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Improve error message when abstract class cannot be constructed (#1814)
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Marcono1234 authored Feb 4, 2022
1 parent 565b7a1 commit 47dea2e
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import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Modifier;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.ArrayDeque;
Expand Down Expand Up @@ -99,6 +100,11 @@ public <T> ObjectConstructor<T> get(TypeToken<T> typeToken) {
}

private <T> ObjectConstructor<T> newDefaultConstructor(Class<? super T> rawType) {
// Cannot invoke constructor of abstract class
if (Modifier.isAbstract(rawType.getModifiers())) {
return null;
}

final Constructor<? super T> constructor;
try {
constructor = rawType.getDeclaredConstructor();
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package com.google.gson.internal;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.fail;

import java.lang.reflect.Type;
import java.util.Collections;
import java.util.Map;

import org.junit.Test;

import com.google.gson.InstanceCreator;
import com.google.gson.reflect.TypeToken;

public class ConstructorConstructorTest {
private static final Map<Type, InstanceCreator<?>> NO_INSTANCE_CREATORS = Collections.emptyMap();

private abstract static class AbstractClass {
@SuppressWarnings("unused")
public AbstractClass() { }
}
private interface Interface { }

/**
* Verify that ConstructorConstructor does not try to invoke no-arg constructor
* of abstract class.
*/
@Test
public void testGet_AbstractClassNoArgConstructor() {
ConstructorConstructor constructorFactory = new ConstructorConstructor(NO_INSTANCE_CREATORS, true);
ObjectConstructor<AbstractClass> constructor = constructorFactory.get(TypeToken.get(AbstractClass.class));
try {
constructor.construct();
fail("Expected exception");
} catch (RuntimeException exception) {
assertEquals(
"Unable to create instance of class com.google.gson.internal.ConstructorConstructorTest$AbstractClass. "
+ "Registering an InstanceCreator or a TypeAdapter for this type, or adding a no-args constructor may fix this problem.",
exception.getMessage()
);
}
}

@Test
public void testGet_Interface() {
ConstructorConstructor constructorFactory = new ConstructorConstructor(NO_INSTANCE_CREATORS, true);
ObjectConstructor<Interface> constructor = constructorFactory.get(TypeToken.get(Interface.class));
try {
constructor.construct();
fail("Expected exception");
} catch (RuntimeException exception) {
assertEquals(
"Unable to create instance of interface com.google.gson.internal.ConstructorConstructorTest$Interface. "
+ "Registering an InstanceCreator or a TypeAdapter for this type, or adding a no-args constructor may fix this problem.",
exception.getMessage()
);
}
}
}

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