com.vectorprint.ClassHelper Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of VectorPrintCommon Show documentation
Show all versions of VectorPrintCommon Show documentation
Common, mainly helper classes, featuring finding class of generic parameters, thread testing, version information detection, ArrayHelper, CertificateHelper, StringConverter
package com.vectorprint;
/*-
* #%L
* VectorPrintCommon
* %%
* Copyright (C) 2011 - 2018 VectorPrint
* %%
* 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.
* #L%
*/
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.lang.reflect.Array;
import java.lang.reflect.Constructor;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.lang.reflect.WildcardType;
import java.net.URL;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.jar.JarEntry;
import java.util.jar.JarInputStream;
/**
*
* @author Eduard Drenth at VectorPrint.nl
*/
public class ClassHelper {
private ClassHelper() {
}
/**
* Calls {@link #fromPackage(java.lang.Package, java.lang.ClassLoader) } with
* Thread.currentThread().getContextClassLoader().
*/
public static Set> fromPackage(Package pr) throws IOException, FileNotFoundException, ClassNotFoundException {
return fromPackage(pr, Thread.currentThread().getContextClassLoader());
}
/**
* Calls {@link #getClasses(java.lang.ClassLoader, java.lang.String) } with the context class loader from the current
* thread and {@link Package#getName() }
*
* @param p
* @param loader
* @return
* @throws IOException
* @throws FileNotFoundException
* @throws ClassNotFoundException
*/
public static Set> fromPackage(Package p, ClassLoader loader) throws IOException, FileNotFoundException, ClassNotFoundException {
return getClasses(loader, p.getName());
}
/**
* looks for classes in a package either in {@link #getFromDirectory(java.io.File, java.lang.String) directories} or
* in {@link #getFromJARFile(java.lang.String, java.lang.String) jars}.
*
* @param loader
* @param packageName
* @return
* @throws IOException
* @throws FileNotFoundException
* @throws ClassNotFoundException
*/
public static Set> getClasses(ClassLoader loader, String packageName) throws IOException, FileNotFoundException, ClassNotFoundException {
Set> classes = new HashSet<>();
String path = packageName.replace('.', File.separatorChar);
Enumeration resources = loader.getResources(path);
if (resources != null) {
while (resources.hasMoreElements()) {
String filePath = resources.nextElement().getFile();
if (filePath != null) {
// WINDOWS HACK
if (filePath.indexOf("%20") > 0) {
filePath = filePath.replace("%20", " ");
}
if ((filePath.indexOf('!') > 0) & (filePath.indexOf(".jar") > 0)) {
String jarPath = filePath.substring(0, filePath.indexOf('!'))
.substring(filePath.indexOf(':') + 1);
// WINDOWS HACK
if (jarPath.indexOf(':') >= 0) {
jarPath = jarPath.substring(1);
}
classes.addAll(getFromJARFile(jarPath, packageName, loader));
} else {
classes.addAll(
getFromDirectory(new File(filePath), packageName, loader));
}
}
}
}
return classes;
}
/**
* looks for classes in a package in a jar
*
* @param jar
* @param packageName
* @return
* @throws FileNotFoundException
* @throws IOException
* @throws ClassNotFoundException
*/
public static Set> getFromJARFile(String jar, String packageName, ClassLoader loader) throws FileNotFoundException, IOException, ClassNotFoundException {
Set> classes = new HashSet<>(200, 50);
JarInputStream jarFile = new JarInputStream(new FileInputStream(jar));
JarEntry jarEntry;
do {
jarEntry = jarFile.getNextJarEntry();
if (jarEntry != null) {
String className = jarEntry.getName();
if (className.endsWith(".class")) {
// check package
if (className.replace('/', '.').replace(packageName, "").replace(".class", "").lastIndexOf('.') == 0) {
classes.add(Class.forName(className.replace('/', '.').replace(".class", ""), false, loader));
}
}
}
} while (jarEntry != null);
return classes;
}
/**
* looks for classes in a package in a directory
*
* @param directory
* @param packageName
* @return
* @throws ClassNotFoundException
*/
public static Set> getFromDirectory(File directory, String packageName, ClassLoader loader) throws ClassNotFoundException {
Set> classes = new HashSet<>(200, 50);
if (directory.exists()) {
for (String file : directory.list()) {
if (file.endsWith(".class")) {
String name = packageName + '.' + file.replace(".class", "");
Class clazz = Class.forName(name, false, loader);
classes.add(clazz);
}
}
}
return classes;
}
/**
* find the runtime class for a class parameter when you know the declaring class. Calls {@link #findParameterClasses(java.lang.Class, java.lang.Class)
* }
*
* @param subclass the subclass of the parameterized class whose parameter class we want to know
* @param paramNum the index of the parameter on the parameterized class whose class we want to know
* @param classWithParameter the class that declares the parameter whose class we are looking for
* @return a class or null
*/
public static Class findParameterClass(int paramNum, Class subclass, Class classWithParameter) {
return findParameterClasses(subclass, classWithParameter).get(paramNum);
}
/**
* find the runtime classes of the parameters of a class or interface. The strategy is to visit the subclass and its
* parent classes to find the classes of the classWithParameters
*
*
* @param subclass the subclass of the parameterized class whose parameter class we want to know
* @param classWithParameter the class that declares the parameter whose class we are looking for
* @return a List of java class for the class parameters, or null
*/
public static List> findParameterClasses(Class subclass, Class classWithParameter) {
List> parameterClasses = null;
// conditions
TypeVariable[] params = classWithParameter.getTypeParameters();
if (params.length > 0) { // parameters have to be present
parameterClasses = new ArrayList<>(params.length);
// to keep track of where parameters go in the class hierarchy
Map> varsPrevious = new HashMap<>(3);
Map> varsCurrent = new HashMap<>(3);
Type parent = subclass;
while ((parent = getGenericSuperType((Class) parent, classWithParameter)) != null) {
if (parent instanceof ParameterizedType) {
ParameterizedType pa = (ParameterizedType) parent;
TypeVariable[] pars = getClass(pa.getRawType()).getTypeParameters();
int i = 0;
for (Type t : pa.getActualTypeArguments()) {
/*
* the number of getActualTypeArguments and getTypeParameters of the parent is always the same
*
* when t is a typevariable, we may find its class in previously processed type variables
*
* working this way finds the correct type, also when order of parameters changes in the hierarchy
*/
if (t instanceof TypeVariable) {
varsCurrent.put(pars[i++], (varsPrevious.containsKey(t)) ? varsPrevious.get(t) : null);
} else {
varsCurrent.put(pars[i++], getClass(t));
}
}
parent = pa.getRawType();
}
varsPrevious.clear();
varsPrevious.putAll(varsCurrent);
varsCurrent.clear();
}
for (TypeVariable tv : params) {
parameterClasses.add(varsPrevious.get(tv));
}
}
return parameterClasses;
}
/**
* returns either the generic superclass or a generic interface, but only when it is assignable from the typed
* classWithParameter argument
*
* @param
* @param subclass
* @param classWithParameter
* @return
*/
public static Type getGenericSuperType(Class subclass, Class classWithParameter) {
if (subclass.getSuperclass() != null && classWithParameter.isAssignableFrom(subclass.getSuperclass())) {
return subclass.getGenericSuperclass();
} else {
int i = 0;
for (Class in : subclass.getInterfaces()) {
if (classWithParameter.isAssignableFrom(in)) {
return subclass.getGenericInterfaces()[i];
}
i++;
}
return null;
}
}
/**
* when possible return the class of the type argument, otherwise null
*
* @param type
* @return
*/
public static Class getClass(Type type) {
if (type instanceof Class) {
return (Class) type;
} else if (type instanceof ParameterizedType) {
return (Class) ((ParameterizedType) type).getRawType();
} else if (type instanceof GenericArrayType) {
Type componentType = ((GenericArrayType) type).getGenericComponentType();
Class componentClass = getClass(componentType);
if (componentClass != null) {
return Array.newInstance(componentClass, 0).getClass();
} else {
return null;
}
} else if (type instanceof TypeVariable) {
return null;
} else if (type instanceof WildcardType) {
return null;
} else {
return null;
}
}
/**
* Calls {@link #getClasses(java.lang.ClassLoader, java.lang.String) } with the contextclassloader of the current
* thread and the first argument which should be a package name.
*
* @param args
* @throws IOException
* @throws FileNotFoundException
* @throws ClassNotFoundException
*/
public static void main(String[] args) throws IOException, FileNotFoundException, ClassNotFoundException {
if (args.length < 1) {
System.out.println("pass a package name as argument");
} else {
System.out.println(getClasses(Thread.currentThread().getContextClassLoader(), args[0]));
}
}
/**
* find the first declared constructor accepting certain parameters.
* @param
* @param clazz
* @param parameters
* @return
*/
public static Constructor findConstructor(Class clazz, Class... parameters) {
for (Constructor con : clazz.getDeclaredConstructors()) {
Class[] parameterTypes = con.getParameterTypes();
if (parameters.length != parameterTypes.length) {
continue;
}
boolean ok = true;
for (int i = 0; i < parameters.length; i++) {
if (!parameters[i].isAssignableFrom(parameterTypes[i])) {
ok = false;
break;
}
}
if (ok) {
return (Constructor) con;
}
}
return null;
}
}