assertions

  1. An assertion is a logical judgment that checks for something that should not happen

  2. The Assert keyword was introduced in JDK1.4 and is enabled with the JVM parameter -enableassertions

  3. The Assert assertion utility class is provided in SpringBoot and is typically used for data validity checking

    // The object parameter must be Not Null. Otherwise, an exception will be thrown
The message parameter is used to customize exception information.
void notNull(Object object, String message)
// The parameter must be Null; otherwise, an exception will be thrown and not allowed.
// The opposite of the notNull() method assertion rule
void isNull(Object object, String message)
// The argument must be True, otherwise an exception will be thrown and not allowed.
void isTrue(boolean expression, String message)
// The parameter (List/Set) must Not be Empty. Otherwise, an exception will be thrown
void notEmpty(Collection collection, String message)
// The argument (String) must have a length (i.e., Not Empty), otherwise an exception will be thrown and Not allowed
void hasLength(String text, String message)
// The parameter (String) must have content (i.e., Not Blank), otherwise an exception will be thrown
void hasText(String text, String message)
// If the parameter is an instance of the specified type, an exception will be thrown
void isInstanceOf(Class type, Object obj, String message)
SubType must be a subclass or implementation class of superType. Otherwise, an exception will be thrown
void isAssignable(Class superType, Class subType, String message)
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Objects, arrays, collections

ObjectUtils

  1. Gets basic information about an object

    // Get the class name of the object. If argument is null, return string: "null"
String nullSafeClassName(Object obj)
// Returns 0 if the argument is null
int nullSafeHashCode(Object object)
// If the argument is null, the string "null" is returned.
String nullSafeToString(boolean[] array)
// Get the object HashCode (hexadecimal string). If the argument is null, 0 is returned
String getIdentityHexString(Object obj)
// Get the class name and HashCode of the object. If null is used, the string "" is returned.
String identityToString(Object obj)
// Equivalent to the toString() method, but null returns the string ""
String getDisplayString(Object obj)
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  2. Judge the tool

    // Check whether the array is empty
boolean isEmpty(Object[] array)
// Check whether the argument object is an array
boolean isArray(Object obj)
// Determine whether the array contains the specified element
boolean containsElement(Object[] array, Object element)
// Return true for equal or both null values
boolean nullSafeEquals(Object o1, Object o2)
/* Check whether the parameter object is empty by using the following criteria: Optional: option.empty () Array: length == 0 CharSequence: length == 0 Collection: Collection.isEmpty() Map: Map.isEmpty() */
boolean isEmpty(Object obj)
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  3. Other tools and methods

    // Appends a new element to the end of the argument array and returns a new array
<A, O extends A> A[] addObjectToArray(A[] array, O obj)
// Native base type array --> wrapper class array
Object[] toObjectArray(Object source)
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StringUtils

  1. String judgment tool

    // Check whether the string is null, or "". Note that strings containing whitespace are non-empty
boolean isEmpty(Object str)
// Checks if the string ends with the specified content. Ignore case
boolean endsWithIgnoreCase(String str, String suffix)
// Determine if the string has a specified content beginning. Ignore case
boolean startsWithIgnoreCase(String str, String prefix) 
// Whether to include whitespace
boolean containsWhitespace(String str)
// Check that the string is Not Empty and the length is Not 0, that is, Not Empty
boolean hasLength(CharSequence str)
// Determine if the string contains actual content, i.e., Not just whitespace, i.e., Not Blank
boolean hasText(CharSequence str)
// Determines whether the string contains a substring at the specified index.
boolean substringMatch(CharSequence str, int index, CharSequence substring)
// Count the number of occurrences of the stator in a string
int countOccurrencesOf(String str, String sub)
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  2. String manipulation tool

    // Find and replace the specified substring
String replace(String inString, String oldPattern, String newPattern)
// Remove specific characters from the tail
String trimTrailingCharacter(String str, char trailingCharacter) 
// Remove specific characters from the header
String trimLeadingCharacter(String str, char leadingCharacter)
// Remove the header whitespace
String trimLeadingWhitespace(String str)
// Remove the header whitespace
String trimTrailingWhitespace(String str)
// Remove the header and tail whitespace
String trimWhitespace(String str)
// Remove the beginning, end, and middle whitespace
String trimAllWhitespace(String str)
// Delete the specified substring
String delete(String inString, String pattern)
// Delete the specified character.
String deleteAny(String inString, String charsToDelete)
// Executes the trim() method on each entry of the array
String[] trimArrayElements(String[] array)
// Decode the URL string
String uriDecode(String source, Charset charset)
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  3. Path-related tool methods

    // Parse the path string to optimize the ".."
String cleanPath(String path)
// Parse the path string, parse out the filename part
String getFilename(String path)
// Parse the path string to resolve the file name extension
String getFilenameExtension(String path)
// Compare two strings to see if they are the same path. The.. in the path is automatically processed.
boolean pathEquals(String path1, String path2)
// Delete the suffix in the file path name
String stripFilenameExtension(String path) 
// Get the last part of it with a ". "delimiter
String unqualify(String qualifiedName)
// Get the last part of the delimiter with the specified character
String unqualify(String qualifiedName, char separator)
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CollectionUtils

  1. Set judgment tool

    // Check whether List/Set is empty
boolean isEmpty(Collection
          collection)
// Check whether Map is empty
boolean isEmpty(Map
          map)
// Check whether the List/Set contains an object
boolean containsInstance(Collection
          collection, Object element)
// Use an iterator to determine if a List/Set contains an object
boolean contains(Iterator
          iterator, Object element)
// Check whether List/Set contains any of the objects
boolean containsAny(Collection
          source, Collection
          candidates)
// Determine if each element in List/Set is unique. There are no duplicate elements in List/Set
boolean hasUniqueObject(Collection
          collection)
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  2. Set manipulation tool

    // Add elements from the Array to the List/Set
<E> void mergeArrayIntoCollection(Object array, Collection<E> collection)  
// Add key-value pairs from Properties to the Map
<K,V> void mergePropertiesIntoMap(Properties props, Map<K,V> map)
// Returns the last element in the List
<T> T lastElement(List<T> list)  
// Return the last element in Set
<T> T lastElement(Set<T> set) 
// Return the first element of the argument source that exists in the argument source
<E> E findFirstMatch(Collection
          source, Collection
         
           candidates)
         
// Returns the element of the specified type in List/Set.
<T> T findValueOfType(Collection
          collection, Class
         
           type)
         
// Returns the element of the specified type in List/Set. If the first type is not found, the second type is looked for, and so on
Object findValueOfType(Collection
          collection, Class
         [] types)
// Returns the type of the element in List/SetClass<? >findCommonElementType(Collection
          collection)
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Files, resources, IO streams

FileCopyUtils

  1. The input

    // Read from a file into a byte array
byte[] copyToByteArray(File in)
// Read from the input stream into a byte array
byte[] copyToByteArray(InputStream in)
// Read into a string from the input stream
String copyToString(Reader in)
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  2. The output

    // From byte array to file
void copy(byte[] in, File out)
// From file to file
int copy(File in, File out)
// From the byte array to the output stream
void copy(byte[] in, OutputStream out) 
// From input stream to output stream
int copy(InputStream in, OutputStream out) 
// From input stream to output stream
int copy(Reader in, Writer out)
// From string to output stream
void copy(String in, Writer out)
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ResourceUtils

  1. Get the file from the resource path

    // Check if the string is a valid URL string.
static boolean isUrl(String resourceLocation)
/ / get the URL
static URL getURL(String resourceLocation) 
// Get the file (it can't be used in JAR, it needs to be a separate file)
static File	getFile(String resourceLocation)
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  2. Resource

    // File system resource D:\...
FileSystemResource
// URL resources, such as file://... http://...
UrlResource
// Resources in the classpath, classpth:...
ClassPathResource
// Resources in the context of the Web container (jar, WAR)
ServletContextResource
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    // Check whether the resource exists
boolean exists(a)
// Get the File object from the resource
File getFile(a)
// Get the URI object from the resource
URI getURI(a)
// Get the URI object from the resource
URL getURL(a)
// Get the InputStream of the resource
InputStream getInputStream(a)
// Obtain the description of the resource
String getDescription(a)
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StreamUtils

  1. The 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)
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  2. The output

    byte[] copyToByteArray(InputStream in)
String copyToString(InputStream in, Charset charset)
// Discard the contents of the input stream
int drain(InputStream in) 
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Reflection, AOP

ReflectionUtils

  1. Access method

    // Find the specified method in the class
Method findMethod(Class
          clazz, String name) 
// As above, provide additional method parameter types as search criteria
Method findMethod(Class
          clazz, String name, Class
         ... paramTypes) 
// Get all methods in the class, including inherited ones
Method[] getAllDeclaredMethods(Class
          leafClass) 
// Find the specified constructor in the class
Constructor<T> accessibleConstructor(Class
         
           clazz, Class
          ... parameterTypes)
          
// Is the equals() method
boolean isEqualsMethod(Method method) 
// is the hashCode() method
boolean isHashCodeMethod(Method method) 
// is the toString() method
boolean isToStringMethod(Method method) 
// Is a method inherited from the Object class
boolean isObjectMethod(Method method) 
// Checks whether a method declares to throw the specified exception
boolean declaresException(Method method, Class
          exceptionType) 
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  2. Execution method

    // Execute method
Object invokeMethod(Method method, Object target)  
// As above, provide method parameters
Object invokeMethod(Method method, Object target, Object... args) 
// Cancel the Java permission check. For subsequent execution of the private method
void makeAccessible(Method method) 
// Cancel the Java permission check. For subsequent execution of the private constructor
void makeAccessible(Constructor
          ctor) 
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  3. For field

    // Find the specified attribute in the class
Field findField(Class
          clazz, String name) 
// As above, more types of attributes are provided
Field findField(Class
          clazz, String name, Class
          type) 
// Whether it is a "public static final" property
boolean isPublicStaticFinal(Field field) 
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  4. Set the field

    // Get the field value of the target object
Object getField(Field field, Object target) 
// Set the field value of the target object to value
void setField(Field field, Object target, Object value) 
// Peer assignment of attributes of the same class
void shallowCopyFieldState(Object src, Object dest)
// Cancel the Java permission control check. For subsequent reads and writes of the private property
void makeAccessible(Field field) 
// Perform a callback for each attribute of the class
void doWithFields(Class
          clazz, ReflectionUtils.FieldCallback fc) 
// Same as above, add attribute filter function.
void doWithFields(Class
          clazz, ReflectionUtils.FieldCallback fc, ReflectionUtils.FieldFilter ff) 
// Same as above, except for inherited attributes
void doWithLocalFields(Class
          clazz, ReflectionUtils.FieldCallback fc) 
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AopUtils

  1. Determine the agent type

    // Determine if it is a Spring proxy object
boolean isAopProxy(a)
// Determine whether it is a JDK dynamic proxy object
isJdkDynamicProxy(a)
// Determine if it is a CGLIB proxy object
boolean isCglibProxy(a)
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  2. Gets the class of the proxied object

    // Get the proxied target classClass<? > getTargetClass()Copy the code

AopContext

  1. Gets the proxy object for the current object

    Object currentProxy(a)
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