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Java example source code file (MembersInjectorLookup.java)

This example Java source code file (MembersInjectorLookup.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

element, membersinjector, membersinjectorlookup, object, override, string, this, typeliteral

The MembersInjectorLookup.java Java example source code

/**
 * Copyright (C) 2009 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.spi;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;

import com.google.inject.Binder;
import com.google.inject.MembersInjector;
import com.google.inject.TypeLiteral;

/**
 * A lookup of the members injector for a type. Lookups are created explicitly in a module using
 * {@link com.google.inject.Binder#getMembersInjector(Class) getMembersInjector()} statements:
 * <pre>
 *     MembersInjector<PaymentService> membersInjector
 *         = getMembersInjector(PaymentService.class);</pre>
 *
 * @author crazybob@google.com (Bob Lee)
 * @since 2.0
 */
public final class MembersInjectorLookup<T> implements Element {

  private final Object source;
  private final TypeLiteral<T> type;
  private MembersInjector<T> delegate;

  public MembersInjectorLookup(Object source, TypeLiteral<T> type) {
    this.source = checkNotNull(source, "source");
    this.type = checkNotNull(type, "type");
  }

  public Object getSource() {
    return source;
  }

  /**
   * Gets the type containing the members to be injected.
   */
  public TypeLiteral<T> getType() {
    return type;
  }

  public <T> T acceptVisitor(ElementVisitor visitor) {
    return visitor.visit(this);
  }

  /**
   * Sets the actual members injector.
   *
   * @throws IllegalStateException if the delegate is already set
   */
  public void initializeDelegate(MembersInjector<T> delegate) {
    checkState(this.delegate == null, "delegate already initialized");
    this.delegate = checkNotNull(delegate, "delegate");
  }

  public void applyTo(Binder binder) {
    initializeDelegate(binder.withSource(getSource()).getMembersInjector(type));
  }

  /**
   * Returns the delegate members injector, or {@code null} if it has not yet been initialized.
   * The delegate will be initialized when this element is processed, or otherwise used to create
   * an injector.
   */
  public MembersInjector<T> getDelegate() {
    return delegate;
  }

  /**
   * Returns the looked up members injector. The result is not valid until this lookup has been
   * initialized, which usually happens when the injector is created. The members injector will
   * throw an {@code IllegalStateException} if you try to use it beforehand.
   */
  public MembersInjector<T> getMembersInjector() {
    return new MembersInjector<T>() {
      public void injectMembers(T instance) {
        checkState(delegate != null,
            "This MembersInjector cannot be used until the Injector has been created.");
        delegate.injectMembers(instance);
      }

      @Override public String toString() {
        return "MembersInjector<" + type + ">";
      }
    };
  }
}

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