Optional parameter in web method now raises error, breaks compatibility with the past [SPR-10584]

[spring-projects-issues]

Alex opened SPR-10584 and commented

A sample method defined as follows:

@RequestMapping(value = "/test")
public String testMethod(Integer n) {
if (n == null)
// do something
else
// do something else
}

stopped working in Spring 3.2.3 (works fine up to 3.2.2) because calling the url like:
http://hostname/context/test?n=
raises a MissingServletRequestParameterException while it should not (it should put a null in n) breaking completely the compatibility with existing apps.

---

Affects: 3.2.3

Issue Links:

• Revert change for SPR-10402 that allowed treating empty values as missing values [SPR-10578] #15207 Revert change for SPR-10402 that allowed treating empty values as missing values ("duplicates")
• Request @RequestParam not enforced with empty values [SPR-10402] #15035 Request @RequestParam not enforced with empty values

0 votes, 5 watchers

[spring-projects-issues]

Rossen Stoyanchev commented

This is most likely the same issue as #15207.

A couple of quick questions. The title says "optional" but in the example it looks like it is required (otherwise it would need to be @RequestParam(required=false)). Also I presume that you have a PropertyEditor or Converter that turns the empty parameter value into null? Neither of these questions changes the fact this is a bug. I'm just confirming.

[spring-projects-issues]

Alex commented

As I understand the specs (and as I always used, like in the provided example), when I declare a parameter without adding the @RequestParam annotation it implies required=false, while if I use it then it implies required=true.

And that's very neat because it leaves the code cleaner.

[spring-projects-issues]

Rossen Stoyanchev commented

The default is required actually if you look in the annotation source:

@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestParam {

	// ... 

	/**
	 * Whether the parameter is required.
	 * <p>Default is {@code true}, leading to an exception thrown in case
	 * of the parameter missing in the request. Switch this to {@code false}
	 * if you prefer a {@code null} in case of the parameter missing.
	 * <p>Alternatively, provide a {@link #defaultValue() defaultValue},
	 * which implicitly sets this flag to {@code false}.
	 */
	boolean required() default true;


	// ... 

[spring-projects-issues]

Rossen Stoyanchev commented

This is fixed with #15207 and will be in 3.2.4 and 4.0.M2