Java tutorial
/* * Copyright 2002-2013 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 com.langnatech.util; import java.util.Collection; import java.util.Map; import org.apache.commons.collections.CollectionUtils; import org.apache.commons.lang3.StringUtils; /** * 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} * 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 AssertUtil { /** * Assert a boolean expression, throwing {@code IllegalArgumentException} if the test result is {@code false}. <pre * class="code">Assert.isTrue(i > 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 > 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 */ public static void hasLength(String text, String message) { if (!StringUtils.isNotEmpty(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 */ 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 */ public static void hasText(String text, String message) { if (!StringUtils.isNotBlank(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 */ 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.isNotEmpty(textToSearch) && StringUtils.isNotEmpty(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 */ 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 (map == null || map.size() == 0) { 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 a ": " or ". " so that the function generate * message looks ok when prepended 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.isNotEmpty(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 a ": " or ". " so that the function generate * message looks ok when prepended 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(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"); } }