com.google.auto.value.processor.TemplateVars Maven / Gradle / Ivy
/*
* 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 static java.nio.charset.StandardCharsets.UTF_8;
import com.google.common.base.Ascii;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.io.ByteStreams;
import com.google.escapevelocity.Template;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.StringReader;
import java.io.UncheckedIOException;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.util.Map;
import java.util.TreeMap;
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() {
ImmutableMap vars = toVars();
return parsedTemplate().evaluate(vars);
}
private ImmutableMap 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);
}
@Override
public String toString() {
return getClass().getSimpleName() + toVars();
}
static Template parsedTemplateForResource(String resourceName) {
try {
return Template.parseFrom(resourceName, TemplateVars::readerFromUrl);
} catch (IOException e) {
throw new UncheckedIOException(e);
}
}
// 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".
// To avoid that issue, we open the jar file directly and load the resource from it. Since that
// doesn't use JarURLConnection, it shouldn't be susceptible to the same bug.
private static Reader readerFromUrl(String resourceName) throws IOException {
URL resourceUrl = TemplateVars.class.getResource(resourceName);
if (resourceUrl == null) {
throw new IllegalArgumentException("Could not find resource: " + resourceName);
}
try {
if (Ascii.equalsIgnoreCase(resourceUrl.getProtocol(), "file")) {
return readerFromFile(resourceUrl);
} else if (Ascii.equalsIgnoreCase(resourceUrl.getProtocol(), "jar")) {
return readerFromJar(resourceUrl);
} else {
return readerFromOther(resourceUrl);
}
} catch (URISyntaxException e) {
throw new IOException(e);
}
}
private static Reader readerFromJar(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.
// We could use the methods from JarURLConnection here, but that would risk provoking the same
// problem that prompted this workaround in the first place.
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));
try (JarFile jar = new JarFile(new File(jarUri));
InputStream in = jar.getInputStream(jar.getJarEntry(entryName))) {
String contents = new String(ByteStreams.toByteArray(in), UTF_8);
return new StringReader(contents);
}
}
// In most execution environments, we'll be dealing with a jar, but we handle individual files
// just for cases like running our tests with Maven.
private static Reader readerFromFile(URL resourceUrl) throws IOException, URISyntaxException {
File resourceFile = new File(resourceUrl.toURI());
return new InputStreamReader(new FileInputStream(resourceFile), UTF_8);
}
// As a fallback, we handle other kinds of URL naively. For example, if we're executing in GraalVM
// code, we might have a `resource:` URL. This code is not currently covered by unit tests.
// See https://github.com/google/auto/issues/1783.
private static Reader readerFromOther(URL resourceUrl) throws IOException {
return new InputStreamReader(resourceUrl.openStream(), UTF_8);
}
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);
}
}