Master Spring Boot’s Built‑In Utility Classes for Faster Development

Spring Boot provides a set of utility classes that simplify common development tasks and improve code quality.

Assert

Logical checks to validate conditions that should never occur.

Enabled via JVM flag -enableassertions (introduced in JDK 1.4).

Spring Boot’s Assert class is used for data validation.

void notNull(Object object, String message)
void isNull(Object object, String message)
void isTrue(boolean expression, String message)
void notEmpty(Collection collection, String message)
void hasLength(String text, String message)
void hasText(String text, String message)
void isInstanceOf(Class type, Object obj, String message)
void isAssignable(Class superType, Class subType, String message)

ObjectUtils

Object information

String nullSafeClassName(Object obj)
int nullSafeHashCode(Object object)
String nullSafeToString(boolean[] array)
String getIdentityHexString(Object obj)
String identityToString(Object obj)
String getDisplayString(Object obj)

Object checks

boolean isEmpty(Object[] array)
boolean isArray(Object obj)
boolean containsElement(Object[] array, Object element)
boolean nullSafeEquals(Object o1, Object o2)
boolean isEmpty(Object obj)

Other utilities

<A, O extends A> A[] addObjectToArray(A[] array, O obj)
Object[] toObjectArray(Object source)

StringUtils

String checks

boolean isEmpty(Object str)
boolean endsWithIgnoreCase(String str, String suffix)
boolean startsWithIgnoreCase(String str, String prefix)
boolean containsWhitespace(String str)
boolean hasLength(CharSequence str)
boolean hasText(CharSequence str)
boolean substringMatch(CharSequence str, int index, CharSequence substring)
int countOccurrencesOf(String str, String sub)

String operations

String replace(String inString, String oldPattern, String newPattern)
String trimTrailingCharacter(String str, char trailingCharacter)
String trimLeadingCharacter(String str, char leadingCharacter)
String trimLeadingWhitespace(String str)
String trimTrailingWhitespace(String str)
String trimWhitespace(String str)
String trimAllWhitespace(String str)
String delete(String inString, String pattern)
String deleteAny(String inString, String charsToDelete)
String[] trimArrayElements(String[] array)
String uriDecode(String source, Charset charset)

CollectionUtils

Collection checks

boolean isEmpty(Collection<?> collection)
boolean isEmpty(Map<?,?> map)
boolean containsInstance(Collection<?> collection, Object element)
boolean contains(Iterator<?> iterator, Object element)
boolean containsAny(Collection<?> source, Collection<?> candidates)
boolean hasUniqueObject(Collection<?> collection)

Collection operations

<E> void mergeArrayIntoCollection(Object array, Collection<E> collection)
<K,V> void mergePropertiesIntoMap(Properties props, Map<K,V> map)
<T> T lastElement(List<T> list)
<T> T lastElement(Set<T> set)
<E> E findFirstMatch(Collection<?> source, Collection<E> candidates)
<T> T findValueOfType(Collection<?> collection, Class<T> type)
Object findValueOfType(Collection<?> collection, Class<?>[] types)
Class<?> findCommonElementType(Collection<?> collection)

FileCopyUtils

Input

byte[] copyToByteArray(File in)
byte[] copyToByteArray(InputStream in)
String copyToString(Reader in)

Output

void copy(byte[] in, File out)
int copy(File in, File out)
void copy(byte[] in, OutputStream out)
int copy(InputStream in, OutputStream out)
int copy(Reader in, Writer out)
void copy(String in, Writer out)

ResourceUtils

Resource handling

static boolean isUrl(String resourceLocation)
static URL getURL(String resourceLocation)
static File getFile(String resourceLocation)

Resource types

FileSystemResource
UrlResource
ClassPathResource
ServletContextResource

Resource operations

boolean exists()
File getFile()
URI getURI()
URL getURL()
InputStream getInputStream()
String getDescription()

StreamUtils

Input

void copy(byte[] in, OutputStream out)
int copy(InputStream in, OutputStream out)
void copy(String in, Charset charset, OutputStream out)
long copyRange(InputStream in, OutputStream out, long start, long end)

Output

byte[] copyToByteArray(InputStream in)
String copyToString(InputStream in, Charset charset)
int drain(InputStream in)

ReflectionUtils

Method handling

Method findMethod(Class<?> clazz, String name)
Method findMethod(Class<?> clazz, String name, Class<?>... paramTypes)
Method[] getAllDeclaredMethods(Class<?> leafClass)
Constructor<T> accessibleConstructor(Class<T> clazz, Class<?>... parameterTypes)
boolean isEqualsMethod(Method method)
boolean isHashCodeMethod(Method method)
boolean isToStringMethod(Method method)
boolean isObjectMethod(Method method)
boolean declaresException(Method method, Class<?> exceptionType)

Method invocation

Object invokeMethod(Method method, Object target)
Object invokeMethod(Method method, Object target, Object... args)
void makeAccessible(Method method)
void makeAccessible(Constructor<?> ctor)

Field handling

Field findField(Class<?> clazz, String name)
Field findField(Class<?> clazz, String name, Class<?> type)
boolean isPublicStaticFinal(Field field)
Object getField(Field field, Object target)
void setField(Field field, Object target, Object value)
void shallowCopyFieldState(Object src, Object dest)
void makeAccessible(Field field)
void doWithFields(Class<?> clazz, ReflectionUtils.FieldCallback fc)
void doWithFields(Class<?> clazz, ReflectionUtils.FieldCallback fc, ReflectionUtils.FieldFilter ff)
void doWithLocalFields(Class<?> clazz, ReflectionUtils.FieldCallback fc)

AopUtils

boolean isAopProxy()
boolean isJdkDynamicProxy()
boolean isCglibProxy()
Class<?> getTargetClass()

AopContext

Object currentProxy()

By leveraging these built‑in Spring Boot utilities, developers can reduce boilerplate code, improve readability, and increase overall productivity when building backend applications.