Eclipse Auto Deploy Doesn't Include Native Libraries

Question

I have a Java webapp in eclipse. I have auto-deploy enabled, so whenever I make a change, eclipse automatically redeploys the webapp to my local Tomcat server, and all I have to do is refresh the page. This has worked fine and dandy up until now.

However, I recently added this dependency:

    <dependency>
        <groupId>com.eclipsesource.j2v8</groupId>
        <artifactId>j2v8_win32_x86_64</artifactId>
        <version>3.1.6</version>
    </dependency>

This dependency includes some native libraries (.dll files on my Windows machine). When I manually deploy (by right-clicking the project, clicking "run as" and then "run on server"), this works fine. I can use the library exactly like I'd expect.

If I then make a change (any change, even adding a comment), eclipse does its automatic redeploy. But when I try to use that library (by simply refreshing the page and running the exact same code again), I get this error:

java.lang.UnsatisfiedLinkError: Could not load J2V8 library. Reasons: 
    no j2v8_win32_x86_64 in java.library.path

So it appears that eclipse is failing to load the native libraries upon auto-deploy, even though it works fine when I deploy manually.

The value of java.library.path is the same in both cases though:

C:\Program Files\Java\jdk1.8.0_65\bin;
C:\WINDOWS\Sun\Java\bin;
C:\WINDOWS\system32;
C:\WINDOWS;
C:\ProgramData\Oracle\Java\javapath;
C:\Program Files\ImageMagick-6.9.0-Q16;
C:\Program Files (x86)\NVIDIA Corporation\PhysX\Common;
C:\Program Files\ImageMagick-6.8.9-Q16;
C:\Program Files\Java\jdk1.8.0_65;
c:\Program Files (x86)\Intel\iCLS Client\;
c:\Program Files\Intel\iCLS Client\;
C:\WINDOWS\system32;
C:\WINDOWS;
C:\WINDOWS\System32\Wbem;
C:\WINDOWS\System32\WindowsPowerShell\v1.0\;
C:\Program Files\Intel\Intel(R) Management Engine Components\DAL;
C:\Program Files\Intel\Intel(R) Management Engine Components\IPT;
C:\Program Files (x86)\Intel\Intel(R) Management Engine Components\DAL;
C:\Program Files (x86)\Intel\Intel(R) Management Engine Components\IPT;
C:\Program Files\WIDCOMM\Bluetooth Software\;
C:\Program Files\WIDCOMM\Bluetooth Software\syswow64;
C:\Program Files\TortoiseSVN\bin;
C:\Program Files (x86)\IVI Foundation\VISA\WinNT\Bin;
C:\Program Files (x86)\leJOS NXJ\bin;
C:\Program Files (x86)\Windows Live\Shared;
C:\Program Files\OpenVPN\bin;
C:\Program Files\Java\jdk1.8.0_65\bin;
C:\Program Files\apache-ant-1.9.3\bin;
C:\Program Files\apache-maven-3.2.1\bin;
C:\Users\Kevin\Desktop\gradle-2.2.1\bin;
;
C:\Program Files (x86)\SSH Communications Security\SSH Secure Shell;
.

In both cases, the location of . is C:\Users\Kevin\Desktop\eclipse\., and in both cases it contains the same files:

#log.txt#save#
.eclipseproduct
artifacts.xml
configuration
crawl.log
derby.log
dropins
eclipse.exe
eclipse.ini
eclipsec.exe
epl-v10.html
features
notice.html
p2
plugins
Queue.zip
readme
server
StaticVoidGames.log
StaticVoidGames_SystemErr.txt
StaticVoidGames_SystemOut.txt

The line of code that throws the exception is:

V8 runtime = V8.createV8Runtime();

That code works fine when I deploy manually, but it fails upon subsequent auto-deploys.

My googling got me to this forum post which only says "there may be problems upon reload" but doesn't offer any solutions. So, my questions are:

• Why isn't eclipse including native libraries upon automatic redeploy?

• Can I tell eclipse to include native libraries upon automatic redeploy? Is there some setting I'm not seeing?

• If automatic redeploy simply doesn't support native libraries, is there some official source saying that?

Answer 1

DLL's are tied to a specific classloader. When we redeploy, that means that the classloader used for our application is destroyed. Unfortunately the Java Virtual Machine does not allow a second classloader to reload a DLL again.

I think its possible to create a Jar file that loads the DLL and add it to the classpath of Tomcat itself, instead of adding it to our application. Normally Tomcat have a "shared" directory where such jar files can be added that will be shared by all applications.

Demo:

1.Change the jar scope to provided so it can be used only in compile time.

        <dependency>
            <groupId>com.eclipsesource.j2v8</groupId>
            <artifactId>j2v8_win32_x86_64</artifactId>
            <version>3.1.6</version>
            <scope>provided</scope>
        </dependency>

2. Create a 'shared' folder inside tomcat folder

3. Paste j2v8_win32_x86_64-3.1.6.jar to shared folder

4. Append ${catalina.home}/shared/*.jar to shared.loader property in catalina.properties

Reference :

http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4225434 http://grokbase.com/t/tomcat/users/06acn8f491/jni-native-libraries-and-tomcat-reloading-web-apps