Java tutorial
/* * ReflectClass.java - Dump a class using Reflection. * * Copyright (c) 1997 Chuck McManis, All Rights Reserved. * * Permission to use, copy, modify, and distribute this software * and its documentation for NON-COMMERCIAL purposes and without * fee is hereby granted provided that this copyright notice * appears in all copies. * * CHUCK MCMANIS MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE * SUITABILITY OF THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING * BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. CHUCK MCMANIS * SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT * OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES. */ import java.lang.reflect.*; import java.util.*; public class ReflectClass { static String tName(String nm, Hashtable ht) { String yy; String arr; if (nm.charAt(0) != '[') { int i = nm.lastIndexOf("."); if (i == -1) return nm; // It's a primitive type, ignore it. else { yy = nm.substring(i + 1); if (ht != null) ht.put(nm, yy); // note class types in the hashtable. return yy; } } arr = "[]"; if (nm.charAt(1) == '[') yy = tName(nm.substring(1), ht); else { switch (nm.charAt(1)) { case 'L': yy = tName(nm.substring(nm.indexOf("L") + 1, nm.indexOf(";")), ht); break; case 'I': yy = "int"; break; case 'V': yy = "void"; break; case 'C': yy = "char"; break; case 'D': yy = "double"; break; case 'F': yy = "float"; break; case 'J': yy = "long"; break; case 'S': yy = "short"; break; case 'Z': yy = "boolean"; break; case 'B': yy = "byte"; break; default: yy = "BOGUS:" + nm; break; } } return yy + arr; } public static void main(String args[]) { Constructor cn[]; Class cc[]; Method mm[]; Field ff[]; Class c = null; Class supClass; String x, y, s1, s2, s3; Hashtable classRef = new Hashtable(); if (args.length == 0) { System.out.println("Please specify a class name on the command line."); System.exit(1); } try { c = Class.forName(args[0]); } catch (ClassNotFoundException ee) { System.out.println("Couldn't find class '" + args[0] + "'"); System.exit(1); } /* * Step 0: If our name contains dots we're in a package so put * that out first. */ x = c.getName(); if (x.lastIndexOf(".") != -1) { y = x.substring(0, x.lastIndexOf(".")); System.out.println("package " + y + ";\n\r"); } /* * Let's use the Reflection API to sift through what is * inside this class. * * Step 1: Collect referenced classes * This step is used so that I can regenerate the import statements. * It isn't strictly required of course, Java works just fine with * fully qualified object class names, but it looks better when you * use 'String' rather than 'java.lang.String' as the return type. */ ff = c.getDeclaredFields(); for (int i = 0; i < ff.length; i++) { x = tName(ff[i].getType().getName(), classRef); } cn = c.getDeclaredConstructors(); for (int i = 0; i < cn.length; i++) { Class cx[] = cn[i].getParameterTypes(); if (cx.length > 0) { for (int j = 0; j < cx.length; j++) { x = tName(cx[j].getName(), classRef); } } } mm = c.getDeclaredMethods(); for (int i = 0; i < mm.length; i++) { x = tName(mm[i].getReturnType().getName(), classRef); Class cx[] = mm[i].getParameterTypes(); if (cx.length > 0) { for (int j = 0; j < cx.length; j++) { x = tName(cx[j].getName(), classRef); } } } // Don't import ourselves ... classRef.remove(c.getName()); /* * Step 2: Start class description generation, start by printing * out the import statements. * * This is the line that goes 'public SomeClass extends Foo {' */ for (Enumeration e = classRef.keys(); e.hasMoreElements();) { System.out.println("import " + e.nextElement() + ";"); } System.out.println(); /* * Step 3: Print the class or interface introducer. We use * a convienience method in Modifer to print the whole string. */ int mod = c.getModifiers(); System.out.print(Modifier.toString(mod)); if (Modifier.isInterface(mod)) { System.out.print(" interface "); } else { System.out.print(" class "); } System.out.print(tName(c.getName(), null)); supClass = c.getSuperclass(); if (supClass != null) { System.out.print(" extends " + tName(supClass.getName(), classRef)); } System.out.println(" {"); /* * Step 4: Print out the fields (internal class members) that are declared * by this class. * * Fields are of the form [Modifiers] [Type] [Name] ; */ System.out.println("\n\r/*\n\r * Field Definitions.\r\n */"); for (int i = 0; i < ff.length; i++) { Class ctmp = ff[i].getType(); int md = ff[i].getModifiers(); System.out.println(" " + Modifier.toString(md) + " " + tName(ff[i].getType().getName(), null) + " " + ff[i].getName() + ";"); } /* * Step 5: Print out the constructor declarations. * * We note the name of the class which is the 'name' for all * constructors. Also there is no type, so the definition is * simplye [Modifiers] ClassName ( [ Parameters ] ) { } * */ System.out.println("\n\r/*\n\r * Declared Constructors. \n\r */"); x = tName(c.getName(), null); for (int i = 0; i < cn.length; i++) { int md = cn[i].getModifiers(); System.out.print(" " + Modifier.toString(md) + " " + x); Class cx[] = cn[i].getParameterTypes(); System.out.print("( "); if (cx.length > 0) { for (int j = 0; j < cx.length; j++) { System.out.print(tName(cx[j].getName(), null)); if (j < (cx.length - 1)) System.out.print(", "); } } System.out.print(") "); System.out.println("{ ... }"); } /* * Step 6: Print out the method declarations. * * Now methods have a name, a return type, and an optional * set of parameters so they are : * [modifiers] [type] [name] ( [optional parameters] ) { } */ System.out.println("\n\r/*\n\r * Declared Methods.\n\r */"); for (int i = 0; i < mm.length; i++) { int md = mm[i].getModifiers(); System.out.print(" " + Modifier.toString(md) + " " + tName(mm[i].getReturnType().getName(), null) + " " + mm[i].getName()); Class cx[] = mm[i].getParameterTypes(); System.out.print("( "); if (cx.length > 0) { for (int j = 0; j < cx.length; j++) { System.out.print(tName(cx[j].getName(), classRef)); if (j < (cx.length - 1)) System.out.print(", "); } } System.out.print(") "); System.out.println("{ ... }"); } /* * Step 7: Print out the closing brace and we're done! */ System.out.println("}"); } }