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HADOOP-17126. implement non-guava Precondition checkNotNull 

This adds a new class org.apache.hadoop.util.Preconditions which is

* @Private/@Unstable
* Intended to allow us to move off Google Guava
* Is designed to be trivially backportable
  (i.e contains no references to guava classes internally)

Please use this instead of the guava equivalents, where possible.

Contributed by: Ahmed Hussein

Change-Id: Ic392451bcfe7d446184b7c995734bcca8c07286e
This commit is contained in:
Steve Loughran 2021-09-17 11:06:13 +01:00
parent 103ef9c711
commit 9188fa8cce
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hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/Preconditions.java Normal file
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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.hadoop.util;
import java.util.function.Supplier;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
/**
* <p>This class replaces {@code guava.Preconditions} which provides helpers
* to validate the following conditions:
* <ul>
* <li>An invalid {@code null} obj causes a {@link NullPointerException}.</li>
* <li>An invalid argument causes an {@link IllegalArgumentException}.</li>
* <li>An invalid state causes an {@link IllegalStateException}.</li>
* <li>An invalid index causes an {@link IndexOutOfBoundsException}.</li>
* </ul>
*/
@InterfaceAudience.Private
@InterfaceStability.Unstable
public final class Preconditions {
private static final Logger LOG =
LoggerFactory.getLogger(Preconditions.class);
private static final String VALIDATE_IS_NOT_NULL_EX_MESSAGE =
"The argument object is NULL";
private Preconditions() {
}
/**
* <p>Preconditions that the specified argument is not {@code null},
* throwing a NPE exception otherwise.
*
* <p>The message of the exception is
* &quot;The validated object is null&quot;.</p>
*
* @param <T> the object type
* @param obj the object to check
* @return the validated object
* @throws NullPointerException if the object is {@code null}
* @see #checkNotNull(Object, Object)
*/
public static <T> T checkNotNull(final T obj) {
return checkNotNull(obj, VALIDATE_IS_NOT_NULL_EX_MESSAGE);
}
/**
* <p>Preconditions that the specified argument is not {@code null},
* throwing a NPE exception otherwise.
*
* <p>The message of the exception is {@code errorMessage}.</p>
*
* @param <T> the object type
* @param obj the object to check
* @param errorMessage the message associated with the NPE
* @return the validated object
* @throws NullPointerException if the object is {@code null}
* @see #checkNotNull(Object, String, Object...)
*/
public static <T> T checkNotNull(final T obj,
final Object errorMessage) {
if (obj == null) {
throw new NullPointerException(String.valueOf(errorMessage));
}
return obj;
}
/**
* <p>Preconditions that the specified argument is not {@code null},
* throwing a NPE exception otherwise.
*
* <p>The message of the exception is {@code String.format(f, m)}.</p>
*
* @param <T> the object type
* @param obj the object to check
* @param message the {@link String#format(String, Object...)}
* exception message if valid. Otherwise,
* the message is {@link #VALIDATE_IS_NOT_NULL_EX_MESSAGE}
* @param values the optional values for the formatted exception message
* @return the validated object
* @throws NullPointerException if the object is {@code null}
* @see #checkNotNull(Object, Supplier)
*/
public static <T> T checkNotNull(final T obj, final String message,
final Object... values) {
// Deferring the evaluation of the message is a tradeoff between the cost
// of constructing lambda Vs constructing a string object.
// Using lambda would allocate an object on every call:
// return checkNotNull(obj, () -> String.format(message, values));
if (obj == null) {
String msg;
try {
msg = String.format(message, values);
} catch (Exception e) {
LOG.debug("Error formatting message", e);
msg = VALIDATE_IS_NOT_NULL_EX_MESSAGE;
}
throw new NullPointerException(msg);
}
return obj;
}
/**
* <p>Preconditions that the specified argument is not {@code null},
* throwing a NPE exception otherwise.
*
* <p>The message of the exception is {@code msgSupplier.get()}.</p>
*
* @param <T> the object type
* @param obj the object to check
* @param msgSupplier the {@link Supplier#get()} set the
* exception message if valid. Otherwise,
* the message is {@link #VALIDATE_IS_NOT_NULL_EX_MESSAGE}
* @return the validated object (never {@code null} for method chaining)
* @throws NullPointerException if the object is {@code null}
*/
public static <T> T checkNotNull(final T obj,
final Supplier<String> msgSupplier) {
if (obj == null) {
String msg;
try {
// note that we can get NPE evaluating the message itself;
// but we do not want this to override the actual NPE.
msg = msgSupplier.get();
} catch (Exception e) {
// ideally we want to log the error to capture. This may cause log files
// to bloat. On the other hand, swallowing the exception may hide a bug
// in the caller. Debug level is a good compromise between the two
// concerns.
LOG.debug("Error formatting message", e);
msg = VALIDATE_IS_NOT_NULL_EX_MESSAGE;
}
throw new NullPointerException(msg);
}
return obj;
}
/* @VisibleForTesting */
static String getDefaultNullMSG() {
return VALIDATE_IS_NOT_NULL_EX_MESSAGE;
}
}

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hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/util/TestPreconditions.java Normal file
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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.hadoop.util;
import org.junit.Test;
import org.apache.hadoop.test.LambdaTestUtils;
public class TestPreconditions {
private static final String NON_NULL_STRING = "NON_NULL_OBJECT";
private static final String NON_INT_STRING = "NOT_INT";
private static final String EXPECTED_ERROR_MSG = "Expected-Error-MSG";
private static final String EXPECTED_ERROR_MSG_ARGS =
EXPECTED_ERROR_MSG + " %s number %d";
private static final String NULL_FORMATTER = null;
private String errorMessage;
@Test
public void testCheckNotNullSuccess() {
Preconditions.checkNotNull(NON_NULL_STRING);
// null supplier
Preconditions.checkNotNull(NON_NULL_STRING, null);
// ill-formated string supplier
Preconditions.checkNotNull(NON_NULL_STRING, ()-> String.format("%d",
NON_INT_STRING));
// null pattern to string formatter
Preconditions.checkNotNull(NON_NULL_STRING, NULL_FORMATTER, null, 1);
// null arguments to string formatter
Preconditions.checkNotNull(NON_NULL_STRING, EXPECTED_ERROR_MSG_ARGS,
null, null);
// illegal format exception
Preconditions.checkNotNull(NON_NULL_STRING, "message %d %d",
NON_INT_STRING, 1);
// insufficient arguments
Preconditions.checkNotNull(NON_NULL_STRING, EXPECTED_ERROR_MSG_ARGS,
NON_INT_STRING);
// null format in string supplier
Preconditions.checkNotNull(NON_NULL_STRING,
() -> String.format(NULL_FORMATTER, NON_INT_STRING));
}
@Test
public void testCheckNotNullFailure() throws Exception {
// failure without message
LambdaTestUtils.intercept(NullPointerException.class,
Preconditions.getDefaultNullMSG(),
() -> Preconditions.checkNotNull(null));
// failure with message
errorMessage = EXPECTED_ERROR_MSG;
LambdaTestUtils.intercept(NullPointerException.class,
errorMessage,
() -> Preconditions.checkNotNull(null, errorMessage));
// failure with Null message
LambdaTestUtils.intercept(NullPointerException.class,
null,
() -> Preconditions.checkNotNull(null, errorMessage));
// failure with message format
errorMessage = EXPECTED_ERROR_MSG + " %s";
String arg = "NPE";
String expectedMSG = String.format(errorMessage, arg);
LambdaTestUtils.intercept(NullPointerException.class,
expectedMSG,
() -> Preconditions.checkNotNull(null, errorMessage, arg));
// failure with multiple arg message format
errorMessage = EXPECTED_ERROR_MSG_ARGS;
expectedMSG =
String.format(errorMessage, arg, 1);
LambdaTestUtils.intercept(NullPointerException.class,
expectedMSG,
() -> Preconditions.checkNotNull(null, errorMessage, arg, 1));
// illegal format will be thrown if the case is not handled correctly
LambdaTestUtils.intercept(NullPointerException.class,
Preconditions.getDefaultNullMSG(),
() -> Preconditions.checkNotNull(null,
errorMessage, 1, NON_INT_STRING));
// illegal format will be thrown for insufficient Insufficient Args
LambdaTestUtils.intercept(NullPointerException.class,
Preconditions.getDefaultNullMSG(),
() -> Preconditions.checkNotNull(null, errorMessage, NON_NULL_STRING));
// illegal format in supplier
LambdaTestUtils.intercept(NullPointerException.class,
Preconditions.getDefaultNullMSG(),
() -> Preconditions.checkNotNull(null,
() -> String.format(errorMessage, 1, NON_INT_STRING)));
// insufficient arguments in string Supplier
LambdaTestUtils.intercept(NullPointerException.class,
Preconditions.getDefaultNullMSG(),
() -> Preconditions.checkNotNull(null,
() -> String.format(errorMessage, NON_NULL_STRING)));
// null formatter
LambdaTestUtils.intercept(NullPointerException.class,
Preconditions.getDefaultNullMSG(),
() -> Preconditions.checkNotNull(null,
() -> String.format(NULL_FORMATTER, NON_NULL_STRING)));
}
}