Java 脚本引擎

Java 脚本引擎

Java脚本教程 - Java脚本引擎Java Scripting API有许多类和接口。它们在javax.script包中。 ScriptEngine 接口是其实例执行以脚本语言编写的脚本的接口ScriptEngineFactory执行两个任务：创建脚本引擎的实例。提供有关脚本引擎的信息，如引擎名称，版本，语言等。AbstractScriptEngine类是一个抽象类，并为ScriptEngine接口提供了部分实现。ScriptEngineManager类发现和实例化脚本引擎。可用的引擎以下代码显示如何列出所有可用的脚本引擎。import java.util.List;

import javax.script.ScriptEngineFactory;

import javax.script.ScriptEngineManager;

public class Main {

public static void main(String[] args) {

ScriptEngineManager manager = new ScriptEngineManager();

// Get the list of all available engines
List<ScriptEngineFactory> list = manager.getEngineFactories();
// Print the details of each engine
for (ScriptEngineFactory f : list) {
  System.out.println("Engine Name:" + f.getEngineName());
  System.out.println("Engine Version:" + f.getEngineVersion());
  System.out.println("Language Name:" + f.getLanguageName());
  System.out.println("Language Version:" + f.getLanguageVersion());
  System.out.println("Engine Short Names:" + f.getNames());
  System.out.println("Mime Types:" + f.getMimeTypes());
  System.out.println("===");
}

}

}

上面的代码生成以下结果。例子以下代码显示了如何使用JavaScript，Groovy，Jython和JRuby在标准输出上打印消息。如果脚本引擎不可用，程序会向用户提示错误消息。import javax.script.ScriptEngine;

import javax.script.ScriptEngineManager;

import javax.script.ScriptException;

public class Main {

public static void main(String[] args) {

// Get the script engine manager

ScriptEngineManager manager = new ScriptEngineManager();

// Try executing scripts in Nashorn, Groovy, Jython, and JRuby
execute(manager, "JavaScript", "print("Hello JavaScript")");
execute(manager, "Groovy", "println("Hello Groovy")");
execute(manager, "jython", "print "Hello Jython"");
execute(manager, "jruby", "puts("Hello JRuby")");

}

public static void execute(ScriptEngineManager manager, String engineName,

String script) {

ScriptEngine engine = manager.getEngineByName(engineName);
if (engine == null) {
  System.out.println(engineName + " is not available.");
  return;
}
try {
  engine.eval(script);
} catch (ScriptException e) {
  e.printStackTrace();
}

}

}

上面的代码生成以下结果。找出语法要获得用于在标准输出上打印消息的语法，请使用ScriptEngineFactory类中的方法getOutputStatement（String toDisplay）。以下代码段显示了如何获取Nashorn的语法。import javax.script.ScriptEngine;

import javax.script.ScriptEngineFactory;

import javax.script.ScriptEngineManager;

import javax.script.ScriptException;

public class Main {

public static void main(String[] args) {

// Get the script engine factory for Nashorn

ScriptEngineManager manager = new ScriptEngineManager();

ScriptEngine engine = manager.getEngineByName("JavaScript");

ScriptEngineFactory factory = engine.getFactory();

    // Get the script
    String script = factory.getOutputStatement("\"w3cschool\"");
    System.out.println("Syntax: " + script);
    // Evaluate the script
    try {
  engine.eval(script);
} catch (ScriptException e) {
  // TODO Auto-generated catch block
  e.printStackTrace();
}

}

}

上面的代码生成以下结果。