Java tutorial
/* * Copyright 2002-2018 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 * * https://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; import java.util.function.Supplier; import org.springframework.lang.Nullable; /** * 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="https://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 Sam Brannen * @author Colin Sampaleanu * @author Rob Harrop * @since 1.1.2 */ public abstract class Assert { /** * Assert a boolean expression, throwing an {@code IllegalStateException} * if the expression evaluates to {@code false}. * <p>Call {@link #isTrue} if you wish to throw an {@code 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 {@code expression} is {@code false} */ public static void state(boolean expression, String message) { if (!expression) { throw new IllegalStateException(message); } } /** * Assert a boolean expression, throwing an {@code IllegalStateException} * if the expression evaluates to {@code false}. * <p>Call {@link #isTrue} if you wish to throw an {@code IllegalArgumentException} * on an assertion failure. * <pre class="code"> * Assert.state(id == null, * () -> "ID for " + entity.getName() + " must not already be initialized"); * </pre> * @param expression a boolean expression * @param messageSupplier a supplier for the exception message to use if the * assertion fails * @throws IllegalStateException if {@code expression} is {@code false} * @since 5.0 */ public static void state(boolean expression, Supplier<String> messageSupplier) { if (!expression) { throw new IllegalStateException(nullSafeGet(messageSupplier)); } } /** * Assert a boolean expression, throwing an {@code IllegalStateException} * if the expression evaluates to {@code false}. * @deprecated as of 4.3.7, in favor of {@link #state(boolean, String)} */ @Deprecated public static void state(boolean expression) { state(expression, "[Assertion failed] - this state invariant must be true"); } /** * Assert a boolean expression, throwing an {@code IllegalArgumentException} * if the expression evaluates to {@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 {@code expression} is {@code false} */ public static void isTrue(boolean expression, String message) { if (!expression) { throw new IllegalArgumentException(message); } } /** * Assert a boolean expression, throwing an {@code IllegalArgumentException} * if the expression evaluates to {@code false}. * <pre class="code"> * Assert.isTrue(i > 0, () -> "The value '" + i + "' must be greater than zero"); * </pre> * @param expression a boolean expression * @param messageSupplier a supplier for the exception message to use if the * assertion fails * @throws IllegalArgumentException if {@code expression} is {@code false} * @since 5.0 */ public static void isTrue(boolean expression, Supplier<String> messageSupplier) { if (!expression) { throw new IllegalArgumentException(nullSafeGet(messageSupplier)); } } /** * Assert a boolean expression, throwing an {@code IllegalArgumentException} * if the expression evaluates to {@code false}. * @deprecated as of 4.3.7, in favor of {@link #isTrue(boolean, String)} */ @Deprecated 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(@Nullable Object object, String message) { if (object != null) { throw new IllegalArgumentException(message); } } /** * Assert that an object is {@code null}. * <pre class="code"> * Assert.isNull(value, () -> "The value '" + value + "' must be null"); * </pre> * @param object the object to check * @param messageSupplier a supplier for the exception message to use if the * assertion fails * @throws IllegalArgumentException if the object is not {@code null} * @since 5.0 */ public static void isNull(@Nullable Object object, Supplier<String> messageSupplier) { if (object != null) { throw new IllegalArgumentException(nullSafeGet(messageSupplier)); } } /** * Assert that an object is {@code null}. * @deprecated as of 4.3.7, in favor of {@link #isNull(Object, String)} */ @Deprecated public static void isNull(@Nullable 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(@Nullable 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, () -> "The class '" + clazz.getName() + "' must not be null"); * </pre> * @param object the object to check * @param messageSupplier a supplier for the exception message to use if the * assertion fails * @throws IllegalArgumentException if the object is {@code null} * @since 5.0 */ public static void notNull(@Nullable Object object, Supplier<String> messageSupplier) { if (object == null) { throw new IllegalArgumentException(nullSafeGet(messageSupplier)); } } /** * Assert that an object is not {@code null}. * @deprecated as of 4.3.7, in favor of {@link #notNull(Object, String)} */ @Deprecated public static void notNull(@Nullable 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 * @throws IllegalArgumentException if the text is empty * @see StringUtils#hasLength */ public static void hasLength(@Nullable 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, () -> "Name for account '" + account.getId() + "' must not be empty"); * </pre> * @param text the String to check * @param messageSupplier a supplier for the exception message to use if the * assertion fails * @throws IllegalArgumentException if the text is empty * @since 5.0 * @see StringUtils#hasLength */ public static void hasLength(@Nullable String text, Supplier<String> messageSupplier) { if (!StringUtils.hasLength(text)) { throw new IllegalArgumentException(nullSafeGet(messageSupplier)); } } /** * Assert that the given String is not empty; that is, * it must not be {@code null} and not the empty String. * @deprecated as of 4.3.7, in favor of {@link #hasLength(String, String)} */ @Deprecated public static void hasLength(@Nullable String text) { hasLength(text, "[Assertion failed] - this String argument must have length; it must not be null or empty"); } /** * Assert that the given String contains 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 * @throws IllegalArgumentException if the text does not contain valid text content * @see StringUtils#hasText */ public static void hasText(@Nullable String text, String message) { if (!StringUtils.hasText(text)) { throw new IllegalArgumentException(message); } } /** * Assert that the given String contains 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 for account '" + account.getId() + "' must not be empty"); * </pre> * @param text the String to check * @param messageSupplier a supplier for the exception message to use if the * assertion fails * @throws IllegalArgumentException if the text does not contain valid text content * @since 5.0 * @see StringUtils#hasText */ public static void hasText(@Nullable String text, Supplier<String> messageSupplier) { if (!StringUtils.hasText(text)) { throw new IllegalArgumentException(nullSafeGet(messageSupplier)); } } /** * Assert that the given String contains valid text content; that is, it must not * be {@code null} and must contain at least one non-whitespace character. * @deprecated as of 4.3.7, in favor of {@link #hasText(String, String)} */ @Deprecated public static void hasText(@Nullable 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(@Nullable 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, forbidden, () -> "Name must not contain '" + forbidden + "'"); * </pre> * @param textToSearch the text to search * @param substring the substring to find within the text * @param messageSupplier a supplier for the exception message to use if the * assertion fails * @throws IllegalArgumentException if the text contains the substring * @since 5.0 */ public static void doesNotContain(@Nullable String textToSearch, String substring, Supplier<String> messageSupplier) { if (StringUtils.hasLength(textToSearch) && StringUtils.hasLength(substring) && textToSearch.contains(substring)) { throw new IllegalArgumentException(nullSafeGet(messageSupplier)); } } /** * Assert that the given text does not contain the given substring. * @deprecated as of 4.3.7, in favor of {@link #doesNotContain(String, String, String)} */ @Deprecated public static void doesNotContain(@Nullable String textToSearch, String substring) { doesNotContain(textToSearch, substring, () -> "[Assertion failed] - this String argument must not contain the substring [" + substring + "]"); } /** * Assert that an array contains elements; that is, it must not be * {@code null} and must contain at least one element. * <pre class="code">Assert.notEmpty(array, "The array must contain 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 contains no elements */ public static void notEmpty(@Nullable Object[] array, String message) { if (ObjectUtils.isEmpty(array)) { throw new IllegalArgumentException(message); } } /** * Assert that an array contains elements; that is, it must not be * {@code null} and must contain at least one element. * <pre class="code"> * Assert.notEmpty(array, () -> "The " + arrayType + " array must contain elements"); * </pre> * @param array the array to check * @param messageSupplier a supplier for the exception message to use if the * assertion fails * @throws IllegalArgumentException if the object array is {@code null} or contains no elements * @since 5.0 */ public static void notEmpty(@Nullable Object[] array, Supplier<String> messageSupplier) { if (ObjectUtils.isEmpty(array)) { throw new IllegalArgumentException(nullSafeGet(messageSupplier)); } } /** * Assert that an array contains elements; that is, it must not be * {@code null} and must contain at least one element. * @deprecated as of 4.3.7, in favor of {@link #notEmpty(Object[], String)} */ @Deprecated public static void notEmpty(@Nullable Object[] array) { notEmpty(array, "[Assertion failed] - this array must not be empty: it must contain at least 1 element"); } /** * Assert that an array contains no {@code null} elements. * <p>Note: Does not complain if the array is empty! * <pre class="code">Assert.noNullElements(array, "The array must contain 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(@Nullable Object[] array, String message) { if (array != null) { for (Object element : array) { if (element == null) { throw new IllegalArgumentException(message); } } } } /** * Assert that an array contains no {@code null} elements. * <p>Note: Does not complain if the array is empty! * <pre class="code"> * Assert.noNullElements(array, () -> "The " + arrayType + " array must contain non-null elements"); * </pre> * @param array the array to check * @param messageSupplier a supplier for the exception message to use if the * assertion fails * @throws IllegalArgumentException if the object array contains a {@code null} element * @since 5.0 */ public static void noNullElements(@Nullable Object[] array, Supplier<String> messageSupplier) { if (array != null) { for (Object element : array) { if (element == null) { throw new IllegalArgumentException(nullSafeGet(messageSupplier)); } } } } /** * Assert that an array contains no {@code null} elements. * @deprecated as of 4.3.7, in favor of {@link #noNullElements(Object[], String)} */ @Deprecated public static void noNullElements(@Nullable Object[] array) { noNullElements(array, "[Assertion failed] - this array must not contain any null elements"); } /** * Assert that a collection contains elements; that is, it must not be * {@code null} and must contain at least one element. * <pre class="code">Assert.notEmpty(collection, "Collection must contain 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 * contains no elements */ public static void notEmpty(@Nullable Collection<?> collection, String message) { if (CollectionUtils.isEmpty(collection)) { throw new IllegalArgumentException(message); } } /** * Assert that a collection contains elements; that is, it must not be * {@code null} and must contain at least one element. * <pre class="code"> * Assert.notEmpty(collection, () -> "The " + collectionType + " collection must contain elements"); * </pre> * @param collection the collection to check * @param messageSupplier a supplier for the exception message to use if the * assertion fails * @throws IllegalArgumentException if the collection is {@code null} or * contains no elements * @since 5.0 */ public static void notEmpty(@Nullable Collection<?> collection, Supplier<String> messageSupplier) { if (CollectionUtils.isEmpty(collection)) { throw new IllegalArgumentException(nullSafeGet(messageSupplier)); } } /** * Assert that a collection contains elements; that is, it must not be * {@code null} and must contain at least one element. * @deprecated as of 4.3.7, in favor of {@link #notEmpty(Collection, String)} */ @Deprecated public static void notEmpty(@Nullable Collection<?> collection) { notEmpty(collection, "[Assertion failed] - this collection must not be empty: it must contain at least 1 element"); } /** * Assert that a collection contains no {@code null} elements. * <p>Note: Does not complain if the collection is empty! * <pre class="code">Assert.noNullElements(collection, "Collection must contain non-null elements");</pre> * @param collection the collection to check * @param message the exception message to use if the assertion fails * @throws IllegalArgumentException if the collection contains a {@code null} element * @since 5.2 */ public static void noNullElements(@Nullable Collection<?> collection, String message) { if (collection != null) { for (Object element : collection) { if (element == null) { throw new IllegalArgumentException(message); } } } } /** * Assert that a collection contains no {@code null} elements. * <p>Note: Does not complain if the collection is empty! * <pre class="code"> * Assert.noNullElements(collection, () -> "Collection " + collectionName + " must contain non-null elements"); * </pre> * @param collection the collection to check * @param messageSupplier a supplier for the exception message to use if the * assertion fails * @throws IllegalArgumentException if the collection contains a {@code null} element * @since 5.2 */ public static void noNullElements(@Nullable Collection<?> collection, Supplier<String> messageSupplier) { if (collection != null) { for (Object element : collection) { if (element == null) { throw new IllegalArgumentException(nullSafeGet(messageSupplier)); } } } } /** * Assert that a Map contains entries; that is, it must not be {@code null} * and must contain at least one entry. * <pre class="code">Assert.notEmpty(map, "Map must contain 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 contains no entries */ public static void notEmpty(@Nullable Map<?, ?> map, String message) { if (CollectionUtils.isEmpty(map)) { throw new IllegalArgumentException(message); } } /** * Assert that a Map contains entries; that is, it must not be {@code null} * and must contain at least one entry. * <pre class="code"> * Assert.notEmpty(map, () -> "The " + mapType + " map must contain entries"); * </pre> * @param map the map to check * @param messageSupplier a supplier for the exception message to use if the * assertion fails * @throws IllegalArgumentException if the map is {@code null} or contains no entries * @since 5.0 */ public static void notEmpty(@Nullable Map<?, ?> map, Supplier<String> messageSupplier) { if (CollectionUtils.isEmpty(map)) { throw new IllegalArgumentException(nullSafeGet(messageSupplier)); } } /** * Assert that a Map contains entries; that is, it must not be {@code null} * and must contain at least one entry. * @deprecated as of 4.3.7, in favor of {@link #notEmpty(Map, String)} */ @Deprecated public static void notEmpty(@Nullable 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, "Foo expected");</pre> * @param type the type to check against * @param obj the object to check * @param message a message which will be prepended to provide further context. * If it is empty or ends in ":" or ";" or "," or ".", a full exception message * will be appended. If it ends in a space, the name of the offending object's * type will be appended. In any other case, a ":" with a space and the name * of the offending object's type will be appended. * @throws IllegalArgumentException if the object is not an instance of type */ public static void isInstanceOf(Class<?> type, @Nullable Object obj, String message) { notNull(type, "Type to check against must not be null"); if (!type.isInstance(obj)) { instanceCheckFailed(type, obj, message); } } /** * Assert that the provided object is an instance of the provided class. * <pre class="code"> * Assert.instanceOf(Foo.class, foo, () -> "Processing " + Foo.class.getSimpleName() + ":"); * </pre> * @param type the type to check against * @param obj the object to check * @param messageSupplier a supplier for the exception message to use if the * assertion fails. See {@link #isInstanceOf(Class, Object, String)} for details. * @throws IllegalArgumentException if the object is not an instance of type * @since 5.0 */ public static void isInstanceOf(Class<?> type, @Nullable Object obj, Supplier<String> messageSupplier) { notNull(type, "Type to check against must not be null"); if (!type.isInstance(obj)) { instanceCheckFailed(type, obj, nullSafeGet(messageSupplier)); } } /** * 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 * @throws IllegalArgumentException if the object is not an instance of type */ public static void isInstanceOf(Class<?> type, @Nullable Object obj) { isInstanceOf(type, obj, ""); } /** * Assert that {@code superType.isAssignableFrom(subType)} is {@code true}. * <pre class="code">Assert.isAssignable(Number.class, myClass, "Number expected");</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 provide further context. * If it is empty or ends in ":" or ";" or "," or ".", a full exception message * will be appended. If it ends in a space, the name of the offending sub type * will be appended. In any other case, a ":" with a space and the name of the * offending sub type will be appended. * @throws IllegalArgumentException if the classes are not assignable */ public static void isAssignable(Class<?> superType, @Nullable Class<?> subType, String message) { notNull(superType, "Super type to check against must not be null"); if (subType == null || !superType.isAssignableFrom(subType)) { assignableCheckFailed(superType, subType, message); } } /** * Assert that {@code superType.isAssignableFrom(subType)} is {@code true}. * <pre class="code"> * Assert.isAssignable(Number.class, myClass, () -> "Processing " + myAttributeName + ":"); * </pre> * @param superType the super type to check against * @param subType the sub type to check * @param messageSupplier a supplier for the exception message to use if the * assertion fails. See {@link #isAssignable(Class, Class, String)} for details. * @throws IllegalArgumentException if the classes are not assignable * @since 5.0 */ public static void isAssignable(Class<?> superType, @Nullable Class<?> subType, Supplier<String> messageSupplier) { notNull(superType, "Super type to check against must not be null"); if (subType == null || !superType.isAssignableFrom(subType)) { assignableCheckFailed(superType, subType, nullSafeGet(messageSupplier)); } } /** * 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, ""); } private static void instanceCheckFailed(Class<?> type, @Nullable Object obj, @Nullable String msg) { String className = (obj != null ? obj.getClass().getName() : "null"); String result = ""; boolean defaultMessage = true; if (StringUtils.hasLength(msg)) { if (endsWithSeparator(msg)) { result = msg + " "; } else { result = messageWithTypeName(msg, className); defaultMessage = false; } } if (defaultMessage) { result = result + ("Object of class [" + className + "] must be an instance of " + type); } throw new IllegalArgumentException(result); } private static void assignableCheckFailed(Class<?> superType, @Nullable Class<?> subType, @Nullable String msg) { String result = ""; boolean defaultMessage = true; if (StringUtils.hasLength(msg)) { if (endsWithSeparator(msg)) { result = msg + " "; } else { result = messageWithTypeName(msg, subType); defaultMessage = false; } } if (defaultMessage) { result = result + (subType + " is not assignable to " + superType); } throw new IllegalArgumentException(result); } private static boolean endsWithSeparator(String msg) { return (msg.endsWith(":") || msg.endsWith(";") || msg.endsWith(",") || msg.endsWith(".")); } private static String messageWithTypeName(String msg, @Nullable Object typeName) { return msg + (msg.endsWith(" ") ? "" : ": ") + typeName; } @Nullable private static String nullSafeGet(@Nullable Supplier<String> messageSupplier) { return (messageSupplier != null ? messageSupplier.get() : null); } }