Class.forName question

Hello,
I am receiving a ClassNotFoundException on a class in my application during a Class.forName call and I have no idea why. The class is present at the correct path, all words are spelled correctly, and all case-sensitivity is correct. If I even try to instantiate the object which the class represents in my code, it works fine.
I actually realized that there are two separate java files in my workspace, with the same path and same class name. One just happens to be in a bundled JAR file in WEB-INF and the other is in my code base. Would these duplicate classes cause this CNFE? I guess I'm just a little in the dark over how the method works.

Yes, that's right. Jars in the server run in a classloader which doesn't have access to any of the web applications that happen to be on the server.
One way to avoid this problem is to not put your application's jar files in the server's classpath. Put them all in the WEB-INF/lib directory. If this involves putting copies of the jar file in several applications, then so be it.
Or some servers have a configuration option allowing the application's class loader to be "parent first". Sometimes this helps that sort of thing. But basically you're wrestling with a pig here so don't expect to come out of the experience clean.

Similar Messages

Classload.load and Class.forName question

I know there are several threads about this, but I have a doubt.
I'm getting a ClassNotFoundException running the JUnitSampler of JMeter.
This test is run by maven (using a specific plugin for it). This plugin creates a new Thread to call JMeter with all the parameters that needs.
The class that the JUnitSampler is trying to run is in the classpath (is not jar).
I know this because I run maven with -X parameter and it shows this:
[DEBUG] Test Classpath :
[DEBUG] /path/to/project/target/classes
[DEBUG] /path/to/project/target/test-classesLooking at JUnitSampler code I can see this
theclazz = Thread.currentThread().getContextClassLoader().loadClass(className.trim());Is there any reason that the class couldn't be found?

No idea - it is your code.It's JMeter code, not mine.You said it couldn't find your test classes.
>
My original question was about if there were any
difference in using
Class.forName
or
Thread.currentThread().getContextClassLoader().loadClass
No idea. You can print the class loader though.
That was because the JUnitSampler is using the second
option to instantiate the test classes, and
I was receiving a ClassNotFoundException. That
problem is now solved, because it can find the class,
but is unable to cast it to TestCase.
I want to know if there is a way to put my test
classes in the ClassLoader that JMeter is using.You have an instance of some class.
To create that class it was loaded by a class loader.
You can get that class loader via the methods of java.lang.Class.
You can use that class loader to load your class.
That might or might not solve your problem.
Because there are any number of ways it can fail to solve you problem. Below is one, one of many, that might do it.
It won't solve it if you have already loaded your class via the system loaders which will happen if you use absolutely any reference to it.

Question about Class.forName()

I am trying to get an instance of a class by its name. Now, I have tried both creating it with the class's actual name and with the class's name including the package path and both times I got a java.lang.ClassNotFoundException: my/package/MyClass.
I am reading the name out of a properties file and that's working just fine according to my logging information btu here is the code anyway:
Properties prop = new Properties();
try{
     java.io.FileInputStream in = new java.io.FileInputStream(inv.getPath());
     prop.load(in);
     String temp = prop.getProperty("myclass1");
     Class c = Class.forName(temp);
     rollen.put("user",c.newInstance());
     temp = prop.getProperty("myclass2");
     c = Class.forName(temp);
     rollen.put("admin",c.newInstance());
}catch(Exception e){
     //I'm doing some more logging here, guess that's not very interesting
}I deleted all the logging info from this code snippet to make it shorter. But I can tell you that the name does get read out as my.package.MyClass - and the package and class name are correct...
The entries in the properties files look like this:
myclass1=my.package.MyClass
myclass2=my.package.MyOtherClass
Can you help me fix this, please?

Is your classpath okay? I tried this:
pkg\MyClass.javapackage pkg;
public class MyClass {
    public MyClass () {
        System.out.println ("Woohoo!");
}Test.javapublic class Test {
    public static void main (String[] parameters) throws Exception {
        Class.forName ("pkg.MyClass").newInstance ();
}This outputsWoohoo!as expected.
Kind regards,
  Levi

Error in Class.forName("com.mysql.jdbc.driver")

Hi forum,
Please help me to solve the issue.
im using the following jsp code for genrating the reports using JASPER REPORTS
the JSP FILE
<%@ page contentType="text/html;charset=windows-1252"%>
<%@ page import="java.io.*"%>
<%@ page import="java.util.*"%>
<%@ page import="java.sql.*"%>
<%@ page import="javax.sql.DataSource"%>
<%@ page import="javax.naming.InitialContext"%>
<%@ page import="net.sf.jasperreports.engine.*"%>
<%@ page import="net.sf.jasperreports.engine.design.JasperDesign"%>
<%@ page import="net.sf.jasperreports.engine.xml.JRXmlLoader"%>
<%@ page import="net.sf.jasperreports.engine.export.*" %>
<%@ page import ="net.sf.jasperreports.engine.*"%>
<%@ page import ="net.sf.jasperreports.engine.JasperFillManager"%>
<%@ page import ="net.sf.jasperreports.engine.JRException"%>
<%@ page import="net.sf.jasperreports.engine.JasperReport"%>
<%@ page import="net.sf.jasperreports.engine.JasperPrint"%>
<html>
<body bgcolor="00ffcc">
<%
try{
Connection con = null;
String url="jdbc:mysql://localhost/customer";
String username = "root";
String password = "cmsadmin";
InputStream input=new FileInputStream(new File("C:/Documents and Settings/user/My Documents/NetBeansProjects/jasperreports/web/helloworld.xml"));
JasperDesign design = JRXmlLoader.load(input);
JasperReport report = JasperCompileManager.compileReport(design);
Map params = new HashMap();
params.put("reportTitle", "helloworld");
params.put("author", "Muthu Kumar");
params.put("startDate", (new java.util.Date()).toString());
params.put("ReportTitle", "PDF JasperReport");
<img class="emoticon" src="images/emoticons/confused.gif" border="0" alt="" />Class.forName("com.mysql.jdbc.Driver");<img class="emoticon" src="images/emoticons/confused.gif" border="0" alt="" /><img src="images/emoticons/confused.gif" border="0" alt="" />
con = DriverManager.getConnection(url,username,password);
JasperPrint print = JasperFillManager.fillReport(report, params, con);
OutputStream output=new FileOutputStream(new File("C:/Documents and Settings/user/My Documents/NetBeansProjects/jasperreports/helloreportworld.pdf"));
JasperExportManager.exportReportToPdfStream(print, output);
// JasperViewer.viewReport(print);
catch(SQLException es) {
out.println(es);
catch(JRException ex){
//ex.printStackTrace();
out.println(ex);
%>
</body>
</html>The error it is saying is in the line Class.forName(....) ;
Please look for the emoctions with question mark
i DOn know what to do.
Please help
Im comparin the below JRXML file as with the above code
<?xml version="1.0"?>
<!DOCTYPE jasperReport
PUBLIC "-//JasperReports//DTD Report Design//EN"
"http://jasperreports.sourceforge.net/dtds/jasperreport.dtd">
<jasperReport name="helloworld">
<parameter name="reportTitle" class="java.lang.String"/>
<parameter name="author" class="java.lang.String"/>
<parameter name="startDate" class="java.lang.String"/>
<queryString>
<![CDATA[SELECT * FROM customer order by UserID ]]>
</queryString>
<field name="UserID" class="java.lang.String"/>
<field name="UserName" class="java.lang.String"/>
<field name="City" class="java.lang.String"/>
<field name="State" class="java.lang.String"/>
<title>
<band height="60">
<textField>
<reportElement x="0" y="10" width="500" height="40"/>
<textElement textAlignment="Center">
<font size="24"/>
</textElement>
<textFieldExpression class="java.lang.String">
<![CDATA[$P{reportTitle}]]>
</textFieldExpression>
</textField>
<textField>
<reportElement x="0" y="40" width="500" height="20"/>
<textElement textAlignment="Center"/>
<textFieldExpression class="java.lang.String">
<![CDATA["Run by: " + $P{author}
+ " on " + $P{startDate}]]>
</textFieldExpression>
</textField>
</band>
</title>
<columnHeader>
<band height="30">
<rectangle>
<reportElement x="0" y="0" width="500" height="25"/>
<graphicElement/>
</rectangle>
<staticText>
<reportElement x="5" y="5" width="50" height="15"/>
<textElement/>
<text><![CDATA[UserID]]></text>
</staticText>
<staticText>
<reportElement x="55" y="5" width="150" height="15"/>
<text><![CDATA[UserName]]></text>
</staticText>
<staticText>
<reportElement x="205" y="5" width="255" height="15"/>
<text><![CDATA[City, State]]></text>
</staticText>
</band>
</columnHeader>
<detail>
<band height="20">
<textField>
<reportElement x="5" y="0" width="50" height="15"/>
<textElement/>
<textFieldExpression class="java.lang.String">
<![CDATA[$F{UserID}]]>
</textFieldExpression>
</textField>
<textField>
<reportElement x="55" y="0" width="150" height="15"/>
<textElement/>
<textFieldExpression class="java.lang.String">
<![CDATA[$F{UserName}]]>
</textFieldExpression>
</textField>
<textField>
<reportElement x="205" y="0" width="255" height="15"/>
<textElement/>
<textFieldExpression class="java.lang.String">
<![CDATA[$F{City} + ", " + $F{State}]]>
</textFieldExpression>
</textField>
</band>
</detail>
</jasperReport>

Glass_Fish wrote:
I have set the classpath in the environment variables in the my computer properties.The web container has it's own properties. The "system" classpath means absolutely nothing to it. Read your server's documentation.

Class.forName() ????

Hello, I have the following problem:
1. I create a class with "Class comp1 = Class.forName(strName);"
2. With creating an instance custom the constructor some parameters.
3. With "Constructor[ ] myconstr = comp1.getConstructors();" I get all Constructors.
4. With "Class[ ] paramTypes = myconstr.getParameterTypes();" I get the parameter types
question: Can I find somehow parameter name?
Thanks for your help!!!
Hallo, ich habe folgendes Problem:
1. Ich erzeuge eine Klasse mit "Class comp1 = Class.forName(strName);"
2. Beim Erzeugen einer Instanz brauch der Konstruktor einige Parametern.
3. Mit "Constructor[] myconstr = comp1.getConstructors();" bekomme ich alle Konsturktoren.
4. Mit "Class[] paramTypes = myconstr[i].getParameterTypes();" kann ich die Parametertypen bekommen
Frage: Kann ich irgendwie Parametername rausfinden?
Vielen Dank f�r die Hilfe!!!

A method signature consists of the methods name and the parameter types. Nothing more is stored in the class-files. So there is no way to address a parameter by it's name in java.
You may want to do something like:
Class[] paramTypes=new Class[] { A.class, B.class };
Constructor constructor=C.class.getConstructor(paramTypes);
C cObj= (C) constructor.newInstance(new Object[] ( a, b));

How to create an object of our own class by using Class.forName()??

how to create an object of our own class by using Class.forName()??
plzz anser my qustion soon..

Class.forName does not create an object. It returns a reference to the Class object that describes the metadata for the class in question--what methods and fields it has, etc.
To create an object--regardless of whether it's your class or some other class--you could call newInstance on the Class object returned from Class.forName, BUT only if that class has a no-arg constructor that you want to call.
Class<MyClass> clazz = Class.forName("com.mycompany.MyClass");
MyClass mine = clazz.newInstance();If you want to use a constructor that takes parameters, you'll have to use java.lang.reflect.Constructor.
Google for java reflection tutorial for more details.
BUT reflection is often abused, and often employe when not needed. Why is it that you think you need this?

ClassNotFoundException when using Class.forName(), thx

in a study app, i try to use Class.forName() to load any class then get its properties (fields, methods etc. vs reflect).
the (Frame based) app is in directory:
c:\app\StudyApp.class
there is a "Open class" button on the app, click the button, i use FileChooser to open any class file.
i.e. open a class (assume it is not packaged)
d:\dir\TheClass.class
coding in StudyApp.java is:
Class cls=Class.forName("TheClass");
now a ClassNotFoundException throws when call Class.forName() above.
it is easy to understand why throw the exception because i never tell where the class is. it is in directory
d:\dir
my question is: how to tell VM the directory.
the directory d:\dir can not be applied to -classpath when run java.exe StudyApp, because the directory is random one at run-time.
i tried to change System property (i.e. "java.class.path", 'user.dir" etc. none of them can fix the problem.
thanks in advance for any help

This probably does a lot more than you need:
import java.util.*;
import java.io.*;
import java.util.jar.*;
import java.lang.*;
public class ClassFileFinder extends ClassLoader
     List cpath = new LinkedList();
     void addFile(File f) {
          if(f.isDirectory() || (f.isFile() && f.canRead() &&
                                      f.getName().endsWith(".jar")))
               cpath.add(f);
     public byte[] classData(String className) {
          String cname = className.replace('.', File.separatorChar) + ".class";
          Iterator it = cpath.iterator();
          while(it.hasNext()) {
               File f = (File)it.next();
               try {
                    if(f.isDirectory()) {
                         File cFile = new File(f, cname);
                         if(cFile.isFile()) {
                              byte[] buf = new byte[(int)cFile.length()];
                              InputStream in = new FileInputStream(cFile);
                              int off = 0, l;
                              while((l = in.read(buf, off, buf.length - off)) > 0) {
                                   off += l;
                                   if(off >= buf.length) break;
                              in.read(buf);
                              in.close();
                              return buf;
                    } else if (f.isFile()) {
                         JarFile jar = new JarFile(f);
                         JarEntry ent = jar.getJarEntry(cname);
                         if(ent != null) {
                              byte[] buf = new byte[(int)ent.getSize()];
                              int off = 0, l;
                              InputStream in = jar.getInputStream(ent);
                              while((l = in.read(buf, off, buf.length - off)) > 0) {
                                   off += l;
                                   if(off >= buf.length) break;
                              in.close();
                              return buf;
               } catch (IOException e) {
          return null;
     public Class findClass(String className) throws ClassNotFoundException{
          byte[] data = classData(className);
          if(data == null)
               return getParent().loadClass(className);
          else
               return defineClass(className,data,0, data.length);
}Create an instance, Add directories and/or jar files with addFile then loadClass the class you want.

Why Class.forName?...

I'm trying to understand the use of Class.forName in JDBC programing. �What is the really goal for this class?
try{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
} catch(ClassNotFoundException ex){
// something
Regards.

I'm trying to understand the use of Class.forName in
JDBC programing. �What is the really goal for this
class?There are two implied questions...
-What does it do?
1. The class is loaded. All classes are loaded this way but normally the compiler does the work for you.
2. When a class is loaded, if there are any 'static initializers' in the class then those are run. Again true for any class when it is loaded.
3. JDBC drivers have a static initializer which registers the driver with the JDBC driver manager. See the DriverManager.registerDriver(Driver driver) method and the JDBC spec for more specific info.
-Why it is done this way?
As a guess because the original JDBC implementor(s) just found out about static initializers and thought they were 'cool'. It would be just as easy and more meaningful to do it using a different methodology.

Class.forName() debunked

This issue is about: Dynamic loading and Inheritance.
Debugging an odd ClassNotFoundException in a J2EE Application, I was involved investigating deeply Class.ForName(). This method - namely the version with only the class name as parameter - is used inside xsdbeans.jar, an optiopnal library, shipped with IBM WebSphere 5.x. Moving the jar from the EAR classloader to the server runtime classloader caused weird behavior on my app.
I try to simplify the core question:
Suppose class E extends B. Base class B declares an instance method, dynLoad(String name) that uses internally Class.forName(String name).
Say 'e' an instance of E. Invoking e.dynLoad("Foo"), Class.forName("Foo") should use the ClassLoader of current class. But which is the 'current class': E or B? Is it the class of current object (E) or the declaring superclass (B)?
My instinctive answer was: E. But my J2EE app was behaving as the current class was B. Indeed E and B may be defined by different classloaders, and this makes a big difference.
A rapid lookup at Sun's docs confirmed my first hypothesis:
http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Class.html#forName(java.lang.String)
> Returns the Class object associated with the class or interface with the given string name.
Invoking this method is equivalent to:
Class.forName(className, true, currentLoader)
where currentLoader denotes the defining class loader of the current class.
ok, this is a little misleading, but going on:
http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Class.html#forName(java.lang.String,%20boolean,%20java.lang.ClassLoader)
> For example, in an instance method the expression:
>
Class.forName("Foo")
is equivalent to:
Class.forName("Foo", true, this.getClass().getClassLoader())
Not equivocal. The current class is the class of current object, no matter (apparently) if the instance method is declared in a superclass.
Right? Wrong. Here a minimal counter-example:
//-- B.java
import java.net.*;
public class B {
    public void dynLoad(String name) throws Exception {
        System.out.println(getClass().getSuperclass()
            + " defining classloader is: "
            + getClass().getSuperclass().getClassLoader());
        System.out.println(getClass()
            + " defining classloader is: "
            + getClass().getClassLoader());
        System.out.println("\n1) Class.forName(\""+name+"\");");
        // Loading with 'currentLoader'
        Class.forName(name)
            .newInstance();
        System.out.println("\n2) Class.forName(\""+name
            +"\", true, this.getClass().getClassLoader());");
        // This should be equivalent (by Sun J2SE API spec)
        Class.forName(name, true, this.getClass().getClassLoader())
            .newInstance();
    public static void main(String[] args) {
        ClassLoader syscl = ClassLoader.getSystemClassLoader();
        if (!URLClassLoader.class.isInstance(syscl)) {
            System.err.println("Cannot continue the trick.");
            System.exit(1);
        URL[] urls = ((URLClassLoader)syscl).getURLs();
        // Yet Another ClassLoader
        URLClassLoader yacl = new URLClassLoader(urls) {
            // Force Parent-last delegation policy to assure
            // demanded classes are defined by _this_ classloader
            public Class loadClass(String name)
                throws ClassNotFoundException {
                Class c = findLoadedClass(name);
                if (c == null) {
                    try {
                        // Simulate no visibility to base class to assure
                        // it is _not_ defined by this classloader too
                        if (name.equalsIgnoreCase("B")) {
                            throw new ClassNotFoundException();
                        c = findClass(name);
                    } catch (ClassNotFoundException e) {
                        c = getParent().loadClass(name);
                return c;
        try {
            // Loading class E with a different classloader
            Class c = yacl.loadClass("E");
            c.getMethod("dynLoad", new Class[]{String.class})
                .invoke(c.newInstance(), new Object[]{"Foo"});
        } catch (Exception ex) {
            ex.printStackTrace();
            System.exit(1);
//-- E.java
public class E extends B {
//-- Foo.java
public class Foo {
public Foo() {
    System.out.println(getClass()
      + " defining classloader is: "
      + getClass().getClassLoader());
}Running above B.main() produce the following output on Sun JDK 1.3, 1.4.2, 1.5:
> class B defining classloader is: sun.misc.Launcher$AppClassLoader@3d200480
class E defining classloader is: B$1@3d2c0480
1) Class.forName("Foo");
class Foo defining classloader is: sun.misc.Launcher$AppClassLoader@3d200480
2) Class.forName("Foo", true, this.getClass().getClassLoader());
class Foo defining classloader is: B$1@3d2c0480
The evidence is that classloader used is not the same. in the case 1) it uses the classloader of superclass B. Hence the two form of Class.forName() invocation are not equivalent, as stated in Sun documentation.
Disclosure
The evidence is confirmed and explained looking at Sun's implementation of java.lang.Class.java and java.lang.ClassLoader.java: finally the Class.forName(String name) relies on sun.reflect.Reflection.getCallerClass(int) to find the famous 'current class' mentioned in the javadocs. This undocumented method returns the i-th caller class of current stack frames; each stack frame represents a method invocation coupled with its declaring class.
I wonder why in Sun docs this poorly explained issue was remaining immutable from 1.3 to date. Furthermore: which was the intended behavior? Another reason to the long said "Class.forName() is evil..." or am I missing something?
regards, Lorenzo

Of course, it comes down to the question: What is the current class?
Not something well defined. You are looking for this.getClass(), it's taking the class at compile time. If it went your way, woundn't that create an inconsistency in forName in static vs instance contexts?
Actually I think the static approach is more natural, because it means that forName behaves the way that resolving external references work. Your way would also go against the spirit of Java security policies which requires references down the classloader chain something to be treated with suspision.
The mechanism intended, I think, for these situations is the contextClassLoader property of Thread. When executing plugin type code the contextClassLoader should be set to the ClassLoader that loaded the plugin, and any references to resources or dynamic class loads from the plugin should be made using the contextClassLoader. This enables your shared library code to access classes and resources on behalf of the plugin code with access to classes and resources inside the plugin.
Thus, if you write library code or other container stuff likely to be called from a plugin you should probably always use:
Class cls = Thread.currentThread().getContextClassLoader().loadClass("foo");

Create a ADF component by Class.forName (11g)

Hello,
I'm loading a list of components by an XML, and I'd like to create an istance by Class.forName, for example:
UIComponent componet = (UIComponent)Class.forName("oracle.adf.view.rich.component.rich.input.RichInputText").newInstance();
but the system give me this error:
java.lang.ClassNotFoundException: oracle.adf.view.rich.component.rich.input.RichInputText
In the class there is the import RichInputText of and in the same class this works:
oracle.adf.view.rich.component.rich.input.RichInputText title = new RichInputText();
Any idea?
Thank you,
Cristian

Hi,
If I create my component extending Container, clients could think it's a Container (but in fact, I only used the Container feature to layout the component).
For instance, if a API client call myCustom.add(aWidget), it will break the layout of my custom component.
I can tell in the javadoc that this component must not be used as a container.
But there are other situations when a client can inadvertantly think it's a container.
Imagine that you write a method addTreeListener() that recursively register a listener to all components of a container. I don't want the Canvas and Scrollbar of my custom component to call back the listeners, but I want to hide my custom component to hide its internal and call back the listeners.
As I said, it's mainly a design question, but I wanted to improve my custom component...
Pierre M�tras

Class.forName error ??

I got error below. Most time, my code call Class.forName("com.perf.perfectform.ViewController"), it works fine. But some time, it throw error below. I print out a lot message , and I have no idea about what cause this error ?? Who has some idea how to debug this error ? what is possible reason ?
Thanks, gary
P.S. com.perf.perfectform.ViewController ----- it is a java class
java.lang.ClassNotFoundException: com.perf.perfectform.ViewController
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at com.perf.perfectform.ExecuteUpdate.<init>(ExecuteUpdate.java)
at com.perf.perfectform.StartUp.main(StartUp.java)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.zerog.lax.LAX.g([DashoPro-V1.2-120198])
at ZPUs.run([DashoPro-V1.2-120198])

Question:
1) are you doing the reading and writing on a separate Thread and then load the class on a separate thread? Solution -> synchronize
2) are you running more than one instance of your application? Solution -> FileLock
3) finally (this looks like what is most probably happening). Are you using a separate ClassLoader when you try to instantiate your ViewController? If you are still on the same ClassLoader and at some point in time (before you overwrote your jar file), you tried to instantiate ViewController which does not exist in the classpath yet (meaning you've got a ClassNotFoundException before overwriting the ViewController's jar file) then no matter how hard you try to instantiate your ViewController class. You'll still get a ClassNotFoundException. Solution -> use a new ClassLoader
Regards,
Noel

What to do with Class.forName(), Class.getName() when Obfuscating

hi,
I have been asked at my company to perform Obfuscation of our project-code, The problem I have been facing is,
We have got too many Class.forName(), Class.getName() calls in our Project-code, which is really hindering the process of Obfuscating all the Classes (refrences in code may break for all these classes which are dynamically being asked for, hence the project may suffer). And it is a pain-in-neck to really resolve which classes to exclude so that code should not break after obfuscation.
What my question is:
Do we have some automated tool to take care of all these Reflection API calls, so that work left to us is minimal?
If not, Do we have some short-cut (program, tool etc.) to identify all the classes which should be excluded?

Which program are you using when obfuscating?
In RetroGuard you can for example avoid certain class names, or packages, to be obfuscated.

Class.ForName, is it possible?

if a class has not been compiled, in other words, the class is only a name in .java file, could we use Class.ForName to get its information?
if not, is there any other idea to get the class info from .java file? -- i mean, not open the jave file as buffer to read what text is on it - is there a method similar to Class.ForName in the case?
thx

if a class has not been compiled, in other words, the
class is only a name in .java file, could we use
Class.ForName to get its information?No. Class.forName only works on compiled classes within the classpath.
if not, is there any other idea to get the class info
from .java file? -- i mean, not open the jave file as
buffer to read what text is on it - is there a method
similar to Class.ForName in the case?If your question is how to get class info by not compiling it one,
and not reading the .java source file two, the answer again is no.
Simply because the demand is unreasonable.
If your question is Is there any helper class to read .java
source file and give back the class info, the answer is yes. And
the java compiler is exactly what this helper class is. Do you know
javac is actually a java program, and in turn it is a java
class?
Let me know if this is what you are looking for and need more info
on how to compile a java file inside another class.
--lichu

Instantiating object using Class.forName()

What is the difference between instantiating using Class.forName() method and instantiating using the new operator?

The difference is that you can use the new operator to instantiate an object, but you can't do it using Class.forName().
But seriously folks...
Presumably you're talking about Class.newInstance()--which often appears right on the heels of Class.forName().
New gives you compile-time checks you don't get with Class.forName(). If it compiles with new, then you know the constructor in question exists on the class in question.
With Class.newInstance() (and it's cousin (also called newInstance, I think) in the Constructor class), you can't be sure until you actually execute it whether that constructor even exists.
New requires you to know the class at compile time. NewInstance lets you defer the specific class until runtime.
New is simpler and more direct.
(Did I just do your homwork for you? Hope not.)

Class.forName("com.proj.someclass").newInstance()

This works fine if "someclass" is in classpath but doesn't work if "someclass" is in jar file. How to make it work with classes packed into jar?

Hi Mike.
I think you need to write your own customized ClassLoader. Haven't done it myself, but I know the question has been up before, and ansered, and problem solved... Do some search. And maybee you coud be more specific about what you want to achive. Is this an applet or an application? And why do you need to use Class.forName? And why do you want the class to be in a .jar file?
Ragnvald Barth
Software enigneer

Class.forName question

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