Why doesn’t Forge use the JRE shipped with Minecraft?

[Cadiboo]

Minecraft’s launcher downloads the Java it needs to run, why doesn’t Forge use this pre installed Java instead of requiring end-users to download the same (I assume it’s the same) version themselves?

Edited October 3, 2018 by Cadiboo
users->end-users

[DaemonUmbra]

I believe this is because the JRE that Minecraft ships with is

1) Horrifically out of date

2) Not exactly "installed" on the user's system, it's more just extracted into Minecraft's program files, so there are no registry keys or environment variables pointing to it, a program that wants to use it has to already know where it is.

[Cadiboo]

12 minutes ago, DaemonUmbra said:

I believe this is because the JRE that Minecraft ships with is

1) Horrifically out of date

2) Not exactly "installed" on the user's system, it's more just extracted into Minecraft's program files, so there are no registry keys or environment variables pointing to it, a program that wants to use it has to already know where it is.

We’re being forced to use the same JRE anyway though, so we can’t exactly help the out of date part and don’t we already know exactly where it is? 

[Draco18s]

Note that for programming you also need the JDK...which Minecraft does not autodownload.

[Cadiboo]

2 hours ago, Draco18s said:

Note that for programming you also need the JDK...which Minecraft does not autodownload.

I assume that that’s only for people who are developing mods (& Forge etc.) though, I don’t see why the end-users of Forge & mods need to redownload Java when it appears that Forge could just directly use Minecraft’s Java.

Edited October 3, 2018 by Cadiboo

[LexManos]

That is exactly the case, The JRE that the Minecraft launcher installs does not actually inform the OS that it's installed anywhere.

So running the jar normally, or through Launch4J has no idea that install even exists.

We are working on a a new exe wrapper that is specifically tailored to Minecraft, and will check the known default Minecraft locations as well as the known installed JREs. 

But that's still in the works and needs a lot more testing.

 

Until then, we're stuck with this.

 

[IdrisQe]

Unpopular opinion but honestly, I would just keep it as-is.

Better to inconvienience users very slightly into downloading an updated Java every few months (which takes like... 15 minutes) than letting them unwittingly use the broken, dangerously unsecure old version Minecraft ships with. If anything, Forge should complain when the Java version is too old.

Security and functionality trumps very, very minor user inconvienience. At least in my eyes.

[Cadiboo]

1 hour ago, IdrisQe said:

Unpopular opinion but honestly, I would just keep it as-is.

Better to inconvienience users very slightly into downloading an updated Java every few months (which takes like... 15 minutes) than letting them unwittingly use the broken, dangerously unsecure old version Minecraft ships with. If anything, Forge should complain when the Java version is too old.

Security and functionality trumps very, very minor user inconvienience. At least in my eyes.

This isn’t an unpopular opinion at all, it’s a great idea. However, we still have to use (target/retain comparability with) the Java version that Minecraft uses because all their code is written in it. It seems to me that Mojang has fallen down on pretty much everything except for adding features so far. They don’t have a Modding API, lots of their code is badly written, lots of their code is old and should be updated and, as you said, they use a very outdated java version. Also Forge’s Internals use some Java Internals like Sun’s classloader (I think) that only work on specific versions of java (i.e. the version of Java that Minecraft uses). This is why Forge breaks on Java 9 (I think). I also pretty sure that a lot of effort went into making Forge work with Java 9 for 1.13 though.

[Cadiboo]

10 hours ago, diesieben07 said:

• Double clicking the installer jar file will use any system-installed Java, there is no way to change this.
• The .exe version of the installer uses Launch4j as far as I know, which also uses any system-installed Java.

 

3 hours ago, LexManos said:

That is exactly the case, The JRE that the Minecraft launcher installs does not actually inform the OS that it's installed anywhere.

So running the jar normally, or through Launch4J has no idea that install even exists.

We are working on a a new exe wrapper that is specifically tailored to Minecraft, and will check the known default Minecraft locations as well as the known installed JREs. 

But that's still in the works and needs a lot more testing.

 

Until then, we're stuck with this.

 

Thanks! This is what I was looking for. Any idea why Forge didn’t initially (when it was created) start by using Minecrafts Java though? It seems like it would have been the logical way to streamline the installation for end-users. Then again, Forge probably wasn’t created with end-users in mind who didn’t know how to install Java.

[Animefan8888]

55 minutes ago, Cadiboo said:

 

Thanks! This is what I was looking for. Any idea why Forge didn’t initially (when it was created) start by using Minecrafts Java though? It seems like it would have been the logical way to streamline the installation for end-users. Then again, Forge probably wasn’t created with end-users in mind who didn’t know how to install Java.

Minecraft didn't start using there own Java until sometime around the new launcher.

[Draco18s]

4 minutes ago, Animefan8888 said:

Minecraft didn't start using there own Java until sometime around the new launcher.

[Cadiboo]

7 minutes ago, Animefan8888 said:

Minecraft didn't start using their own Java until sometime around the new launcher.

That makes sense, thanks!

[Animefan8888]

39 minutes ago, Draco18s said:

Yes I know, but my phone doesn't agree with me or I'm just typing to fast. And I didn't feel like fixing it.

[Draco18s]

17 minutes ago, Animefan8888 said:

Yes I know, but my phone doesn't agree with me or I'm just typing to fast. And I didn't feel like fixing it.

I've been there.

My tablet doesn't know the word "do"

[IdrisQe]

 

10 hours ago, Cadiboo said:

I also pretty sure that a lot of effort went into making Forge work with Java 9 for 1.13 though.

Wait, does 1.13 require Java 9? That will be a headache for anyone wanting multiple instances... Since you'd need Java 8 for a 1.12.2 instance or below, and Java 9 for 1.13+... And Java automatically uninstalls other versions when you install a new one now. Oh boy.

[Cadiboo]

46 minutes ago, IdrisQe said:

 

Wait, does 1.13 require Java 9? That will be a headache for anyone wanting multiple instances... Since you'd need Java 8 for a 1.12.2 instance or below, and Java 9 for 1.13+... And Java automatically uninstalls other versions when you install a new one now. Oh boy.

I believe that Minecraft (or most of it at least) should work with pretty much any Java >= Java_8u151. However it was designed to work with Java_8u151 (the JRE that it ships with). It does not require any specific Java (except that the Java you use must be compatible with Java_8u151). Forge on the other hand currently requires Java 8 because

10 hours ago, Cadiboo said:

Forge’s Internals use some Java Internals like Sun’s classloader (I think) that only work on specific versions of java

You would have to ask someone else for a concrete reason as to why a lot of work went into making Forge able to use Java 9 (for the 1.13 version of Forge), but here’s my speculation:

- They were already rewriting the entirety of the mod loading system (The Internals that use Java’s (Sun’s) Internals)

- It will allow modders to use new Java features not available in Java 8

- Security patches/upgrades etc.

- Performance patches/upgrades etc.

- Newer versions of software is almost universally better.

[DaemonUmbra]

I think I've seen manual Java installation (Not auto-update) prompt for what versions to remove with the new installation, for which deselect all (don't remove any) is an option.

However a new Java version will take over for simple "java" invocations via CLI, so this would require specifying the full path to the outdated Java binary/binaries.

 

Note: I have not installed Java fresh in a long time so your mileage may vary.

[Cadiboo]

On Mac (at least in my experience) new Java versions don’t physically delete or uninstall previous versions, they just change JAVA_HOME and other variables to the new installation, and leave the old installations alone in the JavaVirtualMachines folder. Removing the new installation (& setting JAVA_HOME to the old installation) seems to revert the update.