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| import java.io.*; | |
| public class FileSystemClassLoader extends ClassLoader { | |
| private String rootDir; | |
| public FileSystemClassLoader(String rootDir) { | |
| this.rootDir = rootDir; | |
| } | |
| protected Class<?> findClass(String name) throws ClassNotFoundException { | |
| byte[] classData = getClassData(name); | |
| if (classData == null) { | |
| throw new ClassNotFoundException(); | |
| } | |
| else { | |
| return defineClass(name, classData, 0, classData.length); | |
| } | |
| } | |
| private byte[] getClassData(String className) { | |
| String path = classNameToPath(className); | |
| InputStream ins = null; | |
| ByteArrayOutputStream baos = null; | |
| try { | |
| ins = new FileInputStream(path); | |
| baos = new ByteArrayOutputStream(); | |
| int bufferSize = 4096; | |
| byte[] buffer = new byte[bufferSize]; | |
| int bytesNumRead = 0; | |
| while ((bytesNumRead = ins.read(buffer)) != -1) { | |
| baos.write(buffer, 0, bytesNumRead); | |
| } | |
| return baos.toByteArray(); | |
| } catch (IOException e) { | |
| e.printStackTrace(); | |
| } finally | |
| { | |
| closeIO(ins); | |
| closeIO(baos); | |
| } | |
| return null; | |
| } | |
| private void closeIO(Closeable closeable) | |
| { | |
| if (closeable == null) return; | |
| try | |
| { | |
| closeable.close(); | |
| } catch (IOException e) | |
| { | |
| e.printStackTrace(); | |
| } | |
| } | |
| private String classNameToPath(String className) { | |
| return rootDir + File.separatorChar | |
| + className.replace('.', File.separatorChar) + ".class"; | |
| } | |
| } |
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| import java.io.ByteArrayOutputStream; | |
| import java.io.InputStream; | |
| import java.net.URL; | |
| public class NetworkClassLoader extends ClassLoader { | |
| private String rootUrl; | |
| public NetworkClassLoader(String rootUrl) { | |
| this.rootUrl = rootUrl; | |
| } | |
| protected Class<?> findClass(String name) throws ClassNotFoundException { | |
| byte[] classData = getClassData(name); | |
| if (classData == null) { | |
| throw new ClassNotFoundException(); | |
| } | |
| else { | |
| return defineClass(name, classData, 0, classData.length); | |
| } | |
| } | |
| private byte[] getClassData(String className) { | |
| String path = classNameToPath(className); | |
| try { | |
| URL url = new URL(path); | |
| InputStream ins = url.openStream(); | |
| ByteArrayOutputStream baos = new ByteArrayOutputStream(); | |
| int bufferSize = 4096; | |
| byte[] buffer = new byte[bufferSize]; | |
| int bytesNumRead = 0; | |
| while ((bytesNumRead = ins.read(buffer)) != -1) { | |
| baos.write(buffer, 0, bytesNumRead); | |
| } | |
| return baos.toByteArray(); | |
| } catch (Exception e) { | |
| e.printStackTrace(); | |
| } | |
| return null; | |
| } | |
| private String classNameToPath(String className) { | |
| return rootUrl + "/" | |
| + className.replace('.', '/') + ".class"; | |
| } | |
| } |
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loadClass时传入类的全名。findClass方法就可以直接触发子类的方法，而没有第2点的问题。