JDK 11.0.2 compilation fails with javac NPE on anonymous parameterized class type inference
JavaJavacType InferenceJava 11Compiler BugJava Problem Overview
Code (spring-web 5.1.2)
public static void main(String[] args) {
RestTemplate restTemplate = new RestTemplate();
HttpHeaders headers = new HttpHeaders();
headers.set(HttpHeaders.AUTHORIZATION, "token");
HttpEntity<Object> requestEntity = new HttpEntity<>(headers);
ResponseEntity<Object> test = restTemplate.exchange(
"https://example.com",
HttpMethod.GET,
new HttpEntity<>(headers),
new ParameterizedTypeReference<>() { // fails here
});
}
OracleJDK 1.8 (expected output)
> cannot infer type arguments for
> org.springframework.core.ParameterizedTypeReference
> reason: cannot use '<>' with anonymous inner classes
OracleJDK 11.0.2 (not expected output)
> compiler message file broken: key=compiler.misc.msg.bug
> arguments=11.0.2, {1}, {2}, {3}, {4}, {5}, {6}, {7}
> java.lang.NullPointerException at
> jdk.compiler/com.sun.tools.javac.comp.Flow$FlowAnalyzer.visitApply(Flow.java:1235)
> at
> jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1634)
> at
> jdk.compiler/com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
> at
> jdk.compiler/com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:398)
> at
> jdk.compiler/com.sun.tools.javac.comp.Flow$FlowAnalyzer.visitVarDef(Flow.java:989)
> ...
If I change diamond operator to explicit type
new ParameterizedTypeReference<>(){}
to new ParameterizedTypeReference<Object>(){}
then the code compiles successfully on both JDKs.
Is it a known compiler bug?
Java Solutions
Solution 1 - Java
Bug (JDK-8212586) has been already submitted and fixed in version 12.
Minimal, verifiable example:
public static void main(String[] args) {
new Bug<>(){};
}
static class Bug<T> {
Bug() {
test(new ParameterizedTypeReference<>(){});
}
void test(ParameterizedTypeReference<T> typeReference) {
}
}
Fix has been also backported to JDK 11 - https://bugs.openjdk.java.net/browse/JDK-8220578.
Available starting JDK 11.0.4.
Solution 2 - Java
I Had the same error,you need to create a function :
ParameterizedTypeReference<Object> createParameterizedTypeReference(){ return new ParameterizedTypeReference<>(){}; }
and call it :
ResponseEntity<Object> test = restTemplate.exchange(
"https://example.com",
HttpMethod.GET,
new HttpEntity<>(headers),
createParameterizedTypeReference() {
});
Solution 3 - Java
As pointed out in previous comments, the problem is with parametrized anonymous classes, e.g. when using TypeToken from Guava, this does NOT work:
public List<SomeClass> list() {
return getData(new TypeToken<>() { });
}
But this DOES work:
public List<SomeClass> list() {
return getData(new TypeToken<List<SomeClass>>() { });
}
I tried that in versions 11.0.3 - 11.0.7 versions and all contains the bug.
Solution 4 - Java
Java 11.0.7 has the same problem.
This changed from:
new ParameterizedTypeReference<>() {
})
to this:
new ParameterizedTypeReference<HashMap<String, MyClass>>() {
})
Solution 5 - Java
I've fixed this problem on my machine by upgrading to AdoptOpenJDK 11.0.8.