spring-util-对参数校验的支持 org.springframework.util.Assert

org.springframework.util.Assert

 Assert.notNull(object, message);

实现如下：

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/*
 * 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.
 *
 *

Useful for identifying programmer errors early and clearly at runtime.
 *
 *

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.
 *
 *

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.
 *
 *

This class is similar to JUnit's assertion library. If an argument value is
 * deemed invalid, an {@link IllegalArgumentException} is thrown (typically).
 * For example:
 *
 *

 * Assert.notNull(clazz, "The class must not be null");
 * Assert.isTrue(i > 0, "The value must be greater than zero");

 *
 *

Mainly for internal use within the framework; consider
 * Apache's Commons Lang
 * 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}.
*

Assert.isTrue(i > 0, "The value must be greater than zero");

* @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}.
*

Assert.isTrue(i > 0);

* @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} .
*

Assert.isNull(value, "The value must be null");

* @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} .
*

Assert.isNull(value);

* @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} .
*

Assert.notNull(clazz, "The class must not be null");

* @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} .
*

Assert.notNull(clazz);

* @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.
*

Assert.hasLength(name, "Name must not be empty");

* @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.
*

Assert.hasLength(name);

* @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.
*

Assert.hasText(name, "'name' must not be empty");

* @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.
*

Assert.hasText(name, "'name' must not be empty");

* @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.
*

Assert.doesNotContain(name, "rod", "Name must not contain 'rod'");

* @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.
*

Assert.doesNotContain(name, "rod");

* @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.
*

Assert.notEmpty(array, "The array must have elements");

* @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.
*

Assert.notEmpty(array);

* @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!
*

Assert.noNullElements(array, "The array must have non-null elements");

* @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!
*

Assert.noNullElements(array);

* @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.
*

Assert.notEmpty(collection, "Collection must have elements");

* @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.
*

Assert.notEmpty(collection, "Collection must have elements");

* @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.
*

Assert.notEmpty(map, "Map must have entries");

* @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.
*

Assert.notEmpty(map);

* @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.
*

Assert.instanceOf(Foo.class, foo);

* @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.
*

Assert.instanceOf(Foo.class, foo);

* @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}.
*

Assert.isAssignable(Number.class, myClass);

* @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}.
*

Assert.isAssignable(Number.class, myClass);

* @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.
*

Assert.state(id == null, "The id property must not already be initialized");

* @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}.
*

Call {@link #isTrue(boolean)} if you wish to
* throw {@link IllegalArgumentException} on an assertion failure.
*

Assert.state(id == null);

* @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");
}


}