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alternate solutions to "JDA Member may not be null" error

I'm trying to make it so when someone with the role "Owner" types the mute command, it takes the person they #mentioned and gives them the "Muted" role.
The rest of the code works on it's own, the only part that is not working is the line
event.getGuild().addRoleToMember(member,event.getGuild().getRoleById(0)).complete();
and the variable "member" is defined by
Member member = event.getGuild().getMemberById(mentionid);
The full chunk of code is:
package radishmouse.FoodWorld.Events;
import net.dv8tion.jda.api.EmbedBuilder;
import net.dv8tion.jda.api.entities.Member;
import net.dv8tion.jda.api.events.message.guild.GuildMessageReceivedEvent;
import net.dv8tion.jda.api.hooks.ListenerAdapter;
import radishmouse.FoodWorld.FoodWorld;
public class GuildMessageReceived extends ListenerAdapter {
public void onGuildMessageReceived(GuildMessageReceivedEvent event) {
String[] args = event.getMessage().getContentRaw().split("\\s+");
if (args[0].equalsIgnoreCase(FoodWorld.prefix + "mute")) {
if (hasRole("Owner", event)) {
if (args.length == 2) {
String mentionid = args[1].replace("<#!", "").replace(">", "");
Member member = event.getGuild().getMemberById(mentionid);
event.getGuild().addRoleToMember(member, event.getGuild().getRoleById(0)).complete();
EmbedBuilder msg = FoodWorld.sendMessage(null, "idk " + mentionid + member, "Blue");
event.getChannel().sendMessageEmbeds(msg.build()).queue();
}
else {
EmbedBuilder msg = FoodWorld.sendMessage("Specify Who To Mute", "Usage: " + FoodWorld.prefix + "mute [#mention who to mute]", "Blue");
event.getChannel().sendMessageEmbeds(msg.build()).queue();
}
}
}
/* If the bot ever sends a message, then add a ❌ reaction so users can delete that message */
if (event.getAuthor().equals(event.getJDA().getSelfUser())) {
event.getMessage().addReaction("❌").queue();
}
}
private boolean hasRole(String string, GuildMessageReceivedEvent event) {
Boolean toReturn = false;
for(int i=0; i < event.getMember().getRoles().size(); i++){
if("Owner".equals(event.getMember().getRoles().get(i).getName())){
toReturn = true;
}
}
return toReturn;
}
For reference, I'm following this tutorial on youtube: tutorial.
I'm not the most familiar with JDA and don't know how this would be done in an easier way.

Instead of parsing the string:
String mentionid = args[1].replace("<#!", "").replace(">", "");
Member member = event.getGuild().getMemberById(mentionid);
Use getMentionedMembers:
List<Member> mentions = event.getMessage().getMentionedMembers();
if (mentions.isEmpty()) {
EmbedBuilder msg = FoodWorld.sendMessage("Specify Who To Mute", "Usage: " + FoodWorld.prefix + "mute [#mention who to mute]", "Blue");
event.getChannel().sendMessageEmbeds(msg.build()).queue();
} else {
Member member = mentions.get(0);
event.getGuild().addRoleToMember(member, event.getGuild().getRoleById(0)).queue();
EmbedBuilder msg = FoodWorld.sendMessage(null, "idk " + member.getId() + member, "Blue");
event.getChannel().sendMessageEmbeds(msg.build()).queue();
}

Classloading from package spawns NoClassDefFoundError

I have a small program that attempts to allow plugins via class files copied to a specific ext directory.
The program is derived from https://javaranch.com/journal/200607/Plugins.html and I have attempted to simplify it and add on a directory scanning ability to scan packages and directories that the original code lacks.
When running the original code, it works. When I add on my directory and package scanning capability and test it on a demo package, it fails. Below are the samples.
The directory layout of the system accepting dynamically loaded class files as plugins:
testpack-+
|
+---PluginDemo.java
|
+---PluginFunction.java
The test plugin's directory layout:
b-+
|
+---Fibonacci.java
testpack-+
|
+---PluginFunction.java
The PluginDemo code with custom class loader:
package testpack;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.util.*;
public class PluginDemo extends ClassLoader {
static String pluginsDir = "ext";
static File basePluginDir = null;
File directory;
static List plugins;
public static void main(String args[]) {
PluginDemo demo = new PluginDemo();
basePluginDir = new File(System.getProperty("user.dir") + File.separator + pluginsDir);
demo.getPlugins(pluginsDir, "");
}
PluginDemo() {
plugins = new ArrayList();
}
protected void getPlugins(String directory, String parent) {
File dir = new File(System.getProperty("user.dir") + File.separator + directory);
if (dir.exists() && dir.isDirectory()) {
String[] files = dir.list();
for (int i = 0; i < files.length; i++) {
try {
// Allows recursive targetting of nested directories
String newTargetFile = System.getProperty("user.dir") + File.separator + directory + File.separator
+ files[i];
System.out.println("Targetting: " + newTargetFile);
File currentTarget = new File(newTargetFile);
if (currentTarget.isDirectory()) {
String newDirectoryTarget = directory + File.separator + files[i];
getPlugins(newDirectoryTarget, files[i]);
}
if (!files[i].endsWith(".class"))
continue;
String childFile = parent + File.separator + files[i].substring(0, files[i].indexOf("."));
Class c = loadClass(childFile);
Class[] intf = c.getInterfaces();
for (int j = 0; j < intf.length; j++) {
if (intf[j].getName().equals("PluginFunction")) {
PluginFunction pf = (PluginFunction) c.newInstance();
plugins.add(pf);
continue;
}
}
} catch (Exception ex) {
System.err.println("File " + files[i] + " does not contain a valid PluginFunction class.");
ex.printStackTrace();
}
}
}
}
public Class loadClass(String name) throws ClassNotFoundException {
return loadClass(name, true);
}
public Class loadClass(String classname, boolean resolve) throws ClassNotFoundException {
try {
Class c = findLoadedClass(classname);
if (c == null) {
try {
c = findSystemClass(classname);
} catch (Exception ex) {
}
}
if (c == null) {
String filename = classname.replace('.', File.separatorChar) + ".class";
// Create a File object. Interpret the filename relative to the
// directory specified for this ClassLoader.
File baseDir = new File(System.getProperty("user.dir"));
File f = new File(baseDir, PluginDemo.pluginsDir + File.separator + filename);
int length = (int) f.length();
byte[] classbytes = new byte[length];
DataInputStream in = new DataInputStream(new FileInputStream(f));
in.readFully(classbytes);
in.close();
c = defineClass(classname, classbytes, 0, length);
}
if (resolve)
resolveClass(c);
return c;
} catch (Exception ex) {
throw new ClassNotFoundException(ex.toString());
}
}
}
The PluginFunction interface code:
package testpack;
public interface PluginFunction {
// let the application pass in a parameter
public void setParameter (int param);
// retrieve a result from the plugin
public int getResult();
// return the name of this plugin
public String getPluginName();
// can be called to determine whether the plugin
// aborted execution due to an error condition
public boolean hasError();
}
The Fibonacci.java code:
package b;
import testpack.PluginFunction;
public class Fibonacci implements PluginFunction {
int parameter = 0;
boolean hasError = false;
public boolean hasError() {
return hasError;
}
public void setParameter (int param) {
parameter = param;
}
public int getResult() {
hasError = false;
return fib(parameter);
}
protected int fib (int n) {
if (n < 0) {
hasError = true;
return 0;
}
if (n == 0)
return 0;
else if (n == 1)
return 1;
else
return fib(n-1) + fib(n-2);
}
public String getPluginName() {
return "Fibonacci";
}
}
The output with errors:
Targetting: C:\Users\Administrator\eclipse-workspace\TestPluginSystem\ext\b\Fibonacci.class
Exception in thread "main" java.lang.NoClassDefFoundError: b\Fibonacci (wrong name: b/Fibonacci)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:760)
at java.lang.ClassLoader.defineClass(ClassLoader.java:642)
at testpack.PluginDemo.loadClass(PluginDemo.java:89)
at testpack.PluginDemo.loadClass(PluginDemo.java:65)
at testpack.PluginDemo.getPlugins(PluginDemo.java:47)
at testpack.PluginDemo.getPlugins(PluginDemo.java:40)
at testpack.PluginDemo.main(PluginDemo.java:19)
I would need help to get this package and directory scanning capable classloader working. Thanks.

Looking at the error and method ClassLoader.defineClass, I think the name parameter must have . as package separators, not / or \.
In your code in getPlugins the childFile is constructed using File.separator
String childFile = parent + File.separator + files[i].substring(0, files[i].indexOf("."));
Class c = loadClass(childFile);

Multithread PDF manipulation

I'm writing a java program whose operation is summarized as follows:
The subfolder with the specified name is selected in the source
folder.
All the pdfs are taken and converted into txt files in
the target folder.
The name of an item is searched inside the
txt.
If the name is found then the pdf from source to target is
copied.
All the txt from the target folder are deleted, in this
way all the pdfs containing the searched word remain.
"It all works", the problem is that the txt files are not deleted from target and I can not understand why. Thanks in advance, best regards.
Launcher.java:
import java.lang.String;
import java.util.Scanner;
import java.io.File;
public class Launcher {
// campi
int status = 1;
static String source = "C:\\Users\\MyUser\\Desktop\\source\\";
static String target = "C:\\Users\\MyUser\\Desktop\\target\\";
public static void main(String [] args) {
// strings
String src = source;
String item = "";
// init
Scanner scan = new Scanner(System.in);
System.out.print("\nFornitore: ");
src += scan.nextLine().toUpperCase() + "\\";
System.out.print("Item: ");
item = scan.nextLine();
// notifier
Launcher launcher = new Launcher();
// threads
MakerThread maker = new MakerThread(launcher, src, target);
SearcherThread searcher = new SearcherThread(launcher, src, target, item);
CleanupThread cleaner = new CleanupThread(launcher, target);
// run
maker.start();
searcher.start();
cleaner.start();
}
}
MakerThread.java:
import java.io.File;
public class MakerThread extends Thread {
// campi
String src = "";
String target = "";
Launcher launcher;
// costruttore
public MakerThread(Launcher launcher, String src, String target) {
this.src = src;
this.target = target;
this.launcher = launcher;
}
// metodi
#Override
public void run() {
try{
synchronized (launcher) {
File folder = new File(this.src);
for (File f : folder.listFiles()) {
// spin-lock
while (launcher.status != 1){
launcher.wait();
}
if(f.isFile() && f.getName().endsWith("pdf")) {
System.out.println("PDF TROVATO: " + f.getName());
// input
String input = win_str(src + f.getName());
// output
String output = target;
output += f.getName().replaceAll(".pdf", ".txt");
output = win_str(output);
// command
String command = "cmd /C java -jar ./pdfbox-app-2.0.11.jar ExtractText ";
command += input + " " + output;
Process p1 = Runtime.getRuntime().exec(command);
p1.waitFor();
}
}
// set status, awake other threads
launcher.status = 2;
launcher.notifyAll();
}
}catch (Exception e) {
System.out.println("Exception: "+e.getMessage());
}
}
private String win_str(String str) {
return "\"" + str + "\"";
}
}
SearcherThread.java:
import java.io.File;
import java.io.BufferedReader;
import java.io.FileReader;
public class SearcherThread extends Thread {
// campi
String src = "";
String target = "";
String item = "";
Launcher launcher;
// costruttore
public SearcherThread(Launcher launcher, String src, String target, String item) {
this.target = target;
this.src = src;
this.item = item;
this.launcher = launcher;
}
// metodi
#Override
public void run() {
try{
synchronized (launcher) {
File folder = new File(this.target);
for(File f : folder.listFiles()) {
// spin-lock
while (launcher.status != 2){
launcher.wait();
}
if(f.isFile() && f.getName().endsWith("txt")) {
System.out.println("SEARCHING IN: " + f.getName());
// init
String line;
BufferedReader br = new BufferedReader(new FileReader(new File(target+f.getName())));
// txt search
while((line = br.readLine()) != null) {
if(line.contains(item)) {
System.out.println(" [" + item + "]" + " trovato in " + f.getName() + "\n");
// input
String pdf = f.getName().replaceAll(".txt", ".pdf");
String input = win_str(src+pdf);
// output
String output = win_str(target);
// command
String command = "cmd /C copy " + input + " " + output;
Process p1 = Runtime.getRuntime().exec(command);
p1.waitFor();
break;
}
}
}
}
// set status, awake other threads
launcher.status = 3;
launcher.notifyAll();
}
}catch (Exception e) {
System.out.println("Exception: "+e.getMessage());
}
}
private String win_str(String str) {
return "\"" + str + "\"";
}
}
CleanupThread.java:
import java.io.File;
public class CleanupThread extends Thread {
// campi
String target = "";
Launcher launcher;
// costruttore
public CleanupThread(Launcher launcher, String target) {
this.target = target;
this.launcher = launcher;
}
// metodi
#Override
public void run() {
try{
synchronized (launcher) {
File folder = new File(this.target);
for (File f : folder.listFiles()) {
// spin-lock
while (launcher.status != 3){
launcher.wait();
}
if(f.isFile() && f.getName().endsWith("txt")) {
System.out.println("CLEANING UP: " + f.getName());
// input
String input = win_str(target + f.getName());
// command
String command = "cmd /C del " + input;
Process p1 = Runtime.getRuntime().exec(command);
p1.waitFor();
}
}
// set status, awake other threads
launcher.status = 1;
launcher.notifyAll();
}
}catch (Exception e) {
System.out.println("Exception: "+e.getMessage());
}
}
private String win_str(String str) {
return "\"" + str + "\"";
}
}

How to find out where a class originates from at runtime?

I'm having this weird issue where a class from some transitive dependency keeps showing up at runtime, shadowing a newer version of the class from the (correct) first level dependency, even though I thought I made sure that I excluded the older version from all other dependencies I declare (this is in a Maven/IntelliJ setup)
More specifically, at runtime the app fails with a NoClassDefFoundError, since during class loading a wrong version of the owning class is loaded, which has a field of a type that does not exist in newer versions of the library that class is defined in. To illustrate:
// lib.jar:wrong-version
class Owner {
private SomeType f;
}
// lib.jar:new-version
class Owner {
private OtherType f;
}
At runtime, the class loader finds a reference to the symbol Owner and attempts to load the version that has SomeType, which in return does not exist anymore. This is even though I excluded wrong-version where ever I could spot it.
I also ran mvn dependency:tree to see if the old version is still being pulled in somewhere, but it's not!
In order to further debug this, I was wondering if there is a way to find out where a class loader was reading a specific class from, i.e. which file? Is that possible? Or even better, build a list of origins where a certain symbol is defined, in case it's defined more than once?
Sorry if this is vague, but the problem is rather nebulous.

The following code will search the whole classpath for a particular class. With no arguments it will dump every class it finds and then you can pipe to grep or redirect to a file. It looks inside jars...
Usage: WhichClass or WhichClass package.name (note no .class)
Apologies for the lack of comments ...
import java.io.File;
import java.io.IOException;
import java.util.Enumeration;
import java.util.StringTokenizer;
import java.util.Vector;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
public final class WhichClass {
private WhichClass() {
}
static Vector<String> scratchVector;
public static void main(final String[] argv) {
Vector v;
if ((argv.length == 0) || "-all".equals(argv[0])) {
v = findClass(null);
} else {
v = findClass(argv[0]);
}
for (int i = 0; i < v.size(); i++) {
System.out.println(v.elementAt(i));
}
}
static String className(final String classFile) {
return classFile.replace('/', '.').substring(0, classFile.length() - ".class".length());
}
static Vector findClass(final String className) {
if (className != null) {
scratchVector = new Vector<String>(5);
} else {
scratchVector = new Vector<String>(5000);
}
findClassInPath(className, setupBootClassPath());
findClassInPath(className, setupClassPath());
return scratchVector;
}
static void findClassInPath(final String className, final StringTokenizer path) {
while (path.hasMoreTokens()) {
String pathElement = path.nextToken();
File pathFile = new File(pathElement);
if (pathFile.isDirectory()) {
try {
if (className != null) {
String pathName = className.replace('.', System.getProperty("file.separator").charAt(0)) + ".class";
findClassInPathElement(pathName, pathElement, pathFile);
} else {
findClassInPathElement(className, pathElement, pathFile);
}
} catch (IOException e) {
e.printStackTrace();
}
} else if (pathFile.exists()) {
try {
if (className != null) {
String pathName = className.replace('.', '/') + ".class";
ZipFile zipFile = new ZipFile(pathFile);
ZipEntry zipEntry = zipFile.getEntry(pathName);
if (zipEntry != null) {
scratchVector.addElement(pathFile + "(" + zipEntry + ")");
}
} else {
ZipFile zipFile = new ZipFile(pathFile);
Enumeration entries = zipFile.entries();
while (entries.hasMoreElements()) {
String entry = entries.nextElement().toString();
if (entry.endsWith(".class")) {
String name = className(entry);
scratchVector.addElement(pathFile + "(" + entry + ")");
}
}
}
} catch (IOException e) {
System.err.println(e + " while working on " + pathFile);
}
}
}
}
static void findClassInPathElement(final String pathName, final String pathElement, final File pathFile)
throws IOException {
String[] list = pathFile.list();
for (int i = 0; i < list.length; i++) {
File file = new File(pathFile, list[i]);
if (file.isDirectory()) {
findClassInPathElement(pathName, pathElement, file);
} else if (file.exists() && (file.length() != 0) && list[i].endsWith(".class")) {
String classFile = file.toString().substring(pathElement.length() + 1);
String name = className(classFile);
if (pathName != null) {
if (classFile.equals(pathName)) {
scratchVector.addElement(file.toString());
}
} else {
scratchVector.addElement(file.toString());
}
}
}
}
static StringTokenizer setupBootClassPath() {
String classPath = System.getProperty("sun.boot.class.path");
String separator = System.getProperty("path.separator");
return new StringTokenizer(classPath, separator);
}
static StringTokenizer setupClassPath() {
String classPath = System.getProperty("java.class.path");
String separator = System.getProperty("path.separator");
return new StringTokenizer(classPath, separator);
}
}

If you know the fully qualified name of the class, say somelib.Owner, you can try calling the following in your code:
public void foo() {
URL url = somelib.Owner.class.getClassLoader().getResource("somelib/Owner.class");
System.out.println(url);
}

Read escaped quote as escaped quote from xml

I load xml file into DOM model and analyze it.
The code for that is:
public class MyTest {
public static void main(String[] args) {
Document doc = XMLUtils.fileToDom("MyTest.xml");//Loads xml data to DOM
Element rootElement = doc.getDocumentElement();
NodeList nodes = rootElement.getChildNodes();
Node child1 = nodes.item(1);
Node child2 = nodes.item(3);
String str1 = child1.getTextContent();
String str2 = child2.getTextContent();
if(str1 != null){
System.out.println(str1.equals(str2));
}
System.out.println();
System.out.println(str1);
System.out.println(str2);
}
}
MyTest.xml
<tests>
<test name="1">ff1 "</test>
<test name="2">ff1 "</test>
</tests>
Result:
true
ff1 "
ff1 "
Desired result:
false
ff1 "
ff1 "
So I need to distinguish these two cases: when the quote is escaped and is not.
Please help.
Thank you in advance.
P.S. The code for XMLUtils#fileToDom(String filePath), a snippet from XMLUtils class:
static {
DocumentBuilderFactory dFactory = DocumentBuilderFactory.newInstance();
dFactory.setNamespaceAware(false);
dFactory.setValidating(false);
try {
docNonValidatingBuilder = dFactory.newDocumentBuilder();
} catch (ParserConfigurationException e) {
}
}
public static DocumentBuilder getNonValidatingBuilder() {
return docNonValidatingBuilder;
}
public static Document fileToDom(String filePath) {
Document doc = getNonValidatingBuilder().newDocument();
File f = new File(filePath);
if(!f.exists())
return doc;
try {
Transformer transformer = TransformerFactory.newInstance().newTransformer();
DOMResult result = new DOMResult(doc);
StreamSource source = new StreamSource(f);
transformer.transform(source, result);
} catch (Exception e) {
return doc;
}
return doc;
}

I've take a look on source code of apache xerces and propose my solution (but it is monkey patch).
I've wrote simple class
package a;
import java.io.IOException;
import org.apache.xerces.impl.XMLDocumentScannerImpl;
import org.apache.xerces.parsers.NonValidatingConfiguration;
import org.apache.xerces.xni.XMLString;
import org.apache.xerces.xni.XNIException;
import org.apache.xerces.xni.parser.XMLComponent;
public class MyConfig extends NonValidatingConfiguration {
private MyScanner myScanner;
#Override
#SuppressWarnings("unchecked")
protected void configurePipeline() {
if (myScanner == null) {
myScanner = new MyScanner();
addComponent((XMLComponent) myScanner);
}
super.fProperties.put(DOCUMENT_SCANNER, myScanner);
super.fScanner = myScanner;
super.fScanner.setDocumentHandler(this.fDocumentHandler);
super.fLastComponent = fScanner;
}
private static class MyScanner extends XMLDocumentScannerImpl {
#Override
protected void scanEntityReference() throws IOException, XNIException {
// name
String name = super.fEntityScanner.scanName();
if (name == null) {
reportFatalError("NameRequiredInReference", null);
return;
}
super.fDocumentHandler.characters(new XMLString(("&" + name + ";")
.toCharArray(), 0, name.length() + 2), null);
// end
if (!super.fEntityScanner.skipChar(';')) {
reportFatalError("SemicolonRequiredInReference",
new Object[] { name });
}
fMarkupDepth--;
}
}
}
You need to add only next line to your main method before start parsing
System.setProperty(
"org.apache.xerces.xni.parser.XMLParserConfiguration",
"a.MyConfig");
And you will have expected result:
false
ff1 "
ff1 "

Looks like you can get the TEXT_NODE child and use getNodeValue (assuming it's not NULL):
public static String getRawContent(Node n) {
if (n == null) {
return null;
}
Node n1 = getChild(n, Node.TEXT_NODE);
if (n1 == null) {
return null;
}
return n1.getNodeValue();
}
Grabbed that from:
http://www.java2s.com/Code/Java/XML/Gettherawtextcontentofanodeornullifthereisnotext.htm

There is no way to do this for the internal entities. XML does not support this concept. Internal entities are just a different way to write the same PSVI content into the text, they are not distinctive.