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Java re-implementation of tiny graphviz
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/*
* Copyright 2022 The graph-support project
*
* 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 org.graphper.util;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
/**
* Utility class for working with reflection and class instantiation.
*/
@SuppressWarnings("all")
public class ClassUtils {
private ClassUtils() {
}
/**
* Creates a new instance of the specified class without parameters.
*
* @param clazz The class to instantiate.
* @return The new instance of the class.
* @throws Exception If instantiation fails.
*/
public static Object newObject(Class clazz) throws Exception {
return newObject(clazz, null, null);
}
/**
* Creates a new instance of the specified class with a single parameter.
*
* @param clazz The class to instantiate.
* @param parameterType The type of the parameter.
* @param param The parameter value.
* @return The new instance of the class.
* @throws Exception If instantiation fails.
*/
public static Object newObjectOne(Class clazz, Class parameterType, Object param)
throws Exception {
return newObject(clazz, new Class[]{parameterType}, param);
}
/**
* Creates a new instance of the specified class with parameters.
*
* @param clazz The class to instantiate.
* @param params The parameter values.
* @return The new instance of the class.
* @throws Exception If instantiation fails.
*/
public static Object newObject(Class clazz, Object... params) throws Exception {
if (params == null || params.length == 0) {
return newObject(clazz);
}
Class[] parameterTypes = new Class[params.length];
for (int i = 0; i < params.length; i++) {
Asserts.illegalArgument(params[i] == null, "Constructor can not have null parameter");
parameterTypes[i] = getClass(params[i]);
}
return newObject(clazz, parameterTypes, params);
}
/**
* Creates a new instance of the specified class with parameters.
*
* @param clazz The class to instantiate.
* @param parameterTypes The types of the parameters.
* @param params The parameter values.
* @return The new instance of the class.
* @throws Exception If instantiation fails.
*/
public static Object newObject(Class clazz, Class[] parameterTypes, Object... params)
throws Exception {
Asserts.nullArgument(clazz, "clazz");
Constructor constructor = clazz.getConstructor(parameterTypes);
return constructor.newInstance(params);
}
/**
* Invokes a method with no parameters on the specified object.
*
* @param obj The object on which to invoke the method.
* @param methodName The name of the method to invoke.
* @return The result of the method invocation.
* @throws Exception If method invocation fails.
*/
public static Object invoke(Object obj, String methodName) throws Exception {
return invoke(obj, methodName, null, null);
}
/**
* Invokes a method with parameters on the specified object.
*
* @param obj The object on which to invoke the method.
* @param methodName The name of the method to invoke.
* @param params The parameter values.
* @return The result of the method invocation.
* @throws Exception If method invocation fails.
*/
public static Object invoke(Object obj, String methodName, Object... params) throws Exception {
if (params == null || params.length == 0) {
return invoke(obj, methodName);
}
Class[] parameterTypes = new Class[params.length];
for (int i = 0; i < params.length; i++) {
Asserts.illegalArgument(params[i] == null, "Method can not have null parameter");
parameterTypes[i] = getClass(params[i]);
}
return invoke(obj, methodName, parameterTypes, params);
}
/**
* Invokes a method with a single parameter on the specified object.
*
* @param obj The object on which to invoke the method.
* @param methodName The name of the method to invoke.
* @param parameterType The type of the parameter.
* @param param The parameter value.
* @return The result of the method invocation.
* @throws Exception If method invocation fails.
*/
public static Object invokeOne(Object obj, String methodName,
Class parameterType, Object param) throws Exception {
return invoke(obj, methodName, new Class[]{parameterType}, param);
}
/**
* Invokes a method with parameters on the specified object.
*
* @param obj The object on which to invoke the method.
* @param methodName The name of the method to invoke.
* @param parameterTypes The types of the parameters.
* @param params The parameter values.
* @return The result of the method invocation.
* @throws Exception If method invocation fails.
*/
public static Object invoke(Object obj, String methodName, Class[] parameterTypes,
Object... params) throws Exception {
Asserts.nullArgument(obj, "obj");
Method method = obj.getClass().getMethod(methodName, parameterTypes);
return method.invoke(obj, params);
}
/**
* Retrieves the value of a field from the specified object.
*
* @param obj The object from which to retrieve the field value.
* @param fieldName The name of the field.
* @return The value of the field.
* @throws Exception If field retrieval fails.
*/
public static Object getField(Object obj, String fieldName) throws Exception {
Asserts.nullArgument(obj, "obj");
Class clazz = obj.getClass();
Field field = clazz.getField(fieldName);
if (!field.isAccessible()) {
field.setAccessible(true);
}
return field.get(obj);
}
/**
* Invokes a static method on the specified class with no parameters.
*
* @param clazz The class on which to invoke the static method.
* @param methodName The name of the static method to invoke.
* @return The result of the static method invocation.
* @throws Exception If static method invocation fails.
*/
public static Object invokeStatic(Class clazz, String methodName) throws Exception {
return invokeStatic(clazz, methodName, null, null);
}
/**
* Invokes a static method on the specified class with parameters.
*
* @param clazz The class on which to invoke the static method.
* @param methodName The name of the static method to invoke.
* @param parameterTypes The types of the parameters.
* @param params The parameter values.
* @return The result of the static method invocation.
* @throws Exception If static method invocation fails.
*/
public static Object invokeStatic(Class clazz, String methodName,
Class[] parameterTypes, Object... params) throws Exception {
Asserts.nullArgument(clazz, "class");
Method method = clazz.getDeclaredMethod(methodName, parameterTypes);
method.setAccessible(true);
return method.invoke(null, params);
}
/**
* Retrieves the value of a static field from the specified class.
*
* @param clazz The class from which to retrieve the static field value.
* @param fieldName The name of the static field.
* @return The value of the static field.
* @throws Exception If static field retrieval fails.
*/
public static Object getStaticField(Class clazz, String fieldName) throws Exception {
Asserts.nullArgument(clazz, "class");
Field field = clazz.getDeclaredField(fieldName);
field.setAccessible(true);
return field.get(null);
}
/**
* Returns a map of the values of all non-static properties of the object.
*
* @param obj object to be acquired
* @return a map of attributes and attribute values
* @throws SecurityException If a security manager, s, is present and any of the
* following conditions is met:
*
*
*
* - the caller's class loader is not the same as the
* class loader of this class and invocation of
* {@link SecurityManager#checkPermission
* s.checkPermission} method with
* {@code RuntimePermission("accessDeclaredMembers")}
* denies access to the declared fields within this class.
*
*
- the caller's class loader is not the same as or an
* ancestor of the class loader for the current class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of this class.
*
*
- if the request is denied.
*
*
* @throws IllegalAccessException if this {@code Field} object is enforcing Java language
* access control and the underlying field is inaccessible.
* @throws IllegalArgumentException if the specified object is not an instance of the class or
* interface declaring the underlying field (or a subclass or
* implementor thereof).
* @throws NullPointerException if the specified object is null and the field is an
* instance field.
* @throws ExceptionInInitializerError if the initialization provoked by this method fails.
*/
public static Map propValMap(Object obj) throws IllegalAccessException {
if (obj == null) {
return Collections.emptyMap();
}
Class cls = obj.getClass();
Field[] fields = cls.getDeclaredFields();
if (fields.length == 0) {
return Collections.emptyMap();
}
Map map = new HashMap<>(fields.length);
for (Field field : fields) {
if (Modifier.isStatic(field.getModifiers())) {
continue;
}
String name = field.getName();
field.setAccessible(true);
Object propVal = field.get(obj);
if (propVal == null) {
continue;
}
field.setAccessible(false);
map.put(name, propVal);
}
return map;
}
public static void modifyField(Object obj, String fieldName, Object value)
throws NoSuchFieldException, IllegalAccessException {
Asserts.nullArgument(obj, "Null object");
Asserts.nullArgument(fieldName, "Null field name");
Class clazz = obj.getClass();
Field field = clazz.getDeclaredField(fieldName);
if (Modifier.isStatic(field.getModifiers())) {
return;
}
boolean accessible = field.isAccessible();
field.setAccessible(true);
field.set(obj, value);
field.setAccessible(accessible);
}
private static Class getClass(Object obj) {
Class clazz = obj.getClass();
if (clazz == Integer.class) {
return Integer.TYPE;
} else if (clazz == Long.class) {
return Long.TYPE;
} else if (clazz == Short.class) {
return Short.TYPE;
} else if (clazz == Byte.class) {
return Byte.TYPE;
} else if (clazz == Double.class) {
return Double.TYPE;
} else if (clazz == Float.class) {
return Float.TYPE;
} else if (clazz == Character.class) {
return Character.TYPE;
} else if (clazz == Boolean.class) {
return Boolean.TYPE;
} else {
return clazz;
}
}
}