it throw another exception in the catch code wrapping the caught exception? If we choose the second variant then the UI should have another try,catch which is too much try,catch maybe. Here is a pseudocode for the first variant.
public String updateSomething()
{
try
{
//Begin transaction here
dataLayer.do1();
dataLayer.do2();
dataLayer.doN();
//Commit transaction code here
}
catch(Exception exc)
{
//Rollback transaction code here
return exc.message;
}
return "";
}
Is this a good practice or should I throw another exception in the catch(then the method will be void)?
I like to return a standard contract to my UI layer from my business layer.
It looks like this:
public class ServiceOperationResult<T>
{
public bool Successful
{
get;
set;
}
public ServiceErrorType ErrorType
{
get;
set;
}
public string ErrorMessage
{
get;
set;
}
public T ReturnData
{
get;
set;
}
}
I use generics so that every service can define what it sends back, and the standard error flags tell the client app what type of error occurred (these are a meta-type, like "Internal error", "External party error", "Business rule validation error") and the app can then react in a standard fashion to these error types.
For instance, business errors are displayed in a red error label, while internal errors get redirected to an error page (in a web app) or close the form (in a windows app)
My pet hate is seeing a red label on a web site (where I expect to see validation errors) and seeing something like "The database server refused your connection" This is the risk that you run by only using a string to return error data.
The best way is wrap exception in some more general type and rethrow it. So updateSomething() must declare that it can throw some sort of Exception (for example: UpdateFailedException) and in catch block you should wrap exception.
public String updateSomething() {
try {
[...]
} catch ( SQLException e ) {
// rollback;
throw new UpdateFailedException(e);
}
}
But catching abstract Exception type is not a good idea. You should wrap only those things which semantic you know. For example: SQLException, DataAccessException (Spring DAO) etc.
If you wrap Exception you easily could wrap InterruptedException of NullPointerException. And this can broke your application.
It's a little unusual to return a String like this (but there's no real reason not too). More usual methods would be:
return a boolean value, and have some method of setting the error message, either by logging it, setting some global "last error" value, or having a pointer to an error construct passed in to your method which you update;
have a void method which throws an exception on failure, and handle it in the calling code (as you suggest)
I have see both of the above used extensively. It's hard to say which is "best". Try to be consistent with the idioms and conventions of the language you are working in and/or the existing code set/libraries you are working with if any.
Probably the best way is to have a custom exception classes specific to layers, once you catch the exception in a particular layer throw the custom exception to the calling layer, having this will have you the following advantage.
you will get the better modular approach to deal with the exception.
the maintenance of the code will be easy when your code complexity increases
you will be having more control on the exception scenarios
for example you catch a exception in the business layer and want to inform Presentation layer
public string DummyFunction
{
try
{
}
catch(Exception ex)
{
throw new businessException();
}
}