com.google.appengine.api.datastore.DatastoreCallbacksImpl Maven / Gradle / Ivy
/*
* Copyright 2021 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
*
* 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 com.google.appengine.api.datastore;
import static com.google.common.base.Throwables.throwIfUnchecked;
import static java.util.Objects.requireNonNull;
import com.google.common.base.Splitter;
import com.google.common.collect.LinkedHashMultimap;
import com.google.common.collect.Maps;
import com.google.common.collect.Multimap;
import java.io.IOException;
import java.io.InputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.List;
import java.util.Map;
import java.util.Properties;
/**
* {@link DatastoreCallbacks} implementation that knows how to parse a datastore callbacks config
* file.
*
*/
class DatastoreCallbacksImpl implements DatastoreCallbacks {
static final String FORMAT_VERSION_PROPERTY = "DatastoreCallbacksFormatVersion";
/**
* The types of the callbacks we support. There must be one enum value per callback annotation,
* and each value must be the simple name of one of these annotation classes.
*/
enum CallbackType {
/** @see PrePut */
PrePut(PutContext.class),
/** @see PostPut */
PostPut(PutContext.class),
/** @see PreDelete */
PreDelete(DeleteContext.class),
/** @see PostDelete */
PostDelete(DeleteContext.class),
/** @see PreGet */
PreGet(PreGetContext.class),
/** @see PostLoad */
PostLoad(PostLoadContext.class),
/** @see PreQuery */
PreQuery(PreQueryContext.class);
final Class> contextClass;
final Class annotationType;
@SuppressWarnings("unchecked")
CallbackType(Class> contextClass) {
this.contextClass = contextClass;
try {
this.annotationType =
(Class)
Class.forName(getClass().getPackage().getName() + "." + this.name());
} catch (ClassNotFoundException e) {
throw new IllegalArgumentException(e);
}
}
}
/**
* Interface that we use to wrap a reflective call to the method that actually implements the
* callback.
*/
interface Callback {
void run(CallbackContext context);
}
/**
* Key is the kind (possibly the empty string), value is a {@link Map} where the key is the {@link
* CallbackType} and the value is a {@link List} of {@link Callback Callbacks}. Given a kind and a
* {@link CallbackType} we can quickly navigate to a list of {@link Callback Callbacks} to run.
*/
private final Map> callbacksByTypeAndKind =
Maps.newHashMap();
private final Multimap noKindCallbacksByType =
LinkedHashMultimap.create();
/**
* Constructs DatastoreCallbacksImpl from a config in the appropriate format.
*
* @param inputStream Provides the config.
* @param ignoreMissingMethods If {@code true}, methods that are referenced in the config that do
* not exist will be ignored. If {@code false}, methods that are referenced in the config that
* do not exist will generate an {@link InvalidCallbacksConfigException}.
*/
DatastoreCallbacksImpl(InputStream inputStream, boolean ignoreMissingMethods) {
if (inputStream == null) {
throw new NullPointerException("inputStream must not be null");
}
Properties props = loadProperties(inputStream);
// We only have a single format version at the moment.
if (!"1".equals(props.get(FORMAT_VERSION_PROPERTY))) {
throw new IllegalArgumentException(
"Unsupported version for datastore callbacks config: "
+ props.get(FORMAT_VERSION_PROPERTY));
}
// Save ourselves some null checking later on.
for (CallbackType callbackType : CallbackType.values()) {
callbacksByTypeAndKind.put(callbackType, LinkedHashMultimap.create());
}
for (String key : props.stringPropertyNames()) {
if (!key.equals(FORMAT_VERSION_PROPERTY)) {
processCallbackWithKey(key, props, ignoreMissingMethods);
}
}
}
/** Loads a {@link Properties} object from the contents of the provided {@link InputStream}. */
private Properties loadProperties(InputStream inputStream) {
Properties props = new Properties();
try {
props.loadFromXML(inputStream);
} catch (IOException e) {
throw new InvalidCallbacksConfigException(
"Unable to read datastore callbacks config file.", e);
}
return props;
}
/**
* Processes the callback in the provided {@link Properties} identified by the provided {@code
* key}.
*/
private void processCallbackWithKey(String key, Properties props, boolean ignoreMissingMethods) {
// The format of the key is .
// Kinds can have '.' in them but callback types cannot, so we split from
// the last occurrence.
// Do not look directly at this regex
String[] kindCallbackTypePair = key.split("\\.(?!.*\\.)");
if (kindCallbackTypePair.length != 2) {
throw new InvalidCallbacksConfigException(
String.format("Could not extract kind and callback type from '%s'", key));
}
String kind = kindCallbackTypePair[0];
CallbackType callbackType;
try {
callbackType = CallbackType.valueOf(kindCallbackTypePair[1]);
} catch (IllegalArgumentException iae) {
throw new InvalidCallbacksConfigException(
String.format("Received unknown callback type %s", kindCallbackTypePair[1]));
}
String value = props.getProperty(key);
// The value is a comma-separated list, where each element of the list is
// of the form :.
// Methods and classnames cannot contain ',' so we can safely split on ','.
for (String method : Splitter.on(',').trimResults().split(value)) {
// Methods and classnames cannot contain ':' so we can safely use the
// standard split function.
String[] classMethodPair = method.split(":");
if (classMethodPair.length != 2) {
throw new InvalidCallbacksConfigException(
String.format(
"Could not extract fully-qualified classname and method from '%s'", method));
}
addCallback(callbackType, kind, classMethodPair[0], classMethodPair[1], ignoreMissingMethods);
}
}
private void addCallback(
CallbackType callbackType,
String kind,
String className,
String methodName,
boolean ignoreMissingMethods) {
Callback callback =
newCallback(
callbackType, className, methodName, callbackType.contextClass, ignoreMissingMethods);
if (callback == null) {
return;
}
if (kind.isEmpty()) {
noKindCallbacksByType.put(callbackType, callback);
} else {
// We're guaranteed to have 1 multimap per callback type so this can't be null.
requireNonNull(callbacksByTypeAndKind.get(callbackType)).put(kind, callback);
}
}
@Override
public void executePrePutCallbacks(PutContext context) {
executeCallbacks(CallbackType.PrePut, context);
}
@Override
public void executePostPutCallbacks(PutContext context) {
executeCallbacks(CallbackType.PostPut, context);
}
@Override
public void executePreDeleteCallbacks(DeleteContext context) {
executeCallbacks(CallbackType.PreDelete, context);
}
@Override
public void executePostDeleteCallbacks(DeleteContext context) {
executeCallbacks(CallbackType.PostDelete, context);
}
@Override
public void executePreGetCallbacks(PreGetContext context) {
executeCallbacks(CallbackType.PreGet, context);
}
@Override
public void executePostLoadCallbacks(PostLoadContext context) {
executeCallbacks(CallbackType.PostLoad, context);
}
@Override
public void executePreQueryCallbacks(PreQueryContext context) {
executeCallbacks(CallbackType.PreQuery, context);
}
private void executeCallbacks(CallbackType callbackType, BaseCallbackContext context) {
context.executeCallbacks(
callbacksByTypeAndKind.get(callbackType), noKindCallbacksByType.get(callbackType));
}
/**
* Instantiates a callback of the appropriate type that, when executed, invokes the method with
* the given name on the given object.
*
* @param className Fully-qualified name of the class with a method that was annotated as a
* callback.
* @param methodName The name of the annotated method.
* @param contextClass The type of the single argument expected by the annotated method.
* @param ignoreMissingMethods If {@code true}, methods that are referenced in the config that do
* not exist will be ignored. If {@code false}, methods that are referenced in the config that
* do not exist will generate an {@link InvalidCallbacksConfigException}.
* @return A {@link Callback} of the appropriate concrete type, or {@code null} if {@code
* ignoreMissingMethods} is {@code true} and the method does not exist.
*/
private Callback newCallback(
CallbackType callbackType,
String className,
String methodName,
Class> contextClass,
boolean ignoreMissingMethods) {
try {
Class cls = loadClass(className);
Method m = cls.getDeclaredMethod(methodName, contextClass);
// non-public is ok
m.setAccessible(true);
// make sure the method has the appropriate annotation
if (!m.isAnnotationPresent(callbackType.annotationType)) {
throw new InvalidCallbacksConfigException(
String.format(
"Unable to initialize datastore callbacks because method %s.%s(%s) is missing "
+ "annotation %s.",
cls.getName(), methodName, contextClass.getName(), callbackType));
}
Object callbackImplementor = newInstance(cls);
return allocateCallback(callbackImplementor, m);
} catch (ClassNotFoundException e) {
if (!ignoreMissingMethods) {
throw new InvalidCallbacksConfigException(
"Unable to initialize datastore callbacks due to missing class.", e);
}
} catch (NoSuchMethodException e) {
if (!ignoreMissingMethods) {
throw new InvalidCallbacksConfigException(
"Unable to initialize datastore callbacks because of reference to missing method.", e);
}
}
return null;
}
/**
* Loads the class identified by the provided fully-qualified classname using the current thread's
* context classloader.
*/
private static Class loadClass(String className) throws ClassNotFoundException {
return Class.forName(className, true, Thread.currentThread().getContextClassLoader());
}
/**
* Constructs and returns an instance of the given class by locating and invoking its no-arg
* constructor.
*/
private static Object newInstance(Class cls) {
// Find a no-arg constructor
Constructor ctor;
try {
ctor = cls.getDeclaredConstructor();
} catch (NoSuchMethodException e) {
throw new InvalidCallbacksConfigException(
String.format(
"Unable to initialize datastore callbacks because class %s does not have a no-arg "
+ "constructor.",
cls.getName()),
e);
}
// non-public is ok
ctor.setAccessible(true);
try {
return ctor.newInstance();
} catch (Exception e) {
throw new InvalidCallbacksConfigException(
String.format(
"Unable to initialize datastore callbacks due to exception received while"
+ " constructing an instance of %s",
cls.getName()),
e);
}
}
private Callback allocateCallback(final Object callbackImplementor, final Method callbackMethod) {
return new Callback() {
@Override
public void run(CallbackContext context) {
try {
callbackMethod.invoke(callbackImplementor, context);
} catch (IllegalAccessException e) {
// shouldn't happen since we made the method accessible
throw new RuntimeException(e);
} catch (InvocationTargetException e) {
// TODO: Check whether it is possible for this to be null
if (e.getCause() != null) {
throwIfUnchecked(e.getCause());
}
// Should not happen since we don't allow checked exceptions.
throw new RuntimeException("Callback method threw a checked exception.", e.getCause());
}
}
};
}
static class InvalidCallbacksConfigException extends RuntimeException {
private static final long serialVersionUID = 7167516026957233487L;
InvalidCallbacksConfigException(String msg, Throwable throwable) {
super(msg, throwable);
}
InvalidCallbacksConfigException(String msg) {
super(msg);
}
}
}
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