Reflection in Java 8 and Java 17 | Together Java | Page 1

hallow rune Feb 12, 2023, 2:01 PM

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hi, I have some Reflection code from Java 8 that works fine but with Java 17 it breaks

old ospreyBOT Feb 12, 2023, 2:02 PM

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<@&987246399047479336> please have a look, thanks.

old ospreyBOT Feb 12, 2023, 2:02 PM

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old osprey <@&987246399047479336> please have a look, thanks.

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hallow rune Feb 12, 2023, 2:02 PM

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the code is the following ```java

public static void enable(String... methods) throws NoSuchFieldException, IllegalAccessException {
    Field declaredFieldMethods = HttpURLConnection.class.getDeclaredField("methods");
    Field declaredFieldModifiers = Field.class.getDeclaredField("modifiers");
    declaredFieldModifiers.setAccessible(true);
    declaredFieldModifiers.setInt(declaredFieldMethods, declaredFieldMethods.getModifiers() & ~Modifier.FINAL);
    declaredFieldMethods.setAccessible(true);
    String[] previous = (String[]) declaredFieldMethods.get(null);
    Set<String> current = new LinkedHashSet<>(Arrays.asList(previous));
    current.addAll(Arrays.asList(methods));
    String[] patched = current.toArray(new String[0]);
    declaredFieldMethods.set(null, patched);
}

old ospreyBOT Feb 12, 2023, 2:02 PM

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hallow rune the code is the following ```java public static void enable(String... metho...

Detected code, here are some useful tools:

hallow rune Feb 12, 2023, 2:02 PM

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I cant find alot regarding Java 17, but its something that should also apparently not be working in Java 8

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some answers on a Stackoverflow where pointing towards Constructor.setAccessible(true) but I am not sure if this is accucare, I tried playing around a bit but I am unsure which Constructor I am ment to modify

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I tried to add this at the top of my method java Constructor<?>[] constructors = Field.class.getDeclaredConstructors(); for (Constructor<?> constructor : constructors) { constructor.setAccessible(true); } but this just errors aswell saying Unable to make java.lang.reflect.Field(java.lang.Class,java.lang.String,java.lang.Class,int,boolean,int,java.lang.String,byte[]) accessible: module java.base does not "opens java.lang.reflect" to unnamed module @7106e68e

old ospreyBOT Feb 12, 2023, 2:03 PM

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hallow rune I tried to add this at the top of my method ```java Constructor<?>[] con...

Detected code, here are some useful tools:

Formatted code

Constructor<? > [] constructors = Field.class .getDeclaredConstructors();
for (Constructor<? > constructor : constructors) {
  constructor.setAccessible(true); }

hallow rune Feb 12, 2023, 2:04 PM

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hallow rune some answers on a Stackoverflow where pointing towards Constructor.setAccessible...

https://stackoverflow.com/questions/73062720/why-reflection-calls-do-not-work-anymore-in-java-17 this was the post I was reading

Stack Overflow

Why Reflection Calls Do Not Work Anymore in Java 17?

We migrated from Java 8 to Java 17 and the following error started to pop up due to a reflection call in the code:
java.lang.IllegalAccessException: class com.twitter.chill.Instantiators$ cannot ac...

wary pilot Feb 12, 2023, 2:27 PM

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hallow rune I tried to add this at the top of my method ```java Constructor<?>[] con...

yes, now internals are sealed so people stop using them

hallow rune Feb 12, 2023, 2:30 PM

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wary pilot yes, now internals are sealed so people stop using them

is there a way to modify it anyways im still stuck trying to make it work

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its just compatibility for Java 17+ because there is no PATCH and OPTIONS in the HttpUrlConnection class for allowed HTTP methods

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I read that it should be able to work if done properly but I cant figure the properly out

wary pilot Feb 12, 2023, 2:31 PM

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hallow rune is there a way to modify it anyways im still stuck trying to make it work

yes, you can use --add-open option
but why would you want to do that ?

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why are you trying to access Field constructor ?

hallow rune Feb 12, 2023, 2:31 PM

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I dont want to access any constructor I want to add two String to this array

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I just read that for Java 17 I am supposed todo something with Constructors to get access to the Fields

wary pilot Feb 12, 2023, 2:32 PM

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hallow rune I dont want to access any constructor I want to add two String to this array

you are, that's what the code you gave is doing

wary pilot Feb 12, 2023, 2:32 PM

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hallow rune I just read that for Java 17 I am supposed todo something with Constructors to g...

wdym

hallow rune Feb 12, 2023, 2:32 PM

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hallow rune I tried to add this at the top of my method ```java Constructor<?>[] con...

You mean this?

wary pilot Feb 12, 2023, 2:32 PM

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yes

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you are trying to access Field's constructor

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why would you want to do that

hallow rune Feb 12, 2023, 2:32 PM

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thats what I tried to add because on the Stackoverflow I linked they were talking about Constructor.setAccessible

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wary pilot Feb 12, 2023, 2:33 PM

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this code is unrelated to what your problem seems to be

hallow rune Feb 12, 2023, 2:33 PM

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oh

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then that was my mistake

wary pilot Feb 12, 2023, 2:33 PM

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I am repeating, you are trying to access the constructor of the class Field

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why are you trying to do that ?

hallow rune Feb 12, 2023, 2:34 PM

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well it doesnt really make sense for me to access the Field class Constructor because the field I want to modify is in HttpURLConneciton

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I was just trying to make something work from reading those comments

wary pilot Feb 12, 2023, 2:34 PM

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right so

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how are you creating the HttpURLConnection ?

hallow rune Feb 12, 2023, 2:36 PM

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doing the same for HttpURLConnection is giving the same error, assuming its still because of --add-open, I did add that as args though

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in which context, for reflection or how its used within my code

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within my code its would be
(HttpsURLConnection) URL(String).openConnection()

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I am aware this it Https*

wary pilot Feb 12, 2023, 2:38 PM

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so

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instead of that

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you should use HttpClient and HttpRequest

hallow rune Feb 12, 2023, 2:38 PM

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but thats not available in Java 8

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thats 11

wary pilot Feb 12, 2023, 2:38 PM

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but that's available in java 17

hallow rune Feb 12, 2023, 2:39 PM

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yeah but I just want to add something so people running Java 17 wont Crash on startup

wary pilot Feb 12, 2023, 2:39 PM

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can't you just update to java 17 ?

hallow rune Feb 12, 2023, 2:40 PM

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well technically I could but alot of the people run different Versions and most of them are still on Java 8

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I thought some extra lines to the reflection could make it work

wary pilot Feb 12, 2023, 2:40 PM

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hallow rune I thought some extra lines to the reflection could make it work

an argument could make it work

hallow rune Feb 12, 2023, 2:41 PM

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the --add-open ?

wary pilot Feb 12, 2023, 2:41 PM

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hallow rune the --add-open ?

yes

hallow rune Feb 12, 2023, 2:41 PM

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mhm I added that though or is there a specific way to put it

wary pilot Feb 12, 2023, 2:41 PM

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but note that it might be removed at some point

hallow rune Feb 12, 2023, 2:41 PM

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well in theory if its not fixable within my own code I will just make the minimum requirement Java 11 for HttpClient

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because that supports Patch & OPTIONS

wary pilot Feb 12, 2023, 2:44 PM

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hallow rune

should be something in the lines of --add-opens java.base/java.lang=ALL-UNNAMED

hallow rune Feb 12, 2023, 2:44 PM

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wary pilot should be something in the lines of `--add-opens java.base/java.lang=ALL-UNNAMED...

I'll write this down and keep it in mind but I think its time to force people to upgrade

wary pilot Feb 12, 2023, 2:44 PM

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hallow rune because that supports Patch & OPTIONS

HttpRequest supports anything

hallow rune Feb 12, 2023, 2:44 PM

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I know, even HTTP2 🥹

wary pilot Feb 12, 2023, 2:44 PM

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hallow rune I'll write this down and keep it in mind but I think its time to force people to...

but note that you shouldn't do that

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also

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is it an app ?

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or a lib ?

hallow rune Feb 12, 2023, 2:45 PM

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yes its some proxy server for a game that allows you to see internal traffic

wary pilot Feb 12, 2023, 2:45 PM

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because if it is an app, you should provide the jre to customers

hallow rune Feb 12, 2023, 2:45 PM

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and one of the first requests is a PATCH

wary pilot Feb 12, 2023, 2:45 PM

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wary pilot because if it is an app, you should provide the jre to customers

you shouldn't let people use their own jre

hallow rune Feb 12, 2023, 2:45 PM

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like bundle the jre in?

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I read about that once but never figured out how todo that

wary pilot Feb 12, 2023, 2:46 PM

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hallow rune like bundle the jre in?

yes

hallow rune Feb 12, 2023, 2:46 PM

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it would only include the classes that are required to run aswell from what I remember

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I really liked it but never got it to work

wary pilot Feb 12, 2023, 2:46 PM

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you can use tools like jpackage to create an installer

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and then you give this installer

hallow rune Feb 12, 2023, 2:46 PM

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I'll take a look now, and try to get it working myself - I will fall back to this Thread if I run into issues

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I am a bit smarter than I was when I first tried it so I hope I can manage

old ospreyBOT Feb 12, 2023, 2:47 PM

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Due to the JVM and bytecode as intermediate execution stage, turning a Java application into a standalone executable (exe, msi, deb, rpm, dmg, pkg) is not trivial.
However, there exist various tools to do the job. They mostly differ in the details of the solution they create and hence also in their purpose:

jpackage (the official tool) - creates an installer
Launch4J - creates a wrapper executable that unwraps on execution
GraalVM - attempts to create an actual native executable instead of wrappers or installers

This guide explains how to use jpackage, an official tool that is available in all JDKs since Java 16. The tool creates an installer for the application, so the end-user will get an executable that guides them through a setup where they can select installation path and tweak other settings, finally resulting in the application being installed on the machine (with a proper uninstaller, desktop shortcuts, start menu entries, ...): https://i.imgur.com/2V5ovUu.png

As an example, suppose you have a fat jar of your application called HelloWorld.jar, with a main class called Main. Put the jar into a dedicated release folder for simplicity. Execute the following command and you have an installer for your application in a folder called installer:

jpackage --input "release" --dest "installer" --main-class "Main" --main-jar "HelloWorld.jar" --name "HelloWorld" --win-dir-chooser --win-menu --win-shortcut --type exe

See the official documentation for more information on the available commands and for other operating systems:

Here is an example for a more complex setup which also associates file endings to the application, has a custom icon and more: https://pastebin.com/cfzqSKnW

hallow rune Feb 12, 2023, 2:47 PM

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lovely thanks, I'll read now

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well given jpackage ships at Java 16, I assume I can fallback to Launch4J for Java 8

wary pilot Feb 12, 2023, 3:15 PM

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hallow rune well given jpackage ships at Java 16, I assume I can fallback to Launch4J for Ja...

wdym, you won't need java 8 anymore

hallow rune Feb 12, 2023, 3:15 PM

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ah wait true

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it doesnt matter which Version anyone has installed

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my brain wasnt functioning

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I forgot thats the whole point behind this

calm nimbus Feb 12, 2023, 3:29 PM

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hallow rune it doesnt matter which Version anyone has installed

oh yeah right i did forgot that as well lmao

hallow rune Feb 12, 2023, 3:39 PM

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ugh

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I have Java 11/17/19 installed but I removed all Path variables

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I remember it wasnt JAVA_HOME for some higher versions

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guess I just reinstall 17

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ah its not setting the Path variables for 17

ebon oak Feb 12, 2023, 3:42 PM

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you don't need to reinstall

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just to set the path variable

hallow rune Feb 12, 2023, 3:42 PM

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I remember there was more than just JAVA_HOME for 17

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but i dont remember what it was called

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thats why I wanted to reinstall

ebon oak Feb 12, 2023, 3:43 PM

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There is also Path

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where you go into the bin folder and paste it there

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Il show you

hallow rune Feb 12, 2023, 3:43 PM

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is JAVA_HOME supposed to point to the jdk folder or the bin

ebon oak Feb 12, 2023, 3:43 PM

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jdk folder

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and the Path to the bin

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like C:\Program Files\Java\jdk-17.0.3.1\bin for path

hallow rune Feb 12, 2023, 3:45 PM

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am i missing something

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java -version still gives 8 after restarting cmd

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ah Path in System

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OKAY thank you

ebon oak Feb 12, 2023, 3:47 PM

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np

hallow rune Feb 12, 2023, 3:48 PM

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[16:46:55.355] Can not find WiX tools (light.exe, candle.exe)
[16:46:55.355] Download WiX 3.0 or later from https://wixtoolset.org and add it to the PATH.
Error: Invalid or unsupported type: [exe]

do I just jam the wix exe into my jdk17 folder

WiX Toolset

The most powerful set of tools available to create your Windows installation experience.

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or is there some convetion of where to put things like this

ebon oak Feb 12, 2023, 3:48 PM

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why not install wix into a seperate folder like all your applications?

hallow rune Feb 12, 2023, 3:49 PM

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i dont have to install it it just needs the exe

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Ill make a folder in appdata for it

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atleast I think I dont have to install yet I'll see

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ok nvm

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i had to install it

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oh this is so cool

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just turned from 400kb jar to 48mb exe but I guess thats how it is

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or is there a way to optimize this exe somehow

wary pilot Feb 12, 2023, 4:01 PM

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hallow rune

you should remove the path to java 17 here and only keep a path to JAVA_HOME

wary pilot Feb 12, 2023, 4:02 PM

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hallow rune just turned from 400kb jar to 48mb exe but I guess thats how it is

50mb is the weight of the jre so 🤷

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with jpackage and jlink you should be able to tell it to remove unused modules

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but that's all

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you could try graalvm I guess, maybe

hallow rune Feb 12, 2023, 4:06 PM

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wary pilot with jpackage and jlink you should be able to tell it to remove unused modules

https://www.baeldung.com/jlink found this, I am reading

Baeldung

Guide to jlink | Baeldung

Learn how to create a custom, modular JRE that only contains the bare minimum files using jlink.

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since this is an installer how does versioning work

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lets assume i release an exe and then update it a week later

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would it be installed as a seperate program or does it overwrite the previous

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actually I assume itll overwrite

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so I tested jpackage with one of my other tools and it ran fine using jpackage --input "release" --dest "installer" --main-class "Main" --main-jar .\Mundo-1.101-jar-with-dependencies.jar --name "HelloWorld" --win-dir-chooser --win-menu --win-shortcut --type exe

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I installed it using the exe

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but nothing happens when running the Mundo.exe now, the original jar is in the app directory and works fine

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theres no error anywhere either

hallow rune Feb 12, 2023, 4:43 PM

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tried to make another installer using the same command, the installer just errors and insta closes, cant even see anything

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well.. seems like this might be an issue

hallow rune Feb 12, 2023, 4:46 PM

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hallow rune well.. seems like this might be an issue

nevermind, still doesnt work the installer just errors and the process remains running

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if I uninstall Mundo properly the installer works again

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so I have two issues now:
• installed exe does nothing
• unable to launch a new installer (instantly errors)

tidal fossil Feb 12, 2023, 9:42 PM

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Check what it fails on, is there no error code or log

hallow rune Feb 13, 2023, 12:15 AM

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theres nothing

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the exe just closes

#Reflection in Java 8 and Java 17