org.springframework.boot.loader.tools.LayersIndex Maven / Gradle / Ivy
/*
* Copyright 2012-2021 the original author or 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
*
* https://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.springframework.boot.loader.tools;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
/**
* Index describing the layer to which each entry in a jar belongs. Index files are simple
* text files that should be read from top to bottom. Each file defines the layers and
* their content. Layer names are written as quoted strings prefixed by a dash space
* ({@code "- "}) and with a colon ({@code ":"}) suffix. Layer content is either a file or
* directory name written as a quoted string prefixed by space space dash space
* ({@code " - "}). A directory name ends with {@code /}, a file name does not. When a
* directory name is used it means that all files inside that directory are in the same
* layer.
*
* Index files are designed to be compatible with YAML and may be read into a list of
* {@code Map>} instances.
*
* @author Madhura Bhave
* @author Andy Wilkinson
* @author Phillip Webb
* @since 2.3.0
*/
public class LayersIndex {
private final Iterable layers;
private final Node root = new Node();
/**
* Create a new {@link LayersIndex} backed by the given layers.
* @param layers the layers in the index
*/
public LayersIndex(Layer... layers) {
this(Arrays.asList(layers));
}
/**
* Create a new {@link LayersIndex} backed by the given layers.
* @param layers the layers in the index
*/
public LayersIndex(Iterable layers) {
this.layers = layers;
}
/**
* Add an item to the index.
* @param layer the layer of the item
* @param name the name of the item
*/
public void add(Layer layer, String name) {
String[] segments = name.split("/");
Node node = this.root;
for (int i = 0; i < segments.length; i++) {
boolean isDirectory = i < (segments.length - 1);
node = node.updateOrAddNode(segments[i], isDirectory, layer);
}
}
/**
* Write the layer index to an output stream.
* @param out the destination stream
* @throws IOException on IO error
*/
public void writeTo(OutputStream out) throws IOException {
MultiValueMap index = new LinkedMultiValueMap<>();
this.root.buildIndex("", index);
index.values().forEach(Collections::sort);
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out, StandardCharsets.UTF_8));
for (Layer layer : this.layers) {
List names = index.get(layer);
writer.write("- \"" + layer + "\":\n");
if (names != null) {
for (String name : names) {
writer.write(" - \"" + name + "\"\n");
}
}
}
writer.flush();
}
/**
* A node within the index representing a single path segment.
*/
private static class Node {
private final String name;
private final Set layers;
private final List children = new ArrayList<>();
Node() {
this.name = "";
this.layers = new HashSet<>();
}
Node(String name, Layer layer) {
this.name = name;
this.layers = new HashSet<>(Collections.singleton(layer));
}
Node updateOrAddNode(String segment, boolean isDirectory, Layer layer) {
String name = segment + (isDirectory ? "/" : "");
for (Node child : this.children) {
if (name.equals(child.name)) {
child.layers.add(layer);
return child;
}
}
Node child = new Node(name, layer);
this.children.add(child);
return child;
}
void buildIndex(String path, MultiValueMap index) {
String name = path + this.name;
if (this.layers.size() == 1) {
index.add(this.layers.iterator().next(), name);
}
else {
for (Node child : this.children) {
child.buildIndex(name, index);
}
}
}
}
}