Spring的断言工具类Assert的基本使用
org.springframework.util.Assert;
Assert工具类，通常用于数据合法性检查。
平时做判断通常都是这样写：
if(message == null || message.equals("")){
throw new IllegalArgumentException("输入信息错误!");
}
用Assert工具类上面的代码可以简化为：
Assert.hasText(message, "输入信息错误!");
介绍如下：
/**
* 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
* @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");
}
