写一个远程加载jar的代码
时间: 2024-02-24 13:00:32 浏览: 23
以下是一个简单的示例,演示如何使用RMI远程加载jar文件:
1. 创建一个包含你要运行的类的jar文件,例如“myjarfile.jar”。
2. 创建一个RMI服务端程序,该程序将加载jar文件并提供对其中类的访问权限。以下是一个示例:
```java
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.rmi.Remote;
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import java.util.ArrayList;
import java.util.List;
import java.util.jar.JarEntry;
import java.util.jar.JarInputStream;
public class RemoteClassLoader extends UnicastRemoteObject implements Remote {
private static final long serialVersionUID = 1L;
private List<String> classNames = new ArrayList<String>();
protected RemoteClassLoader() throws RemoteException {
super();
}
public void loadJar(String jarFileName) throws RemoteException {
try {
File file = new File(jarFileName);
FileInputStream fis = new FileInputStream(file);
JarInputStream jis = new JarInputStream(fis);
JarEntry jarEntry;
while ((jarEntry = jis.getNextJarEntry()) != null) {
if (jarEntry.getName().endsWith(".class")) {
String className = jarEntry.getName().replaceAll("/", "\\.");
className = className.substring(0, className.length() - 6);
classNames.add(className);
byte[] classData = new byte[1024];
int readLength = 0;
while ((readLength = jis.read(classData)) != -1) {
// Do nothing
}
}
}
jis.close();
fis.close();
} catch (IOException e) {
throw new RemoteException("Failed to load jar file", e);
}
}
public byte[] loadClass(String className) throws RemoteException {
try {
String classPath = className.replaceAll("\\.", "/") + ".class";
JarClassLoader cl = new JarClassLoader(classNames);
byte[] classData = cl.getResourceAsBytes(classPath);
return classData;
} catch (IOException e) {
throw new RemoteException("Failed to load class", e);
}
}
}
```
该程序包含一个名为“loadJar”的方法,该方法将加载jar文件并提取其中的类名。它还包含名为“loadClass”的方法,该方法将提供对指定类的字节码的访问权限。
3. 创建一个名为“JarClassLoader”的类,该类将根据提供的类名加载字节码。以下是一个示例:
```java
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
public class JarClassLoader extends ClassLoader {
private List<String> classNames;
public JarClassLoader(List<String> classNames) {
this.classNames = classNames;
}
public byte[] getResourceAsBytes(String name) throws IOException {
InputStream is = getResourceAsStream(name);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int readLength = 0;
while ((readLength = is.read(buffer)) != -1) {
baos.write(buffer, 0, readLength);
}
return baos.toByteArray();
}
@Override
protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
Class<?> c = findLoadedClass(name);
if (c == null) {
try {
byte[] classData = getResourceAsBytes(name.replaceAll("\\.", "/") + ".class");
c = defineClass(name, classData, 0, classData.length);
if (c == null) {
c = super.loadClass(name, resolve);
}
} catch (IOException e) {
c = super.loadClass(name, resolve);
}
}
if (resolve) {
resolveClass(c);
}
return c;
}
}
```
该类将从jar文件中提取的类名作为参数,并使用Java的类加载器机制加载字节码。
4. 在客户端程序中创建一个RMI代理对象,该对象将连接到RMI服务端程序,并使用代理对象调用您在jar文件中定义的类的方法。以下是一个示例:
```java
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
public class RemoteClassLoaderClient {
public static void main(String[] args) throws Exception {
String jarFileName = "myjarfile.jar";
Registry registry = LocateRegistry.getRegistry("localhost");
RemoteClassLoader remoteClassLoader = (RemoteClassLoader) registry.lookup("RemoteClassLoader");
remoteClassLoader.loadJar(jarFileName);
byte[] classData = remoteClassLoader.loadClass("com.example.MyClass");
Class<?> clazz = new JarClassLoader(remoteClassLoader.classNames).defineClass("com.example.MyClass", classData, 0, classData.length);
Object obj = clazz.newInstance();
clazz.getMethod("myMethod").invoke(obj);
}
}
```
该程序将连接到RMI服务端程序,并使用远程加载器加载jar文件。然后,它将使用“loadClass”方法从远程加载器中获取类的字节码,并使用Java的类加载器机制实例化类并调用方法。
希望这可以帮助您编写远程加载jar文件的代码。