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Java example source code file (CheckedProvideUtils.java)

This example Java source code file (CheckedProvideUtils.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

annotatedelement, annotation, checkedprovider, checkedprovideutils, class, classes, constructor, constructor_rules, could, errors, iterable, reflection, throwable, throwinginject, typeliteral

The CheckedProvideUtils.java Java example source code

/**
 * Copyright (C) 2012 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.throwingproviders;

import com.google.inject.Binder;
import com.google.inject.TypeLiteral;
import com.google.inject.internal.Annotations;
import com.google.inject.internal.Errors;
import com.google.inject.spi.Message;

import java.lang.annotation.Annotation;
import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.Constructor;

/**
 * Utilities for the throwing provider module.
 * 
 * @author sameb@google.com (Sam Berlin)
 */
class CheckedProvideUtils {
  
  private CheckedProvideUtils() {}
  
  private static final String CONSTRUCTOR_RULES =
      "Classes must have either one (and only one) constructor annotated with @ThrowingInject.";
  
  @SuppressWarnings("unchecked") // safe because it's a constructor of the typeLiteral
  static <T> Constructor findThrowingConstructor(
      TypeLiteral<? extends T> typeLiteral, Binder binder) {
    
    Class<?> rawType = typeLiteral.getRawType();
    Errors errors = new Errors(rawType);
    Constructor<?> cxtor = null;
    for (Constructor<?> constructor : rawType.getDeclaredConstructors()) {
      if (constructor.isAnnotationPresent(ThrowingInject.class)) {
        if (cxtor != null) {
          errors.addMessage("%s has more than one constructor annotated with @ThrowingInject. "
              + CONSTRUCTOR_RULES, rawType);
        }

        cxtor = constructor;
        Annotation misplacedBindingAnnotation = Annotations.findBindingAnnotation(
            errors, cxtor, ((AnnotatedElement) cxtor).getAnnotations());
        if (misplacedBindingAnnotation != null) {
          errors.misplacedBindingAnnotation(cxtor, misplacedBindingAnnotation);
        }
      }
    }
    
    if (cxtor == null) {
      errors.addMessage(
          "Could not find a suitable constructor in %s. " + CONSTRUCTOR_RULES, rawType);
    }

    for (Message msg : errors.getMessages()) {
      binder.addError(msg);
    }
    return (Constructor<? extends T>) cxtor;
  }
  
  /** Adds errors to the binder if the exceptions aren't valid. */
  static void validateExceptions(Binder binder,
      Iterable<TypeLiteral actualExceptionTypes,
      Iterable<Class expectedExceptionTypes,
      Class<? extends CheckedProvider> checkedProvider) {
    // Validate the exceptions in the method match the exceptions
    // in the CheckedProvider.
    for (TypeLiteral<?> exType : actualExceptionTypes) {
      Class<?> exActual = exType.getRawType();
      // Ignore runtime exceptions & errors.
      if (RuntimeException.class.isAssignableFrom(exActual)
          || Error.class.isAssignableFrom(exActual)) {
        continue;
      }

      boolean notAssignable = true;
      for (Class<? extends Throwable> exExpected : expectedExceptionTypes) {
        if (exExpected.isAssignableFrom(exActual)) {
          notAssignable = false;
          break;
        }
      }
      if (notAssignable) {
        binder.addError(
            "%s is not compatible with the exceptions (%s) declared in " 
            + "the CheckedProvider interface (%s)",
            exActual, expectedExceptionTypes, checkedProvider);
      }
    }
  }

}

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