使用他的名字在jar中加载类 [英] Load a class in a jar just with his name
本文介绍了使用他的名字在jar中加载类的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我尝试在jar中加载类,但未成功。
URL url = null;
try {
url = new URL(jar:file:+ System.getProperty(user.dir)+ File.separator +games+ File.separator + gameName +!/ ;
} catch(MalformedURLException e){
e.printStackTrace();
}
URL [] urls = {url};
URLClassLoader cl = URLClassLoader.newInstance(urls);
try {
String gameClassPath = null;
JarFile jar = new JarFile(url.getPath()。replace(file:,).replace(!,.jar));
枚举< JarEntry> entries = jar.entries();
while(entries.hasMoreElements()){
JarEntry entry = entries.nextElement();
if(entry.getName()。contains(gameName)){
gameClassPath = entry.getName()。replace('/','。')。replace(。class, );
}
}
this.gameClass = cl.loadClass(gameClassPath);
jar.close();
} catch(ClassNotFoundException | IOException e){
e.printStackTrace();
}
我认为问题来自 URLClassLoader
可能不在正确的地方。
使用OP的更新编辑问题[
我的@spiderman版本仍然有错误。
我确切的说gameClass类型是类<?>
,不是类
,但我不知道差异。
/ p>
String pathToJar = System.getProperty(user.dir)+ File.separator +games+ File.separator + gameName;
String requiredClassName = gameName;
JarFile jarFile = new JarFile(pathToJar +。jar);
枚举< JarEntry> e = jarFile.entries();
URL [] urls = {new URL(jar:file:+ pathToJar +!/)};
URLClassLoader cl = URLClassLoader.newInstance(urls);
while(e.hasMoreElements()){
JarEntry je =(JarEntry)e.nextElement();
if(je.isDirectory()||!je.getName()。endsWith(。class)){
continue;
}
if(je.getName()。contains(requiredClassName)){
System.out.println(requiredClassName +is found!
}
String className = je.getName()。substring(0,je.getName()。length() - 6);
className = className.replace('/','。');
gameClass = cl.loadClass(className);
}
jarFile.close();问题解决了,但我真的不知道为什么要解决这个问题。
...
我使用一个文件和toURI()。toURL()获取url
文件jarFile = new File(System.getProperty(user.dir)+ File.separator +games+ File.separator + gameName +。jar);
URLClassLoader cl = new URLClassLoader(new URL [] {jarFile.toURI()。toURL()});
JarFile jar = new JarFile(jarFile.toString());
枚举< JarEntry> e = jar.entries();
while(e.hasMoreElements()){
JarEntry je =(JarEntry)e.nextElement();
if(je.isDirectory()||!je.getName()。endsWith(。class)){
continue;
}
if(je.getName()。contains(gameName)){
String className = je.getName()。substring(0,je.getName 6);
className = className.replace('/','。');
gameClass = cl.loadClass(className);
System.out.println(gameName +is loaded!);
}
}
jar.close();
cl.close();
I tried to load a class within a jar, without success.
URL url = null;
try {
url = new URL("jar:file:"+System.getProperty("user.dir")+File.separator+"games"+File.separator+gameName+"!/");
} catch (MalformedURLException e) {
e.printStackTrace();
}
URL[] urls = {url};
URLClassLoader cl = URLClassLoader.newInstance(urls);
try {
String gameClassPath = null;
JarFile jar = new JarFile(url.getPath().replace("file:", "").replace("!", ".jar"));
Enumeration<JarEntry> entries = jar.entries();
while (entries.hasMoreElements()) {
JarEntry entry = entries.nextElement();
if (entry.getName().contains(gameName)) {
gameClassPath = entry.getName().replace('/', '.').replace(".class", "");
}
}
this.gameClass = cl.loadClass(gameClassPath);
jar.close();
} catch (ClassNotFoundException | IOException e) {
e.printStackTrace();
}
I think the problem is coming from the URLClassLoader
which may not be at the right place.
Editing the question with the OP's updates[posted in answer section]
I still have error with @spiderman version.
I precise that gameClass type is Class<?>
, not Class
, but I don't know the difference.
String pathToJar = System.getProperty("user.dir")+File.separator+"games"+File.separator+gameName;
String requiredClassName = gameName;
JarFile jarFile = new JarFile(pathToJar+".jar");
Enumeration<JarEntry> e = jarFile.entries();
URL[] urls = {new URL("jar:file:"+pathToJar+"!/")};
URLClassLoader cl = URLClassLoader.newInstance(urls);
while (e.hasMoreElements()) {
JarEntry je = (JarEntry) e.nextElement();
if(je.isDirectory() || !je.getName().endsWith(".class")){
continue;
}
if (je.getName().contains(requiredClassName)){
System.out.println(requiredClassName + " is found!");
}
String className = je.getName().substring(0,je.getName().length()-6);
className = className.replace('/', '.');
gameClass = cl.loadClass(className);
}
jarFile.close();
解决方案
Problem solved, but I don't really know why ... I use a File and toURI().toURL() to get the url
File jarFile = new File(System.getProperty("user.dir")+File.separator+"games"+File.separator+gameName+".jar");
URLClassLoader cl = new URLClassLoader( new URL[]{jarFile.toURI().toURL()} );
JarFile jar = new JarFile(jarFile.toString());
Enumeration<JarEntry> e = jar.entries();
while (e.hasMoreElements()) {
JarEntry je = (JarEntry) e.nextElement();
if(je.isDirectory() || !je.getName().endsWith(".class")){
continue;
}
if (je.getName().contains(gameName)){
String className = je.getName().substring(0,je.getName().length()-6);
className = className.replace('/', '.');
gameClass = cl.loadClass(className);
System.out.println(gameName + " is loaded!");
}
}
jar.close();
cl.close();
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