python call java jar

python脚本如何调用Java的jar文件呢？

HelloWorld.java

public class HelloWorld {

    public static void main(String[] args) {
        System.out.println("hello world");
        String input = args[0];
        String output = input.toUpperCase();
        System.out.print(output);
    }

}

javacaller.py

# python3
# coding = utf-8

from subprocess import Popen, PIPE, STDOUT

mycmd = ['java', '-jar', 'HelloWorld.jar', 'logan']

pipe = Popen(mycmd, stdout=PIPE, stderr=STDOUT)

for line in pipe.stdout:
    print(line, type(line))
    if isinstance(line, bytes):
        line_decode = line.decode('utf-8')
        print('decode:', line_decode, type(line_decode))

print('done')

输出：

b'hello world\n' <class 'bytes'>
decode: hello world
<class 'str'>
b'LOGAN' <class 'bytes'>
decode: LOGAN <class 'str'>
done

注意点:

1. java的 System.out.println自带换行

2. java返回的结果需要decode

参考资料:

How to get the output from .jar execution in python codes?