com.google.auto.value.processor.TemplateVars Maven / Gradle / Ivy
/*
* Copyright (C) 2014 Google, 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 com.google.auto.value.processor;
import com.google.auto.value.processor.escapevelocity.Template;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Maps;
import java.io.BufferedReader;
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.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.util.Map;
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 must be a direct subclass of this class. 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() {
if (getClass().getSuperclass() != TemplateVars.class) {
throw new IllegalArgumentException("Class must extend TemplateVars directly");
}
ImmutableList.Builder fields = ImmutableList.builder();
Field[] declaredFields = getClass().getDeclaredFields();
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);
}
fields.add(field);
}
this.fields = fields.build();
}
/**
* 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 = Maps.newTreeMap();
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) {
InputStream in = TemplateVars.class.getResourceAsStream(resourceName);
if (in == null) {
throw new IllegalArgumentException("Could not find resource: " + resourceName);
}
try {
return templateFromInputStream(in);
} catch (UnsupportedEncodingException e) {
throw new AssertionError(e);
} catch (IOException e) {
return retryParseAfterException(resourceName, e);
} catch (NullPointerException e) {
// https://github.com/google/auto/pull/439 says that we can also get this exception.
// TODO(emcmanus): use IOException | NullPointerException when we drop Java 6 source compat.
return retryParseAfterException(resourceName, e);
} finally {
try {
in.close();
} catch (IOException ignored) {
// We probably already got an IOException which we're propagating.
}
}
}
private static Template retryParseAfterException(String resourceName, Exception exception) {
try {
return parsedTemplateFromUrl(resourceName);
} catch (Throwable t) {
// Chain the original exception so we can see both problems.
Throwable cause;
for (cause = exception; cause.getCause() != null; cause = cause.getCause()) {
}
cause.initCause(t);
throw new AssertionError(exception);
}
}
private static Template templateFromInputStream(InputStream in)
throws UnsupportedEncodingException, IOException {
Reader reader = new BufferedReader(new InputStreamReader(in, "UTF-8"));
return Template.parseFrom(reader);
}
// 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 Template parsedTemplateFromUrl(String resourceName)
throws URISyntaxException, IOException {
URL resourceUrl = TemplateVars.class.getResource(resourceName);
if (resourceUrl.getProtocol().equalsIgnoreCase("file")) {
return parsedTemplateFromFile(resourceUrl);
} else if (resourceUrl.getProtocol().equalsIgnoreCase("jar")) {
return parsedTemplateFromJar(resourceUrl);
} else {
throw new AssertionError("Template fallback logic fails for: " + resourceUrl);
}
}
private static Template parsedTemplateFromJar(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));
try {
JarEntry entry = jar.getJarEntry(entryName);
InputStream in = jar.getInputStream(entry);
return templateFromInputStream(in);
} finally {
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 Template parsedTemplateFromFile(URL resourceUrl)
throws IOException, URISyntaxException {
File resourceFile = new File(resourceUrl.toURI());
InputStream in = new FileInputStream(resourceFile);
try {
return templateFromInputStream(in);
} finally {
in.close();
}
}
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);
}
}