I have 3 fields (name, password, email). I want to check if they are valid or not. I wrote the following
public boolean isValidInput() {
if(name.isValid()){
return false;
}
if(password.isInValid()){
return false;
}
if(email.isInValid()){
return false;
}
return true;
}
so this will give me a single invalid. But what to do if I want to show the invalids all at the same time?
There are multiple ways you can handle this. But each of them need a change in the caller to handle these cases.
Create a custom exception which accepts a list of messages. Every time a validation failed add the error to the list, at the end of isValidInput() if the list is not empty then throw an exception with the list of errors.
Return the list of errors from above, instead of throwing exception.
Return a list of boolean variable and each index in the list will represent the status of a validation (name, email, etc)
Have an Enum of all fields that are present. Return a list of enum that failed. Empty list indicates that no error has occurred.
There are still a lot of other ways to handle this. It all depends on what suits you the best.
I would say, try some of them and see how it goes.
You could simply return an integer from the function like this
public int isValidInput() {
if(name.isValid()){
return 1;
}
if(password.isInValid()){
return 2;
}
if(email.isInValid()){
return 3;
}
return 0;
}
and then check the integer to find out which one failed!
It would be better of course to define static final ints with the names of the errors to make the code more readable and robust.
Related
I am using common FieldSetMapper logic found through searches and in examples on StackOverflow and I have run into a situation which surprised me. Either it is a feature or a bug, but I thought I would present it here for review to see how others handle it.
Using Spring Batch, I have a pipe delimited file which has string and number values which may by optional depending on position. For example:
string|string|number|number|string
string||number||string
In your field set mapper class which implements FieldSetMapper, you usually do some mapping such as:
newThingy.setString1(fieldSet.readString("string1"));
newThingy.setString2(fieldSet.readString("string2"));
newThingy.setValue1(fieldSet.readInt("value1"));
newThingy.setValue2(fieldSet.readInt("value2"));
newThingy.setString3(fieldSet.readString("string3"));
During testing the code for line 1 above worked fine.
For line 2 with the blank values for string2 and value, a Java exception was thrown for the number but not the string:
Caused by: java.lang.NumberFormatException: Unparseable number:
at org.springframework.batch.item.file.transform.DefaultFieldSet.parseNumber(DefaultFieldSet.java:754)
at org.springframework.batch.item.file.transform.DefaultFieldSet.readInt(DefaultFieldSet.java:323)
at org.springframework.batch.item.file.transform.DefaultFieldSet.readInt(DefaultFieldSet.java:335)
at com.healthcloud.batch.mapper.MemberFieldSetMapper.mapFieldSet(MemberFieldSetMapper.java:31)
at com.healthcloud.batch.mapper.MemberFieldSetMapper.mapFieldSet(MemberFieldSetMapper.java:1)
I did some research in the DefaultFieldSetMapper.java class provided by Spring Batch which implements the FieldSet class to try and understand what is going on.
What I found is that the readAndTrim function called by readString returns null if the value read is blank
protected String readAndTrim(int index) {
String value = tokens[index];
if (value != null) {
return value.trim();
}
else {
return null;
}
}
... but when using readInt (and maybe others) we are returning an exception.
private Number parseNumber(String candidate) {
try {
return numberFormat.parse(candidate);
}
catch (ParseException e) {
throw new NumberFormatException("Unparseable number: " + candidate);
}
}
I do see where you can return a default value in some of the methods, but null is obviously not allowed. What I would expect is consistent behavior between all methods in FieldSet implementations which allow one to match the file to my database as the data is read. Blank values in delimited and fixed length files are fairly common.
If number based values cannot be properly handled, I will probably have to convert everything over to String as it is read and then go through the trouble to manual handle the conversion to the database, which obviously defeats the purpose of using Spring Batch.
Am I missing something that I should handle better? I can add more code if needed, I just felt this is commonly used and I could keep this short. Will edit as needed.
Edit: Add info on Unit Tests found for Spring Batch class
The comments in the test case state a default should be set instead, but why? I don't want a default. My database allows a null value in the Integer column. I would have to set the default to some arbitrary number which hopefully no one EVER sends, check for it before insert and then switch to null on insert. I still don't like this "feature."
#Test
public void testReadBlankInt() {
// Trying to parse a blank field as an integer, but without a default
// value should throw a NumberFormatException
try {
fieldSet.readInt(13);
fail();
}
catch (NumberFormatException ex) {
// expected
}
try {
fieldSet.readInt("BlankInput");
fail();
}
catch (NumberFormatException ex) {
// expected
}
}
Always sanity check your input/data. I'll usually throw together a Util class with all the parse/read/verification I need. Bare bones version below...
public static Integer getInteger(FieldSet fs, String key, Integer default) {
if(StringUtils.isNumeric(fs.readString(key))) {
return fs.readInt(key);
} else {
return default;
}
}
I have a method that returns all the names of people in a LinkedList for a plane.
However even though there is a return statement in the method, I'm still getting told there is a missing return statement.
How can I work around this without putting another return statement in? Why isn't it considered valid? Does putting another return statement in change what is returned?
Any feedback is greatly appreciated.
public String check() {
for (Person person: passengers)
{
return person.getName();
}
}
Because if passengers is empty, the loop will never be entered.
If the loop is never entered, assuming the only return statement is in it, we have a serious problem, don't you think ? It's like if there were no return at all.
You need to add another return statement outside of the loop.
Also note that the return will automatically exit the method, so I don't think this is exactly what you wanted as per this sentence in your question :
I have a method that returns all the names of people in a LinkedList
for a plane.
Edit
As per your edit, here how you can return a list containing all names :
return passengers.
.stream()
.map(Person::getName)
.collect(Collectors.toList());
Note that you will need to change the signature of your method to
public List<String> check()
In answer to your question in the comments. You can only return a single object from a function. You could take another container and populate it with the names and return that. For example,
public LinkedList<String> check() {
LinkedList<String> names = new LinkedList<String>();
for (Person person: passengers) {
names.add( person.getName() );
}
return names;
}
What exactly are you trying to accomplish, here?
Currently, check will only ever return the name of the first passenger. Think about how your program flows and what you want it to do.
To answer your question, you need to have an 'escape' for every possible path in your code. Even if a certain block should always catch and return (not by definition, but just by how you think the code should flow), you need to handle the case such that that block doesn't catch and return. This can be done by either fixing the first block so that it really is a catch-all, or by simply returning or throwing an error if the first block doesn't catch.
i.e.
public boolean check() {
...
if (shouldAlwaysBeTrue) return false;
}
doesn't work because shouldAlwaysBeTrue is not true by definition.
public boolean check() {
...
if (shouldAlwaysBeTrue) return false;
return true;
}
I want to verify multiple conditions for validations. Currently, I have it set up such that in case of an error, each condition returns the error message, and an empty string in the absence of any errors. As a result, my code looks something like this:
String error = condition1(argA, argB);
if (!"".equals(error)) {
return error;
}
error = condition2(argC, argD);
.
.
.
and so on.
I wanted to know if there's a more elegant way of doing this in Java (or cofeescript)?
How about rather than having a lot of if statements you just create one method to check since if seems the check is the same for all conditions like.
public String check(String err)
{
if (!"".equals(err))
{
return err;
}
return err;
}
Now whenever you checking you just call the method
check(condition1(argA,argB));
and
check(condition2(argC,argB));
The string returned ofcause you know what to do with it.
Hope that helps
I'm refactoring a very large method with a lot of repetition in it.
In the method there are many while loops which include:
if ( count > maxResults){
// Send error response
sendResponse(XMLHelper.buildErrorXMLString("Too many results found, Please refine your search"), out, session);
break;
I want to extract this as a method, because it happens 3 times in this one method currently, but when I do so I get an error on the break as it is no longer within a loop. The problem is that it is still necessary to break out of the while loops, but only when the maximum number of results are reached.
Any suggestions?
Suppose the method is :
public boolean test(int count, int maXResult) {
if ( count > maxResults) {
// Send error response
sendResponse(XMLHelper.buildErrorXMLString("Too many results found, Please refine your search"), out, session);
return true;
}
return false;
}
Call method from loop as :
while(testCondition) {
if (test(count, maxResults)) {
break;
}
}
This is impossible to do directly.
Most often you want to break because you have found the solution and no longer have to search. So indicate in the called function that there is/was success, for instance by returning a result or a boolean to indicate success. And if the function returns success, then break.
If it is now within a method instead of the while loop have it return a value and then break based on that.
i.e.
public bool refactoredMethod(parameters)
{
if ( count > maxResults){
// Send error response
sendResponse(XMLHelper.buildErrorXMLString("Too many results found, Please refine your search"), out, session);
return true;
}
return false;
}
Try to break the loop in the method using return;
As Thriler says you cant do it directly. You could extract part of it to the method and do something like:
if(isTooManyResults(count)) { break; }
Obviously your isTooManyResults method would need to return true if there are too many results and false otherwise
I have a method from which i am returning object like
public static Object login(DataManager dataManager, String userName, String password)
ArrayList<LoginCredentialsBean> loginCredentialsList = new ArrayList<LoginCredentialsBean>();
String authenticated = "false";
Connection connection = null;
try {
connection = dataManager.getConnection();
} catch (Exception e) {
return ("Having problem in connectiong to databaste: " + e.getMessage());
}
if (connection != null) {
try {
...
try {
ResultSet rs = prepStatement.executeQuery();
try {
while (rs.next()) {
...
loginCredentialsList.add(new LoginCredentialsBean(roleId, orgaCode, passwordExpiryDate, date, status, language));
authenticated = "true";
} //end of while()
} finally {
rs.close();
}
} finally {
prepStatement.close();
}
if (authenticated.equals("true")) {
updateUserLogByInserting(connection, userName);
}
} catch(SQLException e) {
System.out.println("Could not login from dataabse:" + e.getMessage());
} finally {
dataManager.putConnection(connection);
}
}
if (authenticated.equals("true")) {
return loginCredentialsList;
} else {
return authenticated;
}
} //end of login()
Now i am testing it like
public static void main(String... args) {
MoneyTreeServices moneyTreeServices = new MoneyTreeServices();
Object result = moneyTreeServices.login("Admin", "cbas1234");
if (result instanceof ArrayList<?>) {
System.out.println("ArrayList instance");
}
System.out.println(result);
}
It returns me result like
ArrayList instance
[pk.mazars.moneyTree.bean.LoginCredentialsBean#b7ec5d]
I want to ask i am using condition like ArrayList<?>. How can i check that ArrayList that contain LoginCredentialsBean object. Like when i use
if (result instanceof ArrayList<LoginCredentialsBean>) {
}
i get error that
Can not perform instanceof check against parameterized type ArrayList<LoginCredentialsBean>. Use the form ArrayList<?>
I want to check instanceof ArrayList and arraylist has LoginCredentialsBean ?
Thank you.
The short answer is that you can't. Generics are implemented via type erasure - they're effectively a compile-time syntactic sugar to ensure you don't put an Integer into a List<String>.
The runtime objects themselves, however, are just the raw types. An instance of ArrayList doesn't know that it's an ArrayList<String> (or rather, that it was assigned to a variable with that generic type). So when you interrogate it with reflection, you cannot get any generic type info.
There are two broad types of solution I can think of. One is to iterate over the list contents and check their dynamic type - if the first element is a LoginCredentialsBean, for example, then it's reasonable to assume that you have a List<LoginCredentialsBean>. This won't work for empty lists though, which could be a problem, and can potentially give false positives (e.g. a List<Object> allParameters might happen to have a LoginCredentialsBean as its first element...)
The other is to explicitly pass metadata objects around - so in this case you'd return the Object from the login method, along with a token which describes what type of object it is. This could be a simple enum constant; or going to the other extreme you could make the tokens generically typed, such that the compiler can check this against the type of what you're returning and ensure that the tokens are type-correct.
But in any case, instanceof is too little (information), too late.
Mind you, your login method looks... odd. I don't think it should return an Object at all, as that's just lazy and completely subverting the static type system which would help you here. Rather, I think it should just return a List<LoginCredentialsBean> containing the credentials that pertain to the given login.
You have three different paths where you return. The first is if an exception is encountered when connecting to the database - in which case you should throw an exception! Returning a string with the error details is very atypical and confusing - an exceptional condition should be handled as an Exception, that's what they're for.
The other two situations are ones where you're able to look up definitive results. For the failed login case, I would just return an empty list (i.e. this username/password has no credentials whatsoever), while returning the populated list during a successful login.
If you strongly want to be able to distinguish between a login failure, and a successful login (with no credentials), then perhaps return a compound object instead, such as:
class LoginStatus {
final boolean authenticated;
final List<LoginCredentialsBean> credentials;
}
Either way, the caller knows exactly what they're getting back, and can call methods on it appropriately without having to call instanceof and typecast.
Parameterized type info is erased at compile time and instanceof is resolved at (fanfare) runtime - that is why you get that error.
What you could do is iterate over the elements in the List and instanceof them.
Cheers,
You have to check it twice.
if (result instanceof ArrayList<?>) {
System.out.println("ArrayList instance");
//cast
ArrayList<LoginCredentialsBean> list = (ArrayList<LoginCredentialsBean>) result;
///..check if list contains LoginCredentialsBean
for(int i=0; i<list.size(); i++){
if(list.get(i) instanceof LoginCredentialsBean){
System.out.println("LoginCredentialsBean instance");
}
}
}
There is no such thing like "ArrayList that contain LoginCredentialsBean"
ArrayList contains Objects, all the time.
you must iterate over the list and check each object:
for (Object o: result) {
if (!(o instanceof LoginCredentialsBean)) {
//Fail
}
}
you can use the contains(Object o) to check whether the ArrayList contains your object. With the instanceof List to check whether the given object is a List. Because of type erasure at runtime the generic type of the List wont be available
If your login method returns an Object type there is no way to check this the way you try.
Type parameters exist only on compile-time due to type erasure. You need to check if retuned object is a List or Collection or just Iterable, then iterate throuh it and check every item, if it is a instance of LoginCredentialsBean.
However, your code is an example of bad design. A method that returns a String or a list is just wrong. To make it right:
make it return List<LoginCredentialsBean>
throw a checked exception if authentication fails
public static List<LoginCredentialsBean> login(DataManager dataManager, String userName, String password) throws AuthenticationException {...}
Note: Use boolean to keep logical data instead of "true" or "false" strings.