manifold.util

Class ReflectUtil

java.lang.Object

manifold.util.ReflectUtil

public class ReflectUtil
extends Object

A Java reflection utility. Use it to efficiently access classes by name, get/set field values, invoke methods, and use constructors. Notable features include:

• Call a private method
• Get and set the value of a private, final field
• Access fields and methods of a class belonging to an inaccessible module
• Fields, methods, and constructors are cached upon use to improve performance

(Use @Jailbreak to avoid writing reflection code. See Type-safe Reflection.)

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ReflectUtil.ConstructorRef
static class	ReflectUtil.FieldRef
static class	ReflectUtil.LiveFieldRef
static class	ReflectUtil.LiveMethodRef
static class	ReflectUtil.MethodRef
static class	ReflectUtil.WithNull Use to access live methods and fields with possible null return value if not found

Constructor Summary

Constructors

Constructor and Description
ReflectUtil()

Method Summary

Modifier and Type	Method and Description
static ReflectUtil.ConstructorRef	constructor(Class<?> cls, Class<?>... params) Get a ReflectUtil.ConstructorRef to the specified constructor.
static ReflectUtil.ConstructorRef	constructor(String fqn, Class<?>... params) Get a ReflectUtil.ConstructorRef to the specified constructor.
static ReflectUtil.FieldRef	field(Class<?> cls, String name) Get a ReflectUtil.FieldRef to the specified field.
static ReflectUtil.LiveFieldRef	field(Object receiver, String name) Get a ReflectUtil.LiveFieldRef to the specified field.
static ReflectUtil.FieldRef	field(String fqn, String name) Get a ReflectUtil.FieldRef to the specified field.
static ReflectUtil.MethodRef	lambdaMethod(Class<?> lambdaClass) Get a ReflectUtil.MethodRef corresponding with the functional interface implemented by lambdaClass.
static ReflectUtil.MethodRef	method(Class<?> cls, String name, Class... params) Get a ReflectUtil.MethodRef to the specified method.
static ReflectUtil.LiveMethodRef	method(Object receiver, String name, Class... params) Get a ReflectUtil.LiveMethodRef to the specified method.
static ReflectUtil.MethodRef	method(String fqn, String name, Class... params) Get a ReflectUtil.MethodRef to the specified method.
static ReflectUtil.MethodRef	methodFromName(Class<?> cls, String name) Get a ReflectUtil.MethodRef to from the specified name without regard to parameter types.
static void	preloadClassIntoParentLoader(String fqn, URI content, ClassLoader wouldBeLoader, ClassLoader parentLoader) Force class with name fqn to be loaded by parentLoader.
static void	setAccessible(Constructor c)
static void	setAccessible(Field f)
static void	setAccessible(Member m)
static void	setAccessible(Method m)
static Class<?>	type(String fqn) Searches the class loader of this class for the specified name, if not found searches the current thread's context class loader.
static Class<?>	type(String fqn, boolean useCallChain)
static Class<?>	type(String fqn, ClassLoader cl) Searches cl for the specified class fqn.
static Class<?>	type(String fqn, ClassLoader cl, boolean useCallChain)

Methods inherited from class java.lang.Object

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

Constructor Detail

ReflectUtil

public ReflectUtil()

Method Detail

type

public static Class<?> type(String fqn)

Searches the class loader of this class for the specified name, if not found searches the current thread's context class loader.

Parameters:

fqn - The qualified name of the type e.g., "java.lang.String" or "java.lang.String[]"

Returns:

The Class corresponding with fqn or null if not found

type

public static Class<?> type(String fqn,
                            boolean useCallChain)

type

public static Class<?> type(String fqn,
                            ClassLoader cl)

Searches cl for the specified class fqn.

Parameters:

fqn - The qualified name of the type e.g., "java.lang.String"

cl - The class loader to search

Returns:

The Class corresponding with fqn or null if not found

type

public static Class<?> type(String fqn,
                            ClassLoader cl,
                            boolean useCallChain)

method

public static ReflectUtil.LiveMethodRef method(Object receiver,
                                               String name,
                                               Class... params)

Get a ReflectUtil.LiveMethodRef to the specified method. Typical use:

 method(str, "substring", int.class).invoke(2) 

Parameters:

receiver - The object to make the call on

name - The name of the method to call or a '|' separated list of names, where the first found is used

params - The types of the method's parameters

Returns:

A reference to the specified method, throws RuntimeException if the method is not found. Use ReflectUtil.WithNull to avoid the RuntimeException.

method

public static ReflectUtil.MethodRef method(String fqn,
                                           String name,
                                           Class... params)

Get a ReflectUtil.MethodRef to the specified method. Typical use:

 method("java.time.LocalTime", "of", int.class, int.class).invokeStatic(5, 30) 

Parameters:

fqn - The qualified name of the class containing the method

name - The name of the method or a '|' separated list of names, where the first found is used

params - The types of the method's parameters

Returns:

A reference to the specified method or null if not found

method

public static ReflectUtil.MethodRef method(Class<?> cls,
                                           String name,
                                           Class... params)

Get a ReflectUtil.MethodRef to the specified method. Typical use:

 method(LocalTime.class, "of", int.class, int.class).invokeStatic(5, 30) 

Parameters:

cls - The class containing the method

name - The name of the method or a '|' separated list of names, where the first found is used

params - The types of the method's parameters

Returns:

A reference to the specified method or null if not found

methodFromName

public static ReflectUtil.MethodRef methodFromName(Class<?> cls,
                                                   String name)

Get a ReflectUtil.MethodRef to from the specified name without regard to parameter types. If more than one method has the name, the first one encountered is used, in no particular order. This method should be used only when the named method is not overloaded. Typical use:

 methodByName(LocalTime.class, "isAfter").invoke(source, time) 

Parameters:

cls - The class containing the method

name - The name of the method or a '|' separated list of names, where the first found is used

Returns:

A reference to the specified method or null if not found

lambdaMethod

public static ReflectUtil.MethodRef lambdaMethod(Class<?> lambdaClass)

Get a ReflectUtil.MethodRef corresponding with the functional interface implemented by lambdaClass.

 lambdaMethod(function.getClass()).invoke(function, args) 

Returns:

A reference to the specified method or null if not found

field

public static ReflectUtil.LiveFieldRef field(Object receiver,
                                             String name)

Get a ReflectUtil.LiveFieldRef to the specified field. Typical use:

 String name = field(foo, "name").get(); 

Parameters:

receiver - The object having the field

name - The name of the field or a '|' separated list of names, where the first found is used

Returns:

A reference to the specified field, throws RuntimeException if the field is not found. Use ReflectUtil.WithNull to avoid the RuntimeException.

field

public static ReflectUtil.FieldRef field(String fqn,
                                         String name)

Get a ReflectUtil.FieldRef to the specified field. Typical use:

 field("java.time.LocalTime", "hour").get(); 

Parameters:

fqn - The qualified name of the class having the field

name - The name of the field or a '|' separated list of names, where the first found is used

Returns:

A reference to the specified field or null if not found

field

public static ReflectUtil.FieldRef field(Class<?> cls,
                                         String name)

Get a ReflectUtil.FieldRef to the specified field. Typical use:

 field(LocalTime.class, "hour").get(); 

Parameters:

cls - The class having the field

name - The name of the field or a '|' separated list of names, where the first found is used

Returns:

A reference to the specified field or null if not found

constructor

public static ReflectUtil.ConstructorRef constructor(String fqn,
                                                     Class<?>... params)

Get a ReflectUtil.ConstructorRef to the specified constructor. Typical use:

 constructor("java.util.ArrayList", int.class).newInstance(32) 

Parameters:

fqn - The qualified name of the class to construct

params - A list of parameter types for the constructor

Returns:

A reference to the constructor or null if not found

constructor

public static ReflectUtil.ConstructorRef constructor(Class<?> cls,
                                                     Class<?>... params)

Get a ReflectUtil.ConstructorRef to the specified constructor. Typical use:

 constructor(ArrayList.class, int.class).newInstance(32) 

Parameters:

cls - The class to construct

params - A list of parameter types for the constructor

Returns:

A reference to the constructor or null if not found

setAccessible

public static void setAccessible(Field f)

setAccessible

public static void setAccessible(Method m)

setAccessible

public static void setAccessible(Constructor c)

setAccessible

public static void setAccessible(Member m)

preloadClassIntoParentLoader

public static void preloadClassIntoParentLoader(String fqn,
                                                URI content,
                                                ClassLoader wouldBeLoader,
                                                ClassLoader parentLoader)

Force class with name fqn to be loaded by parentLoader. Facilitates the case where a class must be declared in a package defined in a parent class loader in order to subclass and use package-local features defined there.

Note fqn's natural class loader must have the parentLoader in its chain of parent loaders. Also be certain fqn is not already loaded by its natural loader, otherwise LinkageErrors will result.

Parameters:

fqn - The qualified name of the class to load

content - The location of the class resource. With Java 8 this can be wouldBeLoader.getResource(className). But with Java 9 and later the JPMS strictly prohibits a package from existing in two loaders, therefore the class file must be placed in a different package, perhaps prefixed with a suitably named root package, otherwise the VM will throw a LayerInstantiationException when your application loads, before any of your code executes.

wouldBeLoader - The class loader that would naturally load fqn, must have parentLoader in its parent loader chain

parentLoader - The class loader to load the class in, must be in the parent chain of wouldBeLoader