feign.Util Maven / Gradle / Ivy
/*
* Copyright 2013 Netflix, 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 feign;
import java.io.IOException;
import java.lang.reflect.Array;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.WildcardType;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Map;
import static java.lang.String.format;
/**
* Utilities, typically copied in from guava, so as to avoid dependency conflicts.
*/
public class Util {
private Util() { // no instances
}
/**
* The HTTP Content-Length header field name.
*/
public static final String CONTENT_LENGTH = "Content-Length";
/**
* The HTTP Retry-After header field name.
*/
public static final String RETRY_AFTER = "Retry-After";
// com.google.common.base.Charsets
/**
* UTF-8: eight-bit UCS Transformation Format.
*/
public static final Charset UTF_8 = Charset.forName("UTF-8");
/**
* Copy of {@code com.google.common.base.Preconditions#checkArgument}.
*/
public static void checkArgument(boolean expression,
String errorMessageTemplate,
Object... errorMessageArgs) {
if (!expression) {
throw new IllegalArgumentException(
format(errorMessageTemplate, errorMessageArgs));
}
}
/**
* Copy of {@code com.google.common.base.Preconditions#checkNotNull}.
*/
public static T checkNotNull(T reference,
String errorMessageTemplate,
Object... errorMessageArgs) {
if (reference == null) {
// If either of these parameters is null, the right thing happens anyway
throw new NullPointerException(
format(errorMessageTemplate, errorMessageArgs));
}
return reference;
}
/**
* Copy of {@code com.google.common.base.Preconditions#checkState}.
*/
public static void checkState(boolean expression,
String errorMessageTemplate,
Object... errorMessageArgs) {
if (!expression) {
throw new IllegalStateException(
format(errorMessageTemplate, errorMessageArgs));
}
}
/**
* Adapted from {@code com.google.common.base.Strings#emptyToNull}.
*/
public static String emptyToNull(String string) {
return string == null || string.isEmpty() ? null : string;
}
/**
* Adapted from {@code com.google.common.base.Strings#emptyToNull}.
*/
@SuppressWarnings("unchecked")
public static T[] toArray(Iterable iterable, Class type) {
Collection collection;
if (iterable instanceof Collection) {
collection = (Collection) iterable;
} else {
collection = new ArrayList();
for (T element : iterable) {
collection.add(element);
}
}
T[] array = (T[]) Array.newInstance(type, collection.size());
return collection.toArray(array);
}
/**
* Returns an unmodifiable collection which may be empty, but is never null.
*/
public static Collection valuesOrEmpty(Map> map, String key) {
return map.containsKey(key) ? map.get(key) : Collections.emptyList();
}
public static void ensureClosed(Response.Body body) {
if (body != null) {
try {
body.close();
} catch (IOException ignored) { // NOPMD
}
}
}
/**
* Resolves the last type parameter of the parameterized {@code supertype}, based on the {@code genericContext},
* into its upper bounds.
*
* Implementation copied from {@code retrofit.RestMethodInfo}.
*
* @param genericContext Ex. {@link java.lang.reflect.Field#getGenericType()}
* @param supertype Ex. {@code Decoder.class}
* @return in the example above, the type parameter of {@code Decoder}.
* @throws IllegalStateException if {@code supertype} cannot be resolved into a parameterized type using
* {@code context}.
*/
public static Type resolveLastTypeParameter(Type genericContext, Class supertype) throws IllegalStateException {
Type resolvedSuperType = Types.getSupertype(genericContext, Types.getRawType(genericContext), supertype);
checkState(resolvedSuperType instanceof ParameterizedType, "could not resolve %s into a parameterized type %s",
genericContext, supertype);
Type[] types = ParameterizedType.class.cast(resolvedSuperType).getActualTypeArguments();
for (int i = 0; i < types.length; i++) {
Type type = types[i];
if (type instanceof WildcardType) {
types[i] = ((WildcardType) type).getUpperBounds()[0];
}
}
return types[types.length - 1];
}
}