org.springframework.util

Class Assert


  • public abstract class Assert
    extends Object
    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 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.
    Since:
    1.1.2
    Author:
    Keith Donald, Juergen Hoeller, Colin Sampaleanu, Rob Harrop
    • Constructor Summary

      Constructors  
      Constructor and Description
      Assert() 
    • Method Summary

      Methods  
      Modifier and Type Method and Description
      static void doesNotContain(String textToSearch, String substring)
      Assert that the given text does not contain the given substring.
      static void doesNotContain(String textToSearch, String substring, String message)
      Assert that the given text does not contain the given substring.
      static void hasLength(String text)
      Assert that the given String is not empty; that is, it must not be null and not the empty String.
      static void hasLength(String text, String message)
      Assert that the given String is not empty; that is, it must not be null and not the empty String.
      static void hasText(String text)
      Assert that the given 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 the given String has valid text content; that is, it must not be null and must contain at least one non-whitespace character.
      static void isAssignable(Class<?> superType, Class<?> subType)
      Assert that superType.isAssignableFrom(subType) is true.
      static void isAssignable(Class<?> superType, Class<?> subType, String message)
      Assert that superType.isAssignableFrom(subType) is true.
      static void isInstanceOf(Class<?> clazz, Object obj)
      Assert that the provided object is an instance of the provided class.
      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)
      Assert that an object is null .
      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 noNullElements(Object[] array)
      Assert that an array has no null elements.
      static void noNullElements(Object[] array, String message)
      Assert that an array has no null elements.
      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.
    • 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
      • isNull

        public static void isNull(Object object,
                  String message)
        Assert that an object is null .
        Assert.isNull(value, "The value must be null");
        Parameters:
        object - the object to check
        message - the exception message to use if the assertion fails
        Throws:
        IllegalArgumentException - if the object is not null
      • isNull

        public static void isNull(Object object)
        Assert that an object is null .
        Assert.isNull(value);
        Parameters:
        object - the object to check
        Throws:
        IllegalArgumentException - if the object is not null
      • 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 the given String is not empty; that is, it must not be null and not the empty String.
        Assert.hasLength(name, "Name must not be empty");
        Parameters:
        text - the String to check
        message - the exception message to use if the assertion fails
        See Also:
        StringUtils.hasLength(java.lang.CharSequence)
      • hasLength

        public static void hasLength(String text)
        Assert that the given String is not empty; that is, it must not be null and not the empty String.
        Assert.hasLength(name);
        Parameters:
        text - the String to check
        See Also:
        StringUtils.hasLength(java.lang.CharSequence)
      • hasText

        public static void hasText(String text,
                   String message)
        Assert that the given 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
        message - the exception message to use if the assertion fails
        See Also:
        StringUtils.hasText(java.lang.CharSequence)
      • hasText

        public static void hasText(String text)
        Assert that the given 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.CharSequence)
      • doesNotContain

        public static void doesNotContain(String textToSearch,
                          String substring,
                          String message)
        Assert that the given text does not contain the given substring.
        Assert.doesNotContain(name, "rod", "Name must not contain 'rod'");
        Parameters:
        textToSearch - the text to search
        substring - the substring to find within the text
        message - the exception message to use if the assertion fails
      • doesNotContain

        public static void doesNotContain(String textToSearch,
                          String substring)
        Assert that the given text does not contain the given substring.
        Assert.doesNotContain(name, "rod");
        Parameters:
        textToSearch - the text to search
        substring - the substring to find within the text
      • 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
      • noNullElements

        public static void noNullElements(Object[] array,
                          String message)
        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");
        Parameters:
        array - the array to check
        message - the exception message to use if the assertion fails
        Throws:
        IllegalArgumentException - if the object array contains a null element
      • noNullElements

        public static void noNullElements(Object[] array)
        Assert that an array has no null elements. Note: Does not complain if the array is empty!
        Assert.noNullElements(array);
        Parameters:
        array - the array to check
        Throws:
        IllegalArgumentException - if the object array contains a null element
      • 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<?> type,
                        Object obj,
                        String message)
        Assert that the provided object is an instance of the provided class.
        Assert.instanceOf(Foo.class, foo);
        Parameters:
        type - the type to check against
        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)
      • isAssignable

        public static void isAssignable(Class<?> superType,
                        Class<?> subType)
        Assert that superType.isAssignableFrom(subType) is true.
        Assert.isAssignable(Number.class, myClass);
        Parameters:
        superType - the super type to check
        subType - the sub type to check
        Throws:
        IllegalArgumentException - if the classes are not assignable
      • isAssignable

        public static void isAssignable(Class<?> superType,
                        Class<?> subType,
                        String message)
        Assert that superType.isAssignableFrom(subType) is true.
        Assert.isAssignable(Number.class, myClass);
        Parameters:
        superType - the super type to check against
        subType - the sub type 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 classes are not assignable
      • 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