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authorTavian Barnes <tavianator@tavianator.com>2015-07-10 22:01:30 -0400
committerTavian Barnes <tavianator@tavianator.com>2015-07-10 22:01:30 -0400
commit8c7d863828e0bf4b9045075ff3ccd386993dfbb5 (patch)
tree4c8c374d9abb26fea0d9c65a39a8e098c6f260d3
parent28fbf0859c63b2a30555b3295fe738c263c0db6b (diff)
downloadsangria-8c7d863828e0bf4b9045075ff3ccd386993dfbb5.tar.xz
lazy: Fix Lazy<T> when a provider returns null.
-rw-r--r--sangria-lazy/src/main/java/com/tavianator/sangria/lazy/Lazy.java11
-rw-r--r--sangria-lazy/src/test/java/com/tavianator/sangria/lazy/LazyTest.java27
2 files changed, 33 insertions, 5 deletions
diff --git a/sangria-lazy/src/main/java/com/tavianator/sangria/lazy/Lazy.java b/sangria-lazy/src/main/java/com/tavianator/sangria/lazy/Lazy.java
index adf531c..ee42a2f 100644
--- a/sangria-lazy/src/main/java/com/tavianator/sangria/lazy/Lazy.java
+++ b/sangria-lazy/src/main/java/com/tavianator/sangria/lazy/Lazy.java
@@ -56,8 +56,10 @@ import javax.inject.Provider;
* @since 1.2
*/
public final class Lazy<T> {
+ private static final Object SENTINEL = new Object();
+
private final Provider<T> provider;
- private volatile T instance = null;
+ private volatile Object instance = SENTINEL;
@Inject
Lazy(Provider<T> provider) {
@@ -67,15 +69,16 @@ public final class Lazy<T> {
/**
* @return A lazily-produced value of type {@code T}.
*/
+ @SuppressWarnings("unchecked")
public T get() {
// Double-checked locking
- if (instance == null) {
+ if (instance == SENTINEL) {
synchronized (this) {
- if (instance == null) {
+ if (instance == SENTINEL) {
instance = provider.get();
}
}
}
- return instance;
+ return (T) instance;
}
}
diff --git a/sangria-lazy/src/test/java/com/tavianator/sangria/lazy/LazyTest.java b/sangria-lazy/src/test/java/com/tavianator/sangria/lazy/LazyTest.java
index ee6200a..a451a96 100644
--- a/sangria-lazy/src/test/java/com/tavianator/sangria/lazy/LazyTest.java
+++ b/sangria-lazy/src/test/java/com/tavianator/sangria/lazy/LazyTest.java
@@ -36,6 +36,7 @@ import com.google.inject.Provider;
import com.google.inject.spi.DefaultBindingTargetVisitor;
import com.google.inject.spi.Element;
import com.google.inject.spi.Elements;
+import com.google.inject.util.Providers;
import org.junit.Test;
import static com.tavianator.sangria.test.SangriaMatchers.*;
@@ -62,15 +63,26 @@ public class LazyTest {
@Singleton
private static class CountingProvider implements Provider<Abstract> {
int count = 0;
+ private final Provider<Abstract> impl;
@Inject
CountingProvider() {
+ this.impl = new Provider<Abstract>() {
+ @Override
+ public Abstract get() {
+ return new Abstract() { };
+ }
+ };
+ }
+
+ CountingProvider(Abstract instance) {
+ this.impl = Providers.of(instance);
}
@Override
public Abstract get() {
++count;
- return new Abstract() { };
+ return impl.get();
}
}
@@ -186,6 +198,19 @@ public class LazyTest {
assertThat(module, followsBestPractices());
}
+ @Test
+ public void testNull() {
+ Module module = new AbstractModule() {
+ @Override
+ protected void configure() {
+ bind(CountingProvider.class)
+ .toInstance(new CountingProvider(null));
+ }
+ };
+
+ test(Guice.createInjector(module), HasLazy.class);
+ }
+
@Test(expected = CreationException.class)
public void testMissingBinding() {
Guice.createInjector(new AbstractModule() {