com.cedarsoftware.util.io

Class MetaUtils

java.lang.Object

com.cedarsoftware.util.io.MetaUtils

public class MetaUtils
extends Object

This utility class has the methods mostly related to reflection related code.

Author:

John DeRegnaucourt ([email protected])
Copyright (c) Cedar Software LLC

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

License

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.*

Method Summary

Modifier and Type	Method and Description
static Class<?>	classForName(String name, ClassLoader classLoader) Given the passed in String class name, return the named JVM class.
static int	comparePrimitiveToWrapper(Class<?> source, Class<?> destination) Compare a primitive to a primitive Wrapper.
static int	computeInheritanceDistance(Class<?> source, Class<?> destination) Computes the inheritance distance between two classes/interfaces/primitive types.
static String	createCacheKey(Class<?> c, Collection<?> args)
static Optional<Class>	getClassIfEnum(Class<?> c)
static Map<String,Field>	getDeepDeclaredFields(Class<?> c)
static Field	getField(Class<?> c, String field) Return an instance of the Java Field class corresponding to the passed in field name.
static String	getLogMessage(String methodName, Object[] args) Format a nice looking method signature for logging output
static String	getLogMessage(String methodName, Object[] args, int argCharLen)
static <K,V> V	getValue(Map map, K key)
static <K,V> V	getValueWithDefaultForMissing(Map map, K key, V defaultValue)
static <K,V> V	getValueWithDefaultForNull(Map map, K key, V defaultValue)
static int	indexOfBestValue(int[] array) Returns the index of the smallest value in an array.
static boolean	isLogicalPrimitive(Class<?> c)
static boolean	isPrimitive(Class c)
static <T> List<T>	listOf(T... items) For JDK1.8 support.
static void	loadMapDefinition(Map<String,String> map, String resName)
static byte[]	loadResourceAsBytes(String resourceName) Loads resource content as a byte[].
static String	loadResourceAsString(String resourceName) Loads resource content as a String.
static void	loadSetDefinition(Set<String> set, String resName)
static <K,V> Map<K,V>	mapOf() For JDK1.8 support.
static <K,V> Map<K,V>	mapOf(K k, V v)
static <K,V> Map<K,V>	mapOf(K k1, V v1, K k2, V v2)
static <K,V> Map<K,V>	mapOf(K k1, V v1, K k2, V v2, K k3, V v3)
static List<Object>	matchArgumentsToParameters(Collection<Object> values, Parameter[] parameterTypes, boolean useNull) Build a List the same size of parameterTypes, where the objects in the list are ordered to best match the parameters.
static Object	newInstance(Class<?> c, Collection<?> argumentValues) Create a new instance of the passed in class c.
static String	removeLeadingAndTrailingQuotes(String input) Strip leading and trailing double quotes from the passed in String.
static <T> T	safelyIgnoreException(Callable<T> callable, T defaultValue)
static void	safelyIgnoreException(Runnable runnable)
static void	setFieldValue(Field field, Object instance, Object value)
static <T> Set<T>	setOf(T... items) For JDK1.8 support.
static void	setUseUnsafe(boolean state) Globally turn on (or off) the 'unsafe' option of Class construction.
static void	trySetAccessible(AccessibleObject object)

Methods inherited from class java.lang.Object

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

Method Detail

setUseUnsafe

public static void setUseUnsafe(boolean state)

Globally turn on (or off) the 'unsafe' option of Class construction. The unsafe option is used when all constructors have been tried and the Java class could not be instantiated.

Parameters:

state - boolean true = on, false = off.

listOf

@SafeVarargs
public static <T> List<T> listOf(T... items)

For JDK1.8 support. Remove this and change to List.of() for JDK11+

setOf

@SafeVarargs
public static <T> Set<T> setOf(T... items)

For JDK1.8 support. Remove this and change to Set.of() for JDK11+

mapOf

public static <K,V> Map<K,V> mapOf()

For JDK1.8 support. Remove this and change to Map.of() for JDK11+

mapOf

public static <K,V> Map<K,V> mapOf(K k,
                                   V v)

mapOf

public static <K,V> Map<K,V> mapOf(K k1,
                                   V v1,
                                   K k2,
                                   V v2)

mapOf

public static <K,V> Map<K,V> mapOf(K k1,
                                   V v1,
                                   K k2,
                                   V v2,
                                   K k3,
                                   V v3)

getField

public static Field getField(Class<?> c,
                             String field)

Return an instance of the Java Field class corresponding to the passed in field name.

Parameters:

c - class containing the field / field name

field - String name of a field on the class.

Returns:

Field instance if the field with the corresponding name is found, null otherwise.

getDeepDeclaredFields

public static Map<String,Field> getDeepDeclaredFields(Class<?> c)

Parameters:

c - Class instance

Returns:

ClassMeta which contains fields of class. The results are cached internally for performance when called again with same Class.

comparePrimitiveToWrapper

public static int comparePrimitiveToWrapper(Class<?> source,
                                            Class<?> destination)

Compare a primitive to a primitive Wrapper.

Returns:

0 if they are the same, -1 if not. Primitive wrapper classes are consider the same as primitive classes.

computeInheritanceDistance

public static int computeInheritanceDistance(Class<?> source,
                                             Class<?> destination)

Computes the inheritance distance between two classes/interfaces/primitive types.

Parameters:

source - The source class, interface, or primitive type.

destination - The destination class, interface, or primitive type.

Returns:

The number of steps from the source to the destination, or -1 if no path exists.

getClassIfEnum

public static Optional<Class> getClassIfEnum(Class<?> c)

classForName

public static Class<?> classForName(String name,
                                    ClassLoader classLoader)

Given the passed in String class name, return the named JVM class.

Parameters:

name - String name of a JVM class.

classLoader - ClassLoader to use when searching for JVM classes.

Returns:

Class instance of the named JVM class or null if not found.

removeLeadingAndTrailingQuotes

public static String removeLeadingAndTrailingQuotes(String input)

Strip leading and trailing double quotes from the passed in String. If there are more than one set of quotes, ""this is weird"" then all leading and trailing quotes will be removed, yielding this is weird. Note that: """this is "really" weird" will be: this is "really" weird.

matchArgumentsToParameters

public static List<Object> matchArgumentsToParameters(Collection<Object> values,
                                                      Parameter[] parameterTypes,
                                                      boolean useNull)

Build a List the same size of parameterTypes, where the objects in the list are ordered to best match the parameters. Values from the passed in list are used only once or never.

Parameters:

values - A list of potential arguments. This list can be smaller than parameterTypes or larger.

parameterTypes - A list of classes that the values will be matched against.

Returns:

List of values that are best ordered to match the passed in parameter types. This list will be the same length as the passed in parameterTypes list.

indexOfBestValue

public static int indexOfBestValue(int[] array)

Returns the index of the smallest value in an array.

Parameters:

array - The array to search.

Returns:

The index of the smallest value, or -1 if the array is empty.

createCacheKey

public static String createCacheKey(Class<?> c,
                                    Collection<?> args)

newInstance

public static Object newInstance(Class<?> c,
                                 Collection<?> argumentValues)

Create a new instance of the passed in class c. You can optionally pass in argument values that will be best-matched to a constructor on c. You can pass in null or an empty list, in which case, other techniques will be used to attempt to instantiate the class. For security reasons, Process, ClassLoader, ProcessBuilder, Constructor, Method, and Field cannot be instantiated.

Parameters:

c - Class to instantiate.

argumentValues - List of values to supply to a constructor on 'c'. The constructor chosen on 'c' will be the one with a combination of the most fields that are satisfied with non-null values from the 'argumentsValues.' The method will attempt to use values from the list as constructor arguments for the passed in class c, ordering them to best-fit the constructor, by matching the class type of the argument values to the class types of the parameters on 'c' constructors. It will use all constructors exhaustively, until it is successful. If not, then it will look at the 'unsafe' setting and attempt to use that.

Returns:

an instance of the passed in class.

Throws:

JsonIoException - if it could not instantiate the passed in class. In that case, it is best to create a ClassFactory for this specific class, and add that to the ReadOptions as an instantiator that is associated to the class 'c'. In the ClassFactory, the JsonObject containing the data from the associated JsonObject { } is passed in, allowing you to instantiate and load the values in one operation. If you do that, and no further sub-objects exist, or you load the sub-objects in your ClassFactory, make sure to return 'true' for isObjectFinal().

getLogMessage

public static String getLogMessage(String methodName,
                                   Object[] args)

Format a nice looking method signature for logging output

getLogMessage

public static String getLogMessage(String methodName,
                                   Object[] args,
                                   int argCharLen)

getValue

public static <K,V> V getValue(Map map,
                               K key)

getValueWithDefaultForNull

public static <K,V> V getValueWithDefaultForNull(Map map,
                                                 K key,
                                                 V defaultValue)

getValueWithDefaultForMissing

public static <K,V> V getValueWithDefaultForMissing(Map map,
                                                    K key,
                                                    V defaultValue)

setFieldValue

public static void setFieldValue(Field field,
                                 Object instance,
                                 Object value)

trySetAccessible

public static void trySetAccessible(AccessibleObject object)

safelyIgnoreException

public static <T> T safelyIgnoreException(Callable<T> callable,
                                          T defaultValue)

safelyIgnoreException

public static void safelyIgnoreException(Runnable runnable)

isPrimitive

public static boolean isPrimitive(Class c)

Parameters:

c - Class to test

Returns:

boolean true if the passed in class is a Java primitive, false otherwise. The Wrapper classes Integer, Long, Boolean, etc. are considered primitives by this method.

isLogicalPrimitive

public static boolean isLogicalPrimitive(Class<?> c)

Parameters:

c - Class to test

Returns:

boolean true if the passed in class is a 'logical' primitive. A logical primitive is defined as all Java primitives, the primitive wrapper classes, String, Number, and Class. The reason these are considered 'logical' primitives is that they are immutable and therefore can be written without references in JSON content (making the JSON more readable - less @id / @ref), without breaking the semantics (shape) of the object graph being written.

loadMapDefinition

public static void loadMapDefinition(Map<String,String> map,
                                     String resName)

loadSetDefinition

public static void loadSetDefinition(Set<String> set,
                                     String resName)

loadResourceAsString

public static String loadResourceAsString(String resourceName)

Loads resource content as a String.

Parameters:

resourceName - Name of the resource file.

Returns:

Content of the resource file as a String.

loadResourceAsBytes

public static byte[] loadResourceAsBytes(String resourceName)

Loads resource content as a byte[].

Parameters:

resourceName - Name of the resource file.

Returns:

Content of the resource file as a byte[].