org.springframework.util
Class Assert

java.lang.Object
  org.springframework.util.Assert

public abstract class Assert

extends Object

Assert utility class that assists in validating arguments. Useful for identifying programmer errors early and obviously at runtime.

For example, if the contract of a public method states it does not allow 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.

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.

This class is similar to JUnit's assertion library. If an argument value is deemed invalid, an IllegalArgumentException is thrown. 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 Jakarta's Commons Lang >= 2.0 for a more comprehensive suite of assertion utilities.

Since:

1.1.2

Author:

Keith Donald, Juergen Hoeller, Colin Sampaleanu

Constructor Summary

Assert()

Method Summary

static void	hasLength(String text) Assert that a string is not empty; that is, it must not be null and not empty.
static void	hasLength(String text, String message) Assert that a string is not empty; that is, it must not be null and not empty.
static void	hasText(String text) Assert that a string has valid text content; that is, it must not be null and must contain at least one non-whitespace character.
static void	hasText(String text, String message) Assert that a string has valid text content; that is, it must not be null and must contain at least one non-whitespace character.
static void	isInstanceOf(Class clazz, Object obj) Assert that the provided object is an instance of the provided class.
static void	isInstanceOf(Class clazz, Object obj, String message) Assert that the provided object is an instance of the provided class.
static void	isTrue(boolean expression) Assert a boolean expression, throwing IllegalArgumentException if the test result is false.
static void	isTrue(boolean expression, String message) Assert a boolean expression, throwing IllegalArgumentException if the test result is false.
static void	notEmpty(Collection collection) Assert that a collection has elements; that is, it must not be null and must have at least one element.
static void	notEmpty(Collection collection, String message) Assert that a collection has elements; that is, it must not be null and must have at least one element.
static void	notEmpty(Map map) Assert that a Map has entries; that is, it must not be null and must have at least one entry.
static void	notEmpty(Map map, String message) Assert that a Map has entries; that is, it must not be null and must have at least one entry.
static void	notEmpty(Object[] array) Assert that an array has elements; that is, it must not be null and must have at least one element.
static void	notEmpty(Object[] array, String message) Assert that an array has elements; that is, it must not be null and must have at least one element.
static void	notNull(Object object) Assert that an object is not null.
static void	notNull(Object object, String message) Assert that an object is not null.
static void	state(boolean expression) Assert a boolean expression, throwing IllegalStateException if the test result is false.
static void	state(boolean expression, String message) Assert a boolean expression, throwing IllegalStateException if the test result is false.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Assert

public Assert()

Method Detail

isTrue

public static void isTrue(boolean expression,
                          String message)

Assert a boolean expression, throwing IllegalArgumentException if the test result is false.

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

Parameters:

expression - a boolean expression

message - the exception message to use if the assertion fails

Throws:

IllegalArgumentException - if expression is false

isTrue

public static void isTrue(boolean expression)

Assert a boolean expression, throwing IllegalArgumentException if the test result is false.

 Assert.isTrue(i > 0);

Parameters:

expression - a boolean expression

Throws:

IllegalArgumentException - if expression is false

notNull

public static void notNull(Object object,
                           String message)

Assert that an object is not null.

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

Parameters:

object - the object to check

message - the exception message to use if the assertion fails

Throws:

IllegalArgumentException - if the object is null

notNull

public static void notNull(Object object)

Assert that an object is not null.

 Assert.notNull(clazz);

Parameters:

object - the object to check

Throws:

IllegalArgumentException - if the object is null

hasLength

public static void hasLength(String text,
                             String message)

Assert that a string is not empty; that is, it must not be null and not empty.

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

Parameters:

text - the string to check

See Also:

StringUtils.hasLength(java.lang.String)

hasLength

public static void hasLength(String text)

Assert that a string is not empty; that is, it must not be null and not empty.

 Assert.hasLength(name);

Parameters:

text - the string to check

See Also:

StringUtils.hasLength(java.lang.String)

hasText

public static void hasText(String text,
                           String message)

Assert that a string has valid text content; that is, it must not be null and must contain at least one non-whitespace character.

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

Parameters:

text - the string to check

See Also:

StringUtils.hasText(java.lang.String)

hasText

public static void hasText(String text)

Assert that a string has valid text content; that is, it must not be null and must contain at least one non-whitespace character.

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

Parameters:

text - the string to check

See Also:

StringUtils.hasText(java.lang.String)

notEmpty

public static void notEmpty(Object[] array,
                            String message)

Assert that an array has elements; that is, it must not be null and must have at least one element.

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

Parameters:

array - the array to check

message - the exception message to use if the assertion fails

Throws:

IllegalArgumentException - if the object array is null or has no elements

notEmpty

public static void notEmpty(Object[] array)

Assert that an array has elements; that is, it must not be null and must have at least one element.

 Assert.notEmpty(array);

Parameters:

array - the array to check

Throws:

IllegalArgumentException - if the object array is null or has no elements

notEmpty

public static void notEmpty(Collection collection,
                            String message)

Assert that a collection has elements; that is, it must not be null and must have at least one element.

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

Parameters:

collection - the collection to check

message - the exception message to use if the assertion fails

Throws:

IllegalArgumentException - if the collection is null or has no elements

notEmpty

public static void notEmpty(Collection collection)

Assert that a collection has elements; that is, it must not be null and must have at least one element.

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

Parameters:

collection - the collection to check

Throws:

IllegalArgumentException - if the collection is null or has no elements

notEmpty

public static void notEmpty(Map map,
                            String message)

Assert that a Map has entries; that is, it must not be null and must have at least one entry.

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

Parameters:

map - the map to check

message - the exception message to use if the assertion fails

Throws:

IllegalArgumentException - if the map is null or has no entries

notEmpty

public static void notEmpty(Map map)

Assert that a Map has entries; that is, it must not be null and must have at least one entry.

 Assert.notEmpty(map);

Parameters:

map - the map to check

Throws:

IllegalArgumentException - if the map is null or has no entries

isInstanceOf

public static void isInstanceOf(Class clazz,
                                Object obj)

Assert that the provided object is an instance of the provided class.

 Assert.instanceOf(Foo.class, foo);

Parameters:

clazz - the required class

obj - the object to check

Throws:

IllegalArgumentException - if the object is not an instance of clazz

See Also:

Class.isInstance(java.lang.Object)

isInstanceOf

public static void isInstanceOf(Class clazz,
                                Object obj,
                                String message)

Assert that the provided object is an instance of the provided class.

 Assert.instanceOf(Foo.class, foo);

Parameters:

clazz - the required class

obj - the object to check

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 Also:

Class.isInstance(java.lang.Object)

state

public static void state(boolean expression,
                         String message)

Assert a boolean expression, throwing IllegalStateException if the test result is 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");

Parameters:

expression - a boolean expression

message - the exception message to use if the assertion fails

Throws:

IllegalStateException - if expression is false

state

public static void state(boolean expression)

Assert a boolean expression, throwing IllegalStateException if the test result is false. Call isTrue if you wish to throw IllegalArgumentException on an assertion failure.

 Assert.state(id == null);

Parameters:

expression - a boolean expression

Throws:

IllegalStateException - if expression is false