Java 編譯腳本

Java腳本教程 - Java編譯腳本

腳本引擎允許以Java類的形式編譯腳本，然后重復執(zhí)行它。

以下代碼檢查腳本引擎是否實現(xiàn)了可編譯接口:

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.");
    }

  }
}

上面的代碼生成以下結(jié)果。

例子

可編譯接口包含兩個方法:

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

要執(zhí)行編譯腳本，請從CompiledScript類調(diào)用以下eval()方法之一。

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

以下代碼顯示了如何編譯腳本并執(zhí)行它。它使用不同的參數(shù)執(zhí)行相同的編譯腳本兩次。

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);
  }
}

上面的代碼生成以下結(jié)果。