使用自定义类加载器加载资源包

时间:2011-10-27 22:23:15

标签: java classloader

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

public class JarClassLoader extends ClassLoader {

private String path;

public JarClassLoader(String path) {
    this.path = path;
}

@Override
public Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException
{
    Class<?> c = findLoadedClass(name);
    if (c == null) {
        try {
            c = findSystemClass(name);
        } catch (Exception e) {
        }

        if (c != null)
            return c;

        try {

            byte data[] = loadClassData(name);
            c = defineClass(name, data, 0, data.length);

            if (c == null)
                throw new ClassNotFoundException(name);
            if (resolve)
                resolveClass(c);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    return c;
}

private byte[] loadClassData (String classEntry) throws IOException {
    System.out.println(classEntry);

    String filename = classEntry.replace('.', File.separatorChar) + ".class";
    JarFile jar = new JarFile(path);
    JarEntry entry = jar.getJarEntry(filename);
    InputStream is = jar.getInputStream(entry);
    int data;
    ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
    while ((data = is.read()) != -1) {
        byteStream.write(data);
    }

    return byteStream.toByteArray();

}

}

我有一个ClassLoader(上面发布)从jar中加载我需要的所有类文件。它还包含MySQL java驱动程序文件,当它尝试加载那些时,我在com.mysql.jdbc.LocalizedErrorMessages上收到错误,因为这是一个ResourceBundle。我的问题是如何使用自定义类加载器加载资源包?谢谢你的帮助。

1 个答案:

答案 0 :(得分:4)

您需要覆盖并实现findResource()/ findResources()方法。加载资源包属性文件和其他非类文件时使用这些方法。