Java Class(User.java)

package com.example.model;\n\npublic class User {\n\n    private String name;\n\n    public User(String name) {\n        this.name = name;\n    }\n\n    public String getName() {\n        return this.name;\n    }\n}\n\n

I've compiled the Java class and packaged it into a JAR file named gpdemo-0.0.1-SNAPSHOT-plain.jar, and I set it as classpath for zshrc.

Execution command

graalpy --jvm \\\n  --vm-cp=$CLASSPATH \\\n  ./main.py\n\n

Error Message:

User = java.type('com.example.model.User')\nKeyError: 'host symbol com.example.model.User is not defined or access has been denied'\n

What I've Tried:

\n
• Verified that the JAR file is in the correct location and that the class is properly packaged.
\n
• Printed out the Java classpath within the Python script to ensure that the JAR file is included.
\n
• Ensured that GraalVM is installed correctly and that I'm using the --jvm option to enable JVM interop.
\n

Environment Details:

GraalVM Version: Oracle GraalVM 23.0.1+11.1
\nGraalPy Version: GraalPy 3.10.8 (GraalVM CE JVM 23.1.2)
\nOperating System: macOS

Questions:

\n
• Is there something I'm missing in the way I'm specifying the classpath when running the script?
\n
• Do I need to adjust any settings related to host access or permissions to allow Python to access the Java class?
\n
• Has anyone else encountered a similar issue and found a solution?
\n

I tried your example and it printed Alice with no errors. What I did:

\n
• Save your java code as com/example/model/User.java and your python code as main.py
\n
• javac com/example/model/User.java
\n
• graalpy --vm.cp=. main.py
\n

The differences I have from you is that I used the latest release, I'm on Linux and I didn't build a JAR. Could you please try the latest release (24.1.1, the graalpy-jvm variant)?

Trouble Accessing Java Classes from Python Using GraalPy and GraalVM #448

Answered by msimacek

ShuzoShinagawa1102 asked this question in Q&A

Trouble Accessing Java Classes from Python Using GraalPy and GraalVM #448

ShuzoShinagawa1102

Oct 29, 2024 · 2 comments · 3 replies

Answered by msimacek Return to top

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edited

ShuzoShinagawa1102

Oct 29, 2024

Hello everyone, What I want to do I'm trying to access a Java class from a Python script using GraalPy (GraalPython) with GraalVM, but I'm encountering an error that I can't seem to resolve. Python Script (main.py) import java # Get the Java classpath and print it System = java.type("java.lang.System") classpath = System.getProperty("java.class.path") print(f"Java Classpath: {classpath}") # Attempt to access the Java class User = java.type('com.example.model.User') # Create an instance of the Java class user = User('Alice') print(user.getName()) Java Class(User.java) package com.example.model; public class User { private String name; public User(String name) { this.name = name; } public String getName() { return this.name; } } I've compiled the Java class and packaged it into a JAR file named gpdemo-0.0.1-SNAPSHOT-plain.jar, and I set it as classpath for zshrc. Execution command graalpy --jvm \ --vm-cp=$CLASSPATH \ ./main.py Error Message: User = java.type('com.example.model.User') KeyError: 'host symbol com.example.model.User is not defined or access has been denied' What I've Tried: Verified that the JAR file is in the correct location and that the class is properly packaged. Printed out the Java classpath within the Python script to ensure that the JAR file is included. Ensured that GraalVM is installed correctly and that I'm using the --jvm option to enable JVM interop. Environment Details: GraalVM Version: Oracle GraalVM 23.0.1+11.1 GraalPy Version: GraalPy 3.10.8 (GraalVM CE JVM 23.1.2) Operating System: macOS Questions: Is there something I'm missing in the way I'm specifying the classpath when running the script? Do I need to adjust any settings related to host access or permissions to allow Python to access the Java class? Has anyone else encountered a similar issue and found a solution?

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Answered by msimacek Oct 30, 2024

I tried your example and it printed Alice with no errors. What I did:

• Save your java code as com/example/model/User.java and your python code as main.py
• javac com/example/model/User.java
• graalpy --vm.cp=. main.py

The differences I have from you is that I used the latest release, I'm on Linux and I didn't build a JAR. Could you please try the latest release (24.1.1, the graalpy-jvm variant)?

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Replies: 2 comments · 3 replies

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edited

ShuzoShinagawa1102

Oct 29, 2024

Author

additionally, here is the contained classes which are showed by jar tf $CLASSPATH command. MacBook-Pro-4 gpdemo % jar tf $CLASSPATH META-INF/ META-INF/MANIFEST.MF com/ com/example/ com/example/demo/ com/example/demo/GpdemoApplication.class com/example/model/ com/example/model/User.class application.properties

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msimacek

Oct 29, 2024

Collaborator

Hi @ShuzoShinagawa1102, the option for supplying classpath when running through the graalpy launcher is --vm.cp=$CLASSPATH (not -vm-cp).

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edited

ShuzoShinagawa1102 Oct 29, 2024

Author

@msimacek Thank you for pointing that out. It was just a typo on my part, and I am indeed using "--vm.cp" when runnng the command.

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msimacek Oct 30, 2024

Collaborator

I tried your example and it printed Alice with no errors. What I did: Save your java code as com/example/model/User.java and your python code as main.py javac com/example/model/User.java graalpy --vm.cp=. main.py The differences I have from you is that I used the latest release, I'm on Linux and I didn't build a JAR. Could you please try the latest release (24.1.1, the graalpy-jvm variant)?

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ShuzoShinagawa1102 Oct 30, 2024

Author

@msimacek Thank you for your kind response. I installed GraalPy latest release version (24.1.1) that you suggested (https://github.com/oracle/graalpython/releases) and it worked. The command which I executed is here. graalpy --jvm \ --vm.cp=gpdemo-0.0.1-SNAPSHOT-plain.jar \ ./main.py it returned ↓

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