public abstract class Assert extends Object
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 (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 Jakarta's Commons Lang >= 2.0 for a more comprehensive suite of assertion utilities.
Constructor and Description |
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Assert() |
Modifier and Type | Method and Description |
---|---|
static void |
isAssignable(Class<?> superType,
Class<?> subType,
String message)
Assert that
superType.isAssignableFrom(subType) is true . |
static void |
isInstanceOf(Class<?> type,
Object obj,
String message)
Assert that the provided object is an instance of the provided class.
|
static void |
isNull(Object object,
String message)
Assert that an object is
null . |
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(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 . |
public static void isTrue(boolean expression, String message)
IllegalArgumentException
if the test result is false
. Assert.isTrue(i > 0, "The value must be greater than zero");
expression
- a boolean expressionmessage
- the exception message to use if the assertion failsIllegalArgumentException
- if expression is false
public static void isTrue(boolean expression)
IllegalArgumentException
if the test result is false
. Assert.isTrue(i > 0);
expression
- a boolean expressionIllegalArgumentException
- if expression is false
public static void isNull(Object object, String message)
null
. Assert.isNull(value, "The value must be null");
object
- the object to checkmessage
- the exception message to use if the assertion failsIllegalArgumentException
- if the object is not null
public static void notNull(Object object, String message)
null
. Assert.notNull(clazz, "The class must not be null");
object
- the object to checkmessage
- the exception message to use if the assertion failsIllegalArgumentException
- if the object is null
public static void notNull(Object object)
null
. Assert.notNull(clazz);
object
- the object to checkIllegalArgumentException
- if the object is null
public static void notEmpty(Object[] array, String message)
null
and must have at least one element. Assert.notEmpty(array, "The array must have elements");
array
- the array to checkmessage
- the exception message to use if the assertion failsIllegalArgumentException
- if the object array is null
or has no elementspublic static void isInstanceOf(Class<?> type, Object obj, String message)
Assert.instanceOf(Foo.class, foo);
type
- the type to check againstobj
- the object to checkmessage
- 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.IllegalArgumentException
- if the object is not an instance of clazzClass.isInstance(java.lang.Object)
public static void isAssignable(Class<?> superType, Class<?> subType, String message)
superType.isAssignableFrom(subType)
is true
. Assert.isAssignable(Number.class, myClass);
superType
- the super type to check againstsubType
- the sub type to checkmessage
- 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.IllegalArgumentException
- if the classes are not assignablepublic static void state(boolean expression, String message)
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");
expression
- a boolean expressionmessage
- the exception message to use if the assertion failsIllegalStateException
- if expression is false
public static void state(boolean expression)
IllegalStateException
if the test result is false
. Call
isTrue(boolean)
if you wish to throw IllegalArgumentException
on an assertion failure.
Assert.state(id == null);
expression
- a boolean expressionIllegalStateException
- if the supplied expression is false
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