Context.json() does not throw checked exceptions that it actually throws

Actual behavior (the bug) context.json() throws JsonParseException but I’m unable to catch it in a proper way.

Expected behavior context.json() declares exceptions thrown by it.

To Reproduce An example to generate a JsonParseException error:

import io.javalin.Javalin;

public final class Main {
  public static void main(String[] args) {
    Javalin app = Javalin.create().start(12345);
    app.post("/json", ctx -> ctx.result(ctx.bodyAsClass(TestClass2.class).getName()));
  }
}

final class TestClass2 {
  private String name;

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }
}

Then a post of malformed JSON would trigger an exception, e.g. with “=” instead of “:”:

wget --post-data='{"name"="name"}' localhost:12345/json -O /dev/null -q

You get:

[qtpxxxxxxxxxx-xx] WARN io.javalin.core.ExceptionMapper - Uncaught exception
com.fasterxml.jackson.core.JsonParseException: Unexpected character ('=' (code 61)): was expecting a colon to separate field name and value
 at [Source: (String)"{"name"="name"}"; line: 1, column: 9]
	at com.fasterxml.jackson.core.JsonParser._constructError(JsonParser.java:1804)
...

If I try to wrap it with try-catch:

try {
  ctx.result(ctx.bodyAsClass(TestClass2.class).getName());
} catch (JsonParseException e) {
  e.printStackTrace();
}

The compiler would complain:

Exception 'com.fasterxml.jackson.core.JsonParseException' is never thrown in the corresponding try block

This is an error that I can’t ignore it like a warning.

Additional context I’m doing something like this at the time being:

try {
  ctx.result(ctx.bodyAsClass(TestClass2.class).getName());
} catch (Exception e) {
  if (e instanceof JsonParseException) {
    e.printStackTrace();
  }
}

This at least allows me to compile, though there is an IDE warning highlighting:

Condition 'e instanceof JsonParseException' is always 'false' less

[tipsy]

@avshenuk that’s correct, you’ll have to validate it manually if you want to catch your own exception.

[azurvii]

Thanks @tipsy. This is an interesting way of handling exceptions.