net.lenni0451.reflect

Class ClassLoaders

java.lang.Object

net.lenni0451.reflect.ClassLoaders

public class ClassLoaders
extends java.lang.Object

This class contains some useful methods for working with class loaders.

Constructor Summary

Constructors

Constructor and Description
ClassLoaders()

Method Summary

Modifier and Type	Method and Description
static void	addToSystemClassPath(java.net.URL url) Add a URL to the system classpath.
static java.lang.Class<?>	defineAnonymousClass(java.lang.Class<?> parent, byte[] bytecode, java.lang.String... flags) Define an anonymous class.
static java.lang.Class<?>	defineClass(java.lang.ClassLoader classLoader, java.lang.String name, byte[] bytecode) Define a class using the given class loader.
static java.lang.Class<?>	defineClass(java.lang.ClassLoader classLoader, java.lang.String name, byte[] bytecode, int offset, int length, java.security.ProtectionDomain protectionDomain) Define a class using the given class loader.
static java.lang.Class<?>	defineClass(java.lang.ClassLoader classLoader, java.lang.String name, byte[] bytecode, java.security.ProtectionDomain protectionDomain) Define a class using the given class loader.
static java.net.URL[]	getSystemClassPath() Get all URLs of the system classpath.
static void	loadToFront(java.net.URL url) Load a URL into the context class loader and move it to the front of the classpath.

Methods inherited from class java.lang.Object

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

Constructor Detail

ClassLoaders

public ClassLoaders()

Method Detail

addToSystemClassPath

public static void addToSystemClassPath(java.net.URL url)

Add a URL to the system classpath.

Parameters:

url - The URL to add

Throws:

java.lang.IllegalStateException - If the url class path could not be found

getSystemClassPath

public static java.net.URL[] getSystemClassPath()

Get all URLs of the system classpath.

Returns:

The system classpath

Throws:

java.lang.IllegalStateException - If the url class path could not be found

loadToFront

public static void loadToFront(java.net.URL url)

Load a URL into the context class loader and move it to the front of the classpath.
This allows overriding classes in the classpath with classes from an external jar.

Parameters:

url - The URL to load

Throws:

java.lang.IllegalStateException - If the url class path could not be found or the URL could not be found in the classpath

defineClass

public static java.lang.Class<?> defineClass(java.lang.ClassLoader classLoader,
                                             java.lang.String name,
                                             byte[] bytecode)

Define a class using the given class loader.

Parameters:

classLoader - The class loader to use

name - The name of the class

bytecode - The bytecode of the class

Returns:

The defined class

defineClass

public static java.lang.Class<?> defineClass(java.lang.ClassLoader classLoader,
                                             java.lang.String name,
                                             byte[] bytecode,
                                             java.security.ProtectionDomain protectionDomain)

Define a class using the given class loader.

Parameters:

classLoader - The class loader to use

name - The name of the class

bytecode - The bytecode of the class

protectionDomain - The protection domain of the class

Returns:

The defined class

defineClass

public static java.lang.Class<?> defineClass(java.lang.ClassLoader classLoader,
                                             java.lang.String name,
                                             byte[] bytecode,
                                             int offset,
                                             int length,
                                             java.security.ProtectionDomain protectionDomain)

Define a class using the given class loader.

Parameters:

classLoader - The class loader to use

name - The name of the class

bytecode - The bytecode of the class

offset - The offset of the class in the bytecode

length - The length of the class in the bytecode

protectionDomain - The protection domain of the class

Returns:

The defined class

defineAnonymousClass

public static java.lang.Class<?> defineAnonymousClass(java.lang.Class<?> parent,
                                                      byte[] bytecode,
                                                      java.lang.String... flags)

Define an anonymous class.
In Java 15 and above the MethodHandles.Lookup#defineHiddenClass method is used. On older versions the Unsafe#defineAnonymousClass method is used.
The flags are case-insensitive and only used on Java 15 and above.

Parameters:

parent - The parent class

bytecode - The bytecode of the class

flags - The flags to use

Returns:

The defined class

Throws:

java.lang.IllegalArgumentException - If a flag is unknown