io.jsonwebtoken.lang.Classes Maven / Gradle / Ivy
/*
* Copyright (C) 2014 jsonwebtoken.io
*
* 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
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* 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.
*/
package io.jsonwebtoken.lang;
import java.io.InputStream;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.URL;
/**
* Utility methods for working with {@link Class}es.
*
* @since 0.1
*/
public final class Classes {
private Classes() {
} //prevent instantiation
private static final ClassLoaderAccessor THREAD_CL_ACCESSOR = new ExceptionIgnoringAccessor() {
@Override
protected ClassLoader doGetClassLoader() {
return Thread.currentThread().getContextClassLoader();
}
};
private static final ClassLoaderAccessor CLASS_CL_ACCESSOR = new ExceptionIgnoringAccessor() {
@Override
protected ClassLoader doGetClassLoader() {
return Classes.class.getClassLoader();
}
};
private static final ClassLoaderAccessor SYSTEM_CL_ACCESSOR = new ExceptionIgnoringAccessor() {
@Override
protected ClassLoader doGetClassLoader() {
return ClassLoader.getSystemClassLoader();
}
};
/**
* Attempts to load the specified class name from the current thread's
* {@link Thread#getContextClassLoader() context class loader}, then the
* current ClassLoader (Classes.class.getClassLoader()), then the system/application
* ClassLoader (ClassLoader.getSystemClassLoader(), in that order. If any of them cannot locate
* the specified class, an UnknownClassException is thrown (our RuntimeException equivalent of
* the JRE's ClassNotFoundException.
*
* @param fqcn the fully qualified class name to load
* @param The type of Class returned
* @return the located class
* @throws UnknownClassException if the class cannot be found.
*/
@SuppressWarnings("unchecked")
public static Class forName(String fqcn) throws UnknownClassException {
Class clazz = THREAD_CL_ACCESSOR.loadClass(fqcn);
if (clazz == null) {
clazz = CLASS_CL_ACCESSOR.loadClass(fqcn);
}
if (clazz == null) {
clazz = SYSTEM_CL_ACCESSOR.loadClass(fqcn);
}
if (clazz == null) {
String msg = "Unable to load class named [" + fqcn + "] from the thread context, current, or " +
"system/application ClassLoaders. All heuristics have been exhausted. Class could not be found.";
if (fqcn != null && fqcn.startsWith("io.jsonwebtoken.impl")) {
msg += " Have you remembered to include the jjwt-impl.jar in your runtime classpath?";
}
throw new UnknownClassException(msg);
}
return (Class) clazz;
}
/**
* Returns the specified resource by checking the current thread's
* {@link Thread#getContextClassLoader() context class loader}, then the
* current ClassLoader (Classes.class.getClassLoader()), then the system/application
* ClassLoader (ClassLoader.getSystemClassLoader(), in that order, using
* {@link ClassLoader#getResourceAsStream(String) getResourceAsStream(name)}.
*
* @param name the name of the resource to acquire from the classloader(s).
* @return the InputStream of the resource found, or null if the resource cannot be found from any
* of the three mentioned ClassLoaders.
* @since 0.8
*/
public static InputStream getResourceAsStream(String name) {
InputStream is = THREAD_CL_ACCESSOR.getResourceStream(name);
if (is == null) {
is = CLASS_CL_ACCESSOR.getResourceStream(name);
}
if (is == null) {
is = SYSTEM_CL_ACCESSOR.getResourceStream(name);
}
return is;
}
/**
* Returns the specified resource URL by checking the current thread's
* {@link Thread#getContextClassLoader() context class loader}, then the
* current ClassLoader (Classes.class.getClassLoader()), then the system/application
* ClassLoader (ClassLoader.getSystemClassLoader(), in that order, using
* {@link ClassLoader#getResource(String) getResource(name)}.
*
* @param name the name of the resource to acquire from the classloader(s).
* @return the URL of the resource found, or null if the resource cannot be found from any
* of the three mentioned ClassLoaders.
* @since 0.12.0
*/
private static URL getResource(String name) {
URL url = THREAD_CL_ACCESSOR.getResource(name);
if (url == null) {
url = CLASS_CL_ACCESSOR.getResource(name);
}
if (url == null) {
return SYSTEM_CL_ACCESSOR.getResource(name);
}
return url;
}
/**
* Returns {@code true} if the specified {@code fullyQualifiedClassName} can be found in any of the thread
* context, class, or system classloaders, or {@code false} otherwise.
*
* @param fullyQualifiedClassName the fully qualified class name to check
* @return {@code true} if the specified {@code fullyQualifiedClassName} can be found in any of the thread
* context, class, or system classloaders, or {@code false} otherwise.
*/
public static boolean isAvailable(String fullyQualifiedClassName) {
try {
forName(fullyQualifiedClassName);
return true;
} catch (UnknownClassException e) {
return false;
}
}
/**
* Creates and returns a new instance of the class with the specified fully qualified class name using the
* classes default no-argument constructor.
*
* @param fqcn the fully qualified class name
* @param the type of object created
* @return a new instance of the specified class name
*/
@SuppressWarnings("unchecked")
public static T newInstance(String fqcn) {
return (T) newInstance(forName(fqcn));
}
/**
* Creates and returns a new instance of the specified fully qualified class name using the
* specified {@code args} arguments provided to the constructor with {@code ctorArgTypes}
*
* @param fqcn the fully qualified class name
* @param ctorArgTypes the argument types of the constructor to invoke
* @param args the arguments to supply when invoking the constructor
* @param the type of object created
* @return the newly created object
*/
public static T newInstance(String fqcn, Class[] ctorArgTypes, Object... args) {
Class clazz = forName(fqcn);
Constructor ctor = getConstructor(clazz, ctorArgTypes);
return instantiate(ctor, args);
}
/**
* Creates and returns a new instance of the specified fully qualified class name using a constructor that matches
* the specified {@code args} arguments.
*
* @param fqcn fully qualified class name
* @param args the arguments to supply to the constructor
* @param the type of the object created
* @return the newly created object
*/
@SuppressWarnings("unchecked")
public static T newInstance(String fqcn, Object... args) {
return (T) newInstance(forName(fqcn), args);
}
/**
* Creates a new instance of the specified {@code clazz} via {@code clazz.newInstance()}.
*
* @param clazz the class to invoke
* @param the type of the object created
* @return the newly created object
*/
public static T newInstance(Class clazz) {
if (clazz == null) {
String msg = "Class method parameter cannot be null.";
throw new IllegalArgumentException(msg);
}
try {
return clazz.newInstance();
} catch (Exception e) {
throw new InstantiationException("Unable to instantiate class [" + clazz.getName() + "]", e);
}
}
/**
* Returns a new instance of the specified {@code clazz}, invoking the associated constructor with the specified
* {@code args} arguments.
*
* @param clazz the class to invoke
* @param args the arguments matching an associated class constructor
* @param the type of the created object
* @return the newly created object
*/
public static T newInstance(Class clazz, Object... args) {
Class[] argTypes = new Class[args.length];
for (int i = 0; i < args.length; i++) {
argTypes[i] = args[i].getClass();
}
Constructor ctor = getConstructor(clazz, argTypes);
return instantiate(ctor, args);
}
/**
* Returns the {@link Constructor} for the specified {@code Class} with arguments matching the specified
* {@code argTypes}.
*
* @param clazz the class to inspect
* @param argTypes the argument types for the desired constructor
* @param the type of object to create
* @return the constructor matching the specified argument types
* @throws IllegalStateException if the constructor for the specified {@code argTypes} does not exist.
*/
public static Constructor getConstructor(Class clazz, Class... argTypes) throws IllegalStateException {
try {
return clazz.getConstructor(argTypes);
} catch (NoSuchMethodException e) {
throw new IllegalStateException(e);
}
}
/**
* Creates a new object using the specified {@link Constructor}, invoking it with the specified constructor
* {@code args} arguments.
*
* @param ctor the constructor to invoke
* @param args the arguments to supply to the constructor
* @param the type of object to create
* @return the new object instance
* @throws InstantiationException if the constructor cannot be invoked successfully
*/
public static T instantiate(Constructor ctor, Object... args) {
try {
return ctor.newInstance(args);
} catch (Exception e) {
String msg = "Unable to instantiate instance with constructor [" + ctor + "]";
throw new InstantiationException(msg, e);
}
}
/**
* Invokes the fully qualified class name's method named {@code methodName} with parameters of type {@code argTypes}
* using the {@code args} as the method arguments.
*
* @param fqcn fully qualified class name to locate
* @param methodName name of the method to invoke on the class
* @param argTypes the method argument types supported by the {@code methodName} method
* @param args the runtime arguments to use when invoking the located class method
* @param the expected type of the object returned from the invoked method.
* @return the result returned by the invoked method
* @since 0.10.0
*/
public static T invokeStatic(String fqcn, String methodName, Class[] argTypes, Object... args) {
try {
Class clazz = Classes.forName(fqcn);
return invokeStatic(clazz, methodName, argTypes, args);
} catch (Exception e) {
String msg = "Unable to invoke class method " + fqcn + "#" + methodName + ". Ensure the necessary " +
"implementation is in the runtime classpath.";
throw new IllegalStateException(msg, e);
}
}
/**
* Invokes the {@code clazz}'s matching static method (named {@code methodName} with exact argument types
* of {@code argTypes}) with the given {@code args} arguments, and returns the method return value.
*
* @param clazz the class to invoke
* @param methodName the name of the static method on {@code clazz} to invoke
* @param argTypes the types of the arguments accepted by the method
* @param args the actual runtime arguments to use when invoking the method
* @param the type of object expected to be returned from the method
* @return the result returned by the invoked method.
* @since 0.12.0
*/
@SuppressWarnings("unchecked")
public static T invokeStatic(Class clazz, String methodName, Class[] argTypes, Object... args) {
try {
Method method = clazz.getDeclaredMethod(methodName, argTypes);
method.setAccessible(true);
return (T) method.invoke(null, args);
} catch (NoSuchMethodException | InvocationTargetException | IllegalAccessException e) {
Throwable cause = e.getCause();
if (cause instanceof RuntimeException) {
throw ((RuntimeException) cause); //propagate
}
String msg = "Unable to invoke class method " + clazz.getName() + "#" + methodName +
". Ensure the necessary implementation is in the runtime classpath.";
throw new IllegalStateException(msg, e);
}
}
/**
* Returns the {@code instance}'s named (declared) field value.
*
* @param instance the instance with the internal field
* @param fieldName the name of the field to inspect
* @param fieldType the type of field to inspect
* @param field instance value type
* @return the field value
*/
public static T getFieldValue(Object instance, String fieldName, Class fieldType) {
if (instance == null) return null;
try {
Field field = instance.getClass().getDeclaredField(fieldName);
field.setAccessible(true);
Object o = field.get(instance);
return fieldType.cast(o);
} catch (Throwable t) {
String msg = "Unable to read field " + instance.getClass().getName() +
"#" + fieldName + ": " + t.getMessage();
throw new IllegalStateException(msg, t);
}
}
/**
* @since 1.0
*/
private interface ClassLoaderAccessor {
Class loadClass(String fqcn);
URL getResource(String name);
InputStream getResourceStream(String name);
}
/**
* @since 1.0
*/
private static abstract class ExceptionIgnoringAccessor implements ClassLoaderAccessor {
public Class loadClass(String fqcn) {
Class clazz = null;
ClassLoader cl = getClassLoader();
if (cl != null) {
try {
clazz = cl.loadClass(fqcn);
} catch (ClassNotFoundException e) {
//Class couldn't be found by loader
}
}
return clazz;
}
@Override
public URL getResource(String name) {
URL url = null;
ClassLoader cl = getClassLoader();
if (cl != null) {
url = cl.getResource(name);
}
return url;
}
public InputStream getResourceStream(String name) {
InputStream is = null;
ClassLoader cl = getClassLoader();
if (cl != null) {
is = cl.getResourceAsStream(name);
}
return is;
}
protected final ClassLoader getClassLoader() {
try {
return doGetClassLoader();
} catch (Throwable t) {
//Unable to get ClassLoader
}
return null;
}
protected abstract ClassLoader doGetClassLoader() throws Throwable;
}
}
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