/* * Copyright 2002-2016 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. * * <p>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} arguments, {@code 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 configuration initialization * code, there is usually 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> * * <p>Mainly for internal use within the framework; consider * <a href="http://www.mamicode.com/http://commons.apache.org/proper/commons-lang/">Apache‘s Commons Lang</a> * for a more comprehensive suite of {@code String} utilities. * * @author Keith Donald * @author Juergen Hoeller * @author Colin Sampaleanu * @author Rob Harrop * @author Sam Brannen * @since 1.1.2 */public abstract class Assert {    /**     * Assert a boolean expression, throwing {@code IllegalArgumentException}     * if the test result is {@code false}.     * <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}     */    public static void isTrue(boolean expression, String message) {        if (!expression) {            throw new IllegalArgumentException(message);        }    }    /**     * Assert a boolean expression, throwing {@code IllegalArgumentException}     * if the test result is {@code false}.     * <pre class="code">Assert.isTrue(i &gt; 0);</pre>     * @param expression a boolean expression     * @throws IllegalArgumentException if expression is {@code false}     */    public static void isTrue(boolean expression) {        isTrue(expression, "[Assertion failed] - this expression must be true");    }    /**     * Assert that an object is {@code null} .     * <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}     */    public static void isNull(Object object, String message) {        if (object != null) {            throw new IllegalArgumentException(message);        }    }    /**     * Assert that an object is {@code null} .     * <pre class="code">Assert.isNull(value);</pre>     * @param object the object to check     * @throws IllegalArgumentException if the object is not {@code null}     */    public static void isNull(Object object) {        isNull(object, "[Assertion failed] - the object argument must be null");    }    /**     * Assert that an object is not {@code null} .     * <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}     */    public static void notNull(Object object, String message) {        if (object == null) {            throw new IllegalArgumentException(message);        }    }    /**     * Assert that an object is not {@code null} .     * <pre class="code">Assert.notNull(clazz);</pre>     * @param object the object to check     * @throws IllegalArgumentException if the object is {@code null}     */    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} 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     * @throws IllegalArgumentException if the text is empty     */    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} and not the empty String.     * <pre class="code">Assert.hasLength(name);</pre>     * @param text the String to check     * @see StringUtils#hasLength     * @throws IllegalArgumentException if the text is empty     */    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} 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     * @throws IllegalArgumentException if the text does not contain valid text content     */    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} 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     * @throws IllegalArgumentException if the text does not contain valid text content     */    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     * @throws IllegalArgumentException if the text contains the substring     */    public static void doesNotContain(String textToSearch, String substring, String message) {        if (StringUtils.hasLength(textToSearch) && StringUtils.hasLength(substring) &&                textToSearch.contains(substring)) {            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     * @throws IllegalArgumentException if the text contains the substring     */    public static void doesNotContain(String textToSearch, String substring) {        doesNotContain(textToSearch, substring,                "[Assertion failed] - this String argument must not contain the substring [" + substring + "]");    }    /**     * Assert that an array has elements; that is, it must not be     * {@code null} and must have at least one element.     * <pre class="code">Assert.notEmpty(array, "The array must have elements");</pre>     * @param array the array to check     * @param message the exception message to use if the assertion fails     * @throws IllegalArgumentException if the object array is {@code null} or has no elements     */    public static void notEmpty(Object[] array, String message) {        if (ObjectUtils.isEmpty(array)) {            throw new IllegalArgumentException(message);        }    }    /**     * Assert that an array has elements; that is, it must not be     * {@code null} and must have at least one element.     * <pre class="code">Assert.notEmpty(array);</pre>     * @param array the array to check     * @throws IllegalArgumentException if the object array is {@code null} or has no elements     */    public static void notEmpty(Object[] array) {        notEmpty(array, "[Assertion failed] - this array must not be empty: it must contain at least 1 element");    }    /**     * Assert that an array has no null elements.     * Note: Does not complain if the array is empty!     * <pre class="code">Assert.noNullElements(array, "The array must have non-null elements");</pre>     * @param array the array to check     * @param message the exception message to use if the assertion fails     * @throws IllegalArgumentException if the object array contains a {@code null} element     */    public static void noNullElements(Object[] array, String message) {        if (array != null) {            for (Object element : array) {                if (element == null) {                    throw new IllegalArgumentException(message);                }            }        }    }    /**     * Assert that an array has no null elements.     * Note: Does not complain if the array is empty!     * <pre class="code">Assert.noNullElements(array);</pre>     * @param array the array to check     * @throws IllegalArgumentException if the object array contains a {@code null} element     */    public static void noNullElements(Object[] array) {        noNullElements(array, "[Assertion failed] - this array must not contain any null elements");    }    /**     * Assert that a collection has elements; that is, it must not be     * {@code null} and must have at least one element.     * <pre class="code">Assert.notEmpty(collection, "Collection must have elements");</pre>     * @param collection the collection to check     * @param message the exception message to use if the assertion fails     * @throws IllegalArgumentException if the collection is {@code null} or has no elements     */    public static void notEmpty(Collection<?> collection, String message) {        if (CollectionUtils.isEmpty(collection)) {            throw new IllegalArgumentException(message);        }    }    /**     * Assert that a collection has elements; that is, it must not be     * {@code null} and must have at least one element.     * <pre class="code">Assert.notEmpty(collection, "Collection must have elements");</pre>     * @param collection the collection to check     * @throws IllegalArgumentException if the collection is {@code null} or has no elements     */    public static void notEmpty(Collection<?> collection) {        notEmpty(collection,                "[Assertion failed] - this collection must not be empty: it must contain at least 1 element");    }    /**     * Assert that a Map has entries; that is, it must not be {@code null}     * and must have at least one entry.     * <pre class="code">Assert.notEmpty(map, "Map must have entries");</pre>     * @param map the map to check     * @param message the exception message to use if the assertion fails     * @throws IllegalArgumentException if the map is {@code null} or has no entries     */    public static void notEmpty(Map<?, ?> map, String message) {        if (CollectionUtils.isEmpty(map)) {            throw new IllegalArgumentException(message);        }    }    /**     * Assert that a Map has entries; that is, it must not be {@code null}     * and must have at least one entry.     * <pre class="code">Assert.notEmpty(map);</pre>     * @param map the map to check     * @throws IllegalArgumentException if the map is {@code null} or has no entries     */    public static void notEmpty(Map<?, ?> map) {        notEmpty(map, "[Assertion failed] - this map must not be empty; it must contain at least one entry");    }    /**     * Assert that the provided object is an instance of the provided class.     * <pre class="code">Assert.instanceOf(Foo.class, foo);</pre>     * @param clazz the required class     * @param obj the object to check     * @throws IllegalArgumentException if the object is not an instance of clazz     * @see Class#isInstance     */    public static void isInstanceOf(Class<?> clazz, Object obj) {        isInstanceOf(clazz, obj, "");    }    /**     * Assert that the provided object is an instance of the provided class.     * <pre class="code">Assert.instanceOf(Foo.class, foo);</pre>     * @param type the type to check against     * @param obj the object to check     * @param message a message which will be prepended to the message produced by     * the function itself, and which may be used to provide context. It should     * normally end in ":" or "." so that the generated message looks OK when     * appended to it.     * @throws IllegalArgumentException if the object is not an instance of clazz     * @see Class#isInstance     */    public static void isInstanceOf(Class<?> type, Object obj, String message) {        notNull(type, "Type to check against must not be null");        if (!type.isInstance(obj)) {            throw new IllegalArgumentException(                    (StringUtils.hasLength(message) ? message + " " : "") +                    "Object of class [" + (obj != null ? obj.getClass().getName() : "null") +                    "] must be an instance of " + type);        }    }    /**     * Assert that {@code superType.isAssignableFrom(subType)} is {@code true}.     * <pre class="code">Assert.isAssignable(Number.class, myClass);</pre>     * @param superType the super type to check     * @param subType the sub type to check     * @throws IllegalArgumentException if the classes are not assignable     */    public static void isAssignable(Class<?> superType, Class<?> subType) {        isAssignable(superType, subType, "");    }    /**     * Assert that {@code superType.isAssignableFrom(subType)} is {@code true}.     * <pre class="code">Assert.isAssignable(Number.class, myClass);</pre>     * @param superType the super type to check against     * @param subType the sub type to check     * @param message a message which will be prepended to the message produced by     * the function itself, and which may be used to provide context. It should     * normally end in ":" or "." so that the generated message looks OK when     * appended to it.     * @throws IllegalArgumentException if the classes are not assignable     */    public static void isAssignable(Class<?> superType, Class<?> subType, String message) {        notNull(superType, "Type to check against must not be null");        if (subType == null || !superType.isAssignableFrom(subType)) {            throw new IllegalArgumentException((StringUtils.hasLength(message) ? message + " " : "") +                    subType + " is not assignable to " + superType);        }    }    /**     * Assert a boolean expression, throwing {@code IllegalStateException}     * if the test result is {@code false}. Call isTrue if you wish to     * throw IllegalArgumentException on an assertion failure.     * <pre class="code">Assert.state(id == null, "The id property must not already be initialized");</pre>     * @param expression a boolean expression     * @param message the exception message to use if the assertion fails     * @throws IllegalStateException if expression is {@code false}     */    public static void state(boolean expression, String message) {        if (!expression) {            throw new IllegalStateException(message);        }    }    /**     * Assert a boolean expression, throwing {@link IllegalStateException}     * if the test result is {@code false}.     * <p>Call {@link #isTrue(boolean)} if you wish to     * throw {@link IllegalArgumentException} on an assertion failure.     * <pre class="code">Assert.state(id == null);</pre>     * @param expression a boolean expression     * @throws IllegalStateException if the supplied expression is {@code false}     */    public static void state(boolean expression) {        state(expression, "[Assertion failed] - this state invariant must be true");    }}