Question

我写了一个Java示例，代码是：

import org.python.core.PyObject;
import org.python.util.PythonInterpreter;

import javax.script.ScriptEngine;
import javax.script.ScriptEngineFactory;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import java.util.List;

class JythonExample {

  public static void main(String args[]) throws ScriptException {
    listEngines();

    ScriptEngineManager mgr = new ScriptEngineManager();
    ScriptEngine pyEngine = mgr.getEngineByName("python");

    try {
      pyEngine.eval("print \"Python - Hello, world!\"");
    } catch (Exception ex) {
      ex.printStackTrace();
    }

    final PythonInterpreter interpreter = new PythonInterpreter();
    interpreter.exec("print \"Python - Hello, world!\"");

    PyObject result = interpreter.eval("2 + 3");
    System.out.println(result.toString());
  }

  public static void listEngines(){
    ScriptEngineManager mgr = new ScriptEngineManager();
    List<ScriptEngineFactory> factories =
        mgr.getEngineFactories();
    for (ScriptEngineFactory factory: factories) {
      System.out.println("ScriptEngineFactory Info");
      String engName = factory.getEngineName();
      String engVersion = factory.getEngineVersion();
      String langName = factory.getLanguageName();
      String langVersion = factory.getLanguageVersion();
      System.out.printf("\tScript Engine: %s (%s)\n",
          engName, engVersion);
      List<String> engNames = factory.getNames();
      for(String name: engNames) {
        System.out.printf("\tEngine Alias: %s\n", name);
      }
      System.out.printf("\tLanguage: %s (%s)\n",
          langName, langVersion);
    }
  }
}

在pom.xml中，如果我使用：

<dependency>
    <groupId>org.python</groupId>
    <artifactId>jython-standalone</artifactId>
    <version>2.7.0</version>
</dependency>

然后我可以成功运行java -jar target/jython-example-1.0-SNAPSHOT.jar，顺便说一下，我使用maven-assembly-plugin来构建一个可运行的jar。

如果我使用：

<dependency>
    <groupId>org.python</groupId>
    <artifactId>jython</artifactId>
    <version>2.7.0</version>
</dependency>

然后当我运行java -jar target/jython-example-1.0-SNAPSHOT.jar时，我总会收到以下错误：

ScriptEngineFactory Info
    Script Engine: jython (2.7.0)
    Engine Alias: python
    Engine Alias: jython
    Language: python (2.7)
ScriptEngineFactory Info
    Script Engine: Oracle Nashorn (1.8.0_31)
    Engine Alias: nashorn
    Engine Alias: Nashorn
    Engine Alias: js
    Engine Alias: JS
    Engine Alias: JavaScript
    Engine Alias: javascript
    Engine Alias: ECMAScript
    Engine Alias: ecmascript
    Language: ECMAScript (ECMA - 262 Edition 5.1)
java.lang.NullPointerException
    at me.soulmachine.JythonExample.main(JythonExample.java:21)
Exception in thread "main" ImportError: Cannot import site module and its dependencies: No module named site
Determine if the following attributes are correct:
  * sys.path: ['/home/programmer/src/github/JythonExample/JythonExample/target/Lib', '__classpath__', '__pyclasspath__/']
    This attribute might be including the wrong directories, such as from CPython
  * sys.prefix: /home/programmer/src/github/JythonExample/JythonExample/target
    This attribute is set by the system property python.home, although it can
    be often automatically determined by the location of the Jython jar file

You can use the -S option or python.import.site=false to not import the site module

似乎pyEngine是null。

所以我想知道jython-standalone-2.7.0.jar和jython-2.7.0.jar

之间有什么区别

Answer 1

我刚刚发现的一个问题是，maven build 2.7.0不包含lib文件夹。这可能是发布版本的构建错误。我不得不向上移动b2构建，它正确地包含了提供的jar中的lib文件夹。

问题maven 2.7.0 jar：
<dependency> <groupId>org.python</groupId> <artifactId>jython-standalone</artifactId> <version>2.7.0</version> </dependency>

包含lib文件夹的工作maven 2.7.1b2：
<dependency> <groupId>org.python</groupId> <artifactId>jython-standalone</artifactId> <version>2.7.1b2</version> </dependency>

注意：如果您直接从Jython站点下载jar，它会正确包含lib文件夹。它只是maven存储库版本。

Answer 2

我认为造成问题的主要区别在于jython-standalone jar提供了Lib /（包含site.py），而jython jar却没有。

https://github.com/scijava/jython-shaded对问题以及其他问题进行了更深入的描述，并提供了一个替代方法来解决说明中提到的一些问题。

我没有使用scijava的经验：jython-shaded，但是我将它替换为你的pom（对于我的设置，我还必须将jdk.version更改为1.7和JythonExample）并运行示例。

jython-standalone-2.7.0.jar和jython-2.7.0.jar之间有什么区别？

2 个答案: