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:
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。
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。
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。
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。