classpool.java

Javassist是一个开源的分析、编辑和创建Java字节码的类库。是由东京技术学院的数学和计算机科学系的 Shigeru Chiba 所创建的。它已加入了开放源代码JBoss 应用服务器项目,通过使

     * @param superclass the super class.
     * @throws RuntimeException if the existing class is frozen.
     */
    public synchronized CtClass makeClass(String classname, CtClass superclass)
        throws RuntimeException
    {
        checkNotFrozen(classname);
        CtClass clazz = new CtNewClass(classname, this, false, superclass);
        cacheCtClass(classname, clazz, true);
        return clazz;
    }

    /**
     * Creates a new public nested class.
     * This method is called by CtClassType.makeNestedClass().
     *
     * @param classname     a fully-qualified class name.
     * @return      the nested class.
     */
    synchronized CtClass makeNestedClass(String classname) {
        checkNotFrozen(classname);
        CtClass clazz = new CtNewNestedClass(classname, this, false, null);
        cacheCtClass(classname, clazz, true);
        return clazz;
    }

    /**
     * Creates a new public interface.
     * If there already exists a class/interface with the same name,
     * the new interface overwrites that previous one.
     *
     * @param name          a fully-qualified interface name.
     * @throws RuntimeException if the existing interface is frozen.
     */
    public CtClass makeInterface(String name) throws RuntimeException {
        return makeInterface(name, null);
    }

    /**
     * Creates a new public interface.
     * If there already exists a class/interface with the same name,
     * the new interface overwrites that previous one.
     *
     * @param name       a fully-qualified interface name.
     * @param superclass the super interface.
     * @throws RuntimeException if the existing interface is frozen.
     */
    public synchronized CtClass makeInterface(String name, CtClass superclass)
        throws RuntimeException
    {
        checkNotFrozen(name);
        CtClass clazz = new CtNewClass(name, this, true, superclass);
        cacheCtClass(name, clazz, true);
        return clazz;
    }

    /**
     * Appends the system search path to the end of the
     * search path.  The system search path
     * usually includes the platform library, extension
     * libraries, and the search path specified by the
     * <code>-classpath</code> option or the <code>CLASSPATH</code>
     * environment variable.
     *
     * @return the appended class path.
     */
    public ClassPath appendSystemPath() {
        return source.appendSystemPath();
    }

    /**
     * Insert a <code>ClassPath</code> object at the head of the
     * search path.
     *
     * @return the inserted class path.
     * @see javassist.ClassPath
     * @see javassist.URLClassPath
     * @see javassist.ByteArrayClassPath
     */
    public ClassPath insertClassPath(ClassPath cp) {
        return source.insertClassPath(cp);
    }

    /**
     * Appends a <code>ClassPath</code> object to the end of the
     * search path.
     *
     * @return the appended class path.
     * @see javassist.ClassPath
     * @see javassist.URLClassPath
     * @see javassist.ByteArrayClassPath
     */
    public ClassPath appendClassPath(ClassPath cp) {
        return source.appendClassPath(cp);
    }

    /**
     * Inserts a directory or a jar (or zip) file at the head of the
     * search path.
     *
     * @param pathname      the path name of the directory or jar file.
     *                      It must not end with a path separator ("/").
     * @return the inserted class path.
     * @throws NotFoundException    if the jar file is not found.
     */
    public ClassPath insertClassPath(String pathname)
        throws NotFoundException
    {
        return source.insertClassPath(pathname);
    }

    /**
     * Appends a directory or a jar (or zip) file to the end of the
     * search path.
     *
     * @param pathname the path name of the directory or jar file.
     *                 It must not end with a path separator ("/").
     * @return the appended class path.
     * @throws NotFoundException if the jar file is not found.
     */
    public ClassPath appendClassPath(String pathname)
        throws NotFoundException
    {
        return source.appendClassPath(pathname);
    }

    /**
     * Detatches the <code>ClassPath</code> object from the search path.
     * The detached <code>ClassPath</code> object cannot be added
     * to the pathagain.
     */
    public void removeClassPath(ClassPath cp) {
        source.removeClassPath(cp);
    }

    /**
     * Appends directories and jar files for search.
     *
     * <p>The elements of the given path list must be separated by colons
     * in Unix or semi-colons in Windows.
     *
     * @param pathlist      a (semi)colon-separated list of
     *                      the path names of directories and jar files.
     *                      The directory name must not end with a path
     *                      separator ("/").
     * @throws NotFoundException if a jar file is not found.
     */
    public void appendPathList(String pathlist) throws NotFoundException {
        char sep = File.pathSeparatorChar;
        int i = 0;
        for (;;) {
            int j = pathlist.indexOf(sep, i);
            if (j < 0) {
                appendClassPath(pathlist.substring(i));
                break;
            }
            else {
                appendClassPath(pathlist.substring(i, j));
                i = j + 1;
            }
        }
    }

    /**
     * Converts the given class to a <code>java.lang.Class</code> object.
     * Once this method is called, further modifications are not
     * allowed any more.
     * To load the class, this method uses the context class loader
     * of the current thread.  It is obtained by calling
     * <code>getClassLoader()</code>.  
     * 
     * <p>This behavior can be changed by subclassing the pool and changing
     * the <code>getClassLoader()</code> method.
     * If the program is running on some application
     * server, the context class loader might be inappropriate to load the
     * class.
     *
     * <p>This method is provided for convenience.  If you need more
     * complex functionality, you should write your own class loader.
     *
     * <p><b>Warining:</b> A Class object returned by this method may not
     * work with a security manager or a signed jar file because a
     * protection domain is not specified.
     *
     * @see #toClass(CtClass, java.lang.ClassLoader, ProtectionDomain)
     * @see #getClassLoader()
     */
    public Class toClass(CtClass clazz) throws CannotCompileException {
        // Some subclasses of ClassPool may override toClass(CtClass,ClassLoader).
        // So we should call that method instead of toClass(.., ProtectionDomain).
        return toClass(clazz, getClassLoader()); 
    }

    /**
     * Get the classloader for <code>toClass()</code>, <code>getAnnotations()</code> in
     * <code>CtClass</code>, etc.
     * 
     * <p>The default is the context class loader.
     * 
     * @return the classloader for the pool
     * @see #toClass(CtClass)
     * @see CtClass#getAnnotations()
     */
    public ClassLoader getClassLoader() {
        return getContextClassLoader();
    }
    
    /**
     * Obtains a class loader that seems appropriate to look up a class
     * by name. 
     */
    static ClassLoader getContextClassLoader() {
        return Thread.currentThread().getContextClassLoader();
    }

    /**
     * Converts the class to a <code>java.lang.Class</code> object.
     * Do not override this method any more at a subclass because
     * <code>toClass(CtClass)</code> never calls this method.
     *
     * <p><b>Warining:</b> A Class object returned by this method may not
     * work with a security manager or a signed jar file because a
     * protection domain is not specified.
     *
     * @deprecated      Replaced by {@link #toClass(CtClass,ClassLoader,ProtectionDomain)}.
     * A subclass of <code>ClassPool</code> that has been
     * overriding this method should be modified.  It should override
     * {@link #toClass(CtClass,ClassLoader,ProtectionDomain)}.
     */
    public Class toClass(CtClass ct, ClassLoader loader)
        throws CannotCompileException
    {
        return toClass(ct, loader, null);
    }

    /**
     * Converts the class to a <code>java.lang.Class</code> object.
     * Once this method is called, further modifications are not allowed
     * any more.
     *
     * <p>The class file represented by the given <code>CtClass</code> is
     * loaded by the given class loader to construct a
     * <code>java.lang.Class</code> object.  Since a private method
     * on the class loader is invoked through the reflection API,
     * the caller must have permissions to do that.
     *
     * <p>An easy way to obtain <code>ProtectionDomain</code> object is
     * to call <code>getProtectionDomain()</code>
     * in <code>java.lang.Class</code>.  It returns the domain that the
     * class belongs to.
     *
     * <p>This method is provided for convenience.  If you need more
     * complex functionality, you should write your own class loader.
     *
     * @param loader        the class loader used to load this class.
     *                      For example, the loader returned by
     *                      <code>getClassLoader()</code> can be used
     *                      for this parameter.
     * @param domain        the protection domain for the class.
     *                      If it is null, the default domain created
     *                      by <code>java.lang.ClassLoader</code> is used.
     *
     * @see #getClassLoader()
     * @since 3.3
     */
    public Class toClass(CtClass ct, ClassLoader loader, ProtectionDomain domain)
        throws CannotCompileException
    {
        try {
            byte[] b = ct.toBytecode();
            java.lang.reflect.Method method;
            Object[] args;
            if (domain == null) {
                method = defineClass1;
                args = new Object[] { ct.getName(), b, new Integer(0),
                                      new Integer(b.length)};
            }
            else {
                method = defineClass2;
                args = new Object[] { ct.getName(), b, new Integer(0),
                    new Integer(b.length), domain};
            }

            return toClass2(method, loader, args);
        }
        catch (RuntimeException e) {
            throw e;
        }
        catch (java.lang.reflect.InvocationTargetException e) {
            throw new CannotCompileException(e.getTargetException());
        }
        catch (Exception e) {
            throw new CannotCompileException(e);
        }
    }

    private static synchronized Class toClass2(Method method,
            ClassLoader loader, Object[] args)
        throws Exception
    {
        method.setAccessible(true);
        Class clazz = (Class)method.invoke(loader, args);
        method.setAccessible(false);
        return clazz;
    }
}