jetbrick.util.ClassLoaderUtils Maven / Gradle / Ivy
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/**
* Copyright 2013-2023 Guoqiang Chen, Shanghai, China. All rights reserved.
*
* Author: Guoqiang Chen
* Email: [email protected]
* WebURL: https://github.com/subchen
*
* 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 jetbrick.util;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class ClassLoaderUtils {
private static final Map abbreviationMap;
/**
* Returns default class loader (current thread's context)
*/
public static ClassLoader getDefault() {
ClassLoader loader = null;
try {
loader = Thread.currentThread().getContextClassLoader();
} catch (Exception e) {
}
if (loader == null) {
loader = ClassLoaderUtils.class.getClassLoader();
if (loader == null) {
try {
// getClassLoader() returning null indicates the bootstrap ClassLoader
loader = ClassLoader.getSystemClassLoader();
} catch (Exception e) {
// Cannot access system ClassLoader - oh well, maybe the caller can live with
// null...
}
}
}
return loader;
}
/**
* Returns all default class loaders
*/
public static List getDefaults() {
List loaders = new ArrayList(3);
ClassLoader loader = null;
try {
loader = Thread.currentThread().getContextClassLoader();
loaders.add(loader);
} catch (Exception e) {
}
loader = ClassLoaderUtils.class.getClassLoader();
if (loader != null) {
// getClassLoader() returning null indicates the bootstrap ClassLoader
loaders.add(loader);
}
try {
loader = ClassLoader.getSystemClassLoader();
loaders.add(loader);
} catch (Exception e) {
// Cannot access system ClassLoader - oh well, maybe the caller can live with
// null...
}
return loaders;
}
/**
* 使用默认的 ClassLoader 去载入类.
*
* @return null if class not found
*/
public static Class loadClass(final String qualifiedClassName) {
try {
return loadClassEx(qualifiedClassName, Collections. emptyList());
} catch (ClassNotFoundException e) {
return null;
}
}
/**
* 使用默认的 ClassLoader 去载入类.
*
* @return null if class not found
*/
public static Class loadClass(final String qualifiedClassName, ClassLoader loader) {
try {
return loadClassEx(qualifiedClassName, Collections.singletonList(loader));
} catch (ClassNotFoundException e) {
return null;
}
}
/**
* 使用默认的 ClassLoader 去载入类.
*
* @return null if class not found
*/
public static Class loadClass(final String qualifiedClassName, List loaders) {
try {
return loadClassEx(qualifiedClassName, loaders);
} catch (ClassNotFoundException e) {
return null;
}
}
/**
* 使用默认的 ClassLoader 去载入类.
*
* @throws ClassNotFoundException
*/
public static Class loadClassEx(final String qualifiedClassName) throws ClassNotFoundException {
return loadClassEx(qualifiedClassName, Collections. emptyList());
}
/**
* 使用指定的 ClassLoader 去载入类.
*
* @throws ClassNotFoundException
*/
public static Class loadClassEx(final String qualifiedClassName, ClassLoader loader) throws ClassNotFoundException {
return loadClassEx(qualifiedClassName, Collections.singletonList(loader));
}
/**
* 使用指定的 ClassLoader 去载入类.
*
* @throws ClassNotFoundException
*/
public static Class loadClassEx(final String qualifiedClassName, List loaders) throws ClassNotFoundException {
Validate.notNull(qualifiedClassName, "qualifiedClassName must be not null");
if (loaders == null || loaders.isEmpty()) {
loaders = getDefaults();
}
// 尝试基本类型
if (abbreviationMap.containsKey(qualifiedClassName)) {
String className = '[' + abbreviationMap.get(qualifiedClassName);
return doLoadClass(className, loaders).getComponentType();
}
// 尝试用 Class.forName()
try {
String className = getCanonicalClassName(qualifiedClassName);
return doLoadClass(className, loaders);
} catch (ClassNotFoundException e) {
}
// 尝试当做一个内部类去识别: java.util.Map.Entry --> java.util.Map$Entry
if (qualifiedClassName.indexOf('$') == -1) {
int ipos = qualifiedClassName.lastIndexOf('.');
if (ipos > 0) {
try {
String className = qualifiedClassName.substring(0, ipos) + '$' + qualifiedClassName.substring(ipos + 1);
className = getCanonicalClassName(className);
return doLoadClass(className, loaders);
} catch (ClassNotFoundException e) {
}
}
}
throw new ClassNotFoundException(qualifiedClassName);
}
private static Class doLoadClass(String className, List loaders) throws ClassNotFoundException {
for (ClassLoader loader : loaders) {
try {
return Class.forName(className, false, loader);
} catch (ClassNotFoundException e) {
}
}
throw new ClassNotFoundException(className);
}
/**
* 将 Java 类名转为 {@code Class.forName()} 可以载入的类名格式.
*
*
* getCanonicalClassName("int") == "int";
* getCanonicalClassName("int[]") == "[I";
* getCanonicalClassName("java.lang.String") == "java.lang.String";
* getCanonicalClassName("java.lang.String[]") == "[Ljava.lang.String;";
*
*/
public static String getCanonicalClassName(String qualifiedClassName) {
Validate.notNull(qualifiedClassName, "qualifiedClassName must be not null");
String name = StringUtils.deleteWhitespace(qualifiedClassName);
if (name.endsWith("[]")) {
StringBuilder sb = new StringBuilder();
while (name.endsWith("[]")) {
name = name.substring(0, name.length() - 2);
sb.append('[');
}
String abbreviation = abbreviationMap.get(name);
if (abbreviation != null) {
sb.append(abbreviation);
} else {
sb.append('L').append(name).append(';');
}
name = sb.toString();
}
return name;
}
/**
* Finds the resource with the given name.
*
* @param name - The resource name
* @return A URL object for reading the resource, or null if the resource could
* not be found
*/
public static URL getResource(String name) {
return getResource(name, null);
}
/**
* Finds the resource with the given name.
*
* @param name - The resource name
* @return A URL object for reading the resource, or null if the resource could
* not be found
*/
public static URL getResource(String name, ClassLoader classLoader) {
Validate.notNull(name, "resourceName must be not null");
if (name.startsWith("/")) {
name = name.substring(1);
}
if (classLoader != null) {
URL url = classLoader.getResource(name);
if (url != null) {
return url;
}
}
ClassLoader loader = Thread.currentThread().getContextClassLoader();
if (loader != null && loader != classLoader) {
URL url = loader.getResource(name);
if (url != null) {
return url;
}
}
return ClassLoader.getSystemResource(name);
}
/**
* Returns an input stream for reading the specified resource.
*/
public static InputStream getResourceAsStream(String name) throws IOException {
return getResourceAsStream(name, null);
}
/**
* Returns an input stream for reading the specified resource.
*/
public static InputStream getResourceAsStream(String name, ClassLoader classLoader) throws IOException {
URL url = getResource(name, classLoader);
if (url != null) {
return url.openStream();
}
return null;
}
/**
* Returns an input stream for reading the specified class.
*/
public static InputStream getClassAsStream(Class clazz) throws IOException {
return getResourceAsStream(getClassFileName(clazz), clazz.getClassLoader());
}
/**
* Returns an input stream for reading the specified class.
*/
public static InputStream getClassAsStream(String qualifiedClassName) throws IOException {
return getResourceAsStream(getClassFileName(qualifiedClassName));
}
/**
* 获取一个 class 所代表的文件名
*/
public static String getClassFileName(Class clazz) {
if (clazz.isArray()) {
clazz = clazz.getComponentType();
}
return getClassFileName(clazz.getName());
}
/**
* 获取一个 class 所代表的文件名
*/
public static String getClassFileName(String qualifiedClassName) {
return qualifiedClassName.replace('.', '/') + ".class";
}
static {
abbreviationMap = new HashMap();
abbreviationMap.put("boolean", "Z");
abbreviationMap.put("byte", "B");
abbreviationMap.put("short", "S");
abbreviationMap.put("char", "C");
abbreviationMap.put("int", "I");
abbreviationMap.put("long", "J");
abbreviationMap.put("float", "F");
abbreviationMap.put("double", "D");
}
}
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