Ctrl-Fallback

Library to quick search for methodhandles if you are not sure that the method will be in your application at launch (mostly for internal jdk api)

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com.ydo4ki.ctrlf.MethodSequence and MethodFinder are classes that helps you to get MethodHandle for the first found method in the sequence

To create MethodSequence use MethodSequence::of(...)
It takes MethodType or Class<?> of field type and method used to search (SearchMode)

Every search mode represents one of "find" methods in MethodHandles.Lookup:

SearchMode	Linked with	Takes arguments (signature)
SearchMode.findStatic	MethodHandles.Lookup::findStatic	(String method_owner, String method_name)
SearchMode.findVirtual	MethodHandles.Lookup::findVirtual	(String method_owner, String method_owner)
SearchMode.bind	MethodHandles.Lookup::bind	(Object receiver, String method_owner)
SearchMode.findGetter	MethodHandles.Lookup::findGetter	(String field_owner, String field_name)
SearchMode.findSetter	MethodHandles.Lookup::findSetter	(String field_owner, String field_name)
SearchMode.findStaticGetter	MethodHandles.Lookup::findStaticGetter	(String field_owner, String field_name)
SearchMode.findStaticSetter	MethodHandles.Lookup::findStaticSetter	(String field_owner, String field_name)
SearchMode.findConstructor	MethodHandles.Lookup::findConstructor	(String constructor_owner)
SearchMode.findSpecial	MethodHandles.Lookup::findSpecial	(String method_owner, String method_name, String special_caller)

Example:

import java.lang.invoke.MethodHandles;

private static final MethodHandle caller = MethodSequence.of(MethodHandles.lookup() /* lookup to use */, MethodType.methodType(Class.class, int.class), SearchMode.findStatic)
		.find("sun.reflect.Reflection","getCallerClass") // trying to find internal jdk method
		.orElse("me.random.Java9StackWalkerFallback","getCallerClass9") // if internal method is absent or access denied, try to load class from java 9 to use faster implementation with stackwalker
		// you can add as many .orElse(...) as you want here
		.fallback("me.random.CallersSlow","getCallerClass") // if all previous methods not found, use slow fallback that works everywhere
		.methodHandle(); // will throw exception if fallback was not loaded somehow nothing found

Also, if some parameters are repeated more often than others, you can set a default value for them:

private static final MethodHandle caller = MethodSequence.of(MethodType.methodType(Class.class, int.class), SearchMode.findStatic).withName("getCallerClass")
		.find("sun.reflect.Reflection") // name = "getCallerClass"
		.orElse("me.random.Java9StackWalkerFallback", "getCallerClass9") // override default name value
		.fallback("me.random.CallersSlow") // name = "getCallerClass"
		.methodHandle();

For more details see javadoc

Installation

Maven

<dependency>
    <groupId>com.ydo4ki</groupId>
    <artifactId>Ctrl-Fallback</artifactId>
    <version>1.0.0</version>
</dependency>

Gradle

implementation 'com.ydo4ki:Ctrl-Fallback:1.0.0'