在Java中直接調用js代碼
不能調用瀏覽器中定義的js函數,會拋出異常提示ReferenceError: “alert” is not defined。
package com.sinaapp.manjushri;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException; /** * 直接調用js代碼 */
public class ScriptEngineTest {
public static void main(String[] args) {
ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine engine = manager.getEngineByName("javascript");
try {
engine.eval("var a=3; var b=4;print (a+b);");
// 不能調用瀏覽器中定義的js函數
// engine.eval("alert(\"js alert\");");
// 錯誤,會拋出alert引用不存在的異常
} catch (ScriptException e) {
e.printStackTrace();
}
}
}
輸出結果:7
在Java中綁定js變量
package com.sinaapp.manjushri;
import javax.script.Bindings;
import javax.script.ScriptContext;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
public class ScriptEngineTest2 {
public static void main(String[] args) {
ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine engine = manager.getEngineByName("javascript");
engine.put("a", 4); engine.put("b", 3);
Bindings bindings = engine.getBindings(ScriptContext.ENGINE_SCOPE);
try {
// 只能爲Double,使用Float和Integer會拋出異常
Double result = (Double) engine.eval("a+b");
System.out.println("result = " + result);
engine.eval("c=a+b");
Double c = (Double)engine.get("c");
System.out.println("c = " + c);
} catch (ScriptException e) {
e.printStackTrace();
}
}
}
輸出:result = 7.0
c = 7.0
在Java中調用js文件中的function,傳入調用參數,並獲取返回值
// expression.js
function merge(a, b) {
c = a * b;
return c;
}
在Java代碼中讀取js文件,並參數兩個參數,然後回去返回值package com.sinaapp.manjushri;
import java.io.FileReader;
import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
/** * Java調用並執行js文件,傳遞參數,並活動返回值 * * @author manjushri */
public class ScriptEngineTest {
public static void main(String[] args) throws Exception {
ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine engine = manager.getEngineByName("javascript");
String jsFileName = "expression.js";
// 讀取js文件
FileReader reader = new FileReader(jsFileName);
// 執行指定腳本
engine.eval(reader);
if(engine instanceof Invocable) {
Invocable invoke = (Invocable)engine;
// 調用merge方法,並傳入兩個參數
// c = merge(2, 3);
Double c = (Double)invoke.invokeFunction("merge", 2, 3);
System.out.println("c = " + c);
}
reader.close();
}
}
輸出結果:c = 5.0