I have some problems making the exception do that i want!. I have created a servlet, which i want to handle all exceptions. My class building for this scenario that i need help too you see under here:
Servlet:
This exception handling is only for 1 method,
try {
completed = func.addNewOperator(userId, name, ini, cpr, password, role);
}catch (Exception e) {
Error = "There was a problem with database access";
response.sendRedirect("SystemError.jsp?Error_resultat=" + Error);
} catch (IOException e) {
Error = "Error found with connection";
response.sendRedirect("SystemError.jsp?Error_resultat=" + Error);
} catch (RuntimeException e) {
Error = "Error found with entered values";
response.sendRedirect("SystemError.jsp?Error_resultat=" + Error);
} catch (Exception e) {
Error = "Serious error found!";
response.sendRedirect("SystemError.jsp?Error_resultat=" + Error);
The func.addNewOperator is called in my function class:
Function:
A small example from my function method you see under here:
public boolean addNewOperator(String userId, String name, String ini, String cpr, String password, String role ) throws Exception {
int id = Integer.parseInt(userId);
}
So lets say if it can't parse it to and integer, it should throws the exception to my servlet, but this is not working. I want to throw the exception to the servlet, and then the servlet should send a response to open SystemError.jsp with an error message as parameter.
Can anyone see if i forgot something??
The order is whatever matches first, get's executed (as the JLS clearly explains).
If the first catch matches the exception, it executes, if it doesn't, the next one is tried and on and on until one is matched or none are.
So, when catching exceptions you want to always catch the most specific first and then the most generic (as RuntimeException or Exception).
Read more Order of catching exceptions in Java
catch (Exception e) should be last catch block in the chain.
It's worth reading Oracle Java Tutorial - Exceptions
Try in this way and don't forget to log the exception in log file.
try {
completed = func.addNewOperator(userId, name, ini, cpr, password, role);
}catch (SQLException e) {
Error = "There was a problem with database access";
} catch (IOException e) {
Error = "Error found with connection";
} catch (RuntimeException e) {
Error = "Error found with entered values";
} catch (Exception e) {
Error = "Serious error found!";
}
if(Error != null){
response.sendRedirect("SystemError.jsp?Error_resultat=" + Error);
}
NumberFormatException is a RuntimeException.
First, you should never redirect to a jsp page, but forward to it. Normally, jsp files are placed under WEB-INF and are never called directly but allways through server. Here is one example of forwarding (derived from from Java Tips - How to forward requests from Servlet to JSP :) :
request.setAttribute("error", error);
getServletConfig().getServletContext().getRequestDispatcher("/WEB-INF/SystemError.jsp")
.forward(request,response);
and your get error (first letter lowercased because it's a variable) in your jsp via ${error}
And anyway, you shouldn't deal with that at your servlet level but delegates this low level job to the container as explained in that other post from SO : How to Properly Handle Exceptions in a JSP/Servlet App?.
Related
I have Jenkins plugin written in Java. I am capturing all the workflows of execution of plugin in a integer variable in three ways 0(2xx workflows), 1(4xx workflows), 2(5xx workflows) and sending them to SignalFX for metrics. Since this is not an API and errors will be mainly caught in try catch workflow.
I wanted to ask how to read error codes from exception class and categorize them in 2xx, 4xx or 5xx. Are there some rules which I can follow by?
try {
Thread.sleep(60 * 1000);
} catch (InterruptedException e) {
sendToSignalFX(0,data); // 0 means successful state
}
Some of the exceptions classes I will be using are -
Exception, IOException, InterruptedException, ParserConfigurationException, SAXException
I believe you may have to add a method to identify the failure reason from e.getMessage() for one OR have a custom exception to help with your case.
Also if it’s an HTTP request-related exception (from the error response code mentioned in the question details) or something, you may want to add a custom exception, instead of throwing the original exception. In the custom exception, you can add a custom field to get errorCode from the response code.
// MyCustomException.java
public class MyCustomException extends Exception {
String errorReason;
int errorCode;
public MyCustomException(Throwable throwable, String errorReason, int errorCode) {
super(errorReason, throwable);
this.errorReason = errorReason;
this.errorCode = errorCode;
}
}
And in your request handler code:
try {
// otherCode which might cause IOException
// ...
Response response = myHttpRequest();
if (!response.isSuccessful()) {
// identify the error code and set corresponding errorCode to MyCustomException. errorCode
int errorCode = 0;
// parse response.getStatusCode() or equivalent of the library and reassign the value of errorCode
throw new MyCustomException(e, e.getMessage(), errorCode);
}
// ...
// otherCode which might cause IOException
} catch (Exception | IOException e) {
throw new MyCustomException(e, e.getMessage(), 0);
}
I am new to android apps development. Recently,Im writing an application which able to show public ip based on Ipify. So far, i already:
Download the required jar file and put inside libs folder
I also compile file within gradle
Then i import required class it to my class
How to use Ipify, according to its website:
import org.ipify.Ipify;
public class HelloIP {
public static void main(String[] args) throws IOException {
System.out.println(Ipify.getPublicIp());
}
}
I write the following method to be invoked from another class:
public static String getPublicIp() throws IOException{
String ip = Ipify.getPublicIp();
return ip;
}
Another Class
//Get wifi
getWifiName wifiInfo = new getWifiName();
String myIP = wifiInfo.getPublicIp();
However, i keep getting:
Error:(52, 43) error: unreported exception IOException; must be caught
or declared to be thrown
I tried to modify the code and use the following try and catch, but still got the same error.
public static String getPublicIp() throws IOException{
String myip = Ipify.getPublicIp();
try{
return myip;
}
catch (IOException e){
System.out.println("General I/O exception: " + e.getMessage());
e.printStackTrace();
}
}
Im not too good in catch and throw exception, and already spent the whole day for this.I dont have idea anymore to fix this error..T.T
public static String getPublicIp() {
try{
return Ipify.getPublicIp();
}catch (IOException e){
System.out.println("General I/O exception: " + e.getMessage());
e.printStackTrace();
}
return null;
}
In case it didn't help, clean project in your IDE. You may have some data cached and it might be a reason.
Your problem is in another class! As you have declared the method getPublicIp() to throw IOException that class is afraid of receiving the Exception and therefor requests catching it.
In Java you have two types of Exceptions. Checked and unchecked. Checked Exceptions must be caught.
In Java Exceptions are used for marking unexpected situations. For example parsing non-numeric String to a number (NumberFormatException) or calling a method on a null reference (NullPointerException). You can catch them in many ways.
Unchecked Exceptions are those which extend RunTimeException. They are used for marking unexpected states usually caused by user's input. They shouldn't cause harm and should be worked out with business logic. You don't have to catch them, but sometimes you should.
On the other hand there are Checked Exceptions which mark dangerous situations. For example the application being unable to open a file. As those situations are found dangerous, you must catch them.
try{
//some code
} catch (NumberFormatException e1) {
e.printStackTrace() //very important - handles the Exception but prints the information!
} catch (NullPointerException e2) {
e.printStackTrace();
}
or using the fact, that they all extend Exception:
try {
//somecode
} catch (Exception e) {
e.printStackTrace;
};
or since Java 7:
try {
//somecode
} catch (NullPointerException | NumberFormatException e) {
e.printStackTrace;
};
I have a unique constraint on one of my entities and whenever I get a PSQLException which occurs whenever that constraint is violated, I want to respond with a bad request.
This is my exception handler which I tried to implement:
#ControllerAdvice
public class DatabaseExceptionHandler {
#ExceptionHandler(value = PSQLException.class)
#ResponseStatus(HttpStatus.BAD_REQUEST)
public void handleDatabaseExceptions(PSQLException e) {
// i want to respond with a bad request only when this condition is satisfied
//
// if (e.getSQLState().equals("23505")) {
//
// }
}
}
And this is where the model is saved in db:
public DepartmentForHoliday setDepartment(DepartmentForHoliday department) {
if (department.getDepartmentId() == null) {
Department savedDepartment = new Department();
savedDepartment.setName(department.getName());
try {
departmentRepository.save(savedDepartment);
} catch (PSQLException e) {
/*here i have a compiler error which says that this exception is never thrown in the corresponding try block, but where ?*/
}
}
This is the exception that is thrown when I add a duplicate entry:
org.postgresql.util.PSQLException: ERROR: duplicate key value violates unique constraint "uk_1t68827l97cwyxo9r1u6t4p7d"
Detail: Key (name)=(Tech) already exists.
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2458) ~[postgresql-9.4.1211.jre7.jar:9.4.1211.jre7]
How to handle PSQLExceptions ? Should I make my own exception as a wrapper or how to solve this problem ?
Key problem is that PSQLException is wrapped into some Spring exception (which I assume from your code); you have to unwrap it (for example using guava's Throwables):
public DepartmentForHoliday setDepartment(DepartmentForHoliday department) {
if (department.getDepartmentId() == null) {
Department savedDepartment = new Department();
savedDepartment.setName(department.getName());
try {
departmentRepository.save(savedDepartment);
} catch (RuntimeException e) {
Throwable rootCause = com.google.common.base.Throwables.getRootCause(e);
if (rootCause instanceof SQLException) {
if ("23505".equals(((SQLException) rootCause).getSQLState())) {
// do smth interesting :)
}
}
}
}
}
Once you do that you can throw your custom exception and handle it in DatabaseExceptionHandler
You are catching PSQLException. Instead of that, please catch SQLException. With SQLException you will can handle all this SQL exceptions.
You can check the SQLException knowledge at this link
Then in your code just treat the SQLException as you want. The most generic catch clause is the following one:
catch (SQLException e)
{
System.out.println("ERROR: Fetch statement failed: " +
e.getMessage());
}
With this code you are printing the exception. If you want more information, check this
This is quite late, but building on previous responses I was able to solve it as so:
try {
return this.projectRepository.saveAndFlush(patchedProjectEntity);
} catch (DataIntegrityViolationException e) {
if (e.getMostSpecificCause().getClass().getName().equals("org.postgresql.util.PSQLException") && ((SQLException) e.getMostSpecificCause()).getSQLState().equals("23505"))
throw new UniqueConstraintViolationException("", e.getMostSpecificCause());
throw e;
}
Where UniqueConstraintViolationException is a custom exception and handled with a spring controller advice.
You might as well register an exception handler for that wrapped exception (that #radek mentioned) directly.
In your case that's:
#ExceptionHandler(DataIntegrityViolationException::class)
protected fun handleDataIntegrityException(ex: DataIntegrityViolationException, request: WebRequest) : ResponseEntity<SomeBody>{
return ResponseEntity.badRequest().body(someBodyHere)
}
The error is converted within convertHibernateAccessException in org.springframework.orm.jpa.vendorHibernateJpaDialect, which has already processed away from PSQL. You can add a breakpoint there and follow the stacktrace.
There is a lot of proxy'ing happening under the hood, but the takeaway is that there is always a readable, expressive Exception to use directly.
I have this code where I'm catching some exception and throwing a custom exception instead.
#Override
public void config() throws CustomException{
File jsonFile = new File("config.json");
try {
ConfigMapper config = mapper.readValue(jsonFile, ConfigMapper.class);
try {
this.instanceId = Integer.parseInt(config.getConfig().getClientId());
this.configParams = config.getConfig().getConfigParams();
} catch (NumberFormatException ex) {
throw new CustomException("Please provide a valid integer for instance ID", ex);
//LOGGER.log(Level.SEVERE, "error initializing instanceId. Should be an integer " + e);
}
} catch (IOException ex) {
throw new CustomException("Error trying to read/write", ex);
// LOGGER.log(Level.SEVERE, "IOException while processing the received init config params", e);
}
}
I need to write a unit test for this and below is how I wrote it.
#Test
public void should_throw_exception_when_invalid_integer_is_given_for_instanceID(){
boolean isExceptionThrown = false;
try{
Mockito.doThrow(new NumberFormatException()).when(objectMock).config();
barcodeScannerServiceMock.config();
} catch (CustomException ex) {
isExceptionThrown = true;
}
assertTrue(isExceptionThrown);
}
But its throwing a number format exception and not the CustomException as I want it to be. But this makes sense as I'm using the mock object to throw the exception as a result of which my code logic is not executed. But if that's the case, how do I test this scenario? Please advice.
1.) Remove the line Mockito.doThrow(new NumberFormatException()).when(objectMock).config();
2.) Change the Client-ID in your JSON-File to something that cannot be converted to an Integer.
this.instanceId = Integer.parseInt(config.getConfig().getClientId()); will fail due to that and thus throw an exception.
One advice regarding names: The name of your test method should be what's written in the Java-Doc. Just name it "testCustomException" & explain the methods function in the Java-Documentation. There are Naming-Conventions in Java (click here) which are basically general guidelines.
Practicing these is very helpful as it allows you to quickly get into your code again after not working on it for a month or so due to the increased readability.
This is my Exception:
public class MyException extends Exception {
private String errorCode="Unknown_Exception";
public MyException(String message, String errorCode){
super(message);
this.errorCode=errorCode;
}
public String getErrorCode(){
return this.errorCode;
}
}
Now immagine the next scenario, the code is way too long to paste here:
1 I got a Presentation class made in Swing in Presentation package
2 In package calculations I made simple operations with few numbers from received database fields
3 In package connections I got the database connections
Trouble comes here:
-In presentation layer I catch all errors, like this:
try {
//here is a method called updateCombo() wich throws:
//throw new MyException(e.getMessage(),"ERROR_UPDATING_COMBO_BOX");
} catch (MyException ex) {
try {
//Here we process error code, if error is not defined, uses default errors.
processCode(ex);
} catch (MyException ex1) {
Logger.getLogger(Presentacion.class.getName()).log(Level.SEVERE, null, ex1);
}
}
processCode is a simple list with cases, like this:
private void processCode(MyException e) throws MyException {
switch (e.getErrorCode()) {
case "ERROR_UPDATING_COMBO_BOX":
lblErrorText.setText("Error updating combo.");
throw e;
case "ERROR_SELECTING_PRIMARY_KEY":
lblErrorText.setText("Error selecting PK");
throw e;
case "ERROR_OPENING_CONNECTION":
lblErrorText.setText("Error opening connection.");
throw e;
default:
lblErrorText.setText("Excepcion not defined: "+ e.getMessage());
e.printStackTrace();
}
This is the scenario, the connection fails in 3rd package and leads to this:
throw new MyException(e.getMessage(),"ERROR_OPENING_CONNECTION");
As I said, the error is thrown to the upper layer with throws clause in method header, this beeing 2nd package.
2nd package also throws a new exception to Presentation, because of failing connection:
throw new MyException(e.getMessage(),"ERROR_SELECTING_PRIMARY_KEY");
Presentation methods also throw this exception becase 2nd layer failed:
throw new MyException(e.getMessage(),"ERROR_UPDATING_COMBO_BOX");
The main problem:
Using debug i found out that the program does what it has to do. It gets to the connection layer and does this successfully:
throw new MyException(e.getMessage(),"ERROR_OPENING_CONNECTION");
But, in 2nd layer, calculations, if connection fails it throws a new exception:
throw new MyException(e.getMessage(),"ERROR_SELECTING_PRIMARY_KEY");
This is the problem:
throw new
throwing new exception overrides ERROR_OPENING_CONNECTION with ERROR_SELECTING_PRIMARY_KEY. When it gets to presentation due to its "throw new" overrides ERROR_SELECTING_PRIMARY_KEY with ERROR_UPDATING_COMBO_BOX, resulting in the final error shown in the screen:
lblErrorText.setText("Error updating combo.");
Is there any way to return to presentation once first error is caught without overriding by next errors?
Maybe I misunderstood the concept but I want to catch all possible errors because:
-If connection is OK but method in 2nd layer fails it should throw ERROR_SELECTING_PRIMARY_KEY.
-If 2nd layer (calculations) does it OK but there is error in presentation it should lead to ERROR_UPDATING_COMBO_BOX.
You can use e.getCause() which will return a Throwable and check if this cause belongs to MyException. In case it is, you can check the e.getCause() again recursively until you obtain the deepest error code in the stacktrace and perform the validation for this exception.
Here's an example:
public MyException getDeepestException(MyException e) {
Throwable t = e.getCause();
if (t instanceof MyException) {
return getDeepestException((MyException)t);
}
return e;
}
As pointed out by #RealSkeptic, in order to use this approach, you will need to add an additional constructor to your custom exception:
public MyException(String message, Throwable cause, String errorCode){
super(message, cause);
this.errorCode = errorCode;
}
And when throwing your exception, call the proper constructor:
try {
//...
} catch (SomeException e) {
throw new MyException(<a proper message should be here>, e, "ERROR_SELECTING_PRIMARY_KEY");
}
If I understand you correctly, if the exception caught by one package happens to be a MyException, you want the original MyException to be passed up, otherwise (if the exception is some other type of Exception) you want to create a new MyException.
In this case, you should have two catch clauses.
try {
// Whatever you do in the try clause
} catch ( MyException myEx ) {
throw myEx;
} catch ( Exception e ) {
throw new MyException(e.getMessage(),"ERROR_SELECTING_PRIMARY_KEY");
}