Escape % symbol in a java string to apply String.format

Question

In my project (Java/Play framework) I have an error handling routing that checks the response from a web service if the response is an error code, we display the corresponding error message saying what was the problem with the user input, the service checks user input validity.

When the user enter an % symbol, this logic breaks because the error display logic uses

String.format(message, messageArgs);

Which interpolates the messageArgs intro the message String where it finds an %, and if the messageArgs contains an % as well I get an exception.

I need to sanitize, escape or otherwise remove the % from the user inputs, before displaying the message.

message: The requested email address %s is invalid messageArgs: [e-mail]

Any advice on how to do this in Java in the simplest, shortest way?

here's a part of the error log

 java.util.UnknownFormatConversionException: Conversion = 'i'
   at java.util.Formatter$FormatSpecifier.conversion(Formatter.java:2646)
   at java.util.Formatter$FormatSpecifier.<init>(Formatter.java:2675)
   at java.util.Formatter.parse(Formatter.java:2528)
   at java.util.Formatter.format(Formatter.java:2469)
   at java.util.Formatter.format(Formatter.java:2423)
   at java.lang.String.format(String.java:2797)
   at controllers.api.PublicAPI.renderAPIError(PublicAPI.java:176)
   at controllers.api.DeviceAPI.setEmailAddress(DeviceAPI.java:736)
   at play.mvc.ActionInvoker.invokeWithContinuation(ActionInvoker.java:557)
   at play.mvc.ActionInvoker.invoke(ActionInvoker.java:508)
   at play.mvc.ActionInvoker.invokeControllerMethod(ActionInvoker.java:484)
   at play.mvc.ActionInvoker.invokeControllerMethod(ActionInvoker.java:479)
   at play.mvc.ActionInvoker.invoke(ActionInvoker.java:161)
   at Invocation.HTTP Request(Play!)

Thanks!

Ackley

Can you show the error message? I don't think presence of % in messageArgs will be any issue. – Finella

Can you post an example of input that fails? – Choice

Ready just edited the post – Ackley

It will be an issue if use String#format – Ultramarine

I don't get what you mean @archer – Ackley

Hmm. You need to show us the format string - message, and messageArg for which input fails. – Finella

Is this one @RohitJain message: The requested email address %s is invalid messageArgs: [e-mail] – Ackley

Those inputs can't give the exception you have shown. – Finella

Answer 1

In message String, the % sign is escaped with another %. So you will need to double it up: %%
For example: "Bla bla %i bla" -> "Bla bla %%i bla"
In messageArgs String, there is no problem with the % sign and you don't need to escape it

Folse

Answer 2

Use %% in the formatter string when you need to print string %:

String.format("sendOneSuccessCountRate: %7.2f%%"
              ,sendOneSuccessCountRate //0.95
             );

will give you 95.00%

Sixtyfour

Answer 3

If you receive java.util.UnknownFormatConversionException: Conversion = 'i' most possibly you use %i in your message trying to format an integer, this is not correct. You must use %d to format the deciamal integer. Full supported conversion specification could be found here.

Ultramarine