Joiner.java
/*
* Copyright (C) 2008 The Guava Authors
*
* 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 org.glassfish.jersey.internal.guava;
import java.io.IOException;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import static org.glassfish.jersey.internal.guava.Preconditions.checkNotNull;
/**
* An object which joins pieces of text (specified as an array, {@link Iterable}, varargs or even a
* {@link Map}) with a separator. It either appends the results to an {@link Appendable} or returns
* them as a {@link String}. Example: <pre> {@code
* <p>
* Joiner joiner = Joiner.on("; ").skipNulls();
* . . .
* return joiner.join("Harry", null, "Ron", "Hermione");}</pre>
* <p>
* <p>This returns the string {@code "Harry; Ron; Hermione"}. Note that all input elements are
* converted to strings using {@link Object#toString()} before being appended.
* <p>
* <p>If neither {@link #skipNulls()} nor {@link #useForNull(String)} is specified, the joining
* methods will throw {@link NullPointerException} if any given element is null.
* <p>
* <p><b>Warning: joiner instances are always immutable</b>; a configuration method such as {@code
* useForNull} has no effect on the instance it is invoked on! You must store and use the new joiner
* instance returned by the method. This makes joiners thread-safe, and safe to store as {@code
* static final} constants. <pre> {@code
* <p>
* // Bad! Do not do this!
* Joiner joiner = Joiner.on(',');
* joiner.skipNulls(); // does nothing!
* return joiner.join("wrong", null, "wrong");}</pre>
* <p>
* <p>See the Guava User Guide article on <a href=
* "http://code.google.com/p/guava-libraries/wiki/StringsExplained#Joiner">{@code Joiner}</a>.
*
* @author Kevin Bourrillion
* @since 2.0 (imported from Google Collections Library)
*/
public class Joiner {
private final String separator;
private Joiner(String separator) {
this.separator = Preconditions.checkNotNull(separator);
}
/**
* Returns a joiner which automatically places {@code separator} between consecutive elements.
*/
public static Joiner on() {
return new Joiner(", ");
}
/**
* Appends the string representation of each of {@code parts}, using the previously configured
* separator between each, to {@code appendable}.
*
* @since 11.0
*/
private <A extends Appendable> A appendTo(A appendable, Iterator<?> parts) throws IOException {
Preconditions.checkNotNull(appendable);
if (parts.hasNext()) {
appendable.append(toString(parts.next()));
while (parts.hasNext()) {
appendable.append(separator);
appendable.append(toString(parts.next()));
}
}
return appendable;
}
/**
* Appends the string representation of each of {@code parts}, using the previously configured
* separator between each, to {@code builder}. Identical to {@link #appendTo(Appendable,
* Iterable)}, except that it does not throw {@link IOException}.
*
* @since 11.0
*/
private StringBuilder appendTo(StringBuilder builder, Iterator<?> parts) {
try {
appendTo((Appendable) builder, parts);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
return builder;
}
/**
* Returns a {@code MapJoiner} using the given key-value separator, and the same configuration as
* this {@code Joiner} otherwise.
*/
public MapJoiner withKeyValueSeparator() {
return new MapJoiner(this, "=");
}
private CharSequence toString(Object part) {
Preconditions.checkNotNull(part); // checkNotNull for GWT (do not optimize).
return (part instanceof CharSequence) ? (CharSequence) part : part.toString();
}
/**
* An object that joins map entries in the same manner as {@code Joiner} joins iterables and
* arrays. Like {@code Joiner}, it is thread-safe and immutable.
* <p>
* <p>In addition to operating on {@code Map} instances, {@code MapJoiner} can operate on {@code
* Multimap} entries in two distinct modes:
* <p>
* <ul>
* <li>To output a separate entry for each key-value pair, pass {@code multimap.entries()} to a
* {@code MapJoiner} method that accepts entries as input, and receive output of the form
* {@code key1=A&key1=B&key2=C}.
* <li>To output a single entry for each key, pass {@code multimap.asMap()} to a {@code MapJoiner}
* method that accepts a map as input, and receive output of the form {@code
* key1=[A, B]&key2=C}.
* </ul>
*
* @since 2.0 (imported from Google Collections Library)
*/
public static final class MapJoiner {
private final Joiner joiner;
private final String keyValueSeparator;
private MapJoiner(Joiner joiner, String keyValueSeparator) {
this.joiner = joiner; // only "this" is ever passed, so don't checkNotNull
this.keyValueSeparator = Preconditions.checkNotNull(keyValueSeparator);
}
/**
* Appends the string representation of each entry of {@code map}, using the previously
* configured separator and key-value separator, to {@code builder}. Identical to {@link
* #appendTo(Appendable, Map)}, except that it does not throw {@link IOException}.
*/
public StringBuilder appendTo(StringBuilder builder, Map<?, ?> map) {
return appendTo(builder, map.entrySet());
}
/**
* Appends the string representation of each entry in {@code entries}, using the previously
* configured separator and key-value separator, to {@code appendable}.
*
* @since 11.0
*/
public <A extends Appendable> A appendTo(A appendable, Iterator<? extends Entry<?, ?>> parts)
throws IOException {
Preconditions.checkNotNull(appendable);
if (parts.hasNext()) {
Entry<?, ?> entry = parts.next();
appendable.append(joiner.toString(entry.getKey()));
appendable.append(keyValueSeparator);
appendable.append(joiner.toString(entry.getValue()));
while (parts.hasNext()) {
appendable.append(joiner.separator);
Entry<?, ?> e = parts.next();
appendable.append(joiner.toString(e.getKey()));
appendable.append(keyValueSeparator);
appendable.append(joiner.toString(e.getValue()));
}
}
return appendable;
}
/**
* Appends the string representation of each entry in {@code entries}, using the previously
* configured separator and key-value separator, to {@code builder}. Identical to {@link
* #appendTo(Appendable, Iterable)}, except that it does not throw {@link IOException}.
*
* @since 10.0
*/
public StringBuilder appendTo(StringBuilder builder, Iterable<? extends Entry<?, ?>> entries) {
return appendTo(builder, entries.iterator());
}
/**
* Appends the string representation of each entry in {@code entries}, using the previously
* configured separator and key-value separator, to {@code builder}. Identical to {@link
* #appendTo(Appendable, Iterable)}, except that it does not throw {@link IOException}.
*
* @since 11.0
*/
public StringBuilder appendTo(StringBuilder builder, Iterator<? extends Entry<?, ?>> entries) {
try {
appendTo((Appendable) builder, entries);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
return builder;
}
}
}