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JRClassLoader.javaAPI DocExample4169Mon Jan 15 13:33:08 GMT 2001javasec.samples.appd

JRClassLoader

public class JRClassLoader extends ClassLoader

Fields Summary
private URL
urlBase
private static URL
trustedBase
private Hashtable
trustedClasses
private static int
groupNum
private ThreadGroup
threadGroup
Constructors Summary
public JRClassLoader(String base)

        String s = System.getProperty("trustedBase");
        if (s != null)
            try {
                trustedBase = new URL(s);
            } catch (Exception e) {
                throw new IllegalArgumentException(
                                 "Bad value for trustedBase " + s);
            }
    
        try {
            if (!(base.endsWith("/")))
                base = base + "/";
                urlBase = new URL(base);
        } catch (Exception e) {
            throw new IllegalArgumentException(base);
        }
        trustedClasses = new Hashtable(13);
Methods Summary
private static synchronized intgetGroupNum()

        return groupNum++;
java.lang.StringgetHost()

        return urlBase.getHost();
synchronized java.lang.ThreadGroupgetThreadGroup()

        if (threadGroup == null)
            threadGroup = new ThreadGroup("JavaRunner ThreadGroup-"
                                          + getGroupNum());
        return threadGroup;
booleangetTrusted(java.lang.Class c)

        return trustedClasses.get(c) != null;
protected java.lang.ClassloadClass(java.lang.String name, boolean resolve)

        Class c;
        SecurityManager sm = System.getSecurityManager();

        // Step 1 -- Check to make sure that we can access this class
        if (sm != null) {
        int i = name.lastIndexOf('.");
            if (i >= 0)
                sm.checkPackageAccess(name.substring(0, i));
        }

         // Step 2 -- Check for a previously loaded class
         c = findLoadedClass(name);
         if (c != null)
            return c;

        // Step 3 -- Check for system class first
        try {
            c = findSystemClass(name);
            return c;
        } catch (ClassNotFoundException cnfe) {
            // Not a system class, simply continue
        }

        // Step 4 -- Check to make sure that we can define this class
        if (sm != null) {
            int i = name.lastIndexOf('.");
            if (i >= 0)
                sm.checkPackageDefinition(name.substring(0, i));
        }

        // Step 5 -- Read in the class file
        byte data[] = lookupData(name);
        if (data == null)
             return null;

        // Step 6 and 7 -- Define the class from the data; this also
        //         passes the data through the byte code verifier
        c = defineClass(name, data, 0, data.length);
        if (trustedClasses.get(name) != null) {
            trustedClasses.remove(name);
            trustedClasses.put(c, name);
        }

        // Step 8 -- Resolve the internal references of the class
        if (resolve)
            resolveClass(c);

        return c;
byte[]lookupData(java.lang.String n)

        try {
            byte[] b = null;
            String urlName = n.replace('.", '/");

            if (trustedBase != null) {
                URL url = new URL(trustedBase, urlName + ".class");
                b = readData(url);
            }

            if (b == null) {
                URL url = new URL(urlBase, urlName + ".class");
                b = readData(url);
            }
            else trustedClasses.put(n, "dummy");

            return b;
        } catch (Exception e) {
            return null;
        }
byte[]readData(java.net.URL url)

        try {
            InputStream is = url.openConnection().getInputStream();
            BufferedInputStream bis = new BufferedInputStream(is);
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            boolean eof = false;
            while (!eof) {
                int i = bis.read();
                if (i == -1)
                    eof = true;
                else baos.write(i);
            }
            return baos.toByteArray();
        } catch (Exception e) {
            return null;
        }