Jython由"getEngineFactories"列出，而"getEngineByName("jython"))则为"null". [英] Jython listed by `getEngineFactories`, but `getEngineByName("jython")` is `null`

问题描述

我创建了一个默认的Maven Java项目并添加了以下依赖项:

I created a default Maven Java project and added the following dependency:

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

然后我创建了一个包 src/main/java/mypkg 并添加了此类:

Then I created a package src/main/java/mypkg and added this class:

package mypkg;

import javax.script.*;

class JythonMinimalTest {
    public static void main(String[] args) throws Exception {
        String engineName = "python";
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName(engineName);
        if (engine == null) {
            System.err.println("ERROR: `" + engineName + "` not available.");
            System.err.println("Available engines: ");
            for (ScriptEngineFactory factory: manager.getEngineFactories()) {
                System.err.println(factory);
                System.err.println("names:");
                for (String name: factory.getNames()) {
                    System.err.println("  " + name);
                }
            }
            System.exit(999);
        }
        engine.eval("print('hello, world')");
    }
}

当我使用 exec:java 运行它时，

mvn exec:java -Dexec.mainClass=mypkg.JythonMinimalTest

我得到以下神秘输出:

ERROR: `python` not available.
Available engines: 
org.python.jsr223.PyScriptEngineFactory@2b0e6c89
names:
  python
  jython
jdk.nashorn.api.scripting.NashornScriptEngineFactory@46618cb8
names:
  nashorn
  Nashorn
  js
  JS
  JavaScript
  javascript
  ECMAScript
  ecmascript

管理器返回 null ，但随后在下一行中列出可用脚本引擎中的 python / jython .

The manager returns null, but then in the next line lists python/jython among the available script engines.

Nashorn以完全相同的方式工作得很好.我的Jython怎么了?

Nashorn worked just fine in exactly the same way. What am I doing wrong with Jython?

推荐答案

这是一种解决方法:

将此添加到顶部:

import org.python.core.Options;

在调用 getEngineByName 之前，先设置

   Options.importSite = false;

然后创建引擎，没有问题.

Then the engine is created without problems.

从另一个有效的解决方案(在注释中由mzjn提出)是将 jython 工件替换为 jython-standalone .

Another solution that works well (proposed by mzjn in the comments) is to replace the jython artifact by jython-standalone.

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