Package com.ocs.dynamo.utils

Class ClassUtils

java.lang.Object

com.ocs.dynamo.utils.ClassUtils

public final class ClassUtils
extends Object

Author:

patrick.deenen Utility class for dealing with classes and annotations

Method Summary

Modifier and Type	Method	Description
static boolean	canSetProperty(Object obj, String fieldName)	Checks if the specified property can be set for the specified object.
static void	clearFieldValue(Object obj, String fieldName, Class<?> argType)	Clears a field
static <T,S extends T> void	copyFields(T from, S to)
static Class<?>	forClass(String clazz)	forClass which doesn't throw an exception and can handle empty class names
static <T extends Annotation> T	getAnnotation(Class<?> clazz, String fieldName, Class<T> annotationClass)	Tries to retrieve an annotation, by first looking at the field name, and then at the getter method
static <T extends Annotation,R> R	getAnnotationAttributeValue(Field field, Class<T> annotationClass, String attributeName)	Get the value of a field in an annotation
static <T extends Annotation> T	getAnnotationOnField(Class<?> clazz, String fieldName, Class<T> annotationClass)	Return an annotation on a certain field
static <T extends Annotation> T	getAnnotationOnField(Field field, Class<T> annotationClass)	Returns an annotation on a certain field
static <T extends Annotation> T	getAnnotationOnMethod(Class<?> clazz, String fieldName, Class<T> annotationClass)	Looks for an annotation on a getter method
static <T extends Annotation> T	getAnnotationOnMethod(Method method, Class<T> annotationClass)	Looks for an annotation on a (getter) method
static byte[]	getBytes(Object obj, String fieldName)	Retrieves the contents of a field as a byte array
static <T> Constructor<T>	getConstructor(Class<T> clazz, Object... args)	Find constructor based on the types of the given arguments used to instantiate the class with the found constructor
static Field	getField(Class<?> clazz, String fieldName)	Returns a field with a certain name from a class
static Object	getFieldValue(Object obj, String fieldName)	Retrieves a field value
static String	getFieldValueAsString(Object obj, String fieldName)	Returns a field value as a String
static String	getFieldValueAsString(Object obj, String fieldName, String defValue)	Returns a field value as a String
static Method	getGetterMethod(Class<?> clazz, String fieldName)	Retrieves the getter method for a certain property
static int	getMaxLength(Class<?> clazz, String fieldName)	Returns the maximum allowed length of a field
static PropertyDescriptor	getPropertyDescriptorForNestedProperty(Class<?> clazz, String property)	Returns the property descriptor for a nested property
static <T> Class<?>	getResolvedType(Class<T> type, String fieldName, int... indexes)	Return a Class representing the generic parameter for the given indexes.
static Class<?>	getResolvedType(Object object, int... indexes)	Return a Class representing the generic parameter for the given indexes.
static boolean	hasMethod(Object obj, String methodName)	Check if the object has a (public) method that has the specified name
static <T> T	instantiateClass(Class<T> clazz, Object... args)	Instantiate a class with the given arguments; assumed is that all arguments are not null so the types can be determined and a matching constructor can be found.
static void	setBytes(byte[] bytes, Object obj, String fieldName)
static void	setFieldValue(Object obj, String fieldName, Object value)

Methods inherited from class java.lang.Object

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

Method Detail

canSetProperty

public static boolean canSetProperty(Object obj,
                                     String fieldName)

Checks if the specified property can be set for the specified object. This method supports nested properties

Parameters:

obj - the object

fieldName - the name of the field

Returns:

clearFieldValue

public static void clearFieldValue(Object obj,
                                   String fieldName,
                                   Class<?> argType)

Clears a field

Parameters:

obj - the object on which to clear the field

fieldName - the name of the field

argType -

forClass

public static Class<?> forClass(String clazz)

forClass which doesn't throw an exception and can handle empty class names

Parameters:

clazz - The fully qualified class name

Returns:

the specified class and null when class is not found

getAnnotation

public static <T extends Annotation> T getAnnotation(Class<?> clazz,
                                                     String fieldName,
                                                     Class<T> annotationClass)

Tries to retrieve an annotation, by first looking at the field name, and then at the getter method

Parameters:

clazz - the class

fieldName - the name of the field

annotationClass - the annotation class to look for

Returns:

getAnnotationAttributeValue

public static <T extends Annotation,R> R getAnnotationAttributeValue(Field field,
                                                                           Class<T> annotationClass,
                                                                           String attributeName)

Get the value of a field in an annotation

Parameters:

field - The field with annotations

annotionType - The name of the annotation type to find

attributeName - The name of the attribute on the annotation type to find the value

Returns:

the value of the field of the annotation or null when not found

getAnnotationOnField

public static <T extends Annotation> T getAnnotationOnField(Class<?> clazz,
                                                            String fieldName,
                                                            Class<T> annotationClass)

Return an annotation on a certain field

Parameters:

clazz - the class

fieldName - the field name

annotationClass - the class of the annotation

Returns:

getAnnotationOnField

public static <T extends Annotation> T getAnnotationOnField(Field field,
                                                            Class<T> annotationClass)

Returns an annotation on a certain field

Parameters:

field - the field

annotationClass - the annotation class

Returns:

getAnnotationOnMethod

public static <T extends Annotation> T getAnnotationOnMethod(Class<?> clazz,
                                                             String fieldName,
                                                             Class<T> annotationClass)

Looks for an annotation on a getter method

Parameters:

clazz - the class

fieldName - the name of the field (will be prepended with "get")

annotationClass - the class of the annotation to look for

Returns:

getAnnotationOnMethod

public static <T extends Annotation> T getAnnotationOnMethod(Method method,
                                                             Class<T> annotationClass)

Looks for an annotation on a (getter) method

Parameters:

method - the method

annotationClass - the class of the annotation

Returns:

getBytes

public static byte[] getBytes(Object obj,
                              String fieldName)

Retrieves the contents of a field as a byte array

Parameters:

obj -

fieldName -

Returns:

getConstructor

public static <T> Constructor<T> getConstructor(Class<T> clazz,
                                                Object... args)

Find constructor based on the types of the given arguments used to instantiate the class with the found constructor

Parameters:

clazz -

args -

Returns:

getField

public static Field getField(Class<?> clazz,
                             String fieldName)

Returns a field with a certain name from a class

Parameters:

clazz - the class

fieldName - the name of the filed

Returns:

getFieldValue

public static Object getFieldValue(Object obj,
                                   String fieldName)

Retrieves a field value

Parameters:

obj - the object from which to retrieve the field value

fieldName - the name of the field

Returns:

getFieldValueAsString

public static String getFieldValueAsString(Object obj,
                                           String fieldName)

Returns a field value as a String

Parameters:

obj - the object

fieldName - the name of the field

Returns:

getFieldValueAsString

public static String getFieldValueAsString(Object obj,
                                           String fieldName,
                                           String defValue)

Returns a field value as a String

Parameters:

obj - the object

fieldName - the name of the field

defValue - the default value that is used in case of a null value

Returns:

getGetterMethod

public static Method getGetterMethod(Class<?> clazz,
                                     String fieldName)

Retrieves the getter method for a certain property

Parameters:

clazz - the class

fieldName - the name of the property

Returns:

getMaxLength

public static int getMaxLength(Class<?> clazz,
                               String fieldName)

Returns the maximum allowed length of a field

Parameters:

clazz -

fieldName -

Returns:

getPropertyDescriptorForNestedProperty

public static PropertyDescriptor getPropertyDescriptorForNestedProperty(Class<?> clazz,
                                                                        String property)

Returns the property descriptor for a nested property

Parameters:

clazz - the class

property - the name of the property

Returns:

getResolvedType

public static <T> Class<?> getResolvedType(Class<T> type,
                                           String fieldName,
                                           int... indexes)

Return a Class representing the generic parameter for the given indexes. Indexes are zero based; for example given the type Map>, getGeneric(0) will access the Integer. Nested generics can be accessed by specifying multiple indexes; for example getGeneric(1, 0) will access the String from the nested List. For convenience, if no indexes are specified the first generic is returned.

Parameters:

type -

fieldName -

indexes -

Returns:

getResolvedType

public static Class<?> getResolvedType(Object object,
                                       int... indexes)

Return a Class representing the generic parameter for the given indexes. Indexes are zero based; for example given the type Map>, getGeneric(0) will access the Integer. Nested generics can be accessed by specifying multiple indexes; for example getGeneric(1, 0) will access the String from the nested List. For convenience, if no indexes are specified the first generic is returned.

Parameters:

method - or method parameter or type

indexes -

Returns:

hasMethod

public static boolean hasMethod(Object obj,
                                String methodName)

Check if the object has a (public) method that has the specified name

Parameters:

obj -

methodName -

Returns:

instantiateClass

public static <T> T instantiateClass(Class<T> clazz,
                                     Object... args)

Instantiate a class with the given arguments; assumed is that all arguments are not null so the types can be determined and a matching constructor can be found. When no constructor is found null is returned.

Parameters:

clazz -

args -

Returns:

setBytes

public static void setBytes(byte[] bytes,
                            Object obj,
                            String fieldName)

setFieldValue

public static void setFieldValue(Object obj,
                                 String fieldName,
                                 Object value)

Parameters:

obj -

fieldName -

value -

copyFields

public static <T,S extends T> void copyFields(T from,
                                                    S to)