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/OpenJDK 21

Class Lookup

java.lang.Object
jdk.dynalink.linker.support.Lookup
public final class Lookup extends Object
A wrapper around MethodHandles.Lookup that masks checked exceptions. It is useful in those cases when you're looking up methods within your own codebase (therefore it is an error if they are not present).

Field Summary

Modifier and Type Field Description
static final Lookup PUBLIC
A canonical Lookup object that wraps MethodHandles.publicLookup().

Constructor Summary

Constructor Description
Lookup(MethodHandles.Lookup lookup)
Creates a new instance, bound to an instance of MethodHandles.Lookup.

Method Summary

Modifier and Type Method Description
MethodHandle findGetter(Class<?> refc, String name, Class<?> type)
Performs a MethodHandles.Lookup.findGetter(Class, String, Class), converting any encountered IllegalAccessException into an IllegalAccessError and NoSuchFieldException into a NoSuchFieldError.
static MethodHandle findOwnSpecial(MethodHandles.Lookup lookup, String name, Class<?> rtype, Class<?>... ptypes)
Given a lookup, finds using findSpecial(Class, String, MethodType) a method on that lookup's class.
MethodHandle findOwnSpecial(String name, Class<?> rtype, Class<?>... ptypes)
Finds using findSpecial(Class, String, MethodType) a method on that lookup's class.
static MethodHandle findOwnStatic(MethodHandles.Lookup lookup, String name, Class<?> rtype, Class<?>... ptypes)
Given a lookup, finds using findStatic(Class, String, MethodType) a method on that lookup's class.
MethodHandle findOwnStatic(String name, Class<?> rtype, Class<?>... ptypes)
Finds using findStatic(Class, String, MethodType) a method on that lookup's class.
MethodHandle findSpecial(Class<?> declaringClass, String name, MethodType type)
Performs a MethodHandles.Lookup.findSpecial(Class, String, MethodType, Class) on the underlying lookup.
MethodHandle findStatic(Class<?> declaringClass, String name, MethodType type)
Performs a MethodHandles.Lookup.findStatic(Class, String, MethodType) on the underlying lookup.
MethodHandle findVirtual(Class<?> declaringClass, String name, MethodType type)
Performs a MethodHandles.Lookup.findVirtual(Class, String, MethodType) on the underlying lookup.
static MethodHandle unreflect(MethodHandles.Lookup lookup, Method m)
Performs a MethodHandles.Lookup.unreflect(Method), converting any encountered IllegalAccessException into an IllegalAccessError.
MethodHandle unreflect(Method m)
Performs a MethodHandles.Lookup.unreflect(Method), converting any encountered IllegalAccessException into an IllegalAccessError.
static MethodHandle unreflectConstructor(MethodHandles.Lookup lookup, Constructor<?> c)
Performs a MethodHandles.Lookup.unreflectConstructor(Constructor), converting any encountered IllegalAccessException into an IllegalAccessError.
MethodHandle unreflectConstructor(Constructor<?> c)
Performs a MethodHandles.Lookup.unreflectConstructor(Constructor), converting any encountered IllegalAccessException into an IllegalAccessError.
MethodHandle unreflectGetter(Field f)
Performs a MethodHandles.Lookup.unreflectGetter(Field), converting any encountered IllegalAccessException into an IllegalAccessError.
MethodHandle unreflectSetter(Field f)
Performs a MethodHandles.Lookup.unreflectSetter(Field), converting any encountered IllegalAccessException into an IllegalAccessError.

Methods declared in class java.lang.Object

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

Field Details

PUBLIC

public static final Lookup PUBLIC
A canonical Lookup object that wraps MethodHandles.publicLookup().

Constructor Details

Lookup

public Lookup(MethodHandles.Lookup lookup)
Creates a new instance, bound to an instance of MethodHandles.Lookup.
Parameters:
lookup - the MethodHandles.Lookup it delegates to.

Method Details

unreflect

public MethodHandle unreflect(Method m)
Performs a MethodHandles.Lookup.unreflect(Method), converting any encountered IllegalAccessException into an IllegalAccessError.
Parameters:
m - the method to unreflect
Returns:
the unreflected method handle.
Throws:
IllegalAccessError - if the method is inaccessible.

unreflect

public static MethodHandle unreflect(MethodHandles.Lookup lookup, Method m)
Performs a MethodHandles.Lookup.unreflect(Method), converting any encountered IllegalAccessException into an IllegalAccessError.
Parameters:
lookup - the lookup used to unreflect
m - the method to unreflect
Returns:
the unreflected method handle.
Throws:
IllegalAccessError - if the method is inaccessible.

unreflectGetter

public MethodHandle unreflectGetter(Field f)
Performs a MethodHandles.Lookup.unreflectGetter(Field), converting any encountered IllegalAccessException into an IllegalAccessError.
Parameters:
f - the field for which a getter is unreflected
Returns:
the unreflected field getter handle.
Throws:
IllegalAccessError - if the getter is inaccessible.

findGetter

public MethodHandle findGetter(Class<?> refc, String name, Class<?> type)
Performs a MethodHandles.Lookup.findGetter(Class, String, Class), converting any encountered IllegalAccessException into an IllegalAccessError and NoSuchFieldException into a NoSuchFieldError.
Parameters:
refc - the class declaring the field
name - the name of the field
type - the type of the field
Returns:
the unreflected field getter handle.
Throws:
IllegalAccessError - if the field is inaccessible.
NoSuchFieldError - if the field does not exist.

unreflectSetter

public MethodHandle unreflectSetter(Field f)
Performs a MethodHandles.Lookup.unreflectSetter(Field), converting any encountered IllegalAccessException into an IllegalAccessError.
Parameters:
f - the field for which a setter is unreflected
Returns:
the unreflected field setter handle.
Throws:
IllegalAccessError - if the field is inaccessible.
NoSuchFieldError - if the field does not exist.

unreflectConstructor

public MethodHandle unreflectConstructor(Constructor<?> c)
Performs a MethodHandles.Lookup.unreflectConstructor(Constructor), converting any encountered IllegalAccessException into an IllegalAccessError.
Parameters:
c - the constructor to unreflect
Returns:
the unreflected constructor handle.
Throws:
IllegalAccessError - if the constructor is inaccessible.

unreflectConstructor

public static MethodHandle unreflectConstructor(MethodHandles.Lookup lookup, Constructor<?> c)
Performs a MethodHandles.Lookup.unreflectConstructor(Constructor), converting any encountered IllegalAccessException into an IllegalAccessError.
Parameters:
lookup - the lookup used to unreflect
c - the constructor to unreflect
Returns:
the unreflected constructor handle.
Throws:
IllegalAccessError - if the constructor is inaccessible.

findSpecial

public MethodHandle findSpecial(Class<?> declaringClass, String name, MethodType type)
Performs a MethodHandles.Lookup.findSpecial(Class, String, MethodType, Class) on the underlying lookup. Converts any encountered IllegalAccessException into an IllegalAccessError and NoSuchMethodException into a NoSuchMethodError.
Parameters:
declaringClass - class declaring the method
name - the name of the method
type - the type of the method
Returns:
a method handle for the method
Throws:
IllegalAccessError - if the method is inaccessible.
NoSuchMethodError - if the method does not exist.

findStatic

public MethodHandle findStatic(Class<?> declaringClass, String name, MethodType type)
Performs a MethodHandles.Lookup.findStatic(Class, String, MethodType) on the underlying lookup. Converts any encountered IllegalAccessException into an IllegalAccessError and NoSuchMethodException into a NoSuchMethodError.
Parameters:
declaringClass - class declaring the method
name - the name of the method
type - the type of the method
Returns:
a method handle for the method
Throws:
IllegalAccessError - if the method is inaccessible.
NoSuchMethodError - if the method does not exist.

findVirtual

public MethodHandle findVirtual(Class<?> declaringClass, String name, MethodType type)
Performs a MethodHandles.Lookup.findVirtual(Class, String, MethodType) on the underlying lookup. Converts any encountered IllegalAccessException into an IllegalAccessError and NoSuchMethodException into a NoSuchMethodError.
Parameters:
declaringClass - class declaring the method
name - the name of the method
type - the type of the method
Returns:
a method handle for the method
Throws:
IllegalAccessError - if the method is inaccessible.
NoSuchMethodError - if the method does not exist.

findOwnSpecial

public static MethodHandle findOwnSpecial(MethodHandles.Lookup lookup, String name, Class<?> rtype, Class<?>... ptypes)
Given a lookup, finds using findSpecial(Class, String, MethodType) a method on that lookup's class. Useful in classes' code for convenient linking to their own privates.
Parameters:
lookup - the lookup for the class
name - the name of the method
rtype - the return type of the method
ptypes - the parameter types of the method
Returns:
the method handle for the method

findOwnSpecial

public MethodHandle findOwnSpecial(String name, Class<?> rtype, Class<?>... ptypes)
Finds using findSpecial(Class, String, MethodType) a method on that lookup's class. Useful in classes' code for convenient linking to their own privates. It's also more convenient than findSpecial in that you can just list the parameter types, and don't have to specify lookup class.
Parameters:
name - the name of the method
rtype - the return type of the method
ptypes - the parameter types of the method
Returns:
the method handle for the method

findOwnStatic

public static MethodHandle findOwnStatic(MethodHandles.Lookup lookup, String name, Class<?> rtype, Class<?>... ptypes)
Given a lookup, finds using findStatic(Class, String, MethodType) a method on that lookup's class. Useful in classes' code for convenient linking to their own privates. It's easier to use than findStatic in that you can just list the parameter types, and don't have to specify lookup class.
Parameters:
lookup - the lookup for the class
name - the name of the method
rtype - the return type of the method
ptypes - the parameter types of the method
Returns:
the method handle for the method

findOwnStatic

public MethodHandle findOwnStatic(String name, Class<?> rtype, Class<?>... ptypes)
Finds using findStatic(Class, String, MethodType) a method on that lookup's class. Useful in classes' code for convenient linking to their own privates. It's easier to use than findStatic in that you can just list the parameter types, and don't have to specify lookup class.
Parameters:
name - the name of the method
rtype - the return type of the method
ptypes - the parameter types of the method
Returns:
the method handle for the method

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
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https://docs.oracle.com/en/java/javase/21/docs/api/jdk.dynalink/jdk/dynalink/linker/support/Lookup.html