Java 编译脚本

Java脚本教程 – Java编译脚本

脚本引擎允许以Java类的形式编译脚本，然后重复执行它。

以下代码检查脚本引擎是否实现了可编译接口:

import javax.script.Compilable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;

public class Main {
  public static void main(String[] args) throws Exception {
    ScriptEngineManager manager = new ScriptEngineManager();
    ScriptEngine engine = manager.getEngineByName("JavaScript");

    if (engine instanceof Compilable) {
      System.out.println("Script compilation is supported.");
    } else {
      System.out.println("Script compilation is not supported.");
    }

  }
}

上面的代码生成以下结果。

例子

可编译接口包含两个方法:

CompiledScript compile(String script) throws ScriptException
CompiledScript compile(Reader script) throws ScriptException

要执行编译脚本，请从CompiledScript类调用以下eval()方法之一。

Object eval() throws ScriptException
Object eval(Bindings bindings) throws ScriptException
Object eval(ScriptContext context) throws ScriptException

以下代码显示了如何编译脚本并执行它。它使用不同的参数执行相同的编译脚本两次。

import javax.script.Bindings;
import javax.script.Compilable;
import javax.script.CompiledScript;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;

public class Main {
  public static void main(String[] args) throws Exception {
    ScriptEngineManager manager = new ScriptEngineManager();
    ScriptEngine engine = manager.getEngineByName("JavaScript");

    if (!(engine instanceof Compilable)) {
      System.out.println("Script compilation not supported.");
      return;
    }
    Compilable comp = (Compilable) engine;

    CompiledScript cScript = comp.compile("print(n1 + n2)");

    Bindings scriptParams = engine.createBindings();
    scriptParams.put("n1", 2);
    scriptParams.put("n2", 3);
    cScript.eval(scriptParams);

    scriptParams.put("n1", 9);
    scriptParams.put("n2", 7);
    cScript.eval(scriptParams);
  }
}

上面的代码生成以下结果。