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

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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.
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/*
 * 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.inject.rebind.util.SourceWriteUtil;
import com.google.gwt.inject.rebind.util.NameGenerator;
import com.google.gwt.user.rebind.SourceWriter;
import com.google.inject.Inject;
import com.google.inject.Key;

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

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

  private final NameGenerator nameGenerator;
  private String valueToOutput;

  /**
   * 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.isPrimitive() || Number.class.isAssignableFrom(clazz)
        || Character.class.isAssignableFrom(clazz) || Boolean.class.isAssignableFrom(clazz)
        || clazz.isEnum();
  }

  private final SourceWriteUtil sourceWriteUtil;

  @Inject
  public BindConstantBinding(SourceWriteUtil sourceWriteUtil, NameGenerator nameGenerator) {
    this.sourceWriteUtil = sourceWriteUtil;
    this.nameGenerator = nameGenerator;
  }

  /**
   * Sets this binding's key and instance.  Must be called before
   * writeCreatorMethod is invoked.
   *
   * @param key key to bind to
   * @param instance value to bind  to
   */
  public  void setKeyAndInstance(Key key, T instance) {
    Type type = key.getTypeLiteral().getType();

    if (type == String.class) {
      valueToOutput = "\"" + Generator.escape(instance.toString()) + "\"";
    } else if (type == Character.class) {
      valueToOutput = "'" + (Character.valueOf('\'').equals(instance) ? "\\" : "") + instance + "'";
    } else if (type == Float.class) {
      valueToOutput = instance.toString() + "f";
    } else if (type == Long.class) {
      valueToOutput = instance.toString() + "L";
    } else if (type == Double.class) {
      valueToOutput = instance.toString() + "d";
    } else if (instance instanceof Number || instance instanceof Boolean) {
      valueToOutput = instance.toString(); // Includes int & short.
    } else if (instance instanceof Enum) {
      Class clazz = instance.getClass();

      // Enums become anonymous inner classes if they have a custom
      // implementation. Their classname is then of the form "com.foo.Bar$1".
      // We need to be careful here to not clobber inner enums (which also
      // have a $ in their classname). The regex below matches any classname
      // that terminates in a $ followed by a number, i.e. an anonymous class.
      if (clazz.getName().matches(".+\\$\\d+\\z")) {
        clazz = instance.getClass().getEnclosingClass();
      }
      String className = clazz.getCanonicalName();

      valueToOutput = className + "." + ((Enum) instance).name();
    } else {
      throw new IllegalArgumentException("Attempted to create a constant binding with a "
          + "non-constant type: " + type);
    }
  }

  public void writeCreatorMethods(SourceWriter writer, String creatorMethodSignature) {
    assert valueToOutput != null;

    sourceWriteUtil.writeMethod(writer, creatorMethodSignature, "return " + valueToOutput + ";");
  }

  public RequiredKeys getRequiredKeys() {
    return new RequiredKeys(Collections.>emptySet());
  }
}