com.google.gwt.inject.rebind.binding.BindConstantBinding Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of gin Show documentation
GIN (GWT INjection) brings automatic dependency injection to Google Web Toolkit client-side code. GIN is built on top of Guice and uses (a subset of) Guice's binding language.
There is a newer version: 2.1.2
Show newest version
/*
 * Copyright 2008 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.gwt.inject.rebind.binding;

import com.google.gwt.core.ext.Generator;
import com.google.gwt.dev.util.Preconditions;
import com.google.gwt.inject.rebind.GinjectorBindings;
import com.google.gwt.inject.rebind.reflect.NoSourceNameException;
import com.google.gwt.inject.rebind.reflect.ReflectUtil;
import com.google.gwt.inject.rebind.util.InjectorMethod;
import com.google.gwt.inject.rebind.util.NameGenerator;
import com.google.gwt.inject.rebind.util.SourceSnippet;
import com.google.gwt.inject.rebind.util.SourceSnippetBuilder;
import com.google.gwt.inject.rebind.util.SourceSnippets;
import com.google.inject.Key;

import java.lang.reflect.Type;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

/**
 * Binding for a constant value.
 */
public class BindConstantBinding extends AbstractBinding implements Binding {

  private final String valueToOutput;
  private final Key key;

  /**
   * Returns true if the provided key is a valid constant key, i.e. if a
   * constant binding can be legally created for it.
   *
   * @param key key to check
   * @return true if constant key
   */
  public static boolean isConstantKey(Key key) {
    Type type = key.getTypeLiteral().getType();

    if (!(type instanceof Class)) {
      return false;
    }

    Class clazz = (Class) type;
    return clazz == String.class || clazz == Class.class || clazz.isPrimitive()
        || Number.class.isAssignableFrom(clazz) || Character.class.isAssignableFrom(clazz)
        || Boolean.class.isAssignableFrom(clazz) || clazz.isEnum();
  }

  BindConstantBinding(Key key, T instance, Context context) {
    super(context, key);

    this.key = Preconditions.checkNotNull(key);
    this.valueToOutput = getValueToOutput(key, Preconditions.checkNotNull(instance));
  }

  private static  String getValueToOutput(Key key, T instance) {
    Type type = key.getTypeLiteral().getType();

    if (type == String.class) {
      return "\"" + Generator.escape(instance.toString()) + "\"";
    } else if (type == Class.class) {
      return toClassReference((Class) instance);
    } else if (type == Character.class) {
      return "'" + (Character.valueOf('\'').equals(instance) ? "\\" : "") + instance + "'";
    } else if (type == Float.class) {
      return instance.toString() + "f";
    } else if (type == Long.class) {
      return instance.toString() + "L";
    } else if (type == Double.class) {
      return instance.toString() + "d";
    } else if (instance instanceof Number || instance instanceof Boolean) {
      return instance.toString(); // Includes int & short.
    } else if (instance instanceof Enum) {
      return toEnumReference(((Enum) instance));
    } else {
      throw new IllegalArgumentException("Attempted to create a constant binding with a "
          + "non-constant type: " + type);
    }
  }

  public SourceSnippet getCreationStatements(NameGenerator nameGenerator,
      List methodsOutput) throws NoSourceNameException {
    String type = ReflectUtil.getSourceName(key.getTypeLiteral());

    return new SourceSnippetBuilder()
        .append(type).append(" result = ").append(valueToOutput).append(";")
        .build();
  }

  public Collection getDependencies() {
    return Collections.singletonList(
        new Dependency(Dependency.GINJECTOR, key, getContext().toString()));
  }

  private static String toEnumReference(Enum instance) {
    return instance.getDeclaringClass().getCanonicalName() + "." + instance.name();
  }

  private static String toClassReference(Class instance) {
    String canonicalName = instance.getCanonicalName();
    if (canonicalName == null) {
      throw new IllegalArgumentException("Attempted to create a constant binding with a "
          + "a local or anonymous class: " + instance);
    }
    return canonicalName + ".class";
  }
}