Java tutorial
/* * 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 cn.gov.icon.base.util; import java.util.Collection; import java.util.Map; import org.apache.commons.collections.CollectionUtils; import org.apache.commons.collections.MapUtils; import org.apache.commons.lang.ArrayUtils; import org.apache.commons.lang.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</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 > 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 > 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 org.apache.commons.lang.StringUtils#hasLength */ public static void hasLength(String text, String message) { if (StringUtils.isEmpty(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 org.apache.commons.lang.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 org.apache.commons.lang.StringUtils#isBlank */ public static void hasText(String text, String message) { if (StringUtils.isBlank(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 org.apache.commons.lang.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.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 + "]"); } /** * Assert that an array has elements; that is, it must not be * <code>null</code> 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</code> or has no elements */ public static void notEmpty(Object[] array, String message) { if (ArrayUtils.isEmpty(array)) { throw new IllegalArgumentException(message); } } /** * Assert that an array has elements; that is, it must not be * <code>null</code> 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</code> 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</code> element */ public static void noNullElements(Object[] array, String message) { if (array != null) { for (int i = 0; i < array.length; i++) { if (array[i] == 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</code> 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</code> 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</code> 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</code> 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</code> 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</code> * 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</code> or has no entries */ public static void notEmpty(Map<?, ?> map, String message) { if (MapUtils.isEmpty(map)) { throw new IllegalArgumentException(message); } } /** * Assert that a Map has entries; that is, it must not be <code>null</code> * 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</code> 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(message + "Object of class [" + (obj != null ? obj.getClass().getName() : "null") + "] must be an instance of " + type); } } /** * Assert that <code>superType.isAssignableFrom(subType)</code> is * <code>true</code>. * * <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)</code> is * <code>true</code>. * * <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</code> * if the test result is <code>false</code> . 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</code> */ 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</code>. * <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</code> */ public static void state(boolean expression) { state(expression, "[Assertion failed] - this state invariant must be true"); } }