Develop Reference

How to extract try catch outside method?

I have this method sendParameterValueAsMQTTMessage() which I use to publish message via MQTT on a specific topic. I am using try catch two times after another (not nested) but it still seems somewhat ugly and overcrowding the method. I read an article on clean code where Uncle Bob talks about extracting the body of try catch but I seem to not grasp it quite well or at least not in my case.
How could I get rid of the try catch in my method by extracting it outside?
public void sendParameterValueAsMQTTMessage() {
String payload = null;
try {
payload = convertToJSONString("range", String.valueOf(range));
} catch (JSONException e) {
this.logger.log(Level.ERROR, e);
}
MQTTMessage message = new MQTTMessage(MQTTTopics.RANGE_TOPIC,payload,0);
try {
this.client.publish(message);
Thread.sleep(3000);
} catch (Exception e) {
this.logger.log(Level.ERROR, e);
}
}

there are multiple different problems with provided code, here is how I'd refactor it:
public void sendParameterValueAsMQTTMessage() {
final String payload = tryGetPayloadAsJson();
if (payload != null) {
trySendPayloadViaMQTT(payload);
}
}
private String tryGetPayloadAsJson() {
try {
return convertToJSONString("range", String.valueOf(range));
} catch (JSONException e) {
this.logger.log(Level.ERROR, e);
}
return null;
}
private void trySendPayloadViaMQTT(final String payload) {
try {
final MQTTMessage message = new MQTTMessage(MQTTTopics.RANGE_TOPIC, payload, 0);
this.client.publish(message);
Thread.sleep(3000);
} catch (Exception e) {
this.logger.log(Level.ERROR, e);
}
}
one thing which might be improved here based on Uncle Bob's advice is to actually move try/catch outside of trySendPayloadViaMQTT, like this:
public void sendParameterValueAsMQTTMessage() {
final String payload = tryGetPayloadAsJson();
if (payload != null) {
trySendPayloadViaMQTT(payload);
}
}
private String tryGetPayloadAsJson() {
try {
return convertToJSONString("range", String.valueOf(range));
} catch (JSONException e) {
this.logger.log(Level.ERROR, e);
}
return null;
}
private void trySendPayloadViaMQTT(final String payload) {
try {
sendPayloadViaMQTT(payload);
} catch (Exception e) {
this.logger.log(Level.ERROR, e);
}
}
private void sendPayloadViaMQTT(final String payload) {
final MQTTMessage message = new MQTTMessage(MQTTTopics.RANGE_TOPIC, payload, 0);
this.client.publish(message);
Thread.sleep(3000);
}

you can put all of your code in just one try block and set multiple catches, when ever an exception be happened, the catch that is revelated to it will be execute, like:
try{
int a[]=new int[5];
a[5]=30/0;
}
catch(ArithmeticException e)
{
System.out.println("Arithmetic Exception occurs");
}
catch(ArrayIndexOutOfBoundsException e)
{
System.out.println("ArrayIndexOutOfBounds Exception occurs");
}

You can use single general catch for both possible exceptions inside the method as following:
public void sendParameterValueAsMQTTMessage() {
String payload = null;
try {
payload = convertToJSONString("range", String.valueOf(range));
MQTTMessage message = new MQTTMessage(MQTTTopics.RANGE_TOPIC,payload,0);
this.client.publish(message);
Thread.sleep(3000);
} catch (Exception e) {
this.logger.log(Level.ERROR, e);
}
}

public void sendParameterValueAsMQTTMessage() {
String payload = null;
try {
payload = convertToJSONString("range", String.valueOf(range));
} catch (JSONException e) {
this.logger.log(Level.ERROR, e);
}
MQTTMessage message = new MQTTMessage(MQTTTopics.RANGE_TOPIC,payload,0);
publishMessage(message); //extracted in a new method
}
public void publishMessage(MQTTMessage message){
try {
this.client.publish(message);
Thread.sleep(3000);
} catch (Exception e) {
this.logger.log(Level.ERROR, e);
}
}

how do i write test cases for jsonparser, jsonmapping and io exception using mockito

i want to mock this service in controller, so that i can test this. how do i mock coreservice.getRelatedInfo to throw the given exceptions to test them.
i am trying to throw them but, i'm getting error. when i am testing for runtime exception it is working.
#PostMapping("/realtedcustomerinfo")
public ResponseEntity<List<CustomerInfoDTO>>
getRelatedCustomerInfo(#RequestBody RelatedCustomerInfo
relatedCustomerInfo) {
log.info("Start of getRelatedCustomerInfo() input {}",
relatedCustomerInfo);
List<CustomerInfoDTO> customerInfoDTOs = null;
try {
customerInfoDTOs =
coreService.getRelatedCustomerInfo(relatedCustomerInfo);
} catch (JsonParseException e) {
log.error("Exception details", e);
} catch (JsonMappingException e) {
log.error("Exception details", e);
} catch (IOException e) {
log.error("Exception details", e);
}
if (null == customerInfoDTOs) {
log.info("End of getRelatedCustomerInfo() return {}", customerInfoDTOs);
return new ResponseEntity<List<CustomerInfoDTO>>(new ArrayList<CustomerInfoDTO>(), HttpStatus.OK);
}
log.info("End of getRelatedCustomerInfo() return {}", customerInfoDTOs);
return new ResponseEntity<List<CustomerInfoDTO>>(customerInfoDTOs, HttpStatus.OK);
}

Missing return statement, what i am missing

I written a method which will acknowledge the controller by returning true and false, I return true inside try if everything goes fine it will return true and I return false inside catch blocks, but still method shows me error "missing return statement" what is the best way to do it.
The below method written in java will send back the true or false to the controller.
Secondly I want to carry the exception message from here to controller, I think of returning string, is it good approach,
Kindly suggest me the best way to do the exception handling
public boolean pickSalayData(String yearMonth, String regionId, String circleId, Userdetail loginUser) throws MyExceptionHandler {
String tableSuffix = yearMonth.substring(4, 6) + yearMonth.substring(0, 4);
log.info("Pick Salary Data From ERP " + DateUtility.dateToStringDDMMMYYYY(new Date()));
List<SalaryDetailReport> detailReports = hRMSPickSalaryDataDAO.findAll(yearMonth, regionId, circleId);
TransactionDefinition def = new DefaultTransactionDefinition();
TransactionStatus trstatus = transactionManager.getTransaction(def);
try {
List<SalaryDetailReport> salaryDetailReport = null;
int countDetail = 0;
if (detailReports != null && detailReports.size() > 0) {
for (SalaryDetailReport salary : detailReports) {
try {
if (countDetail % COMMIT_COUNT == 0) {
if (salaryDetailReport != null) {
salaryDetailReportDAO.save(salaryDetailReport, tableSuffix);
reportHistoryDAO.save(salaryDetailReport, loginUser);
}
salaryDetailReport = new ArrayList<SalaryDetailReport>();
}
salaryDetailReport.add(salary);
countDetail++;
} catch (Exception e) {
log.error("Error on Save Salary Pay Head Details Data from ERP to Prayas .");
}
}
if (salaryDetailReport != null && salaryDetailReport.size() > 0) {
salaryDetailReportDAO.save(salaryDetailReport, tableSuffix);
reportHistoryDAO.save(salaryDetailReport, loginUser);
}
} else {
throw new MyExceptionHandler("No record for Save in Database from ERP.");
}
salaryDetailReportDAO.update(tableSuffix, regionId, circleId);
List<SalaryDetailReport> reports = salaryDetailReportDAO.findAll(tableSuffix, regionId, circleId);
if (reports != null && reports.size() > 0) {
for (SalaryDetailReport salaryDetail : reports) {
try {
SalaryDetail sd = new SalaryDetail();
sd.setDetailReport(salaryDetail);
salaryDetailDAO.save(sd, tableSuffix);
} catch (Exception e) {
log.error("Error occured", e);
e.printStackTrace();
throw new MyExceptionHandler(" Error :" + e.getMessage());
}
}
System.out.println("data found");
} else {
log.error("Salary Record Not Found.");
throw new MyExceptionHandler("No record Found.");
}
salaryDetailDAO.updateEarningDeduction(tableSuffix);
//salaryDetailDAO.updateEarningDeductionsInSDT();
transactionManager.commit(trstatus);
try {
hRMSPickSalaryDataDAO.update(regionId, circleId, yearMonth);
return true;
} catch (Exception ex) {
log.error("Some error : ", ex);
}
// // System.out.println("Completed =============================");
} catch (MyExceptionHandler ex) {
transactionManager.rollback(trstatus);
ex.printStackTrace();
log.error("Failed to Save Salary data :" + ex.getMessage());
return false;
} catch (Exception ex) {
transactionManager.rollback(trstatus);
ex.printStackTrace();
log.error("Error occured on Save Salary data.", ex);
return false;
}
}

You are missing return statement for the following catch block :
catch (Exception ex) {
log.error("Some error : ", ex);
}
Either you add return statement in this catch block or at the end of mehtod

If this code throws an Exception, then the following catch code will not be entered into and hence there is no return value
try {
hRMSPickSalaryDataDAO.update(regionId, circleId, yearMonth);
return true;
} catch (Exception ex) {
log.error("Some error : ", ex);
**edit**
return `true||false`;
}
} catch (...) {
return something;
}

When using the ExecutorService.invokeAll is there a way of getting all responses even if an exception occurred

In java I want to run multiple threads and get the response back from all of them.
The issue I have is if one of the threads throws an exception when I do the String temp = r.get() it drops into the catch and doesn't give me the response from the remaining threads.
Is there a way of processing all the responses regardless of whether the individual thread threw an exception?
My test code is
ExecutorService es = Executors.newFixedThreadPool(2);
List<CallTest> callList = new ArrayList<>();
callList.add(new CallTest(1));
callList.add(new CallTest(2));
callList.add(new CallTest(3));
callList.add(new CallTest(4));
try {
List<Future<String>> returns = es.invokeAll(callList);
for (Future<String> r : returns) {
String temp = r.get();
System.out.println("returned " + temp);
}
} catch (InterruptedException e) {
System.out.println("Interrupted Exception catch");
e.printStackTrace();
} catch (ExecutionException e) {
System.out.println("Execution Exception catch");
e.printStackTrace();
}

Catch exceptions inside the loop
for (Future<String> r : returns) {
try {
String temp = r.get();
System.out.println("returned " + temp);
} catch (InterruptedException e) {
System.out.println("Interrupted Exception catch");
e.printStackTrace();
} catch (ExecutionException e) {
System.out.println("Execution Exception catch");
e.printStackTrace();
}
}

Other solution:
Override afterExecute method in ThreadPoolExecutor
protected void afterExecute(Runnable r,
Throwable t)
Method invoked upon completion of execution of the given Runnable. This method is invoked by the thread that executed the task. If non-null, the Throwable is the uncaught RuntimeException or Error that caused execution to terminate abruptly.
Sample code from oracle documentation link:
class ExtendedExecutor extends ThreadPoolExecutor {
// ...
protected void afterExecute(Runnable r, Throwable t) {
super.afterExecute(r, t);
if (t == null && r instanceof Future<?>) {
try {
Object result = ((Future<?>) r).get();
} catch (CancellationException ce) {
t = ce;
} catch (ExecutionException ee) {
t = ee.getCause();
} catch (InterruptedException ie) {
Thread.currentThread().interrupt(); // ignore/reset
}
}
if (t != null)
System.out.println(t);
}
}

Get detail messages of chained exceptions Java

I'd like to know how I could throw a "final" Exception, containing a detailed message with all the detailed messages of a number of chained exceptions.
For example suppose a code like this:
try {
try {
try {
try {
//Some error here
} catch (Exception e) {
throw new Exception("FIRST EXCEPTION", e);
}
} catch (Exception e) {
throw new Exception("SECOND EXCEPTION", e);
}
} catch (Exception e) {
throw new Exception("THIRD EXCEPTION", e);
}
} catch (Exception e) {
String allMessages = //all the messages
throw new Exception(allMessages, e);
}
I'm not interested in the full stackTrace, but only in the messages, I wrote. I mean, I'd like to have a result like this:
java.lang.Exception: THIRD EXCEPTION + SECOND EXCEPTION + FIRST EXCEPTION

I think what you need is:
public static List<String> getExceptionMessageChain(Throwable throwable) {
List<String> result = new ArrayList<String>();
while (throwable != null) {
result.add(throwable.getMessage());
throwable = throwable.getCause();
}
return result; //["THIRD EXCEPTION", "SECOND EXCEPTION", "FIRST EXCEPTION"]
}

you can better use it this way, merge the message() of previous Exception with the message() of new Exception you are throwing:
} catch (Exception e) {
throw new Exception("FIRST EXCEPTION" + e.getMessage(), e);
}

Cycle through the exception cause and append the message in each exception.
try
{
try
{
try
{
try
{
throw new RuntimeException("Message");
}
catch (Exception e)
{
throw new Exception("FIRST EXCEPTION", e);
}
}
catch (Exception e)
{
throw new Exception("SECOND EXCEPTION", e);
}
}
catch (Exception e)
{
throw new Exception("THIRD EXCEPTION", e);
}
}
catch (Exception e)
{
String message = e.getMessage();
Throwable inner = null;
Throwable root = e;
while ((inner = root.getCause()) != null)
{
message += " " + inner.getMessage();
root = inner;
}
System.out.println(message);
}
Which prints
THIRD EXCEPTION SECOND EXCEPTION FIRST EXCEPTION Message

You can just add the previous exception message on each exception
This is an example :
public static void main(String[] args) {
try {
try {
try {
try {
throw new Exception();
// Some error here
} catch (Exception e) {
throw new Exception("FIRST EXCEPTION", e);
}
} catch (Exception e) {
Exception e2 = new Exception("SECOND EXCEPTION + " + e.getMessage());
throw e2;
}
} catch (Exception e) {
Exception e3 = new Exception("THIRD EXCEPTION + " + e.getMessage());
throw e3;
}
} catch (Exception e) {
System.out.println(e);
}
}
The result is : java.lang.Exception: THIRD EXCEPTION + SECOND EXCEPTION + FIRST EXCEPTION

Here is a nice utility for converting chained exceptions to string:
public final class ThrowableUtil {
private ThrowableUtil() {}
public static String chainedString(#NonNull Throwable throwable) {
StringBuilder SB = new StringBuilder(throwable.toString());
while((throwable = throwable.getCause()) != null)
SB.append("\ncaused by ").append(throwable);
return SB.toString();
}
public static String chainedString(#NonNull String msg, #NonNull Throwable throwable) {
StringBuilder SB = new StringBuilder(msg);
do {
SB.append("\ncaused by ").append(throwable);
} while((throwable = throwable.getCause()) != null);
return SB.toString();
}
}
Example output:
ThrowableUtil.chainedString(e);
produces
java.io.IOException: Failed to create required video encoder
caused by java.lang.RuntimeException: Invalid mime type
Another example output:
ThrowableUtil.chainedString("Writing of media file failed", e);
produces
Writing of media file failed
caused by java.io.IOException: Failed to create required video encoder
caused by java.lang.RuntimeException: Invalid mime type

I had saved all attributes in a class object with the following example:
public List<ErrorMessage> getMessageList(Throwable throwable) {
List<ErrorMessage> errorMessageList = new ArrayList<ErrorMessage>();
while (throwable != null) {
ErrorMessage message = new ErrorMessage();
message.set_message( throwable.getMessage());
message.set_line(throwable.getStackTrace()[0].getLineNumber());
message.set_methodName(throwable.getStackTrace()[0].getMethodName());
message.set_fileName(throwable.getStackTrace()[0].getFileName() );
message.set_className(throwable.getStackTrace()[0].getClassName());
errorMessageList.add(message);
throwable = throwable.getCause();
}
return errorMessageList;
}

Maybe simpler
try {
// code that throws exception
} catch(Throwable e ) {
var messages = new ArrayList<String>();
do {
messages.add(e.getMessage());
e = e.getCause();
} while( e!= null );
var message = String.join(" -> ", messages);
System.out.println(message);
}