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Java example source code file (NullableInjectionPointTest.java)

This example Java source code file (NullableInjectionPointTest.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, annotation, customnullablefoofield, customnullablefoomethod, documented, foo, inject, injecting, injector, nullable, nullablefooconstructor, nullablefoomethod, provider, provisionexception, target

The NullableInjectionPointTest.java Java example source code

package com.google.inject;

import static com.google.inject.Asserts.assertContains;
import static com.google.inject.Asserts.getDeclaringSourcePart;

import junit.framework.TestCase;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * @author jessewilson@google.com (Jesse Wilson)
 */
public class NullableInjectionPointTest extends TestCase {

  public void testInjectNullIntoNotNullableConstructor() {
    try {
      createInjector().getInstance(FooConstructor.class);
      fail("Injecting null should fail with an error");
    }
    catch (ProvisionException expected) {
      assertContains(
          expected.getMessage(),
          "null returned by binding at " + getClass().getName(),
          "the 1st parameter of " + FooConstructor.class.getName() + ".<init>(", 
          "is not @Nullable");
    }
  }

  public void testInjectNullIntoNotNullableMethod() {
    try {
      createInjector().getInstance(FooMethod.class);
      fail("Injecting null should fail with an error");
    }
    catch (ProvisionException expected) {
      assertContains(
          expected.getMessage(),
          "null returned by binding at " + getClass().getName(),
          "the 1st parameter of " + FooMethod.class.getName() + ".setFoo(",
          "is not @Nullable");
    }
  }

  public void testInjectNullIntoNotNullableField() {
    try {
      createInjector().getInstance(FooField.class);
      fail("Injecting null should fail with an error");
    }
    catch (ProvisionException expected) {
      assertContains(expected.getMessage(),
          "null returned by binding at " + getClass().getName(),
          " but " + FooField.class.getName() + ".foo",
          " is not @Nullable");
    }
  }

  /**
   * Provider.getInstance() is allowed to return null via direct calls to
   * getInstance().
   */
  public void testGetInstanceOfNull() {
    assertNull(createInjector().getInstance(Foo.class));
  }

  public void testInjectNullIntoNullableConstructor() {
    NullableFooConstructor nfc
        = createInjector().getInstance(NullableFooConstructor.class);
    assertNull(nfc.foo);
  }

  public void testInjectNullIntoNullableMethod() {
    NullableFooMethod nfm
        = createInjector().getInstance(NullableFooMethod.class);
    assertNull(nfm.foo);
  }

  public void testInjectNullIntoNullableField() {
    NullableFooField nff
        = createInjector().getInstance(NullableFooField.class);
    assertNull(nff.foo);
  }
  
  public void testInjectNullIntoCustomNullableConstructor() {
    CustomNullableFooConstructor nfc
        = createInjector().getInstance(CustomNullableFooConstructor.class);
    assertNull(nfc.foo);
  }

  public void testInjectNullIntoCustomNullableMethod() {
    CustomNullableFooMethod nfm
        = createInjector().getInstance(CustomNullableFooMethod.class);
    assertNull(nfm.foo);
  }

  public void testInjectNullIntoCustomNullableField() {
    CustomNullableFooField nff
        = createInjector().getInstance(CustomNullableFooField.class);
    assertNull(nff.foo);
  }  

  private Injector createInjector() {
    return Guice.createInjector(
        new AbstractModule() {
          protected void configure() {
            bind(Foo.class).toProvider(new Provider<Foo>() {
              public Foo get() {
                return null;
              }
            });
          }
        });
  }

  /**
   * We haven't decided on what the desired behaviour of this test should be...
   */
  public void testBindNullToInstance() {
    try {
      Guice.createInjector(new AbstractModule() {
        protected void configure() {
          bind(Foo.class).toInstance(null);
        }
      });
      fail();
    } catch (CreationException expected) {
      assertContains(expected.getMessage(),
          "Binding to null instances is not allowed.",
          "at " + getClass().getName(), getDeclaringSourcePart(getClass()));
    }
  }

  public void testBindNullToProvider() {
    Injector injector = Guice.createInjector(new AbstractModule() {
      protected void configure() {
        bind(Foo.class).toProvider(new Provider<Foo>() {
          public Foo get() {
            return null;
          }
        });
      }
    });
    assertNull(injector.getInstance(NullableFooField.class).foo);
    assertNull(injector.getInstance(CustomNullableFooField.class).foo);

    try {
      injector.getInstance(FooField.class);
    }
    catch(ProvisionException expected) {
      assertContains(expected.getMessage(), "null returned by binding at");
    }
  }

  public void testBindScopedNull() {
    Injector injector = Guice.createInjector(new AbstractModule() {
      protected void configure() {
        bind(Foo.class).toProvider(new Provider<Foo>() {
          public Foo get() {
            return null;
          }
        }).in(Scopes.SINGLETON);
      }
    });
    assertNull(injector.getInstance(NullableFooField.class).foo);
    assertNull(injector.getInstance(CustomNullableFooField.class).foo);

    try {
      injector.getInstance(FooField.class);
    }
    catch(ProvisionException expected) {
      assertContains(expected.getMessage(), "null returned by binding at");
    }
  }

  public void testBindNullAsEagerSingleton() {
    Injector injector = Guice.createInjector(new AbstractModule() {
      protected void configure() {
        bind(Foo.class).toProvider(new Provider<Foo>() {
          public Foo get() {
            return null;
          }
        }).asEagerSingleton();
      }
    });
    assertNull(injector.getInstance(NullableFooField.class).foo);
    assertNull(injector.getInstance(CustomNullableFooField.class).foo);

    try {
      injector.getInstance(FooField.class);
      fail();
    } catch(ProvisionException expected) {
      assertContains(expected.getMessage(), "null returned by binding "
          + "at com.google.inject.NullableInjectionPointTest");
    }
  }

  static class Foo { }

  static class FooConstructor {
    @Inject FooConstructor(Foo foo) { }
  }
  static class FooField {
    @Inject Foo foo;
  }
  static class FooMethod {
    @Inject
    void setFoo(Foo foo) { }
  }

  static class NullableFooConstructor {
    Foo foo;
    @Inject NullableFooConstructor(@Nullable Foo foo) {
      this.foo = foo;
    }
  }
  static class NullableFooField {
    @Inject @Nullable Foo foo;
  }
  static class NullableFooMethod {
    Foo foo;
    @Inject void setFoo(@Nullable Foo foo) {
      this.foo = foo;
    }
  }
  
  static class CustomNullableFooConstructor {
    Foo foo;
    @Inject CustomNullableFooConstructor(@Namespace.Nullable Foo foo) {
      this.foo = foo;
    }
  }
  
  static class CustomNullableFooField {
    @Inject @Namespace.Nullable Foo foo;
  }
  static class CustomNullableFooMethod {
    Foo foo;
    @Inject void setFoo(@Namespace.Nullable Foo foo) {
      this.foo = foo;
    }
  }

  @Documented
  @Retention(RetentionPolicy.RUNTIME)
  @Target({ElementType.PARAMETER, ElementType.FIELD})
  @interface Nullable { }
  
  static interface Namespace {
    @Documented
    @Retention(RetentionPolicy.RUNTIME)
    @Target({ElementType.PARAMETER, ElementType.FIELD})
    @interface Nullable { }
  }
}

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