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Java example source code file (Java8LanguageFeatureBindingTest.java)

This example Java source code file (Java8LanguageFeatureBindingTest.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstractmodule, atomicinteger, callable, exception, hello, injector, key, override, predicate, provides, runtimeexception, string, stringprovider, threading, threads, util, uuid

The Java8LanguageFeatureBindingTest.java Java example source code

/**
 * Copyright (C) 2014 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.inject.jdk8;

import com.google.inject.AbstractModule;
import com.google.inject.CreationException;
import com.google.inject.Guice;
import com.google.inject.Inject;
import com.google.inject.Injector;
import com.google.inject.Key;
import com.google.inject.Provider;
import com.google.inject.Provides;
import com.google.inject.ProvisionException;
import com.google.inject.TypeLiteral;

import junit.framework.TestCase;

import java.util.Collections;
import java.util.UUID;
import java.util.concurrent.Callable;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Predicate;

/**
 * Test bindings to lambdas, method references, etc.
 *
 * @author cgdecker@google.com (Colin Decker)
 */
public class Java8LanguageFeatureBindingTest extends TestCase {

  // Some of these tests are kind of weird.
  // See https://github.com/google/guice/issues/757 for more on why they exist.

  public void testBinding_lambdaToInterface() {
    Injector injector = Guice.createInjector(new AbstractModule() {
      @Override
      protected void configure() {
        bind(new TypeLiteral<Predicate() {}).toInstance(o -> o != null);
      }
    });

    Predicate<Object> predicate = injector.getInstance(new Key>() {});
    assertTrue(predicate.test(new Object()));
    assertFalse(predicate.test(null));
  }

  public void testProviderMethod_returningLambda() throws Exception {
    Injector injector = Guice.createInjector(new AbstractModule() {
      @Override
      protected void configure() {}

      @Provides
      public Callable<String> provideCallable() {
        return () -> "foo";
      }
    });

    Callable<String> callable = injector.getInstance(new Key>() {});
    assertEquals("foo", callable.call());
  }

  public void testProviderMethod_containingLambda_throwingException() throws Exception {
    Injector injector = Guice.createInjector(new AbstractModule() {
      @Override
      protected void configure() {}

      @Provides
      public Callable<String> provideCallable() {
        if (Boolean.parseBoolean("false")) { // avoid dead code warnings
          return () -> "foo";
        } else {
          throw new RuntimeException("foo");
        }
      }
    });

    try {
      injector.getInstance(new Key<Callable() {});
    } catch (ProvisionException expected) {
      assertTrue(expected.getCause() instanceof RuntimeException);
      assertEquals("foo", expected.getCause().getMessage());
    }
  }

  public void testProvider_usingJdk8Features() {
    try {
      Guice.createInjector(new AbstractModule() {
        @Override
        protected void configure() {
          bind(String.class).toProvider(StringProvider.class);
        }
      });

      fail();
    } catch (CreationException expected) {
    }

    UUID uuid = UUID.randomUUID();
    Injector injector = Guice.createInjector(new AbstractModule() {
      @Override
      protected void configure() {
        bind(UUID.class).toInstance(uuid);
        bind(String.class).toProvider(StringProvider.class);
      }
    });

    assertEquals(uuid.toString(), injector.getInstance(String.class));
  }

  private static final class StringProvider implements Provider<String> {
    private final UUID uuid;

    @Inject
    StringProvider(UUID uuid) {
      this.uuid = uuid;
    }

    @Override
    public String get() {
      return Collections.singleton(uuid).stream()
          .map(UUID::toString)
          .findFirst().get();
    }
  }

  public void testBinding_toProvider_lambda() {
    Injector injector = Guice.createInjector(new AbstractModule() {
      @Override
      protected void configure() {
        AtomicInteger i = new AtomicInteger();
        bind(String.class).toProvider(() -> "Hello" + i.incrementAndGet());
      }
    });

    assertEquals("Hello1", injector.getInstance(String.class));
    assertEquals("Hello2", injector.getInstance(String.class));
  }

  public void testBinding_toProvider_methodReference() {
    Injector injector = Guice.createInjector(new AbstractModule() {
      @Override
      protected void configure() {
        bind(String.class).toProvider(Java8LanguageFeatureBindingTest.this::provideString);
      }
    });

    Provider<String> provider = injector.getProvider(String.class);
    assertEquals("Hello", provider.get());
  }

  private String provideString() {
    return "Hello";
  }
}

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