From f2ab5e245646a39f474ad7c2e694d1981965ebc4 Mon Sep 17 00:00:00 2001 From: Jonathan Cook Date: Tue, 12 May 2020 18:52:34 +0200 Subject: [PATCH] BAEL-3925 - How to call Python from Java --- java-python-interop/README.md | 5 + java-python-interop/pom.xml | 55 ++++++++ .../interop/ScriptEngineManagerUtils.java | 34 +++++ .../src/main/resources/logback.xml | 13 ++ .../interop/JavaPythonInteropUnitTest.java | 131 ++++++++++++++++++ .../src/test/resources/hello.py | 1 + pom.xml | 3 +- 7 files changed, 241 insertions(+), 1 deletion(-) create mode 100644 java-python-interop/README.md create mode 100644 java-python-interop/pom.xml create mode 100644 java-python-interop/src/main/java/com/baeldung/python/interop/ScriptEngineManagerUtils.java create mode 100644 java-python-interop/src/main/resources/logback.xml create mode 100644 java-python-interop/src/test/java/com/baeldung/python/interop/JavaPythonInteropUnitTest.java create mode 100644 java-python-interop/src/test/resources/hello.py diff --git a/java-python-interop/README.md b/java-python-interop/README.md new file mode 100644 index 0000000000..dc9573ecde --- /dev/null +++ b/java-python-interop/README.md @@ -0,0 +1,5 @@ +## Java Python Interop + +This module contains articles about Java and Python interoperability. + +### Relevant Articles: diff --git a/java-python-interop/pom.xml b/java-python-interop/pom.xml new file mode 100644 index 0000000000..6ee5a0be3b --- /dev/null +++ b/java-python-interop/pom.xml @@ -0,0 +1,55 @@ + + + 4.0.0 + java-python-interop + 0.0.1-SNAPSHOT + java-python-interop + + + com.baeldung + parent-modules + 1.0.0-SNAPSHOT + + + + + org.python + jython-slim + ${jython.version} + + + org.apache.commons + commons-exec + ${commons-exec.version} + + + org.assertj + assertj-core + ${assertj.version} + test + + + + + java-python-interop + + + src/main/resources + true + + + src/test/resources + true + + + + + + 2.7.2 + 1.3 + 3.6.1 + + + \ No newline at end of file diff --git a/java-python-interop/src/main/java/com/baeldung/python/interop/ScriptEngineManagerUtils.java b/java-python-interop/src/main/java/com/baeldung/python/interop/ScriptEngineManagerUtils.java new file mode 100644 index 0000000000..981f174c33 --- /dev/null +++ b/java-python-interop/src/main/java/com/baeldung/python/interop/ScriptEngineManagerUtils.java @@ -0,0 +1,34 @@ +package com.baeldung.python.interop; + +import java.util.List; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import javax.script.ScriptEngineFactory; +import javax.script.ScriptEngineManager; + +public class ScriptEngineManagerUtils { + + private static final Logger LOGGER = LoggerFactory.getLogger(ScriptEngineManagerUtils.class); + + private ScriptEngineManagerUtils() { + } + + public static void listEngines() { + ScriptEngineManager manager = new ScriptEngineManager(); + List engines = manager.getEngineFactories(); + + for (ScriptEngineFactory engine : engines) { + LOGGER.info("Engine name: {}", engine.getEngineName()); + LOGGER.info("Version: {}", engine.getEngineVersion()); + LOGGER.info("Language: {}", engine.getLanguageName()); + + LOGGER.info("Short Names:"); + for (String names : engine.getNames()) { + LOGGER.info(names); + } + } + } + +} diff --git a/java-python-interop/src/main/resources/logback.xml b/java-python-interop/src/main/resources/logback.xml new file mode 100644 index 0000000000..7d900d8ea8 --- /dev/null +++ b/java-python-interop/src/main/resources/logback.xml @@ -0,0 +1,13 @@ + + + + + %d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n + + + + + + + + \ No newline at end of file diff --git a/java-python-interop/src/test/java/com/baeldung/python/interop/JavaPythonInteropUnitTest.java b/java-python-interop/src/test/java/com/baeldung/python/interop/JavaPythonInteropUnitTest.java new file mode 100644 index 0000000000..5ec3a2b61f --- /dev/null +++ b/java-python-interop/src/test/java/com/baeldung/python/interop/JavaPythonInteropUnitTest.java @@ -0,0 +1,131 @@ +package com.baeldung.python.interop; + +import static org.hamcrest.Matchers.containsString; +import static org.hamcrest.Matchers.empty; +import static org.hamcrest.Matchers.hasItem; +import static org.hamcrest.Matchers.is; +import static org.hamcrest.Matchers.not; +import static org.junit.Assert.assertEquals; +import static org.junit.Assert.assertThat; + +import java.io.BufferedReader; +import java.io.ByteArrayOutputStream; +import java.io.File; +import java.io.FileReader; +import java.io.IOException; +import java.io.InputStream; +import java.io.InputStreamReader; +import java.io.StringWriter; +import java.util.List; +import java.util.stream.Collectors; + +import javax.script.ScriptContext; +import javax.script.ScriptEngine; +import javax.script.ScriptEngineManager; +import javax.script.SimpleScriptContext; + +import org.apache.commons.exec.CommandLine; +import org.apache.commons.exec.DefaultExecutor; +import org.apache.commons.exec.ExecuteException; +import org.apache.commons.exec.PumpStreamHandler; +import org.junit.Rule; +import org.junit.Test; +import org.junit.rules.ExpectedException; +import org.python.core.PyException; +import org.python.core.PyObject; +import org.python.util.PythonInterpreter; + +public class JavaPythonInteropUnitTest { + + @Rule + public ExpectedException thrown = ExpectedException.none(); + + @Test + public void givenPythonScript_whenPythonProcessInvoked_thenSuccess() throws Exception { + ProcessBuilder processBuilder = new ProcessBuilder("python", resolvePythonScriptPath("hello.py")); + processBuilder.redirectErrorStream(true); + + Process process = processBuilder.start(); + List results = readProcessOutput(process.getInputStream()); + + assertThat("Results should not be empty", results, is(not(empty()))); + assertThat("Results should contain output of script: ", results, hasItem(containsString("Hello Baeldung Readers!!"))); + + int exitCode = process.waitFor(); + assertEquals("No errors should be detected", 0, exitCode); + } + + @Test + public void givenPythonScriptEngineIsAvailable_whenScriptInvoked_thenOutputDisplayed() throws Exception { + StringWriter output = new StringWriter(); + ScriptContext context = new SimpleScriptContext(); + context.setWriter(output); + + ScriptEngineManager manager = new ScriptEngineManager(); + ScriptEngine engine = manager.getEngineByName("python"); + engine.eval(new FileReader(resolvePythonScriptPath("hello.py")), context); + assertEquals("Should contain script output: ", "Hello Baeldung Readers!!", output.toString() + .trim()); + } + + @Test + public void givenPythonInterpreter_whenPrintExecuted_thenOutputDisplayed() { + try (PythonInterpreter pyInterp = new PythonInterpreter()) { + StringWriter output = new StringWriter(); + pyInterp.setOut(output); + + pyInterp.exec("print('Hello Baeldung Readers!!')"); + assertEquals("Should contain script output: ", "Hello Baeldung Readers!!", output.toString() + .trim()); + } + } + + @Test + public void givenPythonInterpreter_whenNumbersAdded_thenOutputDisplayed() { + try (PythonInterpreter pyInterp = new PythonInterpreter()) { + pyInterp.exec("x = 10+10"); + PyObject x = pyInterp.get("x"); + assertEquals("x: ", 20, x.asInt()); + } + } + + @Test + public void givenPythonInterpreter_whenErrorOccurs_thenExceptionIsThrown() { + thrown.expect(PyException.class); + thrown.expectMessage("ImportError: No module named syds"); + + try (PythonInterpreter pyInterp = new PythonInterpreter()) { + pyInterp.exec("import syds"); + } + } + + @Test + public void givenPythonScript_whenPythonProcessExecuted_thenSuccess() throws ExecuteException, IOException { + String line = "python " + resolvePythonScriptPath("hello.py"); + CommandLine cmdLine = CommandLine.parse(line); + + ByteArrayOutputStream outputStream = new ByteArrayOutputStream(); + PumpStreamHandler streamHandler = new PumpStreamHandler(outputStream); + + DefaultExecutor executor = new DefaultExecutor(); + executor.setStreamHandler(streamHandler); + + int exitCode = executor.execute(cmdLine); + assertEquals("No errors should be detected", 0, exitCode); + assertEquals("Should contain script output: ", "Hello Baeldung Readers!!", outputStream.toString() + .trim()); + } + + private List readProcessOutput(InputStream inputStream) throws IOException { + try (BufferedReader output = new BufferedReader(new InputStreamReader(inputStream))) { + return output.lines() + .collect(Collectors.toList()); + } + } + + private String resolvePythonScriptPath(String filename) { + File file = new File("src/test/resources/" + filename); + return file.getAbsolutePath(); + } + +} diff --git a/java-python-interop/src/test/resources/hello.py b/java-python-interop/src/test/resources/hello.py new file mode 100644 index 0000000000..13275d9257 --- /dev/null +++ b/java-python-interop/src/test/resources/hello.py @@ -0,0 +1 @@ +print("Hello Baeldung Readers!!") \ No newline at end of file diff --git a/pom.xml b/pom.xml index c6addfa6aa..1a56184de2 100644 --- a/pom.xml +++ b/pom.xml @@ -461,7 +461,8 @@ java-lite java-numbers java-numbers-2 - java-numbers-3 + java-numbers-3 + java-python-interop java-rmi java-spi java-vavr-stream