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/*
 * Copyright 2014 Google LLC
 *
 * 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.auto.value.processor;

import com.google.common.base.Throwables;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.escapevelocity.Template;
import java.io.File;
import java.io.FileInputStream;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.util.Map;
import java.util.TreeMap;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

/**
 * A template and a set of variables to be substituted into that template. A concrete subclass of
 * this class defines a set of fields that are template variables, and an implementation of the
 * {@link #parsedTemplate()} method which is the template to substitute them into. Once the values
 * of the fields have been assigned, the {@link #toText()} method returns the result of substituting
 * them into the template.
 *
 * 

The subclass may be a direct subclass of this class or a more distant descendant. Every field * in the starting class and its ancestors up to this class will be included. Fields cannot be * static unless they are also final. They cannot be private, though they can be package-private if * the class is in the same package as this class. They cannot be primitive or null, so that there * is a clear indication when a field has not been set. * * @author Éamonn McManus */ abstract class TemplateVars { abstract Template parsedTemplate(); private final ImmutableList fields; TemplateVars() { this.fields = getFields(getClass()); } private static ImmutableList getFields(Class c) { ImmutableList.Builder fieldsBuilder = ImmutableList.builder(); while (c != TemplateVars.class) { addFields(fieldsBuilder, c.getDeclaredFields()); c = c.getSuperclass(); } return fieldsBuilder.build(); } private static void addFields( ImmutableList.Builder fieldsBuilder, Field[] declaredFields) { for (Field field : declaredFields) { if (field.isSynthetic() || isStaticFinal(field)) { continue; } if (Modifier.isPrivate(field.getModifiers())) { throw new IllegalArgumentException("Field cannot be private: " + field); } if (Modifier.isStatic(field.getModifiers())) { throw new IllegalArgumentException("Field cannot be static unless also final: " + field); } if (field.getType().isPrimitive()) { throw new IllegalArgumentException("Field cannot be primitive: " + field); } fieldsBuilder.add(field); } } /** * Returns the result of substituting the variables defined by the fields of this class (a * concrete subclass of TemplateVars) into the template returned by {@link #parsedTemplate()}. */ String toText() { Map vars = toVars(); return parsedTemplate().evaluate(vars); } private Map toVars() { Map vars = new TreeMap<>(); for (Field field : fields) { Object value = fieldValue(field, this); if (value == null) { throw new IllegalArgumentException("Field cannot be null (was it set?): " + field); } Object old = vars.put(field.getName(), value); if (old != null) { throw new IllegalArgumentException("Two fields called " + field.getName() + "?!"); } } return ImmutableMap.copyOf(vars); } static Template parsedTemplateForResource(String resourceName) { try { return Template.parseFrom(resourceName, TemplateVars::readerFromResource); } catch (UnsupportedEncodingException e) { throw new AssertionError(e); } catch (IOException | NullPointerException | IllegalStateException e) { // https://github.com/google/auto/pull/439 says that we can get NullPointerException. // https://github.com/google/auto/issues/715 says that we can get IllegalStateException return retryParseAfterException(resourceName, e); } } private static Template retryParseAfterException(String resourceName, Exception exception) { try { return Template.parseFrom(resourceName, TemplateVars::readerFromUrl); } catch (IOException t) { // Chain the original exception so we can see both problems. Throwables.getRootCause(exception).initCause(t); throw new AssertionError(exception); } } private static Reader readerFromResource(String resourceName) { InputStream in = TemplateVars.class.getResourceAsStream(resourceName); if (in == null) { throw new IllegalArgumentException("Could not find resource: " + resourceName); } return new InputStreamReader(in, StandardCharsets.UTF_8); } // This is an ugly workaround for https://bugs.openjdk.java.net/browse/JDK-6947916, as // reported in https://github.com/google/auto/issues/365. // The issue is that sometimes the InputStream returned by JarURLCollection.getInputStream() // can be closed prematurely, which leads to an IOException saying "Stream closed". // We catch all IOExceptions, and fall back on logic that opens the jar file directly and // loads the resource from it. Since that doesn't use JarURLConnection, it shouldn't be // susceptible to the same bug. We only use this as fallback logic rather than doing it always, // because jars are memory-mapped by URLClassLoader, so loading a resource in the usual way // through the getResourceAsStream should be a lot more efficient than reopening the jar. private static Reader readerFromUrl(String resourceName) throws IOException { URL resourceUrl = TemplateVars.class.getResource(resourceName); if (resourceUrl == null) { // This is unlikely, since getResourceAsStream has already succeeded for the same resource. throw new IllegalArgumentException("Could not find resource: " + resourceName); } InputStream in; try { if (resourceUrl.getProtocol().equalsIgnoreCase("file")) { in = inputStreamFromFile(resourceUrl); } else if (resourceUrl.getProtocol().equalsIgnoreCase("jar")) { in = inputStreamFromJar(resourceUrl); } else { throw new AssertionError("Template fallback logic fails for: " + resourceUrl); } } catch (URISyntaxException e) { throw new IOException(e); } return new InputStreamReader(in, StandardCharsets.UTF_8); } private static InputStream inputStreamFromJar(URL resourceUrl) throws URISyntaxException, IOException { // Jar URLs look like this: jar:file:/path/to/file.jar!/entry/within/jar // So take apart the URL to open the jar /path/to/file.jar and read the entry // entry/within/jar from it. String resourceUrlString = resourceUrl.toString().substring("jar:".length()); int bang = resourceUrlString.lastIndexOf('!'); String entryName = resourceUrlString.substring(bang + 1); if (entryName.startsWith("/")) { entryName = entryName.substring(1); } URI jarUri = new URI(resourceUrlString.substring(0, bang)); JarFile jar = new JarFile(new File(jarUri)); JarEntry entry = jar.getJarEntry(entryName); InputStream in = jar.getInputStream(entry); // We have to be careful not to close the JarFile before the stream has been read, because // that would also close the stream. So we defer closing the JarFile until the stream is closed. return new FilterInputStream(in) { @Override public void close() throws IOException { super.close(); jar.close(); } }; } // We don't really expect this case to arise, since the bug we're working around concerns jars // not individual files. However, when running the test for this workaround from Maven, we do // have files. That does mean the test is basically useless there, but Google's internal build // system does run it using a jar, so we do have coverage. private static InputStream inputStreamFromFile(URL resourceUrl) throws IOException, URISyntaxException { File resourceFile = new File(resourceUrl.toURI()); return new FileInputStream(resourceFile); } private static Object fieldValue(Field field, Object container) { try { return field.get(container); } catch (IllegalAccessException e) { throw new RuntimeException(e); } } private static boolean isStaticFinal(Field field) { int modifiers = field.getModifiers(); return Modifier.isStatic(modifiers) && Modifier.isFinal(modifiers); } }





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