Call Java Code Using JPype from Python

Things on this page are fragmentary and immature notes/thoughts of the author. Please read with your own judgement!

JPype is easy and intuitive to use. It is the most popular Java interface for Python currently.

:::python
import os
import sys
from pathlib import Path
import jpype


jpype.addClassPath("/path/to.jar")
jpype.startJVM()
print(jpype.java.lang.System.getProperty("java.class.path"))
import ...
obj = SomeClass(...)
obj.someMethod(...)
StaticClass.someMethod(...)


import pyarrow
import pyarrow.jvm
classpath = ":".join(str(jar.resolve()) for jar in Path().glob("*.jar"))
jpype.startJVM(jpype.getDefaultJVMPath(), f"-Djava.class.path={classpath}")
ra = jpype.JPackage("org").apache.arrow.memory.RootAllocator(sys.maxsize)
dm = jpype.JPackage("java").sql.DriverManager
connection = dm.getConnection("jdbc:hive2://hive.server.example.com:10000/default", "user_name", "password")
batch = jpype.JPackage("org").apache.arrow.adapter.jdbc.JdbcToArrow.sqlToArrow(
    connection, "SELECT * FROM some_table", ra
)
df = pyarrow.jvm.record_batch(batch).to_pandas()

Notice that you can import a Java class as usual after the following import.

:::python
import jpype.imports

jpype.addClassPath must be called before starting the JVM. You can use the following statement to check that the correct dependency has been added.
```
 :::python
 print(jpype.java.lang.System.getProperty("java.class.path"))
```

Passing Arguments Between Java and Python¶

https://stackoverflow.com/questions/13637614/jpype-passing-args-to-java

https://jpype.readthedocs.io/en/latest/quickguide.html#primitives

Call Java Code Using JPype from Python

Passing Arguments Between Java and Python¶

References¶