assert.java

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/*
 * Copyright 2002-2007 the original author or authors.
 *
 * 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 org.springframework.util;

import java.util.Collection;
import java.util.Map;

/**
 * Assertion utility class that assists in validating arguments.
 * Useful for identifying programmer errors early and clearly at runtime.
 *
 * <p>For example, if the contract of a public method states it does not
 * allow <code>null</code> arguments, Assert can be used to validate that
 * contract. Doing this clearly indicates a contract violation when it
 * occurs and protects the class's invariants.
 *
 * <p>Typically used to validate method arguments rather than configuration
 * properties, to check for cases that are usually programmer errors rather than
 * configuration errors. In contrast to config initialization code, there is
 * usally no point in falling back to defaults in such methods.
 *
 * <p>This class is similar to JUnit's assertion library. If an argument value is
 * deemed invalid, an {@link IllegalArgumentException} is thrown (typically).
 * For example:
 *
 * <pre class="code">
 * Assert.notNull(clazz, "The class must not be null");
 * Assert.isTrue(i > 0, "The value must be greater than zero");</pre>
 *
 * Mainly for internal use within the framework; consider Jakarta's Commons Lang
 * >= 2.0 for a more comprehensive suite of assertion utilities.
 *
 * @author Keith Donald
 * @author Juergen Hoeller
 * @author Colin Sampaleanu
 * @author Rob Harrop
 * @since 1.1.2
 */
public abstract class Assert {

	/**
	 * Assert a boolean expression, throwing <code>IllegalArgumentException</code>
	 * if the test result is <code>false</code>.
	 * <pre class="code">Assert.isTrue(i &gt; 0, "The value must be greater than zero");</pre>
	 * @param expression a boolean expression
	 * @param message the exception message to use if the assertion fails
	 * @throws IllegalArgumentException if expression is <code>false</code>
	 */
	public static void isTrue(boolean expression, String message) {
		if (!expression) {
			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert a boolean expression, throwing <code>IllegalArgumentException</code>
	 * if the test result is <code>false</code>.
	 * <pre class="code">Assert.isTrue(i &gt; 0);</pre>
	 * @param expression a boolean expression
	 * @throws IllegalArgumentException if expression is <code>false</code>
	 */
	public static void isTrue(boolean expression) {
		isTrue(expression, "[Assertion failed] - this expression must be true");
	}

	/**
	 * Assert that an object is <code>null</code> .
	 * <pre class="code">Assert.isNull(value, "The value must be null");</pre>
	 * @param object the object to check
	 * @param message the exception message to use if the assertion fails
	 * @throws IllegalArgumentException if the object is not <code>null</code>
	 */
	public static void isNull(Object object, String message) {
		if (object != null) {
			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert that an object is <code>null</code> .
	 * <pre class="code">Assert.isNull(value);</pre>
	 * @param object the object to check
	 * @throws IllegalArgumentException if the object is not <code>null</code>
	 */
	public static void isNull(Object object) {
		isNull(object, "[Assertion failed] - the object argument must be null");
	}

	/**
	 * Assert that an object is not <code>null</code> .
	 * <pre class="code">Assert.notNull(clazz, "The class must not be null");</pre>
	 * @param object the object to check
	 * @param message the exception message to use if the assertion fails
	 * @throws IllegalArgumentException if the object is <code>null</code>
	 */
	public static void notNull(Object object, String message) {
		if (object == null) {
			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert that an object is not <code>null</code> .
	 * <pre class="code">Assert.notNull(clazz);</pre>
	 * @param object the object to check
	 * @throws IllegalArgumentException if the object is <code>null</code>
	 */
	public static void notNull(Object object) {
		notNull(object, "[Assertion failed] - this argument is required; it must not be null");
	}

	/**
	 * Assert that the given String is not empty; that is,
	 * it must not be <code>null</code> and not the empty String.
	 * <pre class="code">Assert.hasLength(name, "Name must not be empty");</pre>
	 * @param text the String to check
	 * @param message the exception message to use if the assertion fails
	 * @see StringUtils#hasLength
	 */
	public static void hasLength(String text, String message) {
		if (!StringUtils.hasLength(text)) {
			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert that the given String is not empty; that is,
	 * it must not be <code>null</code> and not the empty String.
	 * <pre class="code">Assert.hasLength(name);</pre>
	 * @param text the String to check
	 * @see StringUtils#hasLength
	 */
	public static void hasLength(String text) {
		hasLength(text,
				"[Assertion failed] - this String argument must have length; it must not be null or empty");
	}

	/**
	 * Assert that the given String has valid text content; that is, it must not
	 * be <code>null</code> and must contain at least one non-whitespace character.
	 * <pre class="code">Assert.hasText(name, "'name' must not be empty");</pre>
	 * @param text the String to check
	 * @param message the exception message to use if the assertion fails
	 * @see StringUtils#hasText
	 */
	public static void hasText(String text, String message) {
		if (!StringUtils.hasText(text)) {
			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert that the given String has valid text content; that is, it must not
	 * be <code>null</code> and must contain at least one non-whitespace character.
	 * <pre class="code">Assert.hasText(name, "'name' must not be empty");</pre>
	 * @param text the String to check
	 * @see StringUtils#hasText
	 */
	public static void hasText(String text) {
		hasText(text,
				"[Assertion failed] - this String argument must have text; it must not be null, empty, or blank");
	}

	/**
	 * Assert that the given text does not contain the given substring.
	 * <pre class="code">Assert.doesNotContain(name, "rod", "Name must not contain 'rod'");</pre>
	 * @param textToSearch the text to search
	 * @param substring the substring to find within the text
	 * @param message the exception message to use if the assertion fails
	 */
	public static void doesNotContain(String textToSearch, String substring, String message) {
		if (StringUtils.hasLength(textToSearch) && StringUtils.hasLength(substring) &&
				textToSearch.indexOf(substring) != -1) {
			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert that the given text does not contain the given substring.
	 * <pre class="code">Assert.doesNotContain(name, "rod");</pre>
	 * @param textToSearch the text to search
	 * @param substring the substring to find within the text
	 */
	public static void doesNotContain(String textToSearch, String substring) {
		doesNotContain(textToSearch, substring,
				"[Assertion failed] - this String argument must not contain the substring [" + substring + "]");
	}