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Reflection.java
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Reflection.java
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package com.github.games647.lagmonitor.traffic;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.bukkit.Bukkit;
/**
* An utility class that simplifies reflection in Bukkit plugins.
*
* @author Kristian
*/
public final class Reflection {
/**
* An interface for invoking a specific constructor.
*/
@FunctionalInterface
public interface ConstructorInvoker {
/**
* Invoke a constructor for a specific class.
*
* @param arguments - the arguments to pass to the constructor.
* @return The constructed object.
*/
Object invoke(Object... arguments);
}
/**
* An interface for invoking a specific method.
*/
@FunctionalInterface
public interface MethodInvoker {
/**
* Invoke a method on a specific target object.
*
* @param target - the target object, or NULL for a static method.
* @param arguments - the arguments to pass to the method.
* @return The return value, or NULL if is void.
*/
Object invoke(Object target, Object... arguments);
}
/**
* An interface for retrieving the field content.
*
* @param <T> - field type.
*/
public interface FieldAccessor<T> {
/**
* Retrieve the content of a field.
*
* @param target - the target object, or NULL for a static field.
* @return The value of the field.
*/
T get(Object target);
/**
* Set the content of a field.
*
* @param target - the target object, or NULL for a static field.
* @param value - the new value of the field.
*/
void set(Object target, Object value);
/**
* Determine if the given object has this field.
*
* @param target - the object to test.
* @return TRUE if it does, FALSE otherwise.
*/
boolean hasField(Object target);
}
// Deduce the net.minecraft.server.v* package
private static final String OBC_PREFIX = Bukkit.getServer().getClass().getPackage().getName();
private static final String NMS_PREFIX = "net.minecraft.server";
private static final String NMS_PREFIX_VERSIONED = OBC_PREFIX.replace("org.bukkit.craftbukkit", NMS_PREFIX);
private static final String VERSION = OBC_PREFIX.replace("org.bukkit.craftbukkit", "").replace(".", "");
// Variable replacement
private static final Pattern MATCH_VARIABLE = Pattern.compile("\\{([^}]+)}");
private Reflection() {
// Seal class
}
/**
* Retrieve a field accessor for a specific field type and name.
*
* @param target - the target type.
* @param name - the name of the field, or NULL to ignore.
* @param fieldType - a compatible field type.
* @return The field accessor.
*/
public static <T> FieldAccessor<T> getField(Class<?> target, String name, Class<T> fieldType) {
return getField(target, name, fieldType, 0);
}
/**
* Retrieve a field accessor for a specific field type and name.
*
* @param className - lookup name of the class, see {@link #getClass(String)}.
* @param name - the name of the field, or NULL to ignore.
* @param fieldType - a compatible field type.
* @return The field accessor.
*/
public static <T> FieldAccessor<T> getField(String className, String name, Class<T> fieldType) {
return getField(getClass(className), name, fieldType, 0);
}
/**
* Retrieve a field accessor for a specific field type and name.
*
* @param target - the target type.
* @param fieldType - a compatible field type.
* @param index - the number of compatible fields to skip.
* @return The field accessor.
*/
public static <T> FieldAccessor<T> getField(Class<?> target, Class<T> fieldType, int index) {
return getField(target, null, fieldType, index);
}
/**
* Retrieve a field accessor for a specific field type and name.
*
* @param className - lookup name of the class, see {@link #getClass(String)}.
* @param fieldType - a compatible field type.
* @param index - the number of compatible fields to skip.
* @return The field accessor.
*/
public static <T> FieldAccessor<T> getField(String className, Class<T> fieldType, int index) {
return getField(getClass(className), fieldType, index);
}
// Common method
private static <T> FieldAccessor<T> getField(Class<?> target, String name, Class<T> fieldType, int index) {
for (final Field field : target.getDeclaredFields()) {
if ((name == null || field.getName().equals(name)) && fieldType.isAssignableFrom(field.getType()) && index-- <= 0) {
field.setAccessible(true);
// A function for retrieving a specific field value
return new FieldAccessor<T>() {
@Override
@SuppressWarnings("unchecked")
public T get(Object target) {
try {
return (T) field.get(target);
} catch (IllegalAccessException e) {
throw new RuntimeException("Cannot access reflection.", e);
}
}
@Override
public void set(Object target, Object value) {
try {
field.set(target, value);
} catch (IllegalAccessException e) {
throw new RuntimeException("Cannot access reflection.", e);
}
}
@Override
public boolean hasField(Object target) {
// target instanceof DeclaringClass
return field.getDeclaringClass().isAssignableFrom(target.getClass());
}
};
}
}
// Search in parent classes
if (target.getSuperclass() != null) {
return getField(target.getSuperclass(), name, fieldType, index);
}
throw new IllegalArgumentException("Cannot find field with type " + fieldType);
}
/**
* Search for the first publicly and privately defined method of the given name and parameter count.
*
* @param className - lookup name of the class, see {@link #getClass(String)}.
* @param methodName - the method name, or NULL to skip.
* @param params - the expected parameters.
* @return An object that invokes this specific method.
* @throws IllegalStateException If we cannot find this method.
*/
public static MethodInvoker getMethod(String className, String methodName, Class<?>... params) {
return getTypedMethod(getClass(className), methodName, null, params);
}
/**
* Search for the first publicly and privately defined method of the given name and parameter count.
*
* @param clazz - a class to start with.
* @param methodName - the method name, or NULL to skip.
* @param params - the expected parameters.
* @return An object that invokes this specific method.
* @throws IllegalStateException If we cannot find this method.
*/
public static MethodInvoker getMethod(Class<?> clazz, String methodName, Class<?>... params) {
return getTypedMethod(clazz, methodName, null, params);
}
/**
* Search for the first publicly and privately defined method of the given name and parameter count.
*
* @param clazz - a class to start with.
* @param methodName - the method name, or NULL to skip.
* @param returnType - the expected return type, or NULL to ignore.
* @param params - the expected parameters.
* @return An object that invokes this specific method.
* @throws IllegalStateException If we cannot find this method.
*/
public static MethodInvoker getTypedMethod(Class<?> clazz, String methodName, Class<?> returnType, Class<?>... params) {
for (final Method method : clazz.getDeclaredMethods()) {
if ((methodName == null || method.getName().equals(methodName)) && (returnType == null) || method.getReturnType().equals(returnType) && Arrays.equals(method.getParameterTypes(), params)) {
method.setAccessible(true);
return (target, arguments) -> {
try {
return method.invoke(target, arguments);
} catch (Exception e) {
throw new RuntimeException("Cannot invoke method " + method, e);
}
};
}
}
// Search in every superclass
if (clazz.getSuperclass() != null) {
return getMethod(clazz.getSuperclass(), methodName, params);
}
throw new IllegalStateException(String.format("Unable to find method %s (%s).", methodName, Arrays.asList(params)));
}
/**
* Search for the first publicly and privately defined constructor of the given name and parameter count.
*
* @param className - lookup name of the class, see {@link #getClass(String)}.
* @param params - the expected parameters.
* @return An object that invokes this constructor.
* @throws IllegalStateException If we cannot find this method.
*/
public static ConstructorInvoker getConstructor(String className, Class<?>... params) {
return getConstructor(getClass(className), params);
}
/**
* Search for the first publicly and privately defined constructor of the given name and parameter count.
*
* @param clazz - a class to start with.
* @param params - the expected parameters.
* @return An object that invokes this constructor.
* @throws IllegalStateException If we cannot find this method.
*/
public static ConstructorInvoker getConstructor(Class<?> clazz, Class<?>... params) {
for (final Constructor<?> constructor : clazz.getDeclaredConstructors()) {
if (Arrays.equals(constructor.getParameterTypes(), params)) {
constructor.setAccessible(true);
return arguments -> {
try {
return constructor.newInstance(arguments);
} catch (Exception e) {
throw new RuntimeException("Cannot invoke constructor " + constructor, e);
}
};
}
}
throw new IllegalStateException(String.format("Unable to find constructor for %s (%s).", clazz, Arrays.asList(params)));
}
/**
* Retrieve a class from its full name, without knowing its type on compile time.
* <p>
* This is useful when looking up fields by a NMS or OBC type.
* <p>
*
* @see Object#getClass()
* @param lookupName - the class name with variables.
* @return The class.
*/
public static Class<Object> getUntypedClass(String lookupName) {
@SuppressWarnings({"rawtypes", "unchecked"})
Class<Object> clazz = (Class) getClass(lookupName);
return clazz;
}
/**
* Retrieve a class from its full name.
* <p>
* Strings enclosed with curly brackets - such as {TEXT} - will be replaced according to the following table:
* </p>
* <table border="1">
* <tr>
* <th>Variable</th>
* <th>Content</th>
* </tr>
* <tr>
* <td>{nms}</td>
* <td>Actual package name of net.minecraft.server.VERSION</td>
* </tr>
* <tr>
* <td>{obc}</td>
* <td>Actual package name of org.bukkit.craftbukkit.VERSION</td>
* </tr>
* <tr>
* <td>{version}</td>
* <td>The current Minecraft package VERSION, if any.</td>
* </tr>
* </table>
*
* @param lookupName - the class name with variables.
* @return The looked up class.
* @throws IllegalArgumentException If a variable or class could not be found.
*/
public static Class<?> getClass(String lookupName) {
return getCanonicalClass(expandVariables(lookupName));
}
/**
* Retrieve a class in the net.minecraft.server.VERSION.* package.
*
* @param name - the name of the class, excluding the package.
* @throws IllegalArgumentException If the class doesn't exist.
*/
public static Class<?> getMinecraftClass(String name, String alias) {
try {
return Class.forName(NMS_PREFIX + '.' + alias);
} catch (ClassNotFoundException e) {
return getCanonicalClass(NMS_PREFIX_VERSIONED + '.' + name);
}
}
/**
* Retrieve a class in the org.bukkit.craftbukkit.VERSION.* package.
*
* @param name - the name of the class, excluding the package.
* @throws IllegalArgumentException If the class doesn't exist.
*/
public static Class<?> getCraftBukkitClass(String name) {
return getCanonicalClass(OBC_PREFIX + '.' + name);
}
/**
* Retrieve a class by its canonical name.
*
* @param canonicalName - the canonical name.
* @return The class.
*/
private static Class<?> getCanonicalClass(String canonicalName) {
try {
return Class.forName(canonicalName);
} catch (ClassNotFoundException e) {
throw new IllegalArgumentException("Cannot find " + canonicalName, e);
}
}
/**
* Expand variables such as "{nms}" and "{obc}" to their corresponding packages.
*
* @param name - the full name of the class.
* @return The expanded string.
*/
private static String expandVariables(String name) {
StringBuffer output = new StringBuffer();
Matcher matcher = MATCH_VARIABLE.matcher(name);
while (matcher.find()) {
String variable = matcher.group(1);
String replacement;
// Expand all detected variables
if ("nms".equalsIgnoreCase(variable)) {
replacement = NMS_PREFIX_VERSIONED;
} else if ("obc".equalsIgnoreCase(variable)) {
replacement = OBC_PREFIX;
} else if ("version".equalsIgnoreCase(variable)) {
replacement = VERSION;
} else {
throw new IllegalArgumentException("Unknown variable: " + variable);
}
// Assume the expanded variables are all packages, and append a dot
if (!replacement.isEmpty() && matcher.end() < name.length() && name.charAt(matcher.end()) != '.') {
replacement += ".";
}
matcher.appendReplacement(output, Matcher.quoteReplacement(replacement));
}
matcher.appendTail(output);
return output.toString();
}
}