net.apexes.commons.lang.Reflect Maven / Gradle / Ivy
/*
* Copyright (c) 2018, apexes.net. All rights reserved.
*
* http://www.apexes.net
*
*/
package net.apexes.commons.lang;
import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.Proxy;
import java.util.LinkedHashMap;
import java.util.Map;
/**
* A wrapper for an {@link Object} or {@link Class} upon which reflective calls
* can be made.
*
* An example of using Reflect is
*
* // Wrap an Object / Class / class name with the on() method:
* Reflect.on("java.lang.String")
* // Invoke constructors using the create() method:
* .create("Hello World")
* // Invoke methods using the call() method:
* .call("toString")
* // Retrieve the wrapped object
*
*
* @author Lukas Eder
*/
public class Reflect {
// ---------------------------------------------------------------------
// Static API used as entrance points to the fluent API
// ---------------------------------------------------------------------
/**
* Wrap a class name.
*
* This is the same as calling on(Class.forName(name))
*
* @param name A fully qualified class name
* @return A wrapped class object, to be used for further reflection.
* @throws ReflectException If any reflection exception occurred.
* @see #on(Class)
*/
public static Reflect on(String name) throws ReflectException {
return on(forName(name));
}
/**
* Wrap a class.
*
* Use this when you want to access static fields and methods on a
* {@link Class} object, or as a basis for constructing objects of that
* class using {@link #create(Object...)}
*
* @param clazz The class to be wrapped
* @return A wrapped class object, to be used for further reflection.
*/
public static Reflect on(Class clazz) {
return new Reflect(clazz);
}
/**
* Wrap an object.
*
* Use this when you want to access instance fields and methods on any
* {@link Object}
*
* @param object The object to be wrapped
* @return A wrapped object, to be used for further reflection.
*/
public static Reflect on(Object object) {
return new Reflect(object);
}
/**
* Conveniently render an {@link AccessibleObject} accessible
*
* @param accessible The object to render accessible
* @return The argument object rendered accessible
*/
public static T accessible(T accessible) {
if (accessible == null) {
return null;
}
if (!accessible.isAccessible()) {
accessible.setAccessible(true);
}
return accessible;
}
// ---------------------------------------------------------------------
// Members
// ---------------------------------------------------------------------
/**
* The wrapped object
*/
private final Object object;
/**
* A flag indicating whether the wrapped object is a {@link Class} (for
* accessing static fields and methods), or any other type of {@link Object}
* (for accessing instance fields and methods).
*/
private final boolean isClass;
// ---------------------------------------------------------------------
// Constructors
// ---------------------------------------------------------------------
private Reflect(Class type) {
this.object = type;
this.isClass = true;
}
private Reflect(Object object) {
this.object = object;
this.isClass = false;
}
// ---------------------------------------------------------------------
// Fluent Reflection API
// ---------------------------------------------------------------------
/**
* Get the wrapped object
*
* @param A convenience generic parameter for automatic unsafe casting
*/
@SuppressWarnings("unchecked")
public T get() {
return (T) object;
}
/**
* Set a field value.
*
* This is roughly equivalent to {@link Field#set(Object, Object)}. If the
* wrapped object is a {@link Class}, then this will set a value to a static
* member field. If the wrapped object is any other {@link Object}, then
* this will set a value to an instance member field.
*
* @param name The field name
* @param value The new field value
* @return The same wrapped object, to be used for further reflection.
* @throws ReflectException If any reflection exception occurred.
*/
public Reflect set(String name, Object value) throws ReflectException {
try {
// Try setting a public field
Field field = type().getField(name);
field.set(object, unwrap(value));
return this;
} catch (Exception e1) {
// Try again, setting a non-public field
try {
accessible(type().getDeclaredField(name)).set(object, unwrap(value));
return this;
} catch (Exception e2) {
throw new ReflectException(e2);
}
}
}
/**
* Get a field value.
*
* This is roughly equivalent to {@link Field#get(Object)}. If the wrapped
* object is a {@link Class}, then this will get a value from a static
* member field. If the wrapped object is any other {@link Object}, then
* this will get a value from an instance member field.
*
* If you want to "navigate" to a wrapped version of the field, use
* {@link #field(String)} instead.
*
* @param name The field name
* @return The field value
* @throws ReflectException If any reflection exception occurred.
* @see #field(String)
*/
public T get(String name) throws ReflectException {
return field(name).get();
}
/**
* Get a wrapped field.
*
* This is roughly equivalent to {@link Field#get(Object)}. If the wrapped
* object is a {@link Class}, then this will wrap a static member field. If
* the wrapped object is any other {@link Object}, then this wrap an
* instance member field.
*
* @param name The field name
* @return The wrapped field
* @throws ReflectException If any reflection exception occurred.
*/
public Reflect field(String name) throws ReflectException {
try {
// Try getting a public field
Field field = type().getField(name);
return on(field.get(object));
} catch (Exception e1) {
// Try again, getting a non-public field
try {
return on(accessible(type().getDeclaredField(name)).get(object));
} catch (Exception e2) {
throw new ReflectException(e2);
}
}
}
/**
* Get a Map containing field names and wrapped values for the fields'
* values.
*
* If the wrapped object is a {@link Class}, then this will return static
* fields. If the wrapped object is any other {@link Object}, then this will
* return instance fields.
*
* These two calls are equivalent
* on(object).field("myField");
* on(object).fields().get("myField");
* fields() {
Map result = new LinkedHashMap();
for (Field field : type().getFields()) {
if (!isClass ^ Modifier.isStatic(field.getModifiers())) {
String name = field.getName();
result.put(name, field(name));
}
}
return result;
}
/**
* Call a method by its name.
*
* This is a convenience method for calling
* call(name, new Object[0])
*
* @param name The method name
* @return The wrapped method result or the same wrapped object if the
* method returns void, to be used for further
* reflection.
* @throws ReflectException If any reflection exception occurred.
* @see #call(String, Object...)
*/
public Reflect call(String name) throws ReflectException {
return call(name, new Object[0]);
}
/**
* Call a method by its name.
*
* This is roughly equivalent to {@link Method#invoke(Object, Object...)}.
* If the wrapped object is a {@link Class}, then this will invoke a static
* method. If the wrapped object is any other {@link Object}, then this will
* invoke an instance method.
*
* Just like {@link Method#invoke(Object, Object...)}, this will try to wrap
* primitive types or unwrap primitive type wrappers if applicable. If
* several methods are applicable, by that rule, the first one encountered
* is called. i.e. when calling
* on(...).call("method", 1, 1);
*
* public void method(int param1, Integer param2);
* public void method(Integer param1, int param2);
* public void method(Number param1, Number param2);
* public void method(Number param1, Object param2);
* public void method(int param1, Object param2);
* void, to be used for further
* reflection.
* @throws ReflectException If any reflection exception occurred.
*/
public Reflect call(String name, Object... args) throws ReflectException {
Class[] types = types(args);
// Try invoking the "canonical" method, i.e. the one with exact
// matching argument types
try {
Method method = type().getMethod(name, types);
return on(method, object, args);
} catch (NoSuchMethodException e) {
// If there is no exact match, try to find one that has a "similar"
// signature if primitive argument types are converted to their wrappers
for (Method method : type().getMethods()) {
if (method.getName().equals(name) && match(method.getParameterTypes(), types)) {
return on(method, object, args);
}
}
throw new ReflectException(e);
}
}
/**
* Call a constructor.
*
* This is a convenience method for calling
* create(new Object[0])
*
* @return The wrapped new object, to be used for further reflection.
* @throws ReflectException If any reflection exception occurred.
* @see #create(Object...)
*/
public Reflect create() throws ReflectException {
return create(new Object[0]);
}
/**
* Call a constructor.
*
* This is roughly equivalent to {@link Constructor#newInstance(Object...)}.
* If the wrapped object is a {@link Class}, then this will create a new
* object of that class. If the wrapped object is any other {@link Object},
* then this will create a new object of the same type.
*
* Just like {@link Constructor#newInstance(Object...)}, this will try to
* wrap primitive types or unwrap primitive type wrappers if applicable. If
* several constructors are applicable, by that rule, the first one
* encountered is called. i.e. when calling
* on(C.class).create(1, 1);
*
* public C(int param1, Integer param2);
* public C(Integer param1, int param2);
* public C(Number param1, Number param2);
* public C(Number param1, Object param2);
* public C(int param1, Object param2);
*
P as(Class
proxyType) {
final InvocationHandler handler = new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
return on(object).call(method.getName(), args).get();
}
};
return (P) Proxy.newProxyInstance(proxyType.getClassLoader(), new Class[]{proxyType}, handler);
}
// ---------------------------------------------------------------------
// Object API
// ---------------------------------------------------------------------
/**
* Check whether two arrays of types match, converting primitive types to
* their corresponding wrappers.
*/
private boolean match(Class[] declaredTypes, Class[] actualTypes) {
if (declaredTypes.length == actualTypes.length) {
for (int i = 0; i < actualTypes.length; i++) {
if (!wrapper(declaredTypes[i]).isAssignableFrom(wrapper(actualTypes[i]))) {
return false;
}
}
return true;
} else {
return false;
}
}
/**
* {@inheritDoc}
*/
@Override
public int hashCode() {
return object.hashCode();
}
/**
* {@inheritDoc}
*/
@Override
public boolean equals(Object obj) {
if (obj instanceof Reflect) {
return object.equals(((Reflect) obj).get());
}
return false;
}
/**
* {@inheritDoc}
*/
@Override
public String toString() {
return object.toString();
}
// ---------------------------------------------------------------------
// Utility methods
// ---------------------------------------------------------------------
/**
* Wrap an object created from a constructor
*/
private static Reflect on(Constructor constructor, Object... args) throws ReflectException {
try {
return on(constructor.newInstance(args));
} catch (Exception e) {
throw new ReflectException(e);
}
}
/**
* Wrap an object returned from a method
*/
private static Reflect on(Method method, Object object, Object... args) throws ReflectException {
try {
accessible(method);
if (method.getReturnType() == void.class) {
method.invoke(object, args);
return on(object);
} else {
return on(method.invoke(object, args));
}
} catch (Exception e) {
throw new ReflectException(e);
}
}
/**
* Unwrap an object
*/
private static Object unwrap(Object object) {
if (object instanceof Reflect) {
return ((Reflect) object).get();
}
return object;
}
/**
* Get an array of types for an array of objects
*
* @see Object#getClass()
*/
private static Class[] types(Object... values) {
if (values == null) {
return new Class[0];
}
Class[] result = new Class[values.length];
for (int i = 0; i < values.length; i++) {
result[i] = values[i].getClass();
}
return result;
}
/**
* Load a class
*
* @see Class#forName(String)
*/
private static Class forName(String name) throws ReflectException {
try {
return Class.forName(name);
} catch (Exception e) {
throw new ReflectException(e);
}
}
/**
* Get the type of the wrapped object.
*
* @see Object#getClass()
*/
public Class type() {
if (isClass) {
return (Class) object;
} else {
return object.getClass();
}
}
/**
* Get a wrapper type for a primitive type, or the argument type itself, if
* it is not a primitive type.
*/
private static Class wrapper(Class type) {
if (boolean.class == type) {
return Boolean.class;
} else if (int.class == type) {
return Integer.class;
} else if (long.class == type) {
return Long.class;
} else if (short.class == type) {
return Short.class;
} else if (byte.class == type) {
return Byte.class;
} else if (double.class == type) {
return Double.class;
} else if (float.class == type) {
return Float.class;
} else if (char.class == type) {
return Character.class;
} else {
return type;
}
}
private static final String THIS_CLASS_NAME = Reflect.class.getName();
/**
* 获取调用本类中方法的其他类名
*
* @return
*/
public static String getInvokeClassName() {
StackTraceElement[] stack = Thread.currentThread().getStackTrace();
int ix = 0;
boolean findThis = false;
while (ix < stack.length) {
StackTraceElement frame = stack[ix];
String className = frame.getClassName();
if (className.equals(THIS_CLASS_NAME) && !findThis) {
findThis = true;
} else if (findThis) {
return className;
}
ix++;
}
return null;
}
}